· c o n t e n t s. introduction. distribution of s pecies m igration l ongevity and rate of...
TRANSCRIPT
T H E A N A T O MY
O F T H E
C O M M O N S Q U I D
L OL IGO PEAL I I,LE SUEUR
,
LEONARD WORCESTER WILLIAMS
H A R V A R D M E D I C A L S C H O O L,
BO S T O N M A S S .
P U BL I S H E D U N D E R T H E P A T R O N A G E O F
T H E A M E R I C A N M U S E U M O F N A T U R A L H I S T O R Y .
N E W - Y O R K C I T Y .
L IBRARY AND P RINTIN G - OFFICEL ATE
E . J . B R I L L .
L E I D E N H O L L A N D .
C O N T E N T S .
INTRODUCTION .
D istribution of S pec iesM i grati onL ongev i ty and Rate of G rowth .
FoodE conomic Val ueReview of P rev i ou s Work .
ANATOMY.
P
P3
P9
S&
10 .
1 1 .
12 .
13 .
14 .
15 .
O rien tat i onG ene ral AnatomyT he S ki nT he S ke le to na E xoske le to nb . E ndoske le to nT he S k u l l o r Cephal i c cart i lagesT he M uscu lar S ystema . M an tle and F i nsb. Foot .
Arms H ectocoty l usS i phon
c . M uscles of the V i sce ra l MassT he HeadT he Pa l l ia l Chamber , V i scera ,
and Pal l ial ComplexT he A l imental y Cana l .Ge neral Form .
P harynx,Jaws
,M usc les Rad u la and G lands
Oe sophagusS tomachCaecu n1
,L i ve1 and Pancreas
I nte stine ,Rectum
,and I nk S ac
The Reprod uct i ve S ystem .
a . Mal e .
b. FemaleT he C i 1 cu latory S ystem(1 . S ystemic C i rcu lati on ; N eph1 id i umb . Respi ratory C i l c u lati on , G i l l .0 . Bl ood gland s , Branch ial gland and Whi t-e Bod iesT he Body Cav i t iesT he N ervo us SystemT he S ense O rgansa . S tatocystsb. E ye .
Bib l i ography
LIST OF TEXT FIGURES .
D iagram of an hypothe tical prim i ti ve mol l usc .
S ag i ttal sect i on of an embryo ; modified from KO R S C H E L T H E IDER.
a late r emb iy o ;
an ad u l t squ i d
T he n uchal carti lage .
Late ral v iew of an ad u l t squ i d
D iagram of the muscles of the fi n .
S ection of fi n .
Ring of an u nsymmetri cal sucker
A . uppe r aspect .
B. late ral aspect .
M uscles of th e s i phon , from above .
T he jaws
A . u ppe r mand ib le .
B. l owe r
C . jaws art i c u lated .
Th ree rows of rad ular teeth
P se udopod ia l rectal ce l l s
I . from a sq u id 2 cm . l o ng .
I I. ad u l t squ i d .
M ode l o f the forward (prox imal ) port i o n of the l umen of the thi rd glan d (bl i n d sac) of theseminal vesi c le
A . from oute r si de .
B. beh i nd (i n section) .
D iagram of the oesophagea l , b uccal , and brach ia l ner ve r i ngs , see n from the si de
16. P hotographs of the gian t nerve ce l l s
A B. two adjacent sagi ttal secti on s of the pedal gangl i on .
C . transve rse secti o n of the peda l gangl i on .
D . med ian sagi tta l sect ion of the visceral gangl i o n .
EXPLANATION OF TEXT FIGURES .
TE XT FIGURE S 1—4 .
A 1, (1
2— 015,
fi rst,second etc. arm .
A n . an us .Ca . caec um .
C .G . ce rebra l gangl i on .
E . eye .
F . fi n .
Ft. foot .G 13. gi l l .Go. gonad .
H . heart.I . G . V i sceral , gangl i on . val ve .
L S . i n k sac .
L . V . latera l s i phona l val ve.
M . nran tle .
M . C . mantle chamber.M e. mese nteron .
TEXT FIGURE 5 . N ucha l carti lage.
d . dorsal po i n t . 1 . lateral po i n t . ventral poin t.
1 . arti c u lar s urface .
2 . groove for the i n sert i on of the si phonal va l ve .
3 . edge for i nsert io n of n uchal re tractor .4 . origi n of cephal i c re tractor .
TE XT F IGURE 6 . L eft si de of the squ i d .
A . anter i or su rface . P . poster i or su rface .
D . dorsal po i n t . V. ven tral po i n t.1 . fi n . 5 . fifth arm .
2 . lateral angle of co l lar (si phonal cart i lage) . 6 . ten tac le .
8 . si phon . 7 . fi rst arm .
4 . aqu i fero us pore . 8 . i r i s.9 . med ian angle of co l lar (pen po i n t) .
TEXT F IGURE 7 . D iagram of the nruscles of the fi n .
1 . m usc les wh i ch pass over the dorsal po i n t of the man tle .
2 . dorsal angle of fin .
3 . muscles con necti ng the fi ns .
4 . late ral angle of fin .
5 . ven tral angle of fi n .
6 . l o ngi t udi nal m usc les .
7 . fi n carti lage .
M o . mouth .
N e. ne phr id i u m .
0 . statocyst .P G . pedal gangl i on .
P h . pharynx .
P n . pen .
S a . sa l i vary gland .
Sh. S he l l .S i . si phon .
S i . f. si phona l fol d s.S i . V. med ian si phonalS .S . she l l sac .
S t. stomach .
V .g. v isce ra l gangl i o n .
S .V. va l ve of si phon .
1,4,6 . uppe r , midd le and l owe r fasc iae O f the fin .
2. muscle b und les paral le l to the surface and perpend ic u lar to the base of the fin .
3 . b lood vesse l .5 . musc le fibres para l le l to the base and su rface of the fin .
7. m irscu lar septa perpend ic ular to the surface of the fin .
TEXT FIGURE 9. R i ng of an u nsymme tri cal s u cke r.
A . from above . 1 . o ut l i ne of ri ng of accessory tee th .
B. i n secti on . 2. out l i ne of sucke r .
TEXT FIGURE 10. T he upper su rface of the si phon .
1 . si phona l (art i c u lar) cart i lage . 4 . the poster ior si phona l protractor .2 . lateral si phonal val ve i n sect ion . 5 . si phonal retractor .3 . the anter ior si phona l p rotractor. 6. obl i q ue s urface of origi n of the si phona l re tractor.
7. l ower wa l l of si phon .
TE XT FIGURE 1 1. T he jaws.
A . the u pper j aw . A l . ala of upper j aw .
B. the l ower j aw . A l .1 l owerC. the jaws arti cu lated . A x. axi s aro u nd wh i ch the jaws move .
R .M . retractor mandi bu li .
1 . Cou rse of the m uscle fibres whi ch d raw down the lower j aw .
2 . uppe r nrusc le fibres of add uctor of jaws.3 . midd le4 . l ower
TEXT FIGURE 12 . Th ree rows of rad u lar tee th .
TE XT FIGURE 13. S ecti o n thro ugh the ep i the l i u m of the rect um .
A . of a squ id 2 cm . l ong. B. of an ad ul t .F.V. food vac uole ?
TE XT FIGURE 14. M odel of the l umen of the forward end of the third glandof the semi nal vesi c le X.
A . from the o uter si de. B. from beh i n d (i n secti on) .
IX
TEXT FIGURE 8. S ection of the fin .
TE XT F IGURE 15. T h e oesophageal,bucca l
, and brach ial nerve r i ngs , seen from the si de .
fi rst , second etc. brach ial gangl ia.
i n frab uccal co n nec ti ve.
propedO- b uccal con necti ve.
cere bro - buccalcerebro- propedalbucco- spanchn icsmal l nerve to the n ucha l and cepha l i c re tractors.v isce ro - ste l late con nect i ve with the pal l ial nerve .
v isce ral ne rve wi th the v i scer'o - branch ia l con necti ve .
h 9?
mws
a
o
p
a
w
N
nerve of s i phona l retractors .cri sta stat i ca.
mac u la stat i ca.
si p hona l ne rve .
ne rve which i s d istr i b u ted to the l ower side of the head .
o l factory ne rve .
nerve wh ich i s d i str i b uted to m usc les of eye .
to base O f arms .Bc . G . brach ial ne rve ring and gangl ia.
B. G . su prabuccal gangl ion .
B. G .1 i n frab uccalce rebral
TE XT FIGURE 16. P hotographs of the giant nerve ce l l and i ts fibre .
adjacen t sagi ttal secti o ns th r u the pedal gangl i on .
transverse secti o nmed ian sag i ttal sect ion showi ng the ch iasnra of the fibres of thegian t ce l l s.
giant ce l l .fibre .
ep i the l i um of the macu la statica .
pedal process of sk u l l i n secti o n .
stato l i th ly i ng i n the cav i ty of the statocyst .siphona l ner ve .
0 . G . o u tl i ne of the opti c gangl i on .
P e. G . peda l gangl io n .
P r . G . propedal gangl i o n .
v i scera l
LIST OF PLATES AND FIGURES .
Frontisp iece. P hotograp hs of a model of a ma le squ i d in The Amer i can M useum of N atu ra l H i story.
P late I,F ig. 1 . Ce pha l i c and preorb i ta l carti lages (en larged fo ur d iamete rs) , r ight- ventra l aspect .
2 . T he gastro - caeca l open i ng see n from be l ow .
3 . S ecti on th r u a symm etr i cal s ucker .4 . an u nsymmetr i ca l s ucke r.5 . D i sta l end of spermatophore .
6 T he arte rial system .
T he al i men tary canal .
P late I I,F i g . 8 . T he venou s system .
9 . Venous and arte rial systems .10. O ute r side of the sperm d uct.1 1 . In ner s ide of proximal port ion of the spe rm d uct.12. D iagram of the sperrrratophoric gland .
13 . O uter s ide of ov i duct.14. I nner s ide of ov i d uct .15 . T he nervo us system , ri ght aspect .
P late I I I , F ig. 16 . T he nervo us system ,anter ior aspect.
17. A sag i ttal secti on of the head .
18 . A m ed ian secti on of a ma le squ i d,left si de.
19. righ t s ide .
20 . L e ns of a very you ng sq u i d .
21 . C i l iary bod y of squ i d 20 mm . l ong .
22 . H ori zon tal secti on th rough the eye and one si de of the head .
P L A T E I .
F ig . 1 . Cephal i c carti lage (sk u l l ) and preorb i tal cart i lages .C .P . cepha l i c process.F .1 large (oesoplrageal ) foranren .
F .2 foramen for the ve i n wh ich con nects the orbi tal si n us and anter ior verra cava.
L . L ig. lateral l igament .L .P . lateral process .P .C . preorb i ta l carti lage .
P .P . peda l p rocess .
F i g. 2. L owe r aspect of the gastro- caecal open i ng .
C. caecum .
E . oesophagus.I . i n testi ne .
P . pancreas with the hepatico- pancreat i c d uct .S t. stomach .
Fig. 3 D rawing (somewhat d iagrammatic) of a m ed ian secti o n of a sucke r , from one of the central rowsof the tentac le . X 15 .
F ig . 4 . S ect i on O f an u nsymmetri cal s ucker .A . artery .
M . margi nal membrane of arm .
N . nerve .
P d . ped i c le of sucke r.R t. ch i t i n r i ng.
S . su perfic ia l b rach ial ve i n .
V. ve i n of s ucker .
01Fig .
G
a
s
man-“v
b
Fig . 6 .
Fig . 7 .
BG .
BG .1
B.L .
CA .
G 0 .
I N .
Fig . 8 .
Fig. 9 .
G I .
G O .
XI I
hepat i c val ve .
i ntesti na l va l ve .
gastri c val ve .
P
99
50
“
0
and i n testi ne .
D i sta l end of a spermatophore .
d i sta l end . 7 . constri c ti on at base of fi lamen t.proxima l end. 8 . con tracti le fi bres of case .
spernr rope . 9.
“ spr ing”.
i n ne r wal l of case . 10. e n largeme n t d i sta l to co n stri ct i on .
o ut-er 11 . fi lam ent .dask- l i ke sac . 12. cav i ty arou nd fi lament .o u ter fl ask t u be . 13 . cavi ties of case .
cav i ty of ou ter fl ask case .
Arte r ia l system ,posteri o r aspect .
L eft s i de of the d igesti ve system .
an us .
su prab ucca l gangl i on .
i n frab u ccal gangl i o n .
b uccal tentac le or lobe .
caecum ; a porti on of the wal l has beenremoved so as to show the r idge be tweenthe l obe s of the caec um and the hepati cv a
gonad .
h eart .i n testi ne .
P L A T E I I .
Venous system,poster i or aspect .
A rte rial and ve nou s systems , le ft si de .
gi l l . P .H . pe r i phe ra l heart .gonad . BL .G D . b l ood glan d .
heart . Br .H . branc lrial heart .
edges of the part i ti o n wh i ch separates the u ppe r and l owe r l obe s of the caec um,the
l owe r l o be hav ing been remove d wi th the adjace n t portio ns o f the l owe r wa l l of the stomach
u ppe r m u scle of r i ng.
l owe r m usc le of r i ng.
sph i n cte r m uscle .
co lu rrrnar epi the l i u m formi ng p i t glands .
co l umnar epi the l i um of the base of sucker.basal m usc le .
c i rc u lar basal m usc le .
l o ngi t u d i nal m uscle fibres of arm .
transverse m uscle fibres of arm .
i n k sac .
L . l i verOE . oesophagus.P A . pancreas.P H . phary nx .
S A med ian sal i vary gland .
S A .1 late ral sal i vary gland .
S I . musc u l us rotator mand ibu l i .S P .G . splanch n i c gangl i on .
S T . stomach .
I . musc u l us levator mandibu l i .
X I I I
I . Ante r i or aorta.
11 .
21 .
31 .
41.
51.
61.
81 .
91 .
101 .
111 .
121 .
131 .
141 .
151 .
161.
171 .
I I .
12.
92 .
ramus to l ower caecal l obe .
r . to adjacen t wa l l s of stomach and caecum .
r. to caecal fo l ds .r . to pancreas.to dorsa l p lexus .to b lood gland .
to si phona l retractors .to l i ver .to n u cha l retractors and man tle .
to cephal i c retractor and part of l i ver .to med ian sal i vary gland .
to eye.
to si phon .
to pharynx .
peda l ramus .
rami to the five arms .
Posteri or aorta.
r . to i nk sac .
r . to rectum .
r. to b ranch ia l heart .r. to sperm d uct or ov id uct .lateral pal l ial arterymed ian pal l ia l artery .
r. to mantle .
r . to fi n .
arte rial p lexus.
I I I . G en i tal aorta . V I I I . Branch ia l artery .
Fig . 10 . O ute r (r igh t) surface of the sperm d uct .
Fig . 11 . I nn e r s u rface of the prox imal port i on of the sperm d uct .
12. D iagram of the spermatophor'
ic gland.
A pp .
C i . C .
D .
D i .
D . P r .
G . S .
P .
P r .
S . C.
Sp . S .
V. 1 .
append ix,the second l oop of the sperm d uct .
c i l iated canal o f Ch u n .
vas defe rens .smal l tubu lar d i verti c u l um from the append ix .
d uct of the prostata.
gen i ta l sac .
pen i s .prostata .
sperm canal o f the first two portion s of the semi nal vesicl e .
spermatophoric sac .
fi rst po rt io n of the semi nal vesi c le .
V . accessory l obe of the first portion of the semi nal vesi cle .
V. 2 .
V . 3 .
seco nd portion of semi nal vesic le .
th i rd
IV . Branch ial ve i n .
V . N ephrid ial s i n u s .
15. ve i n from rectum .
25. v . from l i ver .35. v . from gonad .
45 . v . from heart .55. v . from caecal fo lds.65 . ventro- lateral mant le ve i n .
75. v . from gi l l m uscle and ne rve .
85. v . from bl ood gland .
95. v . from spe rm or ov i d uct .105. v . from n idamental gland .
1 15. v . from venous p lexu s.
VI . Anter ior vena cava.
16 v . from i nk sac .
ga. upper branch .
I b. lower36 . sa l i vary si n us .46 . v . from eye .
56 . O ptic s i n us.66. cephal i c s i n us .76. brach ial s i n u s .86 . i n ne r b uccal si n u s .96 . o uter106. ce ntra l brach ial ve i n .
116. su perfic ial b rach ial v e i n .
25 . v . from l i ver
V I I . P osteri or vena cava.
17 . man tle ve i n .
27. v . from fi n .
V. D .
V. E .
X IV
vas de fere ns .
vas efie rens .
Tire posi t ion of the spermatophore i n the several porti o ns of the gland i s i nd i cated by a heavy l i ne ,with a dot to mark the d i sta l end of the spermatophore .
Fig . 13 .
Fig. 14.
O ute r
In ne ra .
b.
c .E xt. 00 .
I nt.
M o.
Ov. G t.
surface o f the ovi d uct .
su rface of the ov id uct .o uter segmen t of o v i d ucal g land .i n ne r n v n 11
l i ne of attachme nt of the body wal l to the exte rnal o vi d uct .exte rna l ov i d uc t.i n terna li n te rna l open i ng of the ov i d uct .ov id ucal gland .
Fig . 15 . N ervo us system j r igh t aspec t .
P L A T E I I I .
Fig . 16. N ervo us system ; anterior '
aspect.
E R .G . branch ial gangl i on . r . to rect um .
N .O . n uchal cart i lage . r . to i nk sac .
S L .G . ste l late gangl i o n . in terb ra nch ia l comm issure .
S P .G . sp lanch n i c gangl i on . r . to branch ia l heart .1. b ucco - sp lanch n i c con necti ve . branch ial nerve cord .
2. r. to late ral si p honal va l ve. interste l late commissu re .
3 , r . to s i phona l re tractor . nerve from the ste l late gangl i on to the mant le4. ple ural ne rve and viscero - ste l late con necti ve . ste l late componen t of fi n ner ve .
5 . v isce ral ne rve and vi scero - branch ia l con necti ve . v i sce ral6 . r . to cephal i c retrac tor . r . to mantle .
7 . r . t o si p honal retractor . v i sce ro - ste l late con necti ve .
Fig. 17 . M ed ian secti o n of the head . N er ves are represe nted i n ye l l ow,arteries i n pi n k
,ve i n s
,cart i lage
and c h i ti n i n b l ue,m uscle and con necti ve t i ss ue i n ou rnt umber .
1 . cerebra l gangl i on . 17 . i n ne r b ucca l si n us .2. v iscera l 18. oesophagus.3. peda l 19. pa late .
4 . propedal 20. tongue .
5. s uprab ucca l gangl i on . 2 1. rad u la.
6 . i n frab ucca l 22. Open i ng of the left sal i vary gland .
7 . ce rebral p rocess of sk u l l . 23 . d uct of med ian sal i vary gland .
8. statocyst . 24 . uppe r mand i b le .
9 . pedal process of sk u l l . 25 . l owe r10. n ucha l carti lage . 26 . peri stom ial membrane .
11 . p leu ral nerve and v iscero - ste l la‘
te con nect i ve . 27 . l obe of b ucca l membrane.
12. v i sceral nerve and v iscero- branch ial co n nect i ve . 28 . ope n i ng from ou te r to i n ner b uccal s i n us.13. propedo
- b uccal con nect i ve . brachia l s i n us .14. cereb ro- b ucca l 30. upper m uscl e of rad u lar tube.
15 . cerebro—prO pedal 31 . l owero uter b uccal s i n u s . 32 . rrrusc le con nect i ng the i n ne r laure l lae of up
per j aw .
F ig . 18 and 19. M ed ian secti on of squ id .
XV
F ig . 18 left s ide .
Fig . 19 righ t s ide .
A I,A 2 , A
3,e tc . arms one ,
two three ,etc . J.
1 l owerA . lrectocotylus . M .C . mantl e chambe r .A C . accessory gland . N C . n uchal carti lage .
B.L . buccal l obe . N .OL . neplrrid ial coe l om .
C.C. cephal i c carti lage , or sk u l l . OD . odon tophor'e.
CA . cae cum . O E . oesophagu s .CL . coe l om . P A . pancreas.F .C . fi n carti lage . P .L . palat i ne l obe .
G O . gonad . P .M . peristorrrial memb rane .
H . heart . P N . pen .
I .S . i n testi ne . S .G L . s iph onal gland .
L . l i ver . S P .S . spermatophoric sac .
L .
I hepat i c d uct . V.D E . vas de fe rens .J. uppe r j aw .
Fig. 20 . S ect i on th rough the ci l iary body and lens of an em b ryo of 2 mm .
1 . outer layer of ectoderm (ou te r part of ci l iary body ) .2 . i n ne r (i n ne r3 . le ns .4 . processes from the ci l iary body to the lens.
Fig. 21 . S ecti o n th rough the ci l iary bod y of a squ i d of 20 mm .
support i ng l igamen t of lens and ci l iary body . 6 . ep i the l i um of i n ner chambe r.fo ld i n the outer part of the ci l iary body. 7 . fascia supporti ng a fol d of the ci l iary body .
ep i the l i u m of the ou ter chamber of the eye . 8 . fi bres i n fo l d of the c i l iary body .
lame l la of lens. 9 . epi the l i um of c i l iary bodyprocesses of ce l l s of ci l iary body .P
‘
P
Q’
N
E“
Fig. 22. H ori zontal secti o n thr u the eye .
A . muscu lar base of the arms .A .O . outer chambe r of eye .
B.S . outer and i n ne r b uccal s i n uses.C. corneaCa . accessory , or su pport i ng cart i lage of the eye .
C i .B. c i l iary body.C i .M . ci l iary mu sc le (mu scu lu s retractor len tis) .
E . oesophagus.F . fascia separat i ng the l i ve r from th e oeso
phageal srnu s.
I . i r i s .L . lens .
L ig.
M .
0 .G .
P .
P . C.
R .
S ol .
S ic.
T .S .
IVLE .
W .B.1
lateral l i gament of sk u l l .orbi tal fasc ia.
Optic gangl i on .
orbi tal si n us .“aqu i fero us porei n ner chamber of eye .
ret i na.
sc lera.
sk u l l .tentacu lor sac .
l owe r wh i te body.
upper n
THE ANATOMYOF THE COMMON SQUID,
LOLIGO P E A IJI,L E S UE UR .
The Common Squ id,Lol igo peal i i , is a l ittoral species confined to the
Eastern coast of the U nited States . Its exact geographical range has not been
d etermined,but it is found from Maine to South Carol ina and is so abundant
between Cape Cod and Cape Hatteras that it is j ustly cal l ed the “ Common
Squ id”. North of Cape C od the “ Short - finned Squ id Ommastrephes
,is more
common,and south Of Cape Hatteras members Of other species O f Lol igo are
more numerous .
The batlrymetric distribution of the species is also undetermined,but the
fact that its eggs,which are attached to obj ects on the bottom
,have been
dredged from water 25 to 50 fathoms deep indicates that squid go at l east
to that depth .
Our knowledge Of the habits of the squid is very incomplete . Littl e i s
known of the whereabouts Of the squid during the Winter and early Spring
but about the last O f April or the first of M ay large schools , Often containing
thousands Of squid,appear along the shore and are taken by hundreds of barrels
i n the weirs . This first “ run is bel ieved by the New Jersey fisherman to
precede the “ run”of the S ea Bass . After it
,the large school s are not common
,
but throughout the Spring and Summer large schools occasional ly enter the
traps . A few squid are usual ly caught each week until the weirs are taken in
to save them from the November storms . The egg clusters and the young
squid appear two or three weeks after the run Of the large schools and are
common until co ld weather,when both Old and young squid become scarce .
O u r knowledge is not sufficient to j ustify precise and positive assertions
about the l ife history O f the squ id,but the observations stated above tend to
justify the bel ief that the fol lowing sketch is fai rly correct .
The squid probably spend the winter scattered at the bottom 1
) i n moderately
deep water,and as Spring approaches they form large schools that come into
the shal low water . After a short time the large schools are broken up into
1 That th i s statement i s not tr ue i n refe rence to the S hort - finned S qu id , Omnrastrepes , i s shownby the fact that i n N ovem ber and D ecember 1902 large quan tit ies ran ashore on Cape Cod and i n October60 barre l s we re taken i n a si ng le hau l o f one trap . Sma l l q uant i ties of the common squ i d are broughti nto the mark ets at N ew York d uri ng the wi n te r.
smal l schools , containing from a dozen to a hundred or more squid . T he
i nd i viduals of these smal l schools breed near the shore . The first eggs are
depos i ted very soon after the arrival of the squ id and the young begin to hatch
w i thin two or three weeks The young squid,immediately after hatching form
large schools which hold together for a month or more unti l the squid are about
an i nch l ong . In October or November the cold drives the squid into deeper
water . That the migrations O f the squid are bathic rather than zonal is indicated
by the squ id'
s manner of swimming,which does not admit of steady and long
continued rapid motion,and by the fact that they seem to “ run
”before the
S ea Bass whose migration is general ly conceded to be bathic . Both these facts,
however,have l ittl e weight
, b ut unti l we find something to suggest a zOnal
nrigratiorr ,they may be accepted .
The rate of growth and l ongevity Of the squ id have not been accurately
determined because squid do not l ive l ong in aquaria and because the breeding
season is so l ong that the youngest squid of one year are not readily dist inguish
able from the Oldest of the succeeding year . Very l ittl e can be added to the
results Of Professor VE R RJL L’s study Of the rate O f growth Of squid
,which are
substantial ly as fol lows : At Woods Hole,Mass
,i n the middle of Ju ly '
the
largest young Of the year,w hich have developed from eggs deposited in M ay ,
are 20 to 80 mm . l ong . N ear the end Of September the largest immature
squid,which cannot be more than five months O ld
,are between 60 and 90
ni m . l ong . Soon the squ id disappear,and in the fol lowing M ay the squid vary
i n size from 70 to 400 mm . and practical ly all are sexual l y mature . The
smal l est of these represent the younger broods of the preceding year and are
eight or ten months Old . The largest squid that appear in the spring are 8 50
to 400 mm . l ong and,since they can scarcely have grown to that size during
the winter,i t i s probable that they are the adults of the preceding year . Some
writers have maintained that the squ id breed in thei r second year and then die,
but the inferred rate of growth of squ id su ggests that some squ id l ive through
at l east three summers . However,the smal l number O f very large squ id l eads
us to suppose that the greater proportion of the adults of each summer are
unabl e to surv ive until their thi rd or fourth season .
The food of the squ id,so far as known
,consists Of smal l fish
,crustacea
and squid,but since most of ou r knowledge Of their food is derived from the
identification Of undigested food in the stomach,i t is exceedingly probable that
other animals,which do not have easi ly recognizable hard parts
,are also eaten
by the squid . The very young squ id feed largely upon Oopepods and other
smal l or larval crustacea . Squid of every age are greedy and persistent cannibals .
though incomple te account of the embryology O f the squ id, The Deve lopment
Of the Squ id”
. was publ ished in the same year by W . K . BROOKS,and eight
y ears later S . WATASE issued his beautiful work upon the segmentation of the
Ovum and the homology O f the germ layers . The embryology and organogeny
of the common European spec ies,Lol igo vulgaris
,have been carefully studied
by KO L L IKE R,FA U S S E K
,BOBRE T ZKY
,K O RS C H E L T and others . Furthermore
comparative stud ies O f various organs Of the Cephal opoda (not includ ing this
species ) have been publ ished . The reproductive system of Cephalopoda has been
described by J . BROOK ; the coelom by G RO BBE N ; the gil ls by JO UBIN' the ink sac
by G rRO D ; and the skin (chromatophores) by G rR O D ,P HYS A L IX
,R A BL
,CHUN and
others . However,a large amount O f work yet remains to be don e upon the
organogeny,anatomy and
‘
physiology Of the squid . In this work,the vascular ,
al imentary and nervous systems have received especial attention,but an effort
has also been made to give a ful l accoun t of the gross anatomy of the squ id .
In the work dissection has been supplemented by the study of a number of
serial sections of embryos,of young squ id and of adult tissues . The squ id studied
were Obtained at Woods Hole,Mass . and at E lberon
,N . J . The work w as
don e at Princeton U n iversity,at the Marine B iological Laboratory
,Woods Hol e
,
at Brown U niversity,at the Harvard Medical School , and at the Woods Hole
Laboratory Of the U n ited States Fish Commission . I am especial ly indebted to
Professor U LR IC DAHLG REN and to Dr . H . C . BUMPUS for adv ice and assi stance in
this work .
This work,in a l ess compl ete form
,was presented to the faculty of Brown
U niversity in partial fulfi lment of the requi rements for the degree O f Doctor Of
Phil osophy .
M r . W . T . OL IVER,draughtsman
,of Lynn
,Mass . has redrawn or retouched
several Of the figures .
The class to which the Squid belongs,the Cephalopod Mol lusc
,is very highly
special ized . That this special i zation shows itself in a very striking manner in
the general form of the Squid and in the pos ition that it normal ly maintains,wil l
be readily seen after a glance at the d iagrams of an unspecial ized mol lusc and
Of the embryo Of the Squid .
The hypothetical unspecial ized mollusc (text figure 1 ) i s bi lateral ly svrnme
trical, its back is convex ,
and its anterior end,bearing the mouth
,the eyes
,
and a pai r of tentacl es,forms a distinct head . The ventral portion O f the body
is a thick,muscular plate
,the foot
,by means of which the animal creeps .
The upper part Of the arched body contains the viscera and is cal l ed the visceral
dome . From the side of the v isceral dome there arises a ci rcu lar fol d of skin,
the mantle , which hangs downward on all sides so that it encloses between
itself and the visceral mass and the foot, a ring - shaped cavity
,the pal l ial or
mantle cavity . This cavity is largest posteriorly where it contains the anus,
of gil ls , of nephridial Openings , and of sexual openings . These structures
F ig . 1 .
are cal l ed col lectively the pal l ial complex . The visceral dome is covered by a
saucer- shaped or con ical shel l which extends downward over the mantle and
mantle chamber . The intestine is a straight tube which is connected with a
large digestive gland . The
nervous system consists of
a cerebral gangl ion i n the
head,a pedal gangl ion in
the foot,j o ined to the
cerebral gangl ion by a pai r
of ganglionated nerve cords,
and a Visceral gangl ion in
the body al so united to
the cerebral gangl ion by a
pai r of nerve cords .
The general body - form
and arrangemen t of organs
of the unspecial ized mol lusc are for a short time partial ly real ized in embryon ic
Cephalopoda . The egg of the Cephalopoda contains a large amount of yolk
and undergoes a discoidal cleavage , hence the form of the embryo is greatly
modified from its primitive condition . The dorsal surface of the embryo is
S i .F
F ig . 2 .
indicated (text figure 2 ) very early by the appearance of a pit,the beginning of
the shel l gland ,around which the mantle ridge forms . The oral i nvagination and
the anlage of the cephal ic gangl ion mark the anterior end of the embryo . The
large head - folds,partly surrounding the optic pits
,form the greater portion of
the sides of the embryo . The statocyst, the anlagen of the siphon
,and of the
gills l i e on the posterior surface . The foot is represented by a band of tissue
which connects the embryo . w ith the yolk and from which five pai rs of el evations .
the an lagen of the five pairs of arms,proj ect . T he anus has not yet formed
but its future position is indicated
by the mesenteron which l ies
beneath the ectoderm of the back
of the embryo . The essential relations
to be noted are,that the foot is
ventral,the mouth anterior
,and
the shel l - gland dorsal . A more
advanced embryo is represented by
text figure 8 . The convex visceralM C dome of the younger embryo has
- O i become conical and at the same
time the ventral portion of the embryo
- s = has contracted constricting the yolk
sac from the embryo . The mantle
has grown downward so that it now
covers the gills and the newly
formed anus . T he gut is complete
and near its middle,makes an angle
from which tw o evaginations,the
und eveloped stomach and caecum,
proj ect upward . The heart is dorsal“ 1 3 Fig' 4 ' to the gut . The statocysts
,two
pai rs of siphonal fol ds , the pedal , and the visceral gangl ia are on the posterior
side of the embryo between the mantle and the arms . This change may be
summed up by saying that the dorso- ventral axis has elongated whil e the sagittal
and tra nsverse axes have become relatively short . This process continues in the
Decapoda beyond the stage represented in text figure 8 unti l the adult form
(text figure 4 ) is reached .
In the adult Decapod the dorsal and ventral surfaces are reduced to mere
points at the ends of a fusiform body . The reduction of the ventral surface has
been accompanied by a forward growth of the arms until final ly they surround
th e mouth and almost cover the head . A comparison of the structure and habits
of the various Cephalopods shows that the height of the visceral dome and power
of swimming are d irectly proportional . For example : Nautilus,a Tetrabranch
,
the most primitiv e Cephalopod has a low visceral dome . It l ives upon the
bottom and probably swims but l ittle . The Octopoda,the lowest members of
the higher group,the Dibranchiata
,have a higher v isceral dome and , al though
they frequent the bottom,are better swimmers than Nauti lus . The Decapods
,
the highest Cephalopods and the group to which the Squid belongs,have an
extremely elevated v isceral dome and are free swimmers . In fact,the abil ity
to swim is d i rectly dependent upon the elongation of the dorso - ventral axis ; for
the Cephal opoda swim by ej ecting water from the body cavity thru the siphon,
a tube formed by the posterior part of the foot , hence the longer the body the
less the resistance it encounters and the greater the capacity of the mantle cavity .
As the dorso - ventral axis becomes longer,i . e . as the v isceral dome becomes
more elevated it becomes less vertical until,i n the Decapods
,it is horizontal .
Squid swim with equal facil ity either forward or backward,but because of the
above mentioned change of the dorso - ventral axis from the vertical to the
horizontal position,the ventral
,not the anterior surface
,is forward
,the anterior
surface is uppermost,and the dorsal
,not the posterior surface
,is hindmost . The
fact that the axis which is usual ly vertical is horizontal in the Decapods has
natural ly led to great confusion in terminology . The maj ority of systematists,
the Engl ish,French and some American morphologists have used the morphological
terms anterior,posterior
,dorsal
,and ventral in a positional or physiological sense
whil e the German zoologists,and some others have used the same terms in a
strictly morphological sense . In th is description,the terms anterior
,posterior
dorsal,ventral are used in a morphological sense and the terms upper
,lower
,
fore,and hind are employed i n their ordinary meaning . Hence the anterior
surface is uppermost,the ventral surface or point is forward
,and the dorsal
point is backward . Further confusion of terms has arisen because of the partial
un ion of the head with the foot ; in this paper , the term foot denotes al l the
structures formed from the primit ive foot viz . the arms,tentacl es
,and siphon .
The mass formed by the fusion of the true or primitive head with a portion of
the foot,i . e . the arms
,is cal led the head .
The head of the squ id is lance- shaped and is attached by a very short neck
to a cigar - shaped bodv so that the squ id is nearly fusiform . The body consists
of a thick muscular mantle and a v isceral mass enclosed by the mantle . The
otherwise cvl indrical mantle tapers to a dorsal point . Ventral ly the mantle ends
i n a free edge,the col lar
,which surrounds the neck and thru which a conical
muscular tube,the siphon
,proj ects . The col lar articulates by three pai rs of
i nterlocking surfaces with the visceral mass and the siphon,mesial ly w ith the
upper surface of the visceral mass (with the nuchal cartilage) and lateral l y with
each side of the siphon . A pai r of triangular fins is attached to the dorsal point
of the mantle and to three - fifths of the anterior (upper) surface in such a manner
that they form a rhombo idal plate .
The lance - shaped head consists of the true or primitive head and the
anteri or part of the primitive foot . The back part of the head,representing the
true head,is short and is k idney - shaped in cross - section since the posterior
surface is hol l owed out for the accommodation of the siphon . A pai r of large
eyes forms almost the entire sides of the true head and an olfactory fold,j ust
behind the eye,proj ects backward under the col lar . The remai nder of the head
is formed by a circle of ten foot - lobes,comprising eight sessil e arms and two
tentacles,which are attached to the ventral surface of the tru e head and which
surround the mouth . W hil e the Squid is swimming the arms and tentacl es are
pressed together so that they form an acute,thick
,horizontal plate which is
used alternately as a rudder and as a cutwater .
The siphon,a conical muscular tube attached to the lower surface of the
visceral mass and to the head,proj ects downward and forward from the mantl e
chamber between the head and the mantl e . A j et of water ej ected thru the
siphon whose tip may be directed forwar d or backward propels the squ id
backward or forward .
THE SK IN .
G i R O D has studied careful l y the skin of Cephalopods,and this account is
l i ttl e more than a confirmation for this species of his description .
The epidermis is a simple epi thel ium which secretes a very thin striated
cuticl e . It contains smal l clusters of,or m ore rare ly isolated
,cel l s in various stages
of mucous secretion . The shape of i ts cel ls varies according to the stresses to
which it is subj ected . In the embryo and in a contracted state the cel ls are
cubical or columnar,while in the adult or when expanded they are sl ightly or
greatly flattened . The large nucleus l ies near the center of the cel l . A cl early
defined basement membrane is usual ly absent and i rregular protoplasmic processes
interlock with the dermal cel ls . The epidermis which l ines the siphon forms
tw o pairs of glands which were described by H . M uL L E R i n 18 5 3 as characteristic
Cephalopod organs . This description seems,as BROOK has pointed out
,to have
been overlooked by VERR ILL who descr ibed them more recently,by HOYLE
who named them col lecti vely the organ of VERR ILL”
,and by LAUR IE who
adopts H OYL E’s nam e and who does not find them in the adult . T he form of
these glands is described in connection with the siphon . The epithel ium of the
glands is very highly columnar and contains vast numbers of goblet cel ls which
are contiguous or separated by very.
slender resting or recently emptied cells .
A l l the nuclei have a very unusual position at the d ista l ends and the secretion
gathers i n the proximal ends of the cel ls,which seem inverted . The secretion
seems to consist of mucin and the glands seem to be active periodical ly,for at
times they are very conspicuous both in l iv ing and preserved animals,while
agai n they are inconspicuous .
“
The glands are present in both sexes and at
all ages .
HOYLE has described in the embryo of Sepia a trifid and i n that of Loligo
a single l ine of modified epitheli um . The tract in L ol igo is longitudinal and l i es
on the upper and dorsal surface of the mantle between the fins . It seems to
be a row instead of the usual cluster of mucous secreting ce l l s . This has been
cal l ed Hoyle’s organ . W e have fai l ed to find it
,probably because the embryos
examined were too old .
The epidermis also secretes the pen and the ch itin ~l ike rings of the suckers .
These wil l be described in connection with the skeleton and suckers .
10
The do rmis is formed of four i ll - defined layers ; an outer layer of fibrous
connective tissue,a sheet of chromatophores
,a deep fibrous layer and a layer
of irid iocvsts . T he superficial fibrous layer supports the epidermis and has
numerous nerve fibres in i ts deeper‘
portion .
The second layer is characterized by the remarkably special ized chromato
phores . Each chromatophore consists of a pigment cel l,i ts capsul e of elastic
tissue,and a circle of radiating muscle cell s . The chromatophores have been a
subj ect of l i ve ly interest and protracted controversy and i nnumerabl e papers upon
the ir anatomy,ontogeny and physiology have appeared . We have not indu lged
the natural desire to enter upon an extended investigation and discussion of such
beau tiful , attractive and much studied obj ects . We are,however
,i n essential
agreement with C H U N’s resul ts . The pigment cell and muscle cel l s of each
chromatophore ari se from a single mesodermal cel l . T he central cel l secretes a
granular pigment which in our species i s of a dark reddish brown color in the
larger and more numerous chromatophores and yel low in the others . The
pigment i s laid down in a fluid with in a rather sharply marked cavi ty
and the nucleus is gradual ly forced to the periphery and usual ly l ies beneath
the pigment mass . The ye l low pigment i s a l ipochrome,the brown pigment
has been found by Dr . ALSBERG of the Harvard Med ical School,to be melanin
and i s consequently essential l y l ike the ink . The nucleus i s large,takes deep
colors with chromatic stai ns,and has a large nucleolus .
The capsule i s thin,elastic
,and i s formed by a number of cel l s
,a part or
al l of which probably ari se from the original chromatophoric cel l . The flattened,
l ightly stained nuclei are easily distingu ishable from those of the pigment and
muscle cel l s . The elastici ty of thi s sheath keeps the pigment mass spherical
except during the contraction of the muscl e cell s .
The nuclei of the cell s which are to become muscle cel l s group themselves
in an i rregular circle around the pigment cel l . Each cel l sends out a long
tapering process which extends into the loose connective tissue of the dermis
and i s attached either by branches which are attached to the connective tissue,
or fixed by anastomosis with other muscle fibres . The broad central end of the
muscle cell,
or perhaps we should say of a muscular port ion of the chromato
phoric syncytium ,since the boundaries of pigment
,sheath and muscle cel l s are
at l east indistinct i f not absent,
contai ns the el l iptical or oval nucleus
which i s surrounded by a smal l amount of granular protoplasm . The remainder
of the protoplasm is fibri llar . The contraction of the muscle cel l,producing
as i t does a large expansion of the circumference of the p igment cel l,necessar i ly
broadens its own base,and the nucleus takes a position perpendicular to the
12
l n some cel ls the rods form bundl es or sheets wh ich are i ncl ined to one another
i f various angles ; i n other cel ls the rods are all paral le l . The ir id iocysts overlap
one another so as to form from one to many layers . The closely laid rods
reflect and interfere wi th l ight waves , producing a sheen and i ri descence which
is indescribably beautiful . L ike the chromatophores,the iridiocysts are absent
from the integument which is not exposed to l ight,and from the l ower surface
of the fins . The layer of irid iocysts is thickest above the ventral end of the
mantle and hides the dark colored organs in the viscera . The chromatophores
upon the lower side of the head,which is largely protected from light by the
siphon,
are scattered,and the iridiocysts are replaced by a layer of short
broad rods,or platel ets
,placed at right angles to the surface .
THE SKELETON .
A . Exoskeleton . Shel l or Pen .
The shel l of the Squid is represented by the pen,a feather - shaped plate of
chitin wh ich is buried under the skin and muscle of the anterior surface and
which extends from the dorsal to the ventral point of the mantle . The pen is
secreted by the shel l - gland which is formed by an i nvagination of the ectoderm
of the dorsal surface of the very early embryo . The edges of this pit soon unite
w ith one another so that the she l l -gland becomes a closed sac and the shel l or
pen , formerly and morphological ly external,becomes internal . T he inner or
lower wal l of this sac secretes the pen and is formed by a secretory epithel ium
which at first is composed entirely of columnar cel ls,but which
,as the pen
enlarges,becomes cubical or even pavemental except around the edges and
beneath the thick ventral part of the shaft where growth is most active and
where thruout l ife high columnar epithel ium is present . The chitin of the pen
is transparent and almost colorl ess and i s marked by del icate striae,the l ines
of growth,paral lel to the edge . The substance of the pen yields all the usual
chemical reactions of chitin .
The median axis or shaft of the pen is a trough - shaped plate which is
thicker vent-ral ly and which extends the whole length of the pen . T he concave
surface of the shaft is underneath and interlocks with a ridge of the nuchal
carti lage which l ies in the visceral mass j ust behind the neck . The vane or
body of the pen is attached to the sides of the shaft,extending from its dorsal
end three - fourths of its l ength,forming a thin
,fusi form convex sheet which
covers the upper surface of the v isceral mass . At the middle of the vane and
dorsal to this point , the sides of the pen extend nearly or qu ite hal f way around
the v isceral mass,but ventral ly the vane narrows until at the middle of the
body,it covers only the anterior surface of the visceral mass . The inner surface
of the pen is separated from the v iscera by the epithel ium which secretes the
pen,by a strong sheet of connective tissue and by the coelomic epithe l ium .
The upper surface of the ventral end of the shaft is subcutaneous and the muscle
fibres of the mantle are attached to the sides of the shaft . Near the ventral
end of the vane,muscle fibres begin to pass over the shaft and from this point
backward,more and more fibres pass over the pen and fewer are attached to
14
i t un ti l . bey ond the midd l e of the vane,practical l y al l the muscle fibres pass
above the pen and the dorsal end of the pen is deeply buri ed i n the mantle .
The chief muscles of the visceral mass are attached to the inner or lower surface
of the pen .
B . The Endoskeleton .
T he endoske leton consists of a number of disconnected pi eces of carti lage
which protect the brain,form articu lar surfaces . and support muscles . Omitting
the smal l cart i lages which wil l be described in connection with the eye and the
Odontophore,the skel eton consists of el even pieces of carti lage
,v iz . four pai red
carti lages,the fin
,the pal l ial . the siphonal , and the preorb ital carti lages ; and
three unpaired carti lages,the skul l
,the nuchal
,and the postcephal ic carti lages .
T H E SKULL O R CEPHALIC CA RTILAG E .
The skul l (Plate I Fig . l ) is a very i rregular cartilaginous plate,perforated
by a large foramen thru which the oesophagus , the nerves of the viscera and
the arteries of the head pass . The ventral surface of the plate is hollowed out
for the reception of the optic gangl ia and the oesophageal nerve - ring . The lower
portion of the plate contai ns the two large statocystic cavities and the two
Special depressions for the pedal gangl ion in front of,and the visceral gangl ion
above,the statocysts . The carti lage is prolonged into two strong median
,
ventral processes,on e . the cerebral , above the cerebra l gangl ion ,
the other,th e
pedal,below the gangl ion of the same name . These two processes
,one above
and one below the nerve - ring,are connected by a pai r of hour - glass shaped
l igaments,the lateral l igaments
,which separate the front end of the oesophageal
nerve - ring from the optic gangl ia . Each l igament is attached above along the
greater part of one side of the cerebral process and below to one side of the
pedal process . The cerebral and pedal processses ,the lateral l igaments
,and the
lateral portion of the skull form,at each side of the skul l
,a large concavity
which faces outward and forward and which lodges the Optic gangl ion . The
dorsal surface of the skull is a vertical arched plate . Its edge is covered by
the insertion of the retractor muscles of the head and i ts central portion by the
l iver . The ventral surface is very i rregular and is largely covered by gangl ia
but the muscl es of the foot are attached to the cerebral and pedal processes , to
the lateral l igaments,and to the upper and l ower edges of the carti lage . The
tw o statocysts form a pai r of low rounded proj ections from the dorsal surface of
the skul l . The saucer or cup shaped concavities for the v isceral gangl ion above,
and for the pedal gangl ion in front of the statocystic capsu le ,
have been
15
mentioned . T wo or three pai rs of foramina for the transmission of the
statocystic nerves pierce the ventral wal l of the capsule . A foramen at the edge
of the depression for the pedal gangl ion tra nsmits the nerve of the crista .
Another foramen,for the macular nerve . is si tuated a short distance inward
from the foranren for the cristic nerve .
Just in front of the statocysts,tw o pairs of foramina pierce the carti lage
at the base of the pedal process : one pai r al lows the siphonal nerves to pass
from the pedal gangl ion to the siphon ; and the other . which is in front of the
preced ing and is j ust exterior to the lateral l igaments,transmits a pai r of veins
from the orbital s inuses to the anterior vena cava . Several smal l foramina
w hich are represented in the drawings but which do not merit description
transmit smal l b l ood - vessels and nerves .
The two preorbital carti lages (Plate I Fig . l ) are attached side by side to
the pedal process of the sku ll and reach outward and forward between the eyes
and the pharynx . Each cartilage is a
flattened,stocking - shaped bar w hose
tip (toe) projects downward . This bar
l i es agai nst the inner surface of the
eye and supports certain muscles of
the eye .
The nuchal carti lage (text figure 5 )l i es in the muscles of the l iver case
between the l iver and the v entral end of the pen with w hich it articulates . It
is a thick ,quadrangular , trough - shaped plate . Two of its angles are directed
,
one forward ,and one backward
,and the lateral angles are bent downward
around the l iver . On the upper side of the cartilage there is a l inear grooved
surface which articulates w ith the pen . This articular surface has three grooves,
Of which the tw o lateral,articulate with the edges of the pen . T he upper
edges of the lateral siphonal val ves are attached to the carti lage just below the
arti cu lar surface ; the cephal ic retractor is attached to the ventral edge of the
carti lage : and the nuchal retractor is inserted on the dorsal edge and on the
greater portion of the l ower surface of the cartilage .
The postcephal ic. or“ diaphragmal carti lage is a thin oval plate which l ies
j ust behind the head in the lower w al l of the l iver - case between the l iver and
the anter ior vena cava and stiffens the l iver- case .
Each fin carti lage l ies at the base or i nner side of the fin . These will be
further described in connection with the fins (text figure
The siphonal carti lages are a pai r of grooved linear plates attached to the
F ig. 5 .
I O
sides of the siphon . The groove of each carti lage i nterlocks with a corresponding
ridge on one of the pal l ial carti lages .
The pall ial carti lages are ridged l inear plates inserted on the inner surfaces
of the tw o lateral points of the mantle . The siphonal with the pal l ial carti lages,
and the nuchal cartilage with the ventral end of the pen,form three sl id ing
joints which al low the siphon and the neck a large amount of motion and
which , nevertheless , hold them in place . Considerabl e force is required,both
in the l iving and the dead squ id,to disl ocate these j oints .
T H E MUSCULAR SYSTEM .
The muscular organs of the squid include the mantl e,the fins
,the siphon
,
the arms,and the cephal ic and nuchal retractors .
T H E MANTLE .
’ The mantl e (text figure 6) is a bulging
muscular cone , open ventral ly and tapering beyond the middle
to a dorsal point . The free ventral edge of the mantle
surrounds the neck and is cal l ed the col lar . The tips of the
pen and of the two pal l ial cartilages form three equ idistantpoints on the collar
,divid ing it i nto three arcs and
,as
,the
tip of the pen extends farther forward,the two arcs adjacent
to it do not extend as far back as the are between the two
pal l ial cartilages . The former arcs are Opposed to the lateral
s iphonal valves and the latter are embraces th e siphon .
The mantle is formed of long,coarse
,fusiform fibres .
MARCEAU has Shown that each fibre consists of a peripheral
sheath formed of somewhat flattened,spiral l y wound fibri llae
separated by sarcoplasm ,and a core of granular sarcoplasm
which contains the long rod - shaped nucleus . The fibres are
all paral l el and form circular muscle bands wh ich extend from
one side of the pen around the mantle cavity to the opposite
S ide or pass outside the pen and so completely encircle the
body . The muscl e fibres are bound into rectangular bundles
by means of thin muscu lar septa which bind together the two
fasciae that lie on the inner and outer surfaces of the mantle .
The mantle is covered and l ined by the integument which is
reflected from its inner surface over the visceral mass and
Fig “ 6‘ helps to attach it to the mantl e . In addit ion to this attach
ment and to the articulation of the col lar with the bodv , the mantle is attached
to the v isceral mass by a pai r of liganren ts which arise near the middle of the
Visceral rrrass and extend over the edge of the pen to the mantle . However,
the chief connection is furn ished by the pen ,to whose upper surface the mantle
is attached . whereas the large siphonal . nuchal and cephal ic retractors are attached
to its l ower surface .
The pal l ial cavity is very large and extends back nearly to the dorsal po int
of the nrantle . By the expansion and contraction of the mantl e a large quantity
of water is drawn into and expel led from the pal l ial chamber .
The two triangular fins are thin muscle - sheets and together,they form a
fl at rhorrrbo idal plate which is attached to the upper
surface of the mantle and extends from its dorsal
point over of i ts l ength . The longest side , the
base of each fin is attached to the mantle and the
tw o free edges are of nearly equal l ength . T he
dorsal angl es of the two fins form together an acute
angle which ends in a rounded tip . The lateral
angle of each fin is obtuse and very much rounded .
The ventral ends of the fins are some distance apart
and each forms a smal l auricular lobe . T he dorsal
points of the cartilages of the fins are firmly u nited
by strong masses of conn ective tissue but at the
middle the fins are not closely connected and overlap
one anoth er considerably . They are united by a
thin subcutaneous sheet of muscle,which extends
across their upper surfaces,
as wel l as by the
muscles which b ind them to the mantle . The long
attached base of the fin is underlaid and supported
by a strip of carti lage the fin cartilage which
is thin and broad except at i ts dorsal end where it Fig' 7
beconres a strong bar that curves dow nward and inward over the dorsal gpointof the mantle . The fin has very thin free edges
,and increases in th ickness
gradual ly toward the base where it i s attached to the carti lage at an jangle jofabout 30° (text figure The fins are attached to the mantle by the flfollowi ng three muscles . A strong muscular band arises from the lower surface
of the fin carti lage near its dorsal end and passes backward around the tip
of the mantl e to the opposite cartilage . A broad thin sheet of muscle; arises
from the upper su rface of the mantle in front of the fins and is inserted upon
the upper surface of the bases Of the fins . A second broad thin muscle arises
18
from the l ow er surface of the fin and,passing downward
,is inserted partly on
the s ide of the rrrantle and partly upon the Opposite fin .
T he fin (text figure 8 ) is formed by three sets of muscle fibres , l ongitudinal
t ran sverse and vertical,enclosed between three fasciae . Two fasciae are
subcutaneous ,forming the surfaces of the fin
,and the th ird l ies at the middle
of the fin . T he longitud inal muscle fibres form two thin sheets which l ie u pon
the u pper and l ower surfaces of the middle fascia . They extend from one to
the other free edge of the fin . The transverse fibres arise from the obl iquely
incl ined upper surface of the carti lage and,passing outward beneath the
superficial fasciae,are inserted in them and among the muscl es . These fibres
are separated into l ong,strong and lateral l y compressed
bundl es by the short,vertical muscle fibres which
,extending
from the superficial fasciae to the m i ddle fascia,form wal l
l ike septa that extend from the base to th e free edges of the
fin . The bundles of transverse fibres become more slender as
they approach the free edge of the fin . This is due partly
to the loss of fibres by insertion and partly to the branchingFig 8 of the bundles . This reduction of the muscle bundles as
they approach'
the free edge of the fin is partl y counterbalanced by the union of
bundl es w ith one another . The septa of vertical fibres become th inner,l ess
high,and more numerous near the free edge . Each septunr is from to
as th i ck as the bundles which it separates . As i ts fibres approach the middle
fascia they div erge to pass between the longitudinal muscl e - fibres,and hence the
septum seems broader near the fascia. These septa appear through the trans
parent skin of the lower side of the fin as dark l ines . The longitudinal , trans
verse,and vertical fibres together form a strong flex ib l e fin which is able to
make strong upward or downward strokes that instantly change the direction
of the squ id’s motion and also is capable of a sl ow undulat ing movement that
propels the squid slowly forward or backward .
230
and l ifth arms on the other . This sac communicates with its mate and contai n s
the peduncl e of the fourth arm which is attached with the Opposite arm to the
lower side of the head . The peduncle of the tentacl e is oval in section and i s
ve ry ex tensibl e so that the enti re l ength of the tentacle varies from once and
a hal f to thrice the length of the sessil e arms . The club is ovate and acute
and has fou r rows of suckers . The margins of the club bear membranes
somewhat wider than those of the sessi l e arms and the membranes are not
supported by muscular buttresses but by the pedicl es of the external rows - of
suckers . The external surface of the club bears a strong,keel - l ike membrane
similar to the external membrane of the thi rd arm . The d i stal portion of this
membrane is folded upward against the club and lacks chromatophores upon its
upper surface .
While the squ id is swimming the arms are pressed together so that they
form a flattened lance - shaped plate that is used,as a fin
,for steering . The
sessi le arms form a flattened tube which encloses the peduncles of the tentacl es
and from which the two clubs proj ect as the point of the fin .
~ The edges of
the fin are formed by the broad external mem branes of the third arms and of
the cl ubs . The squid always darts at i ts prey with the arms foremost and
j ust as it comes with in reach,i t spreads out the sessi l e arms l ike the rays of a
chrysanthemum and , by extending the peduncles of the tentacl es , thrusts ou t
the clubs,seizes the prey
,and then draws it back to the mouth where i t is
grasped and held by the sessi le arms .
Each arm is composed primari ly of a cyl indrical col um n of muscle which
contains at i ts center a large nerve cord and which supports the suckers and
the marginal membranes of the arm . This central column is formed by a large
number of longitudinal muscle fibres which l i e j ust i nside the superficial fascia
surrounding the column and by numerous short transverse fibres which extend
from side to si de and separate the l ongitudinal fibres into bundles . The transverse
fibres interweave around the large central canal for the nerve and b loodvessels .
One or more broad and thin sheets of longitudinal muscle fibres are attached to
the external surface of this column .
The muscular ridges which support the marginal ri dges or membranes of
the arms are formed by interlaced muscle fibres and are attached to the outer
surface of the above described column by means of fibres which mingle with
the transverse fibres of the arm . The pedicles of the arms are attached in the
same w ay .
The suckers are shal low suction or adhesive cups,stiffened by rings of
chitin - l ike material and attached to the arm by conical muscular stalks or pedicles .
T he size and symmetry of the suckers depend upon the i r age and position . T he
arms grow continual ly and new suckers are added from time to time at the
irre re rapidly growing apex . Hence,except on the tentacles
,the largest suckers
l i e at the base of the arm and the smal lest at the apex . At the base of the
club of the te ntacl e,there are a few suckers that are smal ler than those nearer
the middle of the club . Few,i f any ,
of the suckers are symmetrical and the
maj ority are very unsymmetrical . Those of the central rows of the club are
the largest and most symmetrical w hi l e those of the lateral rows and of the
sessi le arms are very unsymmetrical . The side of the sucker farther from the
center of the arm i s enlarged and the opposite side is correspondingly reduced
so that the most unsymmetrical suckers become l i ttl e more than complex hooks .
This arrangement of the suckers suggests that the obl iquity of the strains to
which they are subj ected when in use causes the asymmetry of the suckers .
The ped icle of the sucker (Plate I , Fig . 5 ) proj ects inward from the inner
surface of the arm . I t is formed by a large number of longitud inal muscle
fibres bound together by a few transverse fibres . The maj ority of the long itudinal
fibres arise from the outer surface of the arm and bend around it beneath the
nrarginal membranes of the arm to the inner surface where they j oin other
fibres arising from the middle of the inner surface of the arm . The pedicle
thus formed contains the nerve and blood vessel s of the sucker an d terminates
in a strong fascia w hich l ines the base of the cup of the sucker , and from
which the muscle fibres of the sucker arise . This cup consists of a very th ick
muscular base with a deep cen tral depression a nd of a low rim supported by a
thick toothed ring of chitin - l ike material . The center of the base of the cup is
formed solely by the top of the pedicl e which is cal l ed the “ piston because it
acts as the pi ston of a pump whenever the arm i s w ithdrawn after the sucker
has been pressed against a surface . The muscle fibres which form the base of
the sucker ari se from the fascia that l ines the cup and that is attached to the‘
pedicl e . The fibres pass obl iquely downward and outward to the outer surface
of the cup and end in a fascia which supports the sides of the sucker . The
outer ends of the fibres are separated by a few smal l bund les of circular.
(sphincter) muscle fibres . The side of the cup is formed chiefly of three muscles .
The largest of these is a strong sphincter which forms its lower part . The
other two muscles arise from the external superficial fascia of the sucker and
one is inserted upon the lower hal f of the ring ; the other upon its upper hal f.
The ring is a b road band which is strengthened by a strong external ridge
that separates the two muscles j ust mentioned . T he free edge of the ring of
the symmetrical suckers has about thirty large teeth separated by as many
smal l teeth . S everal rows of con ical teeth,the accessory teeth
,which gradual ly
increase in height from within outward,are borne by the edge of the sucker
and re inforce the teeth of the ring . Each accessory tooth is secre ted by a
single large epithel ial cel l . The ring and accessory teeth are composed of a
chiti n - l ike substance which differs from chitin in being soluble in dilute alkal i es .
T he external surface of the sucker is covered by low cubical Or fl at epithel ium
and the sides of the cup are covered by a thicker epithel ium which forms short
tubular glands . The inner surface of the side of the cup i s covered by a
colum nar epi thelium which secretes the ring and whose height at each poin t
is proportional to the thickness of the corresponding portion of the ring . The
P ig. 9.
base of the cup is l ined by a columnar epithel ium,whose cel l s several
times as high as broad . T he position of the nuclei of these cel l s var ies greatly,
in some cel l s the nuclei are at the base,i n others at the middle
,and in yet
others at the free end of the cel l s .
The unsymmetrical suckers (Plate I , Fig . 4) have the basal muscle , the
sphincter,and the lower ring muscl e excessively developed on the large side
and correspondingly reduced or lacking on the smal l s ide . The smal ler side of
the ring (text figure 9 ) i s strongly ridged and i s toothless whil e the large side
lacks the ridge and has from five to seven large , strong ,chisel - shaped ,
and
i ncurved teeth . These suckers can serve on ly as hooks but the symmetrical
suckers m ay be pressed agai n st the surface o f obj ects u nti l the water i s driven
from the cup by the inpu shed base and‘piston while when the arm is
withdrawn,they hold by suction ,
often,until the pedicle break s .
A rgonauta. and other O ctopoda have one of the arrrrs transformed into a
sac .which
,after rece iving the spermatophores , is detached and placed in the
mantl e cav ity of the femal e . This modified arm is cal led the Hectocotylus . T he
Decapoda have one or more rarely tw o of the i r arms sl ightly modified or“hectocotvl ized
”. In Loligo (Plate I II , Fig . 18 ) the l eft fifth arm is hectocotyl ized .
Some ten or twelve suckers on each side of the tip of the arm have their ped icles
enlarged and their cups reduced ,the pedicles becoming large blunt cones bearing
minute cups or near the end of the arm both stalk and sucker are reduced .
The inner row of suckers is l ess modified than the outer . The portion of the
arm between the two rows of enlarged pedicles forms a rounded ridge as
high as the pedicle . The hectocotylus probabl y represents the vestige of a
funct ional structure of an ancestral form . It is barely
possibl e that the arm mav be used for the transference of
spermatophores .
The siphon or funn el (text figure 10) developes from
tw o pa irs of ridges which appear upon the posterior surface
of the embryo . The h inder pai r appears between the mantle
and the eye , and forms the siphonal val ves which w i l l be
described later . T he anterior pai r l i es below the gil ls and
anus and between them and the arms . The latter ridges
become elevated and incurved unti l their edges meet and
unite,thus forming a conical tube
,the siphon
,w hich
leads from the mantle cavity to the exterior . This muscular
tube is attached dors al ly by a pair of large muscl es,the
siphonal retractors . Each siphonal retractor is a strong
rounded muscle which,arising from the side of the ventral
end of the vane of the pen ,passes obl iquely downward F ig . 10.
and forward in a depression between the liver above and i n front , and the
stomach,caecum
,and nephridia below and behind
, and terminates in one side
of the siphon .
&
V i ewed from below,the two siphonal retractors appear as
paral l el bands which are separated at the back by the‘
anterior vena cava. and
w hich disappear between the nephridia and the gil l s .
The arrangement of the intrinsic muscles of the siphon is very similar so
that of the mantle fibres except that there are longitud inal fibres which are
apparently continuous with those of the retractor . The maj ority of these fibres
form two pai rs of bundles ; an upper pai r w hich l ies near the median l ine ,and
24
a l ow er pai r which passes obl iquely downward to the middle of the lower
surface . At the side of the siphon,but facing downward is the siphonal
cartilage a grooved plate to which many muscle fibres are attached and which
fits over the corresponding pal l ial carti lage . The siphon is attached to the head
and l i ver case by the two siphonal val ves and the “ bridl e . The latter i s fornred
b y two pai rs of muscles,the siphonal protracters ,
which ari se from the pedal
process of the skul l and pass outward and backward to their i nsertion upon the
upper surface of the mantle . Each siphonal valve i s a rectangular sheet of
muscle which is attached by its upper edge to the nuchal carti lage,by its front
edge to the l iver case and by its lower edge to the siphonal carti lage . The
free edge of th i s valve proj ects backward and prevents water which has entered
the mantle chamber between the val ve and the col lar from escaping again
th rough that opening . Another val ve is formed by a muscular plate which
proj ects outward from the inner surface of the upper hal f of the siphon as far
as the end of the siphon and which prevents water from entering the mantl e
chamber through the siphon . The funnel i s somewhat flattened to fi t the space
between the body and mantle . Its ventral hal f proj ects from the mantle cav ity
and may be directed forward or backward at. wil l . Because of the presence of
the val ve in the siphon the expanding mantle draws water in only over the
lateral s iphonal val ves and,because of the closure of the latter val ves
,expels
the water from the pal l ial chamber on ly through the Siphon . A j et of water
from the siphon directed either forward or backward serves to propel the squid
backward or forward .
The inner surface of the funnel has two pai rs of long,el l ipti cal glands
,the
siphonal glands,whose structure has been described in connection with the
epidermis . The upper glands l i e on the bases of the siphonal retractors and
unite with one another in front . The lower glands are widely separate and l i e
upon the lower wal l of the siphon . The surface of these glands is v isi bly
elevated above the siphonal wal l and is covered w i th sl ime . The function of the
glands is unknown .
MUS CLES i x THE V ISCERAL MASS .
The cep halic and nucha l r etractors. The cephal ic and nuchal retractors W ith
the nuchal and post - cephal ic cartilages which are imbedded in them form a
hollow cone or case which contai ns the l iver. Tire base of th is case is attached
to the skul l,and i ts apex is attached to the middle of the pen . T he cephal ic
retractor arises partly from the pen and partly from the nuchal carti lage and i s
25
i nserted on the dorsal surface of the skul l . Its lower portion which arises from
the pen ,forms a thin sheet of muscl e i n which the post - cephal ic cartilage is
imbedded . Its upper portion is a th ick short sheet of muscle which extends
from the ventro - external edges of the nuchal cartilage to the skull . T he whole
muscle is a cyl inder , short and thick above,and long and thin below .
The nuchal retractor is a thick,strong muscle which arises from the pen
in front of the origin of the cephal ic retractor and which is inserted upon the
dorso - lateral edges and the lower surface of the nuchal carti lage . The cephal ic
and nuchal retractors move the head and also fasten it to the pen .
THE HEAD .
T he head of the squ id consists of the prim itive or true head and a portion
of the foot . T he portion representing the true head is sl ightly longer than broad
and in transverse section is reniform . I t may be compared to the stem of a
lance whose blade is represented by the arms . The head is divided into three
portions viz . : l ) a wedge - shaped dorsal portion consisting of the skul l and the
gangl ia protected by it (oesophageal and Optic gangl ia) ; 2) a similar but more
acutely wedge - shaped ventral portion consisting of an oval pharynx or buccal
bu l b enclosed by the muscular sheath formed by the i nterwoven muscle fibres
at the base of the arms ' 8 ) an hourglass - shaped central portion formed by the
two hemispherical eyes whose convex inner surfaces almost meet at the center
of the head and so separate the skul l and gangl ia behind from the pharynx and
arms below . The maj ority of the muscle fibres which attach the arms and
pharyngeal sheath to the skul l arise from the cephal ic and pedal processes of the
Skull and pass to the arms through the triangu lar spaces above and below the
eyes . The pharyngeal sheath formed largely by these fibres is conical or tent
shaped and is attached to the lateral l igaments as well as to the ventral pro
cesses of the skul l . The oesophagus passes back from the pharynx through a
venous canal which al so holds a pai r of arteri es and the sal ivary duct,and which
is a dorsal continuation of the cavity between the sheath and the pharynx .
Each eye with its gangl ion is enclosed by an unsymmetrical,helmet- shaped
capsule formed of skin and mu scl e and attached to the margin of the optic cup .
Beginning at the cephal ic process,the l ine of attachment of the capsul e to the
sku ll can be traced outward along the upper edge of the sku l l,then downward
along its outer edge,inward along its lower edge as far as the pedal process
,
and final ly upward along the ventral edge of the lat eral l igament . The outer
wal l of the capsule forms the cornea and almost the entire lateral su rface of the
head whil e the inner wal l separates the eve from the sac for the peduncle of
the ten tacle . At the j unction of the outer and the inner wal ls of the capsule
the membrane which connects the third and fifth arms is attached to the capsu l e
so that to a superficial observer the arms seem to be attached to the eye . The
cavity of this capsul e is the outer chamber of the eye and i s in communication
with the exterior by means of the “aqu i ferous pore
”
,a tubu lar ci l iated canal
situated at the ventral edge of the cornea .
28
chambers . E ach respiratory chamber extends al ong the side of the l iver case
from the sl it between the lateral arc of the col lar and the lateral siphonal val ve
which . it wil l be rem embered ,l i es on the side Of the l iver case a short dist
ance behind the head and forrrrs the h ind boundary of the neck , to the long,
longitudinal sl i t between the mantle and the body and siphonal retractor . Each
gi l l arises from the sid e of the body at the level of the origin of the siphonal
retractors and,passing outside thi s muscl e
,extends forward in the respiratory
chamber to the lateral siphonal val ve . A fol d of i ntegument forms a mesentery
which attaches the gil l al ong its whol e l ength to the mantl e . Water entering
the mantle passes between the lateral siphonal val ves and the mantle,over and
through the gi l l s,and then enters the cloacal chamber which extends from the
right and l eft compartments of the hind end of the chamber,forward to the
inner opening of the S iphon,through which the water escapes to the exterior .
The rectum emerges from the lower surface of the body at the level of
the base of the gil l,and extends forward to the proximal open ing of the siphon .
A nephrid ial pore opens through the rounded lower wal l of the viscera at a
point midway between the base of the rectum and the corresponding portion of
the siphonal retractor . I n the femal e,the openings of the nidamental and acces
sory nidamental glands he a short di stance behind the nephridial pore . The
oviduct passes under the - base of the gi l l and emerges from the v isceral mass
into the cloacal chamber betw een the rectum and the l eft siphonal retractor . It
ends a short di stance behind the tip O f the rectum . I n the mal e,the penis
occupies a corresponding position . The genital sac,w hich MARCHAND bel ieves to
be homologous with the n idamen tal gland of the femal e,opens into the mantle
chamber on the outer side of the penis beneath the base of the gil l .
THE ALIMENTARY CANAL .
T he alirrrentary canal (Plate I , Fig . 7) ari ses from a storrradaeunr which fornrs
the epithe l ium of the pharynx . esophagus , and probably of the stomach,and from
a second anlage which forms the caecum,intestine
,rec-tum
,inksac
,l iver and
pancreas and w hose origin has been a mooted point . This anlage is first cl early
seen as a smal l epithel ial cap whose edges rest upon the yolk mass and whose
cavity is bounded below by the yolk . WATASE bel ieves this to be a proctodaeum
but it now seems qu ite clear that a proctodaeum is not formed . Apart from
his view,i t i s general ly agreed that the cel ls forming this cap migrate
singly from the ectoderrrr as do all the entodermal,mesodermal (and yolk ?)
ce l l s of the embryo and later arrange themsel ves in an epithel ium . Hence
we bel ieve that the whole discussion is a essential ly a matter of names . To
BOBR E T ZKY , i t i s mesodermal : to FAUSSER and TE ICHMAN,i t is m esen todermal
and becomes the definitive entoderm ; while to V I A L L E T O N and K O RS C H E T T,i t
is entodermal .
The glands of the gut are a median and a pair of lateral sal ivary glands ,a pai r of compound glands which form the pancreas and l iver
,and the inksac .
T H E PHA RYNX . The mouth (Plate III , Fig . I t ) i s surrounded by the buccal
and peristorn ial membranes . The former is a thin circular sheet attached to the
bases of the arms and extending forward around the latter . The buccal mem brane
i s supported by seven muscular columns which form the proj ecting points of the
scal loped free edge of the membrane . The inner surface of each column bears
ten or twelve stalked suckers arranged in tw o rows . The columns are attached
to the muscu lar ring at the bases of the arms as fol lows ; a median column
between the bases of the first pai r of arms,one between each first and second
arm,one between eac h third and fifth arm and two side by side between the
fifth arms .
The buccal membrane of the femal e has a horseshoe- shaped depression on
i ts inner surface below the mouth . The spermatophores are closely packed on
end in this depression and they forni a white spot w hich ,w hen present , is
a convenient and posit ive mark of the femal e .
The peristorn ial membrane is a tubular fold of integument , arising in the
angle between the base of the buccal membrane and the pharynx and contain ing
30
a strong Sphincter muscle and a thin Sheet of longitudinal fibres which arise from
the equator of the pharynx and end among the circular fibres . T he free edge
of the membrane forms a circu lar l ip . The contraction of the sphincter trans
fornrs the peristorn ial tube into a cone,thus practical ly closing the mouth and
throwing the otherwise smooth or sl ightly wrinkled surface into folds .
The pharynx is armed with a pai r of powerful chi tinous jaws to which a
number of strong muscles are attached . The mandibl es and muscles together
enclose the pharyngeal cavity and form a large oval mass,the pharynx or
buccal bulb,which is enclosed in the muscular case (described in connection
with the foot) formed by the bases of the arms . A pai r of sal ivary glands and
the infrabuccal gangl ion are attached to the dorsal end of the pharynx and the
oesophagus is attached near but a l ittl e above them .
The space between the pharynx and its case is an extensive but incapa
cions bl ood sinus which is div id ed into two cavities,the outer
,and the inner
buccal si nus,by a thin -wal l ed conical muscular tube ' which is attached to the
equator of the pharynx and extends backward to the dorsal end of the pharyn
geal case . This tube or tubular muscle i s the retractor of the pharynx . Its
uniform contraction draws back the pharynx into the sheath whil e the contrae
tion of One or more segments of the muscle ti lts the pharynx in the correspond
ing di rection . The outer buccal sinus contai ns three smal l pharyngeal muscles .
One muscle,the levator mand i bu h which seems to be a Special ized portion or
the pharyngeal retractor,arises j ust outside it from the upper portion of the
pharyngeal case,and passes forward (ventrad) in the median l ine to its i nsertion
on the upper mandible . The other two muscles are a pai r of thin bands which
arise near together from the upper side of the dorsal end of the pharyngeal
case and,passing downward around the pharynx
,are i nserted upon its lower
surface . These muscles rotate the pharynx on its l ong ax is . The pharynx is
easi ly movable so that it can be thrown forward nrore than hal f its own length,
apparently being squeezed ou t by the contraction of the muscl es of the phar
yngeal case , and can be retracted or rotated by the muscles described above .
The inner buccal sinus contai ns the infrabuccal and suprabuccal gangl ia,the
pharyngeal arteries,the duct of the median sal ivary gland ,
and the oesophagus .
It is prol onged backward as a canal th ru the oesophageal nerve ring . The
buccal sinuses are l i ned by the vascular endothel iurn .
The mandibles,or jaws (Text figure 1 1 ) resemble a parrot
’s beak inverted .
The upper mandib l e is l onger,straighter
,and more compressed than the lower
which is strongly convex and closes outside the upper j aw . Each mandible is
formed of two boat - shaped larn el lae which unite at an acute angle and make the
3 1
cutting edge of the j aw . This edge is drawn up into a strong median tooth
w hich is flanked by a pai r of smal l notches . T he pharyngeal muscles are attach
ed to the adjacent surfac es of the lame l lae of each j aw and fi l l the narrow
space between them . The jaws grow constantly by addi tions to their margins
and to thei r unexposed surfaces . They are marked by two sets of fine
striae , the l ines of grow th ,on e set concentric with the point of the j aw and
one set radiating from it . The jaws are brown
ish -black on the cutt ing edges,
ambe r colored
near those edges,
and colorless at the free
margins .
The upper mandible is almost as long as
the pharynx and is shaped l ike the prow of a
very deep and narrow boat . Its inner lamella,
to the dorsal end of which the oesophagus is
attached,forms the greater portion of the l in ing
of the oral cavity . The ou ter lamella is more
strongly curved and is not hal f as large as the
inner . The levator i rrandtbu lz’
is attached to i ts
dorsal end .
The lower nrandible is about hal f as l ong as
the upper but is less compressed and more
curved so that it fits over the distal end of the
inner mandib le . T he inner lamella has nruch
the same shape and size as the outer lamel la of
the upper j aw ; the outer lamella of this j aw ,
is a long,broad band which extends backward
paral l el to the edge of the j aw and forms a
pai r of prominent wings , the alae . The upper
j aw is comparatively fixed while the lower rotates
thru an angle of 45°about an axis which passes
almost thru the middle of each side of the
inner lamella. of the upper j aw . The muscular
fibres (Text figure 1 1 c) which move the jaws arise from the inner lanrella
of the upper j aw and take a spiral course around th is axis . The fibres (8 i n
the figure) from the lower portion of the middl e of the inner lamel la of the
upper j aw pass directly outward and are i nserted in a strong ,superficial fascia
which is attached to the outer laure l la of the lower j aw and which covers
the lower hal f of the pharynx . These fibres form a central column around which
3 2
the other fibre s are wound and arou nd which the lower j aw moves . O ther
fibres (2) which arise from the dorsal end of the same lamel la pass outward and
forward to the inner surface of the ala of the lower j aw . Fibres (4 ) which arise
from the fo rward part of the inner lamel la of the upper j aw pass outward and
downward over the edge of the inner lamella of the lower j aw and are i nserted
upon its outer surface . The contraction of these muscles,causing the j aw to
rotate around the axis (Ax) , draws the lower j aw l ike a visor over the upper
j aw . A pai r of superficial muscles (1) which arise from the back end of the
upper j aw ,pass forward and sl ightly downward to the middle of the outer
lamella of the lower j aw and Open the mouth by drawing the l ower j aw back
ward and downward . T he jaws are sufficiently powerfu l to cut and break the
bones of smal l fish or the pen of a quite large squid .
The mouth contains the two palatin e lobes and the odontophore . Each
palatine lobe is a muscular curtain which is attached to the hind and l ower
edge of the inner lamella of the upper j aw and l ies upon the inner surface of
the same lamel la . The upper edges of the palatine folds are thickened (especial ly
near the d istal end) and proj ect into the mouth,meeting in the median l ine .
The outer surface of each fold is co vered by a columnar mucous - secreting ep ithe
l ium and the inner surface by a columnar epithelium that secretes a thin sheet of
chitin which i s covered with smal l backwardly directed teeth . The odontophore is
attached to the lower part of the hinder end of the upper j aw and proj ects
forward into the mouth cavity,lying bel ow and partial l y between the palatine
lobes . The lower part of the odontophore is quite distinct from the rest and
i s cal l ed (by L I VO N ) the tongue ; the upper part consi sts of the radula and its
appendages . The tongue has a muscular frame work,formed by an upper and
a lower pai r of longi tudinal bands w hich arise from the posterior edge of the
upper j aw and which are bound together by connective tissue and transverse
muscle fibres . The upper surface and the tip of the tongue are covered by a
th in sheet of chitin,but the sides and lower surface are covered by a palisadal
mucous epithel ium which forms a large number of sparingly branched tubular
glands that occupy the spaces between and around the muscles of the tongue .
The radula is secreted by a deep cyl indrical sac which extends backward
from the middle of the pharynx to i ts dorsal end,describing a sl ight curve
,
convex beneath . The sac is l ined by a chiti n - secreting , cubical or pal isadal
epithel ium which,upon all sides except the upper
,i s rai sed into smal l papi l lae
upon which the teeth are secreted . The epithel ium of the upper surface of the
sac forms irregular folds covered by a thin sheet of ch itin which proj ect into
the lumen and occupy the spaces between the teeth . T he teeth and this sheet
88
of chitin are supported by a tough sheet of connective ti ssue,known as the
subra dular membrane . At the ventral end of the radu lar sac the tooth bearing
portion of this membrane is reflected downward over the lower surface of the
odontophore between it and the tongue,whil e the toothless portion of the mem
brane is reflected backward over the sides and top of the odontophore . The
teeth (Text figure 12) are arranged in seven longitudinal and an i ndefinite number
of transverse rows . Each transverse row consists of a central tooth fl anked by
three pai rs of lateral teeth and has,at each end
,a fl at oval plate of chitin .
The central tooth has a strong middl e point and a pai r of l esser lateral points .
The tooth at either side of the center consists of a large inner and a smal l er
outer point . The teeth of the second and third rows from the center are strong,
l ong,curved spikes . New teeth are constantly produced at the base of the radula
and gradual ly push outward until they reach the mou th of the sac where they
are drawn downward and then b ack
ward over the end of the odonto
phore . Whil e in the radular sac,the
points of the teeth proj ect toward
its base (backward) but as they are
drawn over the end of the odonto
phore the teeth point fi rst upward
and then forward so that they rasp F i g . 12 .
food only as the radula i s drawn into its sac .
Two pai rs of muscl es,the radular retractors and protractors
,draw the radula
i n and ou t over the apposed ends of the two radular carti lages which support it .
These carti lages l ie at the side of the radular sac and are sl ightly curved upward
at each end . The dorsal ends of the rod - shaped carti lages are fastened to the
lower part of the dorsal end of the upper j aw by means of muscle fibres which
radiate backward,inward and forward from the j aw to the cartilage . The upper
,
i . e . the concave,side of each cartilage is covered
,except at the end
,by a trans
verse muscle which i s several times as thick as the cart i lage . The fibres of thi s
muscle are sufficientl y curved to be concentric with the carti lage and arise from,
and are attached to ,a fascia which extends from one end of the fibres down
ward under the carti lage and up on the opposite side to the other end of the
same fibres . The only action which I can assign to this pecul iar muscle i s that
the thicken ing of i ts fibres dur ing contrac t ion presses downward the ends of the
raduar carti lage,straighten s it and thereby forces the radular forward . The
radular carti lages are connected by a sheet Of muscle which stretches beneath
the radular retractors . A similar but thicker and narrower sheet of muscle
3 4
be tw e en the carti lage s above the radula and radular retractors forms with the
lowe r musc le an ob l iq uel y c onical tube which contains the radular sac and over
w hose apex the radular membrane i s reflected .
T he radular retractors arise from the dorsal end of the radular carti lages
and ex tend ing forward paral le l to the radula are inserted near the ventral ends
o f the cartilages upon the subradu lar membrane .
The protractors of the radula arise from the lower edge of the upper j aw
and passi ng forward and i nward are inserted upon the reflected d istal end of the
subradular membrane . A snral l portion of the protractor is inserted upon the
toothless portion of the sari re m embrane which ,i t w i l l b e remembered
,covers
the sides and top of the odontophore . The alternate contraction of the retractors
and protracto rs draws the radula back and forth over the ventral end of the
radular cartilages . The teeth act only during retraction hence the retractors are
much more powerful than the protractors .
The mouth,the oesophagus
,the radular sac . the median and the pai red
sal ivary glands and probably the stomach al so arise from the stomadaeum .
The sal i vary glands are relatively simple compound - tubular glands . The lumina
are large and are su rrounded by pal isadal cel l s whose large nuclei are situated
next th e supporting membrane and whose distal hal ves are fi l l ed by large secre
tion vacuoles . The secretion in the l umina i s u sual ly precipitated by fixatives . An
incomplete series of tests showed that aqueous and glycerirre extracts of the median
gland are not O leolytic or amylolytic,and that they are probably proteolytic .
FA L L O IS E finds this to be the case . The glands al so secrete mucin .
HENZE confirms the observations of LO B IANCO , KRAUSE , and L rvou BR IOT,
that the secretion of the posterior sal ivary glands of various cephalopods inj ected
into the ci rculation of crustaceans,even in smal l quantities
,i s qu ickly fatal .
H E N zE finds that the poi son i s an organic base (alkaloid) similar to the poison
of bees and of the skin of salamanders . The gland contai ns also two nitrogenous
substances ; one of these,taurin
,i s verv abundant in the muscles of cephalopods
,
and since VO N Fi‘iR T H has found very l ittl e n itrogen in the secretion of the
nephridi um,H ENZE suggests that the gland i s
,at l east in part
,excretory .
T he pai red or buccal sal ivary glands are partial ly irn bedded i n the muscles
upon the dorsal surface of the pharynx between the ra dula and the oesophagus .
The duct of each gland passes through the palatine lobe and opens into the
nrouth on the inner S ide of the lobe near its ventral end . The median sal ivary
gland is a smal l oval body imbedded in the ventral end of the l iver . I t l ies in
a smal l venous sinus si tuated beneath the oesophagus and between the diverging
v isceral and pal l ial n erves . l ts duct accompanies the oesophagus through the
3 6
broad .horizontal ridge that passes from the stomach to the l eft side of the
caecum between two large l obes of the caecum which proj ect forward above and
be low the intestine and storrraclr so as nearly to encircle the ven tral end of the
latter . The caecurrr is se l dom or never empty but is usual ly partial ly distended
so that it extends about to the middl e of the coelom and when in this condi
tion it is pear Shaped ,the smal l er end being dorsal . A smal l circular band ofmuscl e
fibres div ides the smal l er end from the mai n portion of the sac . This band may
be strongly contracted so as to produce a diaphragm - l ike curtai n perforated by
a large central hol e or it may relax so completely that the caecum becomes
narrowly oval . A number of folds are formed from the l ining of the outer wal l
of the ventral end of the caecum and O f the adjacent portions of the upper and
l ower wal ls . Tire folds are blade - l ike and radiate from the outer end of the crest
that separates the two ventral l obes of the caecum . The folds vary in size and
are arranged l ike the mesenteri es of a sea anemone : that is,the largest folds are
equ idistant from one another,smal l er folds are placed midway between these
sti l l smal l er folds are placed midway between each large and smal l fold,and so
on unti l the smal lest folds are mere ridges . Each fold is corrugated by a series
of ridges which are paral lel to the . free edge of the fol d and which al ternate . on
the opposite s ides of the fold . HENR I finds that the secretion of the caecal folds
assists pancreatic digestion .
The wal l of the caecum is formed of three coats viz . the ou ter pavemental
epithelium of the peritoneum,a middle coat of m uscle fibres
,and a l in ing or
secretory epithel ium . The . latter presents three chief types which are connected
by transitional forms . 1 ) The epithel ium covering the caecal folds and the adjacent
region is th ick,densely cil iated
,and pal isadal . The nucle i l i e at the base of the
cel l s and the di stal portion of the cel ls is often fi l led with granular protoplasm . 2)The epithel ium of the greater part of the remainder of the ventral portion of
the caecum is exceedingly i rregular but the characteristic cel ls are columnar or
club - shaped and usual l y occur in groups of three or more . The nucleu s often l ies at
the di stal end of the cel l,while in other cases the distal end of the cel l is
vacuolated and the nucleus is at the base . The .cell s are sparingly cil iated . 8) The
epithel i um of the dorsal end of the caecum is cubical or pavemental and cil iated .
It is possible that tension may change the epithel ium from one type to another
but this is improbable because the three types often occur close together in a
portion of the wal l which is apparently under uniform strain .
The commun ication (Plate I Fig . 2 ) between the caecum and the neighboring
cavities of the gut is by m eans of a very remarkabl e five -w ay val ve whose lumen
mav be roughly compared to a l etter M . The two upper poi nts of the M - shaped
8 7
l umen Open into the stomach and caecmn . The right arm of the lumen leads
to the oesophagus,the l eft to the hepatic duct and the central point to the
intestine . T he three angles incl uded between the four arms of the lumen are
formed by the wal ls which separate (1) the oesophagus and the intestine,
(2) the stomach from the caecum,and (3) the intestine from the hepatic duct .
The open ings from the oesophagus and from the stomach are circular and are
control l ed by sph incters . The Openings between the caecum and the intestine,
and between the hepatic duct and the caecum have in addition to sphincters,
three adj ustable valves . One val ve which w e may cal l the gastri c valve ,is a
high,h ooked ridge which is situated upon the upper S ide of the Opening from
the caecum to the stomach . Its concave side is directed toward the right i .e .
toward the stomach . A second,the intestinal val ve
,is formed by a high ridge
which arises on the upper wal l of the intestine,passes backward to the opening
betw een the caecum and intestin e,and then curves upward around the edge of
this opening forming here a qu ite high tubercle that proj ects into the caecum .
A ridge arises on the left of the intestinal valve “
and passes backward through
the caeco - intestinal opening and then outward along the edge of the large part ition .
between the upper and lower lobes of the caecum . This ridge ends in a large,
spoon - shaped val ve , the hepatic valve , which l ies j ust behind and above the
opening of the hepatic duct . The concave surface of this valve is turned toward
the open ing and the valve can be turned downward so as to cover the opening
and form a deep groove that,by being pressed against the adjacent wal l
,is
converted into a canal which leads from the hepati c duct to the intestine . By
the contract ion of the caecal open i ng and the turning downward of the hepatic
valve,the caecum can probably be occluded from the rest of the gut whi l e a
passage may remain open from the hepatic duet' to the intestine and through it
to the stomach .
The action of the muscles and valves above described is somewhat conjectural
since it is impossible to observe their normal action . However,a careful study
of al l the data at hand leads to the inference that the fol lowing adjustments
probably occur . 1) The oesophagus opens into the stomach . The food is prevented
from passing out O f the stomach by the contraction of the sphincter between
the stomach and the caecum . The gastric val ve may possibly be drawn into the
opening to serve as a plug . 2) The oesophagus may Open into the caecum . This
adj ustment may be effected by the contraction of the sphincters around the
ventral end of th e stomach and around the intestine accompanied by the relaxa
tion of those around the oesophagus and caecum . 8 ) The stomach opens into the
caecum . This is accomplished by the relaxation of the sphincters around the
38
stomach and caecum and the contraction of those around the oesophagus and
intestine . 4 ) T he stomach may Open into the intesti ne . The relaxation of the
sphincters around the gastric and intesti nal open ings and the contraction of those
around the oesophageal and caecal Openings may produce this connection . 5 ) The
caecum Opens into the intestine . 6 ) T he hepatic duct opens directly into the
caecum . 7 ) The shape and position of the hepatic val ve suggest two possibi l ities
fi rst,that the val ve may close over the hepatic duct and prevent the regurgi
tatien of fluids from the caecum ; second ,that the valve may be apposed to the
caecal wal l so as to form a canal which l eads,even when the opening from the
caecum to the intestine is closed,from the hepatic duct to the intestine so that
the digestive fluids which ord inari ly pass directly from the hepatic duct to the
caecunr may be diverted to the intestine and through it to the stomach . This
second possib il ity is strongly suggested by the form and position of the valve
but there is great doubt whether this ever occurs . The explanation of this
remarkabl e connection between the portions of the gut is to be found in the
great difference in structure a nd in function betw een the stomach and caecum .
The stomach,oesophagus
,and mouth (that is the entire gut as far as the opening
from the stomach to the caecum) are l ined with ch itin and,with the exception
of the glandular epithel ium upon the unexposed surfaces of the tongue and palatine
lobes,is nonglandular . The three sal i vary glands are connected with the m outh
bu t they are so smal l that they can scarcely have a predominant d igestive function
and,unless they do produce a remarkably effective digestive flu id
,the food in the
stomach is not d igested by flu ids produced by the anterior portion of the al im en
tary canal . Nevertheless,the examination of the contents of the stomach of a
large number of squid shows that digestion does take place in the stomach for
the ingested food is found in the stomach in all stages of digestion from
large angular pieces whol ly undigested to a mass of bones and bits of chitin
from which all flesh has been removed . The caecum and intestine,on the other
hand,are l ined by a ci l iated secretory epithel ium and receive the secretion from
the immense digestive glands,the l iver and pancreas . The structure of the
stomach and caecum natural ly leads to the supposition that the stomach i s
merely a crop for storing food until i t can be passed in to the caecum for diges
tion bu t in the large number of individuals examined . bones , chitin ,or pi eces
of undigested food were never found in the caecum while,as has been stated
,
partial ly digested food and i ndigestibl e substances are found in the stomach .
Hence it seems clear that the fi rst stages of digestion,at l east
,occur in the
stomach . Al l these facts lead us to the fo l lowing conclu sion which agrees with
that of BO U RQU E LO T who reached the result from a study of the physiology of
39
d igestion ; that the food is corn rn inu ted and partial ly d igested in the stomach by
the digestive fluids introduced from the caecum or from the pancreas and l iver ;that the partial ly digested food then passes into the caecum for complete digestion
and absorption whil e the bones and indigestible residue are ej ected from the
stomach through the intestine to the exterior . I t i s probable that the fluids from
the l iver and pancreas pass into the caecunr and from it to the stomach but it
is possible,as suggested above
,that these secretions may fl ow directly into the
intestine and thence to the stomach .
T H E LIVER AND P A N OR E A S . These glands arise from two long tubular evagina
tions from the caecal portion of the mesenteron . These tubes extend outward to
the visceral wal l and then forward as far as the sku l l . They are flattened
lateral ly between“ the yolk mass and the v i sceral wal l . At. first the wal l of each
tube is formed by a plain cubical or pal isadal epithel ium but later each tube becomes
d ifferentiated into three portions . The distal portion becomes a large racemose
gland which fuses with i ts mate to form a con ical gland,the l iver . The middle
portion of each forms a short hepatic duct . The proximal portion of the evagina
tion forms one side of the pancreas . The two evaginations,original ly independent
,
are carried out by another evagination of the caecal wal l,
so that they
final ly open together into the caecum . This secondary evagination becomes the
common hepati c duct and i ts wal ls becoming glandular,form the unpaired
portion of the pancreas . The fact that the l iver and pancreas are original l y pai redstructures accounts for the passage of the oesophagus thru the l iver and of the
intestine between the lobes of the pancreas .
The ‘l iver is conical . Its broad v entral end rests upon the Skul l and its
pointed dorsal end l ies beneath the midd le of the pen . The ventral end of the
l iver is i rregular because the median sal ivary gland is imbedded in it and because
the visceral and pal l ial nerves , and the oesophagus and aorta pass obl iquely
through it in deep grooves or i n canals . The groove for the oesophagus and
aorta continues backward to the middl e of the upper surface of the l iver . At
this point,it opens into a canal which passes obliquely downward and backward
to the lower side of the l iver, ending between the hepatic ducts at a point about
one third the l ength of the l iver from its dorsal end . The tw o hepatic ducts
emerge from the l iver,one on each side of the oesophagus and aorta , and pass
imm ediatelv into a space between the siphonal retractors,and above the anterior
vena cava . After a short course in this space . they enter the pancreas which
l ies i n the nephridial cavity . The hepatic ducts and the l iver are attached to sur
rounding tissues by means of loose connective tissue .
The l iver is a compound tubu lar gland of l ight vel low ish - brown col or . The
40
ce l ls of the glandular epi thel ium of the tubules are cubical or columnar and
certain of them are l onger than others and proj ect into the lumen making the
inner surface of the tubul e very i rregular . The large round nucleus l ies at the
base of the cel l and the protoplasrn at the distal end of the cel l i s granular and
often vacuolated . The epi thel ium is supported by a connective tissue frame work
which carries the veins and arteries . The secretion of the l iver is proteolytic .
The hepatic ducts are simpl e,thin -wal l ed
,muscular tubes lying side by side
and l eading from the l iver to the pancreas . The lumen of each duct is continuous
with those of the corresponding l obes of the l i ver and of the pancreas .
The pancreas is a whitish,sl ightly lobulated gland surrounded by the
nephridial sac . As a whol e i t is U - shaped . The tw o arms begin at the points
where the hepatic ducts enter the ventral end of the nephridial sac and pass
backward,one on each side of the intestine . They un ite behind it j ust b efore
the duct enters the caecum . The dorsal part of the pancreas l ies be tween,and
is partial ly adherent to,the tw o ventral l obes of the caecum . The wal l of the
pancreas separates the lumina of the pancreas (the hepatico - pancreatic duct) and
of the nephridium and contains numerou s evagirrations from both cav ities . The
external surface of the gland is covered by a pal isadal epithel ium which i s the
reflected epithel ium of the nephridal cavity . The nucle i of the cell s of thi s epithel ium
are arranged in a regu lar layer near the outer ends of the cel l s . The epithel ium
forming the wal ls of the tubu les of the gland is pavemental or cubical . The
extract of the pancreas is proteolytic,amylolytic
,and O leolytic but it i s possibl e
that the proteolytic enzymes are der ived from the l iver for i t is impracti cable
to remove the hepatic secretion from the lumen of the pancreas .
FA LL O I S E finds that the hepatico -pancreatic secretion i s continous but is much
more copious during digestion . The fluid is acid,colorl ess to brown or yel low
,
is rich in proteids,con tai ns a proteolytic ferment
,amy lase , l ipase and erepsin .
Invertin i s absent .
The gut distal to the caecum passes obl iquely downward to the lower
surface of the v isceral mass and then passes forward some distance . I t is usual l y
div ided , for purposes of description ,i nto tw o portions viz : the intestine which
is a short wide tube extending from the caecum to the lower surface of the
v isceral mass , and the rectum which is a long con ical tube attached to the
lower surface of the v isceral ni ass .
The intestine passes forward from the caecum between the caecal lobes ,and between the oesophagus on the right and the pancreas on the left . Then
it turns sharply downward,passing between the right and l eft lobes of
the pancreas and between the tw o arms of the V - shaped nephridial s inus
4 1
and i n front of the heart which l ies between the nephridium and the pancreas .
The rectum lies j ust beneath the skin of the l ower surface of the visceral
mass . Its upper surface is next to the ventral part of the nephridium and to the
ink sac which separates i t from the anterior vena cava . The rectum is about hal f
as long as the l iver and it extends
from the level of the hinder end of
the l iver to the middle Of the same .
T he forward end of the rectum is
attached to the l iver case by a mesen
tery- l ike fol d of skin . It ends in a smal l
anal chamber from which it i s separated
by an anal sphincter . The ink sac opens
into the anal chamber and the cham
ber opens into the mantle cavi ty through
the transversely oval anus which is
bounded by an upper and
a lower l ip . A pair of
ovat e l eaf- l ike processes ,the rectal val ves
,sup
ported on short round
stalks are attached at
each side of the arms .
T he wal l of the
intestine and rectum has
the usual ci rcular and
l ongitudinal muscles and,
with the exception of the
distal part of the rectum,
i s l ined by a cil iated
columnar epithelium in
which are scattered go
blet cells . The epithel ium of the middle of the rectum is non - cil iated and contains
a large number of goblet cel ls while that of the ventral end is pal isadal , non
cil iated,and contains a larg e
'
number of characteristic cel ls (Text figure
Each of these cell s has a single process from one to four times as long as the
cel l and one hal f or l ess the breadth of the cel l . The maj ori ty of the processes
are blunt,but som e of them taper out i nto fine points wh ile a few are knobbed
or contain a vacuol e in the free end . The processes vary in si ze from mere
F ig . 13 .
o n the free su rfaces of the cells to l ong terrtac le - l ike processes .
This variation l eads to the supposi tion that the processes are capable of be i ng
extended and withdrawn . In young squid the processes retai n the i r i ndependence
but in the adult the processes of several adjacent cel ls fuse and form an i rregular
coral - l ike mass . These masses often contai n bod ies which appear to be food
granu lrs and vacuoles .
In transparent young,5 or 6 mm . long ,
the rectal val ves can be seen
beating downward into the anus and as they descend the anal l ips Open ; as they
rise , the anal l ips close . This action drives water into the rectum and in an
experiment particl es of carrn ine in the water were carried into the rectum .
Contractions of the rectum drove the water out through the anus whil e the
carm ine was retained,probably being screened ou t by the processes
,and w as
then carried by ci l ia as far as the proximal end of the in testine . The appearance
of the rectal cel l s in the adul t leads us to suppose that the processes are tru ly
pseudopodial and that the granules in them are food particles underg oing in tra
cel lu lar digestion . In testinal pseudopodia and i ntra cel lular digestion have not,we
bel ieve,been described in any mollusc and it wil l be surprising if i t i s proven
that structures and habits commonly associated with much simpler animals occur
in the h ighest of the mol lu sca .
T H E INK SAC . The ink sac i s a large pear - shaped organ situated above the
rectum,be l ow the anterior vena cava and the l i ver
,and i n front of the nephridium
whose median portion separates i t from the i ntestine . The ink sac ari ses from
an evagination of the upper side of the distal end of the rectum and becomes
differentiated in to three portions : a dorsal glandular portion,a large conical
reservo i r,and a short duct wh ich leads forward from the smal l end of the
reservoi r to the anal chamber . The glandular portion is oval and consists of a
series of connected chambers l ined by a cubical glandular epithel ium which
secretes the j et black ink . The size of the chambers i ncreases rapidly from the
smal l dorsal chamber to the large ventral chamber which occupies the greater
part of the ventral hal f of the glandular portion and opens in to the reservoi r
thru a smal l open ing in the middle of i ts convex ventral surface . The dorsal
hal f of the glandular portion is attached to the wal l of the sac but the ven tra l
hal f proj ects freely into the reservoi r in which the ink is stored . The reservoi r
i s a conical chamber whose larg e dorsal end i s formed by the glandular portion
of the ink sac and whose narrow ventral end is continuous with the duct from
which it i s separated by a sph incter . This chamber i s homologous with the
reservoi r and the long tubu lar portion of the duct of Sepia while the duct of
Lol igo i s homologous with the smal l te rminal chamber or ampulle” of Sepia
44
m ichog.came within reach and then by a sudden dart captured it . Once caught
the fish is usual ly ki l led by a single b ite through the spinal cord or head but
occasional ly the tai l of the fish is turned toward the mouth and the squid whil e
trying to turn the fish or to bite effectively l ets i t escape unharmed or sl ightly
inj ured . The fish is thrust end on into the month by the arms and the buccal
membranes,and the jaws work rapidl y
,b iting out large pieces which are
swal lowed at once without further mastication . The food is swal lowed so qu ickly
that there is no time for the use of the radula , nor does the food Show any
trace of its action . It is possibl e,however
,that the radula is used upon
resistant obj ects . I f so , i t is evident that the obj ect to be comminuted is hel d
by the palatine lobes again st the upper j aw whi l e the radula i s drawn back and
forth over the end of the odontophore which is pressed against the food . T he
secretion of the median sal i vary gland,
which opens at the tip of the tongue and
from the lateral glands which Open near the ends of the palatine lobes is pou red
upon the food as i t is being comminuted . The food usual ly reaches the stomach
in pi eces so large that one can scarcely explain how th ey were able to pass
through the oesophagus and the sku l l . There the digestib l e porti ons are partiall y
di ssolved probab ly by the action of the fluids from the caecum,intestine
,and
l i ver . The partial ly digested food passes into the caecum and thence into the
i ntestine and rectum for complete digestion and absorption . The indigestibl e portion
of the food is voided through the in testine and rectum .
T H E REP RODUCTIVE SYSTEM .
In both mal e and femal e animals,the sexual gland is median and i s
suspended from the upper wal l of the posterior part of the coelom . The genital
duct is an unpaired,more or l ess convoluted and glandular tube l ying in the
l eft wal l of the body and extending from the l evel of the m iddle of the gonad
nearly to the inner Open ing of the funne l .
A . MALE . The mal e reproducti ve organs are the test is,the complex sperm
duct,and possibly the hectocotyl ized left fifth arm .
The testis i s oval transversely and el l iptical longitud inal ly and i s attached
to the upper median l ine of the coel om ic wal l by a mesentery formed by the
peritoneum which i s reflected over the organ . T he testis consists of a multitude
of tubes placed approximately perpendicular to i ts surface and,on the lower side
of the testi s,open ing into a smal l lumen which in turn Opens by a narrow
longitudinal sl it into the coelom . The testis has a porcelain -white color that,in
bright sunl ight,i s clearly vi sibl e through th e mantle and '
pen of the l iving squ id .
4 5
T he sperrn duct is formed of five portions : the vas deferens,the sperrn a
tophoric gland ,the vas efferens
,the spermatOphoric sac and the pen is . The
Spermatophoric sac forms the proximal,the penis the distal end of a fusiform
longitudinal tube which is paral le l both to the vas deferens and the vas efferens,
and the sperrrratophoric gland connects the distal end of the former with the
proximal end of the latter . The vas deferens (Plate II , Figs . 10 - 1 2) begins in
a cil iated funnel which is placed posteriorly near the median l ine at the l evel of
the opening of the testis . The funnel leads from the coelom to a smal l bu lbu lar
enlarg ement and th is in turn opens into the main portion of the vas deferens
which seems convoluted,since a number of folds
,the remnants of a. primary
convolution,proj ect l ike c avu lae conn iven tes i nto its l umen . Otherw ise the vessel
i s straight and gradual ly increases in d iameter distal ly . It Opens into the sper
rn atophoric gland near the middle of its inner surface .
The sperrn atophoric gland ,an oval and sl ightly flattened organ
,is a speci
al ized portion of the sperm duct which forms two bights in the gland ; the first
directed outward and backward,the second inward and forward . T he former
,the
ves icu la sem ina lis i s formed of three portions and i s much larger than the latter,the
appendix .
1
) The proximal (upper) l imb of the seminal vesicl e is very thick (about
one hal f as broad as l ong) and the Sperm rope passes thru it in a smal l sigmoid
canal ,'
the sperm canal”
,into which open three large glandular bl ind sacs or
pouches . The first of these (Plate I I , Fig . 12,V . I .) is a huge backwardly
d irected,bean shaped sac , which l ies upon the upper and inner surface of the
gland .
'
I ts l ower wal l,which rests upon the second portion of the seminal vesicl e
,
is formed O f a very thick columnar epithel ium (8 20 — 8 40 s ) which differs mark
edly from the epithel ium of the rest of the gland . The remainder of the
wal l of the gland forms a branched tabu lar gland of the type shown in text
figure 14 . T he lumen of this gland is approximately trough - shaped and opens
into the upper side of the proximal part of the sperm canal . The second pouch
(V . 1’ in the figures) is biscuit—shaped and l ies upon the outer surface of the gland .
It opens into the sperm canal j ust behind the opening of the first gland . These two
glands,with the corresponding porti on of the Sperm canal
,form M A ROH A N D
’S first
portion of the spernratophoric gland . The third gland is about as large as the
first and l i es inside above and below the sperm canal with which it comrn un i
1) W e fo l l ow the n omenclat ure used by MARCHAND i n h i s exce l len t work u pon the male reproductivesystem of cephal opods , wi th a sl igh t mod ificat io n
,v iz . the spermatophoric glan d i s the enti re organ
concerned i n the format i on of the sperrn atoplrore , i . e . th e cesicu la seminal i s , the p rostata. and the append ix ;the vas efferens (BR O OK ) i s the d istal port io n of sperm d uct wh ich connects the spermatop lrori c gland and
the spermatophorr’
c sac and i s , t herefore ,M A R O H A N D
’S
“the d ista l pO I ti on of the vas defe ren s”
4 6
cates by a long,sl ightly crescerrtic sl it . The forward portion (about one hal f of
the whole) of this gland is represen ted in text figure l 4 ,A and B .
T he sperm canal passes across the outer su rface of the gland from above
downward and backward in the concavity which i s readi ly seen in te xt figure
14,A
,passing from right to left . (A smal l portion only of the sperm canal has
been model led ) . The sperm canal is connected with the gland by a long,narrow
,
sl it- l ike l umen a portion of which is shown in the figures . The chi ef lumen
becomes larg er toward the h ind end of the gland and forms as a whole a deep
Spoon - shaped cavity w hose outer edge i s connected with the sperm canal whil e
its other edges and both upper and lower surfaces communicate w i th numerous
flattened lumina
In the vertical section of the gland represented in text figure 14,B
,it wi l l
be seen that the maj ority of the lumina at the l eft -
of the chief lumen are
united by a common lumen which opens into the chief lumen a short distance
beyond the last section model led . A similar but smal l er set of cavities is shown
in the upper right hand section of the photograph . These two systems are al so
clearly shown upon the outer su rface of the gland . Thus we see in the photo
graphs,a large series of branching frond - l ike lumina Opening into the forward
edge and partly into the inner edge of the chief lumen,and tw o similar but
smal l er seri es which are converging to the upper and lower sides of the chief
lumen . The most marked flattening of the lumina and of the enclosing cel lu lar
plates is in the longitudinal plane and I bel ieve that the whole structure can be
correctly pictured if one imagines that an extensive elongation accompanies and
modifies the formation of a glan d of the compound tubular type . A rapid e l on
gation of the canal at the time of the formation of the primary evagination
would draw it out i nto a l ong narrow pit and we wil l find that the prostata is
formed of a large series of such simpl e,or sl ightly branched pits . The elongation
would affect the secondary evaginations in a l ess degrees and the tertiary evagi
nations in a sti l l smal l er measure . But three primary evaginations of the seminal
vesicl e would seem to be formed whereas in the prostata a large number have
been formed and are but sl ightly developed .
The term simple tabu lar gland” seems appl icabl e to the type of structure
characteri stic of the prostata . The n idamental and ov iducal glands of the femal e
are of similar structure bu t in them the flattened pits are placed at right angles
to,instead of paral l el to the main duct as i n the prostata . The glands of the
seminal vesicle are twice or thrice compound tabular glands .
The third portion of the seminal ves icle is a large tube i nto whose lumen
there proj ects from its oute r and upper side a large,outwardly concave ridge
F i g . 14 .
which is d iv ided into two portions : a larg e and broad proximal portion,ly ing
in the sharp curve at the beginn ing of the th i rd portion of the seminal vesicle ;and a smal l and narrower
,but much longer d istal portion . The cil iated canal
(Ci . recently d iscovered by CHUN,opens into the distal end Of the th i rd
portion of the seminal vesicl e .
The appendix forms the smal l au ri cular fore l obe of the spermatophoric
gland . I ts wal l i s plai n,except that the epithel ium of the smal l
,widely - open
upper divert icu lunr forms a ser i es of low longitudinal ridges . The distal end Of
the appendix leads to the vas efferens,which extends from a point sl ightly in
front of the d istal end of the vas deferens,nearly to its proximal end . The
prostate or accessory gland is a large ,flattened , broadly ell iptical organ which
extends from the appendix nearly to the hind end of the gland,and l ies inside
and below the cesicu la sem ina l is. I ts wal l forrrrs a series of narrow longitud inal
r idges which separate a series of deep long and narrow pits,so that the gland
is of the simple tabular type . Its central lumen is qu ite large,and surrounds the
proximal part of i ts l ong tubular duct which opens into the appendix .
The appendicular gland (Di) , a slender and relatively short bl ind tube
formed of columnar epithel ium, ,
is nearly one half as l ong as the enti re gland
and extends backward inside the prostata from the d i stal end of the append ix .
The cil iated canal (Plate II , Fig . 12,C i .C . ) is a smal l and long cil iated
tube whose wal l,i n prepared sect ions
,i s thrown into a few low longitudinal
folds . It begins near the h ind end of the gland in a broad cil iated funnel whose
tw o d iverg ent hal ves rest upon the adjacent surfaces of the accessory gland and
the third portion of the seminal vesicl e,and i t Opens into or from the genital
sac,whose wal l covers the gland . The canal extends forward between the acces
sory gland and the third portion of the vesicu lar sem ina l is to the distal end of
the latter which it enters obl iquely . The function and morphological mean ing
of the ci l iated canal are al ike doubtful . MARCHAND finds that i ts ci l ia beat away
from the sac and toward the gland . but its broad flar ing funnel and i ts obl ique
opening into the gland seem to indicate that they must carry fluid into the gland .
MARCHAND bel ieves,however
,that i t i s the distal portion of a second sexual
duct,whose proximal portion has been fused with the vas deferens
,and that
i t corresponds morphological ly to the portion of the in ternal ov iduct which i s
buried in the wal l of the oviducal gland,the latter being the homologu e of the
genital pouch,whereas the nidamental gland corresponds to the vas efferens
,
pen i s and spermatophoric gland ,and has l ost its primitive connection with the
proximal ly fused genital ducts . BO U RxE finds,in Sepia
,that the cil iated canal
leads from the coelorrr to the spernratophoric gland ,and this seems to favor
48
M a ri c uaxo'
s View,fo r he would doubtless say that this is the p roxima l end of the
second and aborted sexual duct,whose distal end i s fused with the functional
duet . U nti l the embryological history of the organs has been fol l owed ,these are
merely vague surmises .
The spermatophoric gland is suspended by the vas deferens and vas efferens
and the connective tissue surrounding them in an ovate sac,the geni tal sac
,
w hich was described first by BROOK and later,and more correctly
,by CHUN . In
I llex the sac opens widely into the mantle cav ity ; i n L oligo c i i lgar is and L . mazmom e
it i s a closed sac ; but in ou r species it i s prolonged forward into a smal l tube
which,at the base of the gi ll
,opens into the mantle cavity . The sac extends
upward between the vas efferens and spermatophoric sac for some distance .
‘
The vas efferens i s a smal l,somewhat flattened tube
,l ined by a cil iated
epithel ium which i s sl ightly folded longitudinal l y . Extending backward from the
spermatOphoric gland ,i t enters obl ique ly the lower surface of the prox imal end
of the spermatophoric sac .
The spermatOphoric sac,or NEEDHAM
’S sac
,i s a thin -wal l ed
,broad tube
w h ich l ies at the side of the V isceral mass , above the spermatOphoric gland and
outside the caecum . I t extends forward from near the beginning of the vas
deferens to the branchial heart,and merges distal ly into the smal l and more
muscular tube,the pen is . The wal l of the sac bears a large number of l ongitud inal
folds,which divide its cavi ty into a number of tubular spaces in which the
sperm atophores are stored in smal l bundl es .
The pen is passes thru the space between the branchial heart,the caecum
and the base of the gil l,from which it is separated by a narrow prolongati on
of the pal l ia l cavity . I t l ies,for the greater part , i n the mantl e cavity between
the gil l and rectum and beiow the siphonal retractor,and term inates near the anus .
The spermatophoric gland secretes very complex cases in which the sper
matozoa are transferred to the femal e . These packets of sperm,the spermato
phores , (Plate I , Fig . 5 ) are stored in larg e numbers in the spermatophoric sac .
The spermatophore consists of a double wal l ed case which encloses a sperm
rope,at one end of which i s the so - cal l ed ejaculatory or flask apparatus . The
case i s a sl ightly curved,slender cyl i nder (eigh teen or twenty times as l ong as
broad) rounded at the ends and somewhat smal l er at one end . The smal l er end
contains the ejaculatory apparatus”
and bears a long tubular fi lament . Thi s
smal l er,
fi lament bearing end,we wi ll cal l the distal end of the spermatophore
and not w ith MARCHAND,the oral end
,for i t is turned away from the mouth when
it i s in i ts final shal l we say functional? posi tion in the buccal pi t of the
femal e . In the spermatophoric gland this end turn s about twice,so that a term
usual lv broken off near the case . The cavi ty of the fi lament is con tinuous with
that. o f the flask and seems to contain the same Opaque fl u id . The cavity around
the fi lament is apparentl y continuous with the cavity between the outer and
i nner wal l s of the case,but it contains a transparent fl u id
,not the granular
flu id which fi l ls the space between the wal ls of the case .
The measurements of the appended table were taken during July,and are
typical , excepting the last .
mm . mm .
mm . mnr .
m nr . mm .
mm . (few present) mm .
This table shows that in general the size of the spermatophore varies with
the size of the squid . The relative l ength.
of the sperm rope varies in different
individual s,but the spernratophores presen t i n the sac at any time are essential ly
al ike . The larg est squid had probably passed the period of sexual activity .
The process of formation , transference , and discharge of the spernratophores
i s not wel l known . T he sperm are packed into a sol id thick colum in the vas
deferens,and seem to pass into the c esi ci i la sem ina lis i n a smal l stream or column
,
for in its second oportion they are arranged in a regular,spiral ly obl ique plate
,
which forms the sperm mm. A sheath,probably the sheath of the sperm rope
is acqu i red in the first or second portion of the seminal vesicle,and MARCHAND
finds that the third section Of the vesicl e secretes the outer case of the sperma
tophore and that in this portion of the gland its prox imal (oral ) end is foremost .
This end of the spernratoplrore enters the duct of the prostata first thru the
appendix and vas efferens . U pon entering the spermatophoric sac,the spernrato
phore turns again,and its proximal end is foremost in the sac and enrerges first
from the penis . The sperm ropes,enclosed in their sheaths
,and with the flasks
attached are deposited in a closely packed cluster in the depression of the buccal
membrane of the femal e . One can scarcely bel ieve that the penis can be extended
to such a l ength that it protrudes from the mantle and deposits the spermatophores
in the buccal p i t,and one i s tempted to bel ieve that they are deposited with
the aid of the hectocotylus . T he mechanism of the disch arg e and the function
of the parts of the spermatophore are not understood . The d ischarged sperma
y
0 1
tephores i n the buccal p i t consist of the sperm rope , enclosed in i ts membrane,
and the flask ,with a smal l po rt ion of the neck and tube . The anterior end of
the rope is attached,probably by means of a sticky substance upon the knob
l ike process above mentioned ,to the buccal membrane . The spermatozoa escape
gradual ly through the flask . T he spernratophores taken from the penis usual ly
d ischarg e and attach themselves to the wal l s of the mantle chamber,or to the
receptacle in which they are placed . By observ ing fresh sperrrratophores in a
watch glass,the d ischarge can be seen
,but it is so rapid that one can only
record the result . The discharg es Obta ined in th is w ay ,vary considerably and
may not be normal . Usual ly the case breaks at or near the distal end and the
sperm rope with the flask apparatus escapes . The prox imal end of the sperm
rope turns aw ay from the case and fixes i tsel f to a neighbor ing obj ect,while
the flask tube remains attached for a time to the case . T he expansion of the
spring is chiefly radial,serv ing to evert the fi lament S O that the th icken ing
becomes external . The flask tube breaks not far from the flask and the sperm
escape as rapid ly as they can free themselves from the rope . The use of the
fi lament and the complex tel escoped tubes,and the st imulus which causes the
spermatophore to d i scharge are unknown . The force necessary for the discharge
of the spermatophore i s furn ished by the elasticity of i ts capsule .
B . The femal e reproductive system .
The female organs of reproduct ion are the ovary,the oviduct with its
glandu lar portion,the ov iducal gland
,a pai r of n idamental and of accessory
nidamental glands,and the buccal p it
,or
“ copulatory pocket” .
The ovary,l ike the testis
,i s a median organ
,but it i s considerably larg er
than the testis . Each ovum is carried in an oval fol l icle upon a slender stalk
fornred mainly by the blood vesse l s of the fol l icle,and these stal ks are clustered
upon the larg er bloodvessels as grapes upon the stem . BERG MANN has shown that
the ova of Cephalopods ari se from cel l s of the coelom ic epithel ium,each of
which migrates into the underlying connective t issue,carrying with it one or
ni ore epithe l ial cel l s which d i v ide rapidly and form the foll icular epithe l ium .
Each ovum increasing in size by growth and by the addition of yolk,is forccd
out of the ovarian stroma into the coelom,and carri es with it a peritoneal and
a connective tissue sheath . The blood vessel s of the fol l icle form a compl ex
capi l lary netw ork around the ovum and the larger vessels fornr ridges which
proj ect into the surface of the ovum . The chorion appears first in the form of
isolated granul es which final l y unite to form a firm Sheet . The micropyle l ies
at the end of the ovum opposite the stalk and,as the connective tissue sheath
is much th inner around the micropyle ,the free end of the ovum seems to
5 2
pro j e c t o u t of a cup- l ike foll icle . T he egg i s oval , te lo lecitlral , and the protoplasm ,
w hich forms a cap under the nricropyle ,extends further downward on one side
of the egg than on the opposite S ide which is somewhat flattened . The flattened
s ide of the egg becomes the posterio r , the side opposite becomes the anterior,
su rface of the embryo .
The oviduct, (Plate I I Figs . 18
,14) l ike the sperm duct , l ies upon the l eft
side of the body . It consists of three portions,the internal ov iduct
,the oviducal
gland and the external o viduct . The first i s a broad,
flattened,thin wal l ed and
sl ightly muscu lar tube which passes forward from the ci l iated funnel,its internal
Opening,to the oviducal gland
,doubles upon itself in a large dorsal Ioop
,and
then enters the ov iducal gland oblique ly from i ts outer side . The entire i nternal
oviduct is peristalt ical ly contracti l e ; its proximal portion and probably the entire
duct is ci l iated . T he three segments of the internal oviduct l ie side by side and
partial ly overlap one a nother .
The ov iducal gland is merely a glandular en largement of the ov iduct . It is
large,oval
,flattened
,and is prolonged into the flaring external oviduct. .Its large
vertical lenticu lar cavity extends nearly to the outer wal l of the gland and d iv ides
it somewhat obl iquely into a Short outer and dorsal segment and a longer inner
and ventral segment which is continuou s with the external oviduct . The outer
segment is perforated near its m iddl e by the internal ov iduct,and the cavity of
the external oviduct extends forward from the m iddle of the inner segment .
The thick wal l of the gland is formed of a vast number of th in curtai n - l ike
septa which extend directl y inward from the exterior to the lumen of the gland .
They form in each segment a single series which extends from the fore end of
the segment around the opening of the internal or external oviduct to the oppo
site side of the same end of the same segment,and S i nce the septa are nearly
perpendicular to the cavity of the gland and of the ov iducts,they are trans
verse ly placed ventral ly arrd radiate from the ov iducts dorsal ly . Each lamella is
covered with a columnar epithel ium which secre tes the mucin or pseudonru cin
of the egg capsule and probably part of that of the egg case . The free edges
an d probably the entire surface of the lamel lae are ci l iated .
The external ov iduct i s a muscular tube whose distal end i s obl ique,
flaring
and more or l ess folded .
The nidamental glands cover the lower surface of the v iscera from the base
of the rectum to the end of the posterior aorta . Their structure is s im ilar to
that of the oviducal gland except that thei r lumina are l ongitud inal and their
lame l lae transverse . The glands together form an e l l iptical flattened mass . Each
gland is l inear except that its outer angles are qu ite rounded . In transverse
53
section each gland i s tr iangular . I ts inner surface is adhe rent to the corre
spond ing surface of the other gland ; i ts upper surface is attached to the v isceral
mass and i ts lower surface faces the mantle cavity . T he flattened longitudinal
lumen extends from the lower inner angle of each gland to i ts upper surface
near i ts outer angle and div ides each gland into two approximately equal and
sim ilar segments .
The accessory n idamental glands are smal l,oval
,l ight - brown masses mottled
with brick red,which l ie on each side of the base of the rectum in front of
the n idamental glands . T he function of these glands is unknown . but it is
be l i eved that they contribute to the formati on of the egg cases .
The ova are probably ferti l i zed within the cavity of the oviducal gland,the
sperm having entered the mantle cavity with the respiratory water . V I A L L E T O N ,
however,bel ieves that the sperm enter the egg case as
,emerging from the
siphon,it passes between the bases of the fifth arms and over the buccal p it .
The eggs are deposited i n elongated gelatinous cases which contain from 50
to 200 eggs,each invested by a spherical capsule . The material of the cases
has been found by VO N FuRT H to be sim ilar to the pseu domucins found in ovar ian
cysts . Each case is attached by a moderately short stalk,which is prolonged
into the body of the case as a tapering core and which is also continuous with
the sheath of the case . T he stalk and core are formed of a sheet of mucin
which is wound in a l eft - handed spiral . Its outer edge is more loosely wound
and stretches obliquely from the core to the sheath of the case,en closing be
tween its successive turns a single row of eggs . The eggs of this closely wound
spiral are separated at i rregular distances at the base of the case . but towards
its middle they are spaced at regular intervals so that they almost form longi
tudinal as well as obl ique rows . There are seven or e ight eggs in each of the
15 to 20 turns of the row,there be i ng in al l 150 to 2 00 eggs in a wel l devel
Oped case . T he core ends about one fourth the length of the case from its
distal end and consequently the eggs beyond th is point are i rregularly crowded
together at the end of the case . The extent and perfection of the spiral core
varies considerably even in the cases of a& single clu ster and i ts existence has
not,we bel ieve
,been noticed prev iously .
The structure of the egg case suggests something of its manner of formation
w hich has not been understood . The unferti l i zed eggs enter the lenticular cavity
of the oviduct from the middle of its ou ter side,and
,i f the secretion of the
gland commences some time before they begin to enter this cavity and i f the
cil ia upon the edges of the lamellae of the gland strike outward and to the left,
the secretion would be rol led into a sol id strand . Furthermore . i f after such a
5 4
strand had begun to form,the eggs emerge from the middle of the wal l of the
gland . they would be caught betw een the successive layers of the continuously
forming sheet and would be carried away in a spiral row . Final ly,if we sup
pose that eggs continue to emerge into the cavity of the ov iducal gland for some
time after the cessation of its greatest activi ty,they would not be enclosed
between the folds of the completed core,but would l i e free in a cavity contai n
ing the l ess dense mucin produced by the gland at the end of the period of activ
i ty ; and as the core of the case,with the eggs partial ly buried in its surface
passes the mouth of the nidamental glands,it probably receives the sheet of
mucin which forms the sheath of the case . The capsu l e of each egg is probably
produced by the oviducal gland . The egg cases are attached in clusters to fixed
obj ects on the bottom and,since a singl e cl uster may contain as many as 1 75
cases and approximately eggs,it is probable that several females
contribute to the formation of each cluster . The appended table records the si ze
of and number of eggs in three typical egg cases .
Length of case,
m .m .
stalk
D iameter of case
stalk
Number of eggs
Length of eggs m .m .
Diameter
Length of egg capsule
Diameter
T H E VA S CU L A R SYSTEM . (Plate I , Fig . 6 ; Plate II F igs . 8,
The vascular system of the squ id is double , cl osed ,and almost perfectly
symmetrical . The arterial bl ood goes out from the systemic heart by either of
three aortae,
the anterior (I) the posterior (II) and the genital (I II) ; from
these i t flows into pai red arteries,capil laries and veins . The venous blood from
the system ic veins may flow entirely in lateral vesse l s or for a short time in
the median anterior vena cava (VI ) or the genital vein It final ly flows from
the lateral nephrid ial vessel (V) into the r ight and l eft branchial hearts . The
blood from the branchial heart flows through the branchial artery (VI I I) to thecapi l lari es of the gi l l and from them the blood
,now arterial , passes thru
the branchial vein (IV) to the systemic heart .
55
T H E SYSTEM IC C IRCULATION .
T H E HEART . T he heart i s a lozenge - shaped,one - chambered
,muscular sac
which l ies mesial ly in the coelom behind the intestine , below the stomach and
caecum,and above the nephridium . Five vessels commun icate with it . They are :
the two large branchial vei ns which enter i ts rounded lateral angles ; two large
median vessels,the anterior and posterior aortae
,which leave the con ical anterior
and posterior proj ections of the heart : and the smal l gen ital aorta which arises
from the ventral edge of the heart . The heart is not qu ite symmetrical ; its
ventral portion and the anterior aorta which arises from it be ing d isp laced
toward the right by the intestine . The exterior of the heart is covered by the
peritoneum or coelomic epithel ium . Its interior is probably l ined by an endothe
l ium and i ts wal l is formed by interlacing muscle fibres between which the
b10 od penetrates some distance . The venous blood is co llected from the tissues
of the heart by two or three veins which are probably connected with capil laries .
The muscle fibres have the character of smooth muscle except that they exhibit
a fai nt striation . MARCEAU,in h is beautiful work upon the structure of the heart
of molluscs,shows that the muscl e fibres of the heart of Cephal opods are l ong
,
cy l indrical and branched . The bran ches of each fibre anastim ose with those of
ot her fibres forming a complex mesh . The fibres,l ike those of the mantle
,
c onsist of a sheath of fibri llae separated by sarcoplasm and a core of cytoplasm
contai n ing the nucleus , but the fibri llae of the cardiac muscl es are paral l e l to the
fibres and are not homogeneous since the striati on is transverse,not obl ique and
is due to the differentiati on of the fibri llae into the structures which in trans
v erse rows form the l ight (isotropic) band div ided by K RA U S E’s membrane and
the dark (an isotropic) band divided by H E N S E N’s l ine . The heart has four valves : a
pai r of semilunar flaps at the end of each branchial vein prevent the return of
blood into the gil l ; a single semi lunar valve at the origin of each of the large
aortae checks the re - fl ow of b lood to the heart .
T H E ANTERIOR AORTA . The anterior aorta arises just inside the v i sceral wal l
a l i ttle in front of the base of the gill . At first i t l i es in the r ight nephrid ia l
wal l,then having been j o ined by the oesophagus
,i t pierces the l iver obl iquely
between the hepatic ducts and emerges in a shal low groove on the upper
surface of the l iver . The aorta with the oesophagus passes forward in this
groove unti l i t ends near the skull in tw o terminal branches . Near i ts
origin the aorta gives off an artery which div ides into four branches and
5 6
suppl ies the pancreas,stomach
,and caecum ; one branch (d ) enters the pancreas ;
one (it) crosses the lower surface of the lower caecal lobe,passing close to
the splanchnic gangl ion,
and then ram ifies over the outer side of the
stomach ; another (b) suppl ies the adherent inner wal l s of the stomach and
caecum ; and the last (c) passes to the outer sid e of the caecum and suppl ies
the caecal folds . A pai r of important arteri es arises from the aorta as i t emerges
on the ante rior surface of the l iver . Each of these immediately d iv ides in to
several branches ; two or three enter the l iver two or more supply the
nuchal and siphonal retractors one branch passes through the supporting
membrane of the gi l l to the branchial gland and the gil l ; another branch
passes through a canal in the mantle w ith the nerves of the fin,to an arterial
plexus (92
) on the upper surface near the dorsal end of the mantle . The latter
artery has a remarkable length compared to its size and has a theoretical
interest which wi ll be discussed later . One of i ts branches anastomoses
with the arteries of the ventral end of the fin,and other branches go to the
mantle . The arteri es of the siphonal retractors enter these muscles near the
middle of the i r length and each div ides into a dorsa l and a v entral branch .
These two b ranches form a l ongitudinal trunk from which smal l arteri es radiate
to the fibres of the muscle . Near the dorsal end of the nuchal carti lage a
median artery arises from the aorta . I t immediately bifurcates and each
branch,after giv ing off smal l branches to the nuchal retractor
,passes through
that muscl e at the edge of the cartilage and enters the mantle under the
ste l late gangl ion to supply the upper ventral'
portion of the mantle . Several
smal l and inconstant arteries arise from the aorta al ong i ts course and supply
such adjacent structu res as muscles,oesophagus
,or l i ver .
The aorta forks near the skul l and the branches passing around the
oesophagus unite behind it,forming an oesophageal arterial r ing . Ten vessels
arise from this r ing : four pai rs ; muscular , optic , pharyngeal , and siphonal ; a
median,the pedal ; and an azygos artery
,the sal i vary . The upper part of the
ring l ies i n the l i ver case and the lower part in the skull . Just before each
term inal branch of the aorta enters the skul l i t bears a, ,peripheral heart
which wil l be discussed later . The origin of the first pai r of arteries of the
ring the muscular is qu ite variabl e,sometimes the arteri es arise at the
bifurcation of the aorta and sometimes j ust distal to the peripheral heart . The
arteries suppliy parts of the l iver and the cephal ic retractors . The sav i larv
artery arises from the left vessel at the distal end of the peripheral heart
and passes back to the sal ivary gland . Just beyond the peripheral heart each
terminal branch of the aorta enters the skul l by passing through the fascia which
58
rectum . In the female the latter al so supplies the nidamental and accessory glands .
A pai r of vessels (32) pass to the branchial hearts and thei r pericard ia . An unpai red
artery (42) arises from the left side of the aorta or from the left vessel of the
preceding pai r to supply the organs of the genital duct,viz . the spermatophoric
sac . the vas deferens,the spermatophoric gland ,
and the pen is i n the mal e,or
the oviduct and oviducal gland in the femal e . After giving off these branches the
aorta div ides in to three terminal arteries,the right
,l eft
,and median pal l ial
arteries . The median mantl e artery (62) passes in mesentery - l ike median fold across
the pal l ial chamber to the lower side of the mantl e . It suppl ies the lower ventral
part of the mantle . The lateral pal l ial artery (52) passes obl iquely across the
v isceral mass between the peritoneum and the integument to the edge of the
pen near the ven tral end of the gonad . Here i t l eav es the v isceral mass and,
after giv ing off tw o arteries to the mantle expands i nto a peripheral heart
as i t enters the mantle . One pal l ial branch passes forward in the tissues of the
mantle ; the other passes backward giving off many branches to the mantle and
passes through i t to the arterial pl exus at the dorsal end of the mantle
The trunk (82
) of the artery p asses obl iquely through the mantl e and enters the
m iddl e of the base of the fi n . As soon as i t enters the fin this vessel divi des
into two bra nches which pass beside the carti lage to the dorsal and ventral
angles of the fin . Some of the dorsal branches anastomose with the vessels of
the pl exus (92
) which covers the anterior dorsal su rface of the mantle . This
plexus is formed by the anastomosis of these vessels with branches from the
lateral mantl e arteries (72
) and from the anterio r aorta .
The arteri es of all parts of the squ id anastomose freely so that an i nj ection
from one artery wil l fi l l two or three others : for example , an inj ection from
the anter ior aorta wil l fill the median mantle artery and an i nj ection of the
right mantl e artery wi l l fil l the l eft artery . The wal l s of the arteri es have three
coats ; an endothel ium ,a layer of circular muscl e fibres
,and a sheath of connective
tissue . The aortae and their larger branches are peristal t ical ly contracti l e and their
muscular fibres are short , fusi form ,and distinctl y cross - striated . The muscle fibres
of the smal l er arteries and arterio les are plain and those of the latter are irregu
larly distributed so that their contraction makes the vessels moni l iform . The large
veins , readi ly d ist inguishabl e from the arteri es because of their thinner wal l s,
are al so peristal tical ly contracti l e but i t has not been determined whether or not
the fibres are striated . The arterioles communicate with a complete system of
capil laries but there are no blood - spaces o r lacunae . The so - cal l ed “ peripheral
hearts occu r upon all the large arteries that l eave the mantl e i .e . upon the fin
vessel s and the terminal branches of the anter ior aorta. The peripheral h eart is
59
a smal l oval body formed by the thickening O f'
the circular muscular coat . Its
lumen is no larger than that O f‘
the artery . An i nj ection mass cannot be driven
past these “ hearts when they are contracted . Their function undoubtedly is to
prevent the transmission Of an excessive blood pressure to the head and fins,
for i t is ev ident that,during the contraction of the mantle
,the viscera are
subj ected to great pressure . If the per i pheral hearts contract in a degree coordi
nate with the contraction of the mantle,the blood pressure in the extrapal lial
vessel s is not d isturbed even by the most violent contractions O f the mantle .
T H E VE i N s . (Plate II fig . The distribution Of the smal l er veins is in general
very similar to that of the corresponding arteri es and usual ly the smal l er branches
of the arteries,veins
,and nerves correspond cl osely to one another bu t the larger
venous trunks have an arrangement total ly d ifferent from that O f the arteri es .
T he arterial system is large l y med ian and anterior or antero - dorsal i n reference
to the al imentary canal ; the venous system is largely bilateral and is posterior
or postero - ventral to the al imentary canal . Moreover the venous system is charac
terized by the great s ize Of its vessel s which form large s inuses and by the
special ization Of a portion Of its central vessels in connect ion with the excretory
organs the nephridia . These organs are formed by the modification O f the wal l s
Of a large sinus which is - shaped l ike the l etter V and i s enclosed in the ne
phrid ial sac . The nephrid ial sinus rece ives the median anterior vena cava and
five or six paired veins : the posterior vena cava,the anterior pal l ial veins , the
splanchnic,the rectal
,and in the femal e the n idamental veins .
T H E POSTER IOR VENA CAVA (VI I Plate II figs . 8 and 9) is a large ,pear- shaped
v essel whose larger end Opens into the nephrid ial sinus,and which is formed
near the peripheral heart Of the lateral pal l ial artery by three ve ins arising
from the fin and from the mantle behind and in front O f i ts point O f origin .
I t crosses the lower surface Of the v isceral mass,on the outer side Of the cor
responding artery,and enters the corresponding arm Of the nephridial sinus
near the end of the posterior aorta .
T H E ANTER IOR VENA CAVA AND ITS TR I BUTAR IES . Each arm has tw o longitud inal
veins ; one in its central canal w ith the brachial artery and nerve and one on
its inner surface between the tw o rows Of suckers . These twenty brachial veins,
meet in a large,thin
,oval brachial sinus (7
6
) below the pharynx . This sinus
Opens near the dorsal end Of the pharynx into the outer buccal sinus (96
) which
surrounds the pharynx and extends from the base O f the peristomial membrane,
from which it receiv es blood,to the entrance O f the skul l where i t opens into
the inner buccal sinus I t contains the rotators O f the pharynx and the
retractor mandi bu l i . The inner sinus (86
) i s separated from the outer by the
pharyngeal re tractor which is attached to the equato r of the pharynx . It rece ives
b lood from the organs of the pharynx and is prolonged dorsal ly i nto the canal
w hich transmits the oesophagus through the skul l . A sinus,the cephal ic
which surrounds the oesophageal nerve ring communicates with th i s canal but I
have not been able to l ocate the exact Opening . This canal opens on each side
i nto the Optic si nuses through a smal l foramen j ust behind the Opening Of the
outer in to the inner buccal s inus (Plate I II Fig . 1 7,
The Optic sinus (56
)
encloses the Optic gangl ion and embraces the inner surface of the eye from which
it receives a number Of veins . These veins are grouped along the upper and
l ower margins O f the sinus where i t i s not overlaid by the white- bodies which
are wedged i n between the eye and the Optic gangl ion . A large vein col lects
blood from the i ris and from the outer portion O f the inner coat O f the eye and
passes over the upper part Of the eye with the corresponding artery to enter
the Optic sinus . A large vein passes from the Optic sinus through the lower part
Of the lateral plate of the skul l to meet a vessel from the Opposite sinus . These
two vessels from the Optic sinuses form the anter ior vena cava and the wal l
intervening between the vessels bears a pai r O f vertical fol ds wh ich form a
val ve that prevents the return O f blood to the head . This val ve is n ecessary in
order that the blood in the large venous sinuses under the visceral mass mav
not be forced into the head by the contraction of the mantl e and hence we
must associate it functional l y with the peripheral hearts”
. The val ve is so effective
that an i nj ection mass can seldom be forced in to the head through the anterio r
vena cava and for this reason the venous system is best inj ected through the
buccal sinuses .
The anterior vena cava (VI ) i s a large,contracti l e median vessel situated
under the l iver case . The ventral third Of the sinus l ies between the siphon and
the l i ver,i ts middl e portion l ies between the siphonal retractors upon the lower
surface O f the vi sceral mass,and its dorsal portion runs above the ink sac to i ts
dorsal end and there Opens into the nephridial sinus . In addition to several smal l
veins from the siphon and l iver case,the anterior vena cava receives ; a pai r O f
veins from the ink sac a large med ian vein from the l iver and a vein
from the sal i vary sinus This sinus surrounds the sal ivary gland ,receives
b lood from that gland and the neighboring portion Of the l iver,and Opens into
the anterior vena cava between the sku l l and the post- cephal i c carti lage . Just
behind thi s Open ing the anterior vena cava expands into an oval chamber whose
si ze and position correspond to the outl ine Of the carti lage . The venous blood
from the two - thirds O f the l iver ventral to the canal for the oesophagus and the
aorta is collected by two median veins which run backward on the upper and
lower surfaces of the l iver. T he upper ve in enters the l iver w ith the oesophagus
and passes more directly through the l i ver so that i t emerges on the lower
surface some distance in front of the exit of the oesophagus and hepatic ducts .
The hepatic: vein,formed by the union of the upper and l ower veins
,passes
through the l iver case and enters the anterior vena cava obl iquely so that the
lower wal l of the ve in forms a val ve .
The b lood from the dorsal thi rd Of the l iver is col lected by a pair of veins
which arise near i ts dorsal point and pass forward to the hepatic duets with
which they enter the nephridial sac . O ne of these vessel s is often smal l or absent
whi le the other is correspondingly large . Within the nephridial sac these veins
pass along the outer wal l of the pancreas,receiving blood from it
,unti l near its
m idd le where they meet other veins . T he right vein unites with the large,
median,geni tal vein (5
5
) which passes with the genital aorta between the
stomach and caecum,receiving venous blood from the stomach and from the
inner wal l of the caecum . It empties into the right arm of the nephridial sinus .
The left vein un ites with a vessel from the caecal fo lds (55
) and with a vei n
from the intestine and then passes out of the pancreas to the l eft arm of the
nephridial sinus .
A pai r O f smal l veins (15
) passes backward from the sides of the rectum
and enters the l ower side of the nephridial s inus almost opposite the entrance Of
the preceding vessels .
Three or four smal l ve ins (45
) from the systemic heart empty into the
nephridial sinus .
The ventral lateral pal l ial vein, (6
5
) formed by the ve ins of one side of the
ventral portion of the mantle,runs backward paral l el to and outside of the
supporting membrane of the gil l . At the base of the gil l i t turns abruptly inward
and,after receiving two vessel s from the gil l and passing above the branchial
heart,enters the nephridial sinus . One (7
5
) Of the veins from the gi l l comes
from the nerve and muscle which l ie within the gil l,the other (8
5
) comes fromthe center O f the branchial gland . The left mantle vein as i t passes over the
branchial heart receives a ventral vein (95
) from the penis or external oviduct
and a dorsal vein from the vas deferens,spermatophoric gland ,
and spermato
phoric sac or from the oviduct and oviducal gland . A vein (1 15
) corresponding
to a branch Of the anterior aorta arises from the venous plexus at the back
of the mantle and passes through the mantle in a canal with the fin nerve to
j oin the ventral mantle vein .
T H E N EPHR ID IAL S INUS . (V) . The median portion of the V - shaped nephridial
s i nus or precava rece i ves the blood from the anterior vena cava and the ends
pharynge al retrac to r which is attached to the equato r of the pharynx . It receives
blood from the organs of the pharynx and i s prolonged dorsal ly into the canal
which transmits the oesophagus th rough the skul l . A sinus,the cephal ic
w hich surrounds the oesophageal nerve ring communicates with th i s canal but I
have not been able to l ocate the exact Opening . This canal Opens on each side
i nto the optic sinuses th rough a smal l foramen j ust beh ind the opening O f the
outer in to the inner buccal s inus (Plate I II Fig . 17,
The Optic sinus (56)
encloses the optic gangl ion and embraces the i nner surface of the eye from which
it receives a. number of veins . These veins are grouped along the upper and
l ower margins of the sinus where it i s not overlaid by the white- bodies which
are wedged in between the eye and the Opti c gangl ion . A large vein (46
) col lects
blood from the ir is and from the outer portion of the inner coat of the eye and
passes over the upper part of the eye with the corresponding artery to enter
the Optic sinus . A large vein passes from the Optic sinus through the lower part
of the lateral plate of the skul l to meet a vessel from the Opposite sinus . These
tw o vessels from the Optic sinuses form the anterior vena cava and the wal l
intervening between the vesse l s bears a pai r of vertical folds wh ich form a
val ve that prevents the return O f blood to the head . This val ve is necessary in
order that the blood in the large venous sinuses under the v isceral mass mav
not be forced into the head by the contraction of‘
the mantle and hence we
must associate it functional l y with the“ peripheral hearts
”. The val ve is so effectiv e
that an inj ect ion mass can seldom be forced in to the head through the anterior
vena cava and for this reason the venous system is best inj ected through the
buccal sinuses .
The anterior vena cava (VI ) i s a large,contracti l e median vessel situated
u nder the li ver case . The ventral third of the sinus l ies between the siphon and
the l iver,i ts middle portion l ies between the s iphonal retractors upon the lower
surface of the vi sceral mass,and i ts dorsal portion runs above the ink sac tO i ts
dorsal end and there opens into the nephridial sinus . In additi on to several smal l
v eins from the siphon and l iver case,the anterior vena cava receives ; a pai r Of
veins from the ink sac a large median vein from the l iver and a vein
from the sal i vary sinus This sinus surrounds the sal ivary gland,receives
blood from that gland and the neighboring portion of the l i ver,and Opens into
the anterior vena cava between the skul l and the post- cephal i c carti lage . Just
behind this Open ing the anterior vena cava expands into an oval chamber whose
si ze and position correspond to the outl ine of the carti lage . The venous blood
from the two - thirds O f the l i ver ventral to the canal for the oesophagus and the
aorta is collected by two median veins which run backward on the upper and
lower surfaces of the l iver . T he upper vein enters the l iver with the oesophagus
and passes more directly through the l iver so that i t emerges on the lower
surface some distance in front of the exit Of the oesophagus and hepatic ducts .
T he hepati c vein , formed by the un ion O f the upper and lower ve in s,passes
through the l iver case and en ters the anterior vena cava obl ique ly so that the
lower wal l of the vein forms a valve .
T he b lood from the dorsal third O f'
the l iv er is col lected by a pair of ve ins
(25
) which arise near i ts dorsal point and pass forward to the hepatic duets with
which they enter the nephridial sac . One O f these vessel s is often smal l or absent
whi l e the other is correspondingly large . Within the nephridial sac these ve ins
pass along the outer wal l Of the pancreas,receiv ing blood from it
,unti l near i ts
m iddle where they meet other ve ins . The right vein unites with the large
median,geni tal ve i n (5
5
) which passes with the genital aorta between the
stomach and caecum,receiving venous blood from the stomach and from the
inner wal l of the caecum . It empties into the right arm of the nephridial sinus .
T he l eft vein un ites with a vessel from the caecal fo lds (55
) and with a vein
from the intestine and then passes ou t of the pancreas to the left arm of the
nephridial sinus .
A pai r of smal l veins (15
) passes backward from the sides of the rectum
and enters the l ower side of the nephridial sinus almost opposite the entrance Of
the preced ing vessels .
Three or four smal l ve ins (45
) from the systemic heart empty into the
nephridial sinus .
The ventral lateral pal l ial vein, (6
5
) formed by the ve in s of one side of the
ventral portion of the mantle,runs backward paral l el to and outside of the
supporting membrane of the gil l . At the base of the gi l l i t tu rns abruptly inward
and,after receiving tw o vessels from the gil l and passing above the branchial
heart,enters the nephrid ial sinus . One (7
5
) of the veins from the gil l comes
from the nerve and muscle which l ie within the gil l,the other (8
5) comes from
the center Of the branchial gland . The left mantl e vein as i t passes over the
branchial heart receives a ventral vein (95
) from the penis or external oviduct
and a dorsal vein from the vas deferens,spermatophoric gland ,
and spermato
phoric sac or from the oviduct and ovidu cal gland . A ve in (1 15
) corresponding
to a branch of the anterior aorta arises from the venous plexus (92
) at the back
of the mantle and passes through the mantl e in a canal with the fin nerve to
joi n the ventral mantle vein .
T H E NEPHR ID IAL SINUS . (V) . The median portion of the V - shaped nephridial
s inus or precava receives the blood from the anterior vena cava and the ends
6 2
of the two arms O f the sinus are continuous with and receive bl ood from the post
erior vena cava . E ach arm Opens in to the ventrO - internal portion of the bran
chial heart which l i es j ust external to the dorsal thi rd of each arm . The median
portion of the sinus is bounded be l ow and behind by the angl e of the gut
formed by the rectum and intestine,i n front by the i nk sac . and above by the
pancreas. The remainder O f the sinus l ies under the pancreas,the heart
,the
d igestive sacs and ,i n the femal e
,above the nidam ental glands
,or i n the mal e
,
j ust above the pal l ial chamber .’
The intestine passes between the two arms of
the sinus as they turn inward to unite with each other and with the anter ior
vena cava . The sinus passes through the nephridial sac and i s only attached to
the nephridial wal l s by its ends and by a narrow band of fascia along the upper
surface of the arms . Faussek has described a pai r of tubular,longitudinal cavities
in the mesoderm of the embryo from which the coelom and the n ephridium
arise . Each tubular cavity soon after its appearance becomes differentiated i nto a
thin -wal l ed dorsal portion which forms the coelom and a narrow thicker wal l ed
ventral portion which communicates with the exterior and becomes the ne
phrid ium . This nephridial tube original ly has no connection with its mate or
with the venous system but as the embryo deve l ops each nephridial cavity
enlarges so that its wal l s become moulded over the surface O f the pancreas , the
intestine, and the veins . The tw o n ephridial cav ities become confluent by the
absorption of their opposed wal ls . In the adul t the nephrid ial sac has the
shape of a. retort whose neck is vertical ly flattened and i s bi lobed . The body of
the flask occupies the greate r portion of the visceral mass between the heart
and the digesti ve sacs beh ind,
and the l i ver and the ink sac in front , and
contai ns the pancreas , the intestine , and a part of the n ephridial s inus . The
neck,
conceiv ing the retort to be inverted,i s d irected backward beneath the
heart and digestive sacs , and i n the female between them and the nidamental
glands . I t contains the arms of the nephridial sinus which are separated dorsal l y
by what remains of the original septum between the nephridial cavities . Conical
tubu lar canals lead from the coe lom to the nephridium passing obl iquely for a
short d istance i n the wal l between the sac and the pal l ial chamber . The canal s
pass into the nephridium j ust above the branchial veins and at the j unction of
the flask with the neck . By this arrangement the i nner wal l of the canal forms
a val ve which prevents the escape of fl uid from the nephrid ium into the coe lom .
The nephridial sac Opens upon the lower surface through tw o papi l lae , which l ie
one on e ither side of the base of the rectum . T he l ining of the nephridial cavi ty
is reflected over al l the structures within the cavity and,except where it covers
the ven ous vessels,i s a ci l iated pavement epitheli um . U pon the sinus and the veins
G4
the anu s . This papi l la gives off al ternate buds from its tip and each bud soon
forms a triangular sheet whose inner and outer margins are formed by a second
ary b ranchial vein and artery . The surface of this sheet grows much more
ra pidl y than the vessels and so it i s throw n into folds'
whose axes are perpen
d ic u lar to the vessels . A tertiary artery forms in every angle Of the folds and a
tert iary vein deve lops in the middle of each fold . T he surface continues to grow
more rapid ly than the vessels and is thrown into a second series of folds whose
axes are perpendicular to those of the first fold . The capi l lar ies of the gil l l i e i n
the fol ds between the tertiary vessels . The bl ood passes from the secondary artery
at the outer edge Of the pinna i . e . the edge towards the mantle into the tertiary
arteries at the edges of the primary folds and from them flows through the
capi l laries toward the center of the fold and i nto the tertiary vein at the middle
of each fold .
The gil l final lv becomes a l ong pinnate structure which l ies beside the l iver
in the pal l ial chamber and extends from the heart to the entrance of the siphon .
The water entering the mantle over the lateral s iphonal val ve passes over and
through the gil l . The gil l proper consists of two longitudinal vess e ls,the branchial
artery and vein,which bear a large number of al ternating pinnae . The latter a re
moulded over a muscular and glandu lar core so that the gi l l is tri hedral . The
two angl es toward s the mantle are formed by the ends O f the two rows of
pinnae and the thi rd , formed by the branchial vein ,i s d irected toward the
l i ver . The branch ial ve in is separated from the artery by a w ater canal which
communicates with the pal l ial chamber between the pinnae . On the outer side
O f‘
the artery the branchial n erve cord and a vein of the systemic c irculation run
the l ength of the gi ll . T he branchial gland,which is enclosed in a sheath of
fascia,l i es between the nerve and the mantl e . Bands of muscl e attached at the
base of the gil l partly to the mantle and partly to the viscera l mass l ie above'
and below the nerve,vein
, and gland . They form on e of the ch i ef connections
betw een the mantle and the v iscera . A thin extensi le sheet of i ntegument
attaches the gi l l to the mantle . This sheet reaches almost to the tip of the gil l
and i s n ecessarv to hold the gil l up aga inst the water ru shing into the pal l ial cav ity .
Each pinna i s attached to the core of the gi l l by a triangular sheet of
fascia which is fastened tO the secondary artery at the l ower edge of the pinna.
The free edge of this membrane is stiffened by an acicu lar rod of chitinous
nature whose broadened base is attached to the side of the gland and whose
apex is fastened to the tip of the pinna The rod is secreted by a tube of
cvl indrical cel ls . BURNE finds in Sepia that these rods are formed of typical cartilage .
The gil l grows continuously at the tip and at the ends of the pinnae so
that the latter become gradual ly smal ler towards the apex of the gil l . Each of
the al ternating branches of the branchial artery (VI II) passes around the canal
of the gil l and j o ins a zigzag longitudinal artery (18
) which is on the same side
of the canal with the branchial vein and so Opposite the artery . In this waythe canal is surrounded by a series of al ternating semicircular vessel s which
unite the longitudinal arteries . Near the middle of each semici rcu lar vessel the
larger portion of each branch of the branchial artery passes out at right angles
to the canal and forms the outer edge of a pinna.
The branchial artery and vein,the anterior and posterior vena cava
,and
the larger branches Of these vessels are peristalt ical ly contracti l e .
D H RERE has found that the oxygen - carrying power of the blood of cephalopods
i s directly proportional to the amout of copper in the blood . The blood coagula
tes re adily and firmly . The blood corpuscles are not numerous i n the blood and
they resemble the lymphocytes of higher an imals .
PROBLEMATIC DU CTLESS G LANDS AND THE BODY CAVITIES .
T he branchial or blood gland,and the “ white bod ies are both isolated
masses of tissue and are probably bl ood glands . The former is long and somewhat
flattened,and forms the center of the core of the gi l l . It is composed of large
oval or cuneate cel ls,radial ly arranged around the bl ood vessels
,from which
they seem to be separated by a vascu lar endothel ium . JO UBI N,however
,bel i eves
that the gland cells form the entire wal l Of the blood vessels . The glan d has no
apparent physiological connection with the gi l l and is not connected with it except
thro ugh a branch of the anterior aorta which passes through the gland and
anastomoses with the branch ial arteries .
The four white bodies (Plate II I Fig . 22,W . B. & W . are compact and
smooth and are wedged in between the optic gangl ia and the eyes . One l ies above
and behind each Optic nerve,another below and i n front of i t . The glands are
richly vascular and their veins Open into the optic sinuses which surrou nd the
glands . The cell s of the glands are smal l and are composed of a relatively large
nucl eus and a smal l cel l body . They are very similar to the blood corpuscl es and
are closely packed without definite order . M i toses are very common,and there
seems little doubt that these glands produce the blood corpuscles . The glands
arise from the ectoderm .
T H E BODY C A VI T I E s .
The vascular - system of the squ id,i s l ined throughout by an endothel ium
which is formed of thin fl at cel ls whose edges are i rregular or sinuous . The
muscular and connective - tissue coats of the arteries and veins become gradual l y
th inner as the vessels become smal l er unti l th ey disappear l eaving a vascular
wal l formed solely by the endothel ium . T he vessels thus formed branch and
anastomose profusely so that they make a complex net -work in the tissues . These
vessel s are the capi l laries and may be recognized not only by the simpl icity of
their wal ls but by the fact that repeated d iv ision does not reduce the si ze Of the
vessels . The primary bodv cavity Of mol luscs consists of the unwal led lacunae
and blood - spaces into which the arteries,and from which the veins
,Open . Such
cavities do not ex ist in the squ id unless possibly in the tissues of the h earts .
The sinuses are all l ined by an endothel ium and no tissues except possibl y those
6 7
of the hearts are directly bathed by the bl ood . My most carefu l preparations
have fai l ed to demonstrate an endothel ium on the inner surface of the branchial
and systemic hearts yet both have intrinsic arteries and ve ins which are
probably connected with capi l laries . MARCEAU finds that the wal ls of the hearts
are either covered by an endothel ium or by glandular epithe l ium . T he presence
O f capi l laries in the Dibranchs has been recognized for a long time but it has
not been known whether lacunae i . e . primary body cavities exist . T he
accepted bel ief has been that they are present and are represented in part by
the sinuses Of the head ; but since capi l laries are found in every part O f the
squ id and lacunae in none we mu st believe that the lacunae do not ex ist . The
sinuses cited as examples of lacunae are certainly bounded by an endothel ium .
T H E COELOM . The coelom or secondary body cavity is formed by the un ion
of the dorsal portion O f the pai r of tubular cav ities whose ventral portion forms
the nephridial sac (compare p . The coelom occupies the dorsal half of the
visceral mass and contains the gonad ,the stomach
,caecum
,intestine
,and the
systemic and the branchi-al hearts . It communicates with the exterior through
the cil iated tubes which lead to the nephridial sac and it i s l ined by a cil iated
pavement epithe l i um,the peritoneum
,which is reflected over the organs within
the cavity . The systemic heart is attached to the lower wal l of the coelom by a
mesentery which is fastened al ong the m edian l ine of its lower surface and also
by the peritoneum reflected over the two branchial veins and the large aortae as
they enter the heart . The branchial hearts are enclosed in coelomic evaginations,
the branchial pericardia,which Open into the coe lom through narrow
’
Obl ique sli ts
near the dorsal end of the systemic heart . The gen ital products are shed into
the coelom,from which they are removed by the cil iated funnels of the vas
deferens or the oviduct . There is apparently nothing to prevent the escape of
the genital products from the coelom through the nephridium unl ess the ci l ia of
the peri toneum drive the ova and sperm toward the Opening O f the sexual duct .
The coelom i s not divided,as in some Dibranchs
,i nto a dorsal genital chamber
and a ventral pericardium which are united by a narrow tube . The coelom nor
mal ly holds a smal l amount of fluid which contains a few amoeboid cel ls . I t is
commonly infested by Cestodes which float in a large amount of fluid .
THE NERVOU S SYSTEM .
The nervous system O f the squid (Plates II fig . 15,I II fig . 16 and Text
Figs . 15 and 16 ) is well central i zed and i s almost perfectly b i lateral ly symmetrical .
The nerve cell s are col l ected in thirty - one gangl ia,all but one of which are
pai red,as fol lows :
cerebral
pleural
pedalform i ng the oesophageal r i ng or brai n .
visceral
propedal cl osely connected with the pedal and cerebral gangl ia .
Optic closely connected with the pleural gangl ia .
suprabuccal connected with the cerebral and pedal gangl ia and
infrabuccal forming the buccal ring .
first brachial
fiffdl d
connected w ith the propedal gangl ia and forming the
fourthbrach i al nerve ri ng .
fifth
ste l late connected with the vi sceral gangl ia .
branchialn
splanchnic unpai red i nfrabuccal gangl ia.
The eight gangl ia which form the oesophageal ring are so completely fused
that i t i s almost or qu ite impossible to determine the bounderies of ind iv idual
gangl ia . Moreover,each member of three pairs of gangl ia
,the propedal , infrabuccal ,
and suprabuccal,unites with its fel low in the m edian l in e forming a median gang
l ion . A sim ilar fusion exists in the cerebral,pedal
, and visceral gangl ia so that
each pai r of these and of the above mentioned gangl ia is indiscriminately termed
a gangl ion or a pai r of gangl ia.
The oesophageal ring is enclosed by the skul l and surrounds the oesophag eal
v enous sinu s and the structures that l ie w ith in the sinus . The top O f the ring
i s formed by the cerebral gangl ia,the sides by the pleural gangl ia
,and the
bottom by the pedal gangl ia i n front and the v isceral gangl ia behind . The pedal
gangl ion l ies di rectly below the cerebral and pleural gangl ia and in front Of the
statocysts whereas the visceral gangl ion l ies above the statocysts and behind the
rest of the ring,blocking the oesophageal canal so that the oesophagus makes a
sharp turn upward to pass above thi s gangl ion . The upper and posterior surfaces
o f the visceral gangl ion are covered by a fascia which extends from the edges
of the large foramen of the sku ll to the oesophagus and so separates the brain
and the oesophageal canal from the l iver .
The cerebra l ganglion gives off tw o pai rs O f connectives,the c erebropedal
and the cerebro -buccal . The former pass downward and forward around the
o esophagus to the propedal gangl ion ,the latter pass forward above the oesophagus
to the suprabuccal gangl ion . Thi s gang
l ion al so receives a connective from the
prOpedal ganglion (propedO-buccal connec
t ive) and gives Off a connective which
passes around the oesophagu s to the ih
frabuccal gangl ion . A long pai r of connec
t ives passes from the infrabuccal gangl ion
to the splanchnic gangl ion .
A short large bundle of fibres passes
from the . pedal to the propedal gangl ion ,which al so receives the above m entioned
connectives (cerebro -
propedal and propedo
buccal connectives) and gives off five
pai rs of connectives to the five pai rs of
brachial gangl ia . Connectives un ite the
first and second,the second and third
,
the thi rd and fi fth brachial gangl ia,and
with the commissures between the gang
l ia of the first pai r and the fifth pai r
form the branchial nerve - ring . Careful search has fai led to reveal any connection
between the gangl ia Of the fourth arms (tentacles) and this ring.
The pleural gangl ion,viewed external ly
,is wel l marked and is readi ly
distinguished from the cerebral gangl ion on one hand and from the pedal and
v isceral gangl ia on the other,but a study of the minute anatomy of the so
c al led gangl ion shows that there is very l ittl e ground for cal l ing the mass of
fibres in which a few nerve cell s are scattered a gangl ion . It is real ly a mass
of nerve tracts passing,
a ) be tween the optic lobes through the base of the
cerebral gangl ion,b) from the Optic gangl ion to the cerebral and pedal gangl ia
,
and c) from the cerebral to the pedal and v isceral gangl ia . Nevertheless,i t is
Fig . 15 .
70
co nvenient to re tai n the term,gangl ion
,as a name for th is region of the
oesophageal ring .
The pleural and cerebral gangl ia (with a sl ight exception mentioned below)consist of smal l cel ls whose nuclei vary in diameter between 4 and 7 micra and
whose cytoplasm is scarcely discernabl e,the tissue having a granular appearance
under a low power of the microscope . A smal l lobe of the cerebral gangl ion,
forming the lower part of its front end and surrounding the tracts which pass
out i nto the cerebro - buccal and cerebro -
prOpedal. connectives
,differs from the rest
of the gangl ion in that the cell s are larger . T he nuclei are from 5 to 18 micra
in diameter and the d iameter O f the cytoplasm is tw ice or three times that of
the nucleus . In contrast to these gangl ia,all the other gangl ia of the squid have
a greater or l ess pr oportion of large cel ls whose nuclei vary from 13 to 20 micra
i n diameter and whose cytoplasm has a diameter two or three times as large as
that of the nucleus .
The optic gangl ia have relatively few large cel l s while all other gangl ia have
a fair,though varying proportion O f them . The difference in the size of the cel l s
is very marked and clearly distinguishes the cerebral and pleural and . in a large
measure,the Optic gangl ia from all other gangl ia .
The nerve cel l s are external and the fibre tracts internal in all gangl ia,though
the boundary between them is often very i rregu lar .
The cerebral ganglion is the largest gangl ion Of the squ id with the exception
of the optic gangl ia . I t fi l ls up the concavity of the cerebral process O f the skul l .
The gangl ion ‘ is rounded except that a smal l l ob e from which the cerebro - buccal
and cerebro -
prOpedal connectiv es arise,proj ects forward from its ventral side . N O
nerves arise from it,it is very close l y conn ected with the se - cal l ed pleural
“ gangl ia thru which it sends fibres to,or receives them from
,the optic
,pedal
,
and v isceral gangl ia . The lower part of the cerebral gangl ion is formed partial ly by
a large tract which connects the tw o Optic lobes and appears to have nothing
to do with the gangl ion thru which it passes . T he fibres w hich form the cerebro
buccal and cerebro -
propedal connectives can be traced in the cerebral gangl ion
some distance . One tract is at first d istingu ishable near the dorsal end of the
gangl ion and as it passes forward it j oi ns the other tract which arises in the
neighborhood of the pleural gangl ion . The fibres of the tract thus formed,at l east
partial l y,cross to the opposite side and as they l eave the ganglion the fibres
form two bundles,the connectives .
The pleural gangl ion is qu ite continuous with and inseparab le from the
cerebral gangl ion above and i s hardly distingu ishabl e from the pedal and v isceral
gangl ia below . Its inner surface rests against the wal l of the oesophageal canal
72
with the fibre s of the neurogl ia cel l s,which are located upon the outer surface
of the inner granular layer . The fibres of the Optic nerve pass inward vertical ly
to the inner plexus,and i n the outer plexus each bears a brush of short straight
processes .
The medul la contains multipolar,or bipolar cel ls Of four types : giant
intermed iate,smal l centripetal and smal l centrifugal cel l s . T he dendri tes of the
cerrtri fugal and of the smal l and intermediate centripetal cel ls are distributed
i n the medul la : those of the giant centripetal cel l s are unu sual ly irregular
(knobbed) , and are distributed to all parts of the gangl ion,but are more numerous
i n the inner plexus . The neuri tes of the centripetal cel l s pass toward,and probably
into,the Optic tract
,while those of the centri fugal cel ls go outward to the
outer and i nner plexuses .
A smal l gangl ion,somewhat larger than a pin - head
,i s situated on the
anterior and dorsal side of the Optic tract . This is the “
ganglion p edu ncu l i”
and seems to be connected with the pleural gangl ion alone and only by a few
fibres . A l l i ts cel l s are smal l and thei r nucle i are separated from one another
only by a distance equal to the d iameter O f a single nucleus .
The pedal gangl ion lies in the concavity O f the pedal process O f the sku l l
below the oesophagus and above the pedal arterv . Its upper surface on each side
of the oesophagus is continuous with the pleural gangl ion and is separated from
the v isceral gangl ion by a septum thru which a large number O f fibres pass .
The pedo -
propedal connectives arise from the ventral end of the pedal gangl ion
and pass forward a short distance to the propedal gangl ion .
The fol lowing nerves arise from the pedal ganglia .
A . Nerves . of special sense .
-1 . Two cristic n erves . Each arises from the back end of the pedal gangl ion
and,as i t enters the carti lage of the skul l , d iv ides into two branches ,
one Of which innervates the ventral transverse portion of the crista,
and - the other the remain der O f the crista . The fibres of this nerve
are unusual ly larg e and stain differential l y so that they can be readi ly
traced for some distance in the gangl ion . The fibres pass along the
surface of the gangl ion for perhaps hal f its l ength and then turn inward
and form at l east a partial chiasma . The fibres have not been traced
beyond& the chiasma .
2 . A pai r O f macular nerves . Each arises from the back end of the gangl ion
some d istance inward from the roots Of the preceding nerve . It passes
immediatel y into the carti lage and,as it passes thru i t to the statocyst
,
73
div ides into several smal l branches which radiate under the macula and
end in it . The fibres of this nerve are much smal l er than those of the
cristic nerve and since they do not‘stain differential ly they cannot b e
traced as readi ly as those of the cristic nerve . The fibres seem to originate
in the gangl ion some distance behind those O f the preceding nerve .
A pai r of ol factory (i?) nerves . Each nerve passes from the si de of the pedal
gangl ion thru the lateral foramen of the skul l with ,and be low ,
the Opti c
tract . It then passes thru the optic cup below and behind the Optic
gangl ion to the edge Of the lateral process Of the skul l which it p ierces
or passes over and ends in the columnar epithel ium of the ol factory pit .
Within the brain the fibres can be fol l owed from the point O f their ex it,
obl iquely upward to a point near the pleural gangl ion .
Other nerves .
4 . A pai r of nerves arises from the back end of the gangl ion some d istance
above the origin of the statocystic nerves , i n fact , at the extreme upper
edge of the ganglion . Each nerve pierces the septum t hat separates the
pedal and visceral ganglia and passing over the outer surface of the latter
enters the cart i lage . In the carti lage the nerve divides and,l eaving the
skull,ends in the cephal ic and nuchal retractors .
T wo nerves arise on each side from the same part of the gangl ion and
are perhaps one with the preced ing nerve . One of these passes thru the
lateral foramen of the skul l and probably innervates the upper and poste
rior muscles of the eye . T he other passes upward thru a foramen to the
upper part of the cephal i c retractor .
A pai r of smal l - nerves arises from the pedal gangl ion a short distance
in front of the last mentioned nerves and each nerve passes forward and
upward around the oesophagus and then outward to the ven trO -anterior
muscles of the eye .
A pai r Of s iphonal nerves arises from the posterior part of the lower :
surface of the gangl ion and each nerve passes at once thru a foramen in
the pedal process to the siphon . While in the foramen the nerve gives
off a branch which enters the optic capsule .
Immediately in front O f the siphonal nerves there arises a median nerve
which goes thru the pedal process and i s d istributed to the muscl es of
the lower side of the head .
A pai r O f nerves arises from the sides Of the front end of the gangl ion .
Each nerve passes outward and forward above the pedal process and the
74
capsule of the eye and be l ow the optic gangl ion . They supply the muscles
and capsul e of the eye .
10 . A pai r of nerve s ari ses from the front end O f the gangl ion and passes
forward w ith and under the pedo -
propedal connectives . At the dorsal end
of the prO pedal gangl ion each nerve turns sharpely downward over the
point of the pedal process and between the bases of the preorbital car
ti lages . I t suppl ies the muscles at the base of the arms .
A pai r of cel ls, (Text Fig . 16 ) the tw o larg est and most remarkabl e cel l s
of the body are situated in the pedal gangl ion . They l ie near the median
l i ne a short distance in front of the statocyst . Each cel l is fusiform and i s
vertical ly placed . The nucleus i s large , round ,and central . The cytoplasm is
granu lar and,l ike the very large nerve process arisi ng from it , stai ns diffe
ren tially with haern alu rn,taking a very distinct blue gray color , which i s
in marked contrast to the other unstained fibres and cel l bodies . The nerve
fibre arises from the backwardly curved upper end of the cel l and passes
backward,upward and inward to the center of the visceral gangl ion
,where it
crosses the median l in e,forming a chiasma with the process of the other cel l .
Beyond the ch iasma the fibre passes into the v i scero - stel late connective of the
side opposite its origin and,entering the stel late gangl ion ,
divides into at l east
four and probably five or even more branches,one Of which enters each of the
larger nerves which arise from that gangl ion,and thus the fibre branches pass
to various parts of the mantl e .
I have been unable to d iscover the ul timate d istribut ion of the fibres or to
make out the central connections of the cel l . These fibres,not previously
described in any mol lusc , resemble closely the fibres of Mauthner in vertebrates
which are also un ique in the nervous system of the an imal,there being b ut
one pai r of cell s which are marked Off both by the size of the cel l s and of their
fibres and by some chemical consti tuent w hich makes them stain differential ly
from nearly all other fibres . These cel l s appear in the embryo and persist
throughout l ife . The very size Of the nerve processes has prevented their dis
covery ,since it is well - nigh impossibl e to bel ieve that such a larg e structure
can be a nerve fibre .
The prOpedal gangl ion l ies directly ventral to the pedal gangl ion and between
the oesophageal canal and the muscles that are attached to the pedal process .
The connective which it receives from the pedal gangl ion,i s incompletely d ivided
into a central,and six pai rs O f lateral bundles . T he gangl ion is also connected
with the cerebral gangl ion by the cerebro -
propedal connective and with the
suprabuccal gangl ion by the bucco -
propedal connective . The former passes
Fig. 16 .
75
upward and backward around the oesophageal canal to the ventral end Of the
cerebral gangl ion . The latter arises from the back end of the gangl ion together
with the former and turns forward and upward around the oesophagus and ends
in the supra- buccal gangl ion . Several smal l nerves arise from the edges Of the
upper surface of the gangl ion . The fibres Of these nerves radiate backward,
upward and forward,and i nnervate the nruscles between the skul l and the base
of the arms . Five pai rs of nerves or connectives come from the - edge of the
ventral surface of the gangl ion and diverg e from one another as they pass
forward around the pharynx from which they are separated by the buccal sinuses .
These ten nerves enter ten brachial gangl ia which l i e in the corresponding arms,
and which are more properly cal l ed rrerve- cords . Each gangl ion or cord extends
from the base to the apex of the arm and tapers regularly from its large base
to a minute poin t . The bases of the gangl ia are connected bv sl ender nerve
tracts which with the ganglia form at the bases of the arms a nerve - ring,the
brachial ring . I t i s not certai n,but probable
,that the gangl ia of the fourth pair
of arms are connected with this ring .
The buccal nerve r ing is formed by the suprabuccal and infrabuccal ganglia,
and encircles the oesophagus j ust back of the pharynx . The suprabuccal gang
l ion is attached to the inner surface of the septum that separates the two
buccal sinuses . Its dorsal surface receives two pairs of connectives,the cerebro
buccal and the propedO - buccal,from the cerebral and propedal gangl ia respectively .
From the ventral end of the gangl ion arise four or five pai rs of nerves which
pass to the muscles of the pharynx,and from the sides arise two connectives
which pass downward around the oesophagus to the infrabuccal gangl ion .
T he infrabuccal gangl ion is attached to the dorsal surface of the pharynx
between the lateral sal i vary glands . Tw o pai rs of nerves from this gangl ion inner
vate the odontophore and a pai r of connectives arises from its dorsal end and
passes backward along the entire length of the oesophagus . These connecti ves,
the bucco - splanchnic,enter the splanchnic
,
‘gastric or“abdominal
”gangl ion
which l ies on the upper surface of the dorsal end of the intestine between
the oesophagus and the caecum .
The splanchnic gangl ion gives Off five large and two or nrore smal l nerves .
The largest nerve passes to the left between the caecum and the pancreas and,
en tering the ridge from which the caecal folds arise,suppl ies them . Two large
nerves arise from the dorsal end of the gangl ion and go between the stomach
and caecum,supplying the inner sides O f both organs . One large and two smal l
nerves from the right side O f the gangl ion pass under the oesophagus to the
upper (anterior) caecal lobe . From the ventral end Of the gangl ion arise the
76
bucco - splarrchn ic connectives and a large nerve wh ich suppl ies the li ver,the
pancreas , and perhaps the intestine . The innervation Of the systemic heart has
not been d iscovered but there is l ittle doubt that the splanchnic gangl ion al so
suppl ies it .
The v isce ral gangl ion is the most dorsal of the oesophageal gangl ia and fits
in to a shal low depression in the skul l above the statocysts . I t i s bound down
to the cart i lage by a tent - shaped sheet of fascia whose top is attached to the
oesophagus and to the anterior hal f Of the great foramen of the skul l and whose
e dges are attached to the r im of the depression that l odges the gangl ion . The
ventral port ion of this sheet i s perforated lateral l y by open ings for the v i scero
pedal and viscero - pl eural connect ives . These connecti ves arise together in the
gangl ion and diverge as - they pass backward,the pedal turn ing downward
,and
the pleural outward . Four pairs of nerves arise from th is gangl ion . Two ar ise
from the dorso - external region of the gangl ion : one passes directly outward to
the lateral siphonal val ve ; and one downward over the dorsal surface of the
skul l cl ose to the attachment of the cephal ic retractor,then thru thi s muscle
i nto the upper surface of the siphon . From - the dorsal surface of the v isceral
gangl ion arise two pai rs of nerves which are united to two pai rs of connec
tives ; the v isceral nerve with the viscero - branchial connecti ve . and the pleural
nerve w ith the v i scerO - stel late connecti ve . The pl eural nerves and the associated
connectives arise from the sides of the dorsal su rface of the gangl ion . Each
bundle of fi bres passes obl ique ly outward and backward thru a deep groove in
the l iver to the dorso - lateral edge of the nuchal cartilage,turns over this edge
,
and passes thru the nuchal retractor which is attached to it . As the bundle
emerg es from this muscl e it d iv ides ; the pl eural nerve passes backward and
the v iscerO - stel late connective at once enters the stel late gangl ion . The pleural
nerve gives O ff a smal l branch to the nu chal retractor as i t l eaves that muscle
and forms the.
greater part of the nerve which innervates the fin .
The two stel late gangl ia are oval and flattened and l i e under the skin O f
the inner surface O f the mantle n ear the dorsal end of the nuchal carti lage and
close to the shaft O f the pen . Each gangl ion sends off eight or ten nerves which
rad iate from its ventral edge . The dorsal part of the gangl ion proj ects back
ward l ike the tai l O f a comma and contains the maj ority O f the larg e nerve cel ls
Of the gangl ion . The stel late gangl ia are connected by a smal l corn rn issu re which
leaves each gangl ion with the viscero - stellate connective an d which passes under
the dorsal end of the nuchal cartilage . A l l but two O f the nerves arisi ng from
the stellate gangl ion enter the mantl e within five o r six mi ll imeters of the gang
l i on and pass at once to the middle Of i ts wal l and are distributed to all parts
78
the v iscerO - branchial connective a very short d istance and then enters the bran
chial heart . I t is possible that this nerve arises from the v isceral ganglion,not
from the b ranclrial,and i t is al so possibl e that th is nerve
,not one from the
splanchnic gangl ion,suppl ies the systemic heart .
T H E SENS E ORG ANS .
The organs of special sense are the statocysts,the eyes
,and the organ
which is probably Olfactory in function . The last i s an area of colummar epithel
iunr si tuated in the concavity at the l ower end of the olfactory crest”
and
i nnervated by a nerve from the pedal gangl ion .
T H E STATOCYSTS .
The statocysts of the Cephal opoda have been described by HAMLYN -HARR IS
and al though he did not have th i s speci es before him ,his description of
the statocysts O f Lol igo vulgar i s holds true for this Species . The statocysts l i e
in the skul l below the visceral,and beh ind the pedal gangl ion . The cav ity of
each is 2 or 8 mm . i n diameter and 3 or more mm . in l ength . They are si de
by side and are separa ted by a th in carti laginous septum . Twelve papi l lae proj ect
into the statocystic cavity . These are situated as fol lows,passing backward from
the first,near the front end
,to the last
,near th e back end of the cavity :
The fi rst posterO -median papi l la .
second beh i nd the preceding .
first median above the preceding .
antero -median
first posterior
anteri or The first anterior,the second median
second median and the second posterior papil lae are
poster ior i ncluded in the same cross section .
th ird posterior
These papi l lae are Side by sid e and
the first which is bent upward is poste
rior to the second which is erect .
This begins as a ridge on the thick
ened posterior part Of the septunr , runs
outward and backward,and ends in a
posterior papil la .
79
The second anterior papi l la . This is sl ightly inside the center of
the anterior surface .
In add ition to these papi llae,there is a prominent r idge which is horizontal
and l i es on the ventral (front) end of the external surface .
The statocystic cavity i s lined by a pavement epi thel ium except in the
region of the macula statica and cri sta statica . The former i s an area of colum
rn nar,c i l iated
,sensory epithel ium covering the ventral or front end of the
cavity . The statol ith,a club shaped concretion rests upon the macula . The
nerve fibres arising from the macula form a number of smal l bundles and these
converging,form two large bundles Of fibres which pass out thru the cartilage
and then unite.The macular nerve thus formed enters the pedal gangl ion and
curv ing outward is lost in the gangl ion j ust outside the roots of the siphonal
nerve . The fibres O f this nerve do not stain d ifferential ly and are smal l so that
i t i s not easy to fol low them far into the ganglion .
The cr ista statica i s a ridge of c i l iated epithel ium which winds over the
wal l s of the statocyst . This ridge begins at the foot Of the first postero -median
papil la runs outward across the floor of the cavity to the front end of the
e xternal horrzorrtal r idge ,passes backward above this ridge between the first and
second external papil lae (passing beneath the overhanging part of the first) then
turns inward across the floor to the back side of the third posterior papil la,
again turns and passes upward to the base of the second anterior papil la where
it ends . T he crista is formed by three or more rows of columnar,cil iated cells
with supporting cell s . The cell s of the centra l row are markedly larger than
those of the two or four latera l rows . The distal ends of the lateral cel ls incl ine
towards the central cel ls so that a ridge is formed which in section has approxi
m ately the outl i ne Of an i sosce l es triangle . The nerve fibres arising from the
anterior tra nsverse portion of the crista form a bundl e which enters the carti lage
near,but separate from
,a larger bundl e arising from the remai nder of the crista.
‘The latter bundle begins at the dorsal (back) end of the crista and,constantly
receiving fibres from it,passes along its upper (anterior) edge . The two bundles
pass ou t of the statocystic cavity at its ventro - external angle and,uniting in the
cartilage,enter the pedal gangl ion . The fibres pass al ong the outer surface Of
the gangl ion unti l beyond the roots Of the siphonal nerves and then bend inward
forming at least a partial chiasma . The fibres have not been tra ced beyond the
ch iasma but are lost in the neuropile of the gangl ion . They are traceable so long
a distance because they are unusual ly larg e and stai n differential l y with lraemalum
or haematoxyl in . The fact that the macular and cristic nerves are markedly
d ifferent does not seem to have been noted by other observers . These two nerves
8 0
diffe r in staining property,size O f fibres
,course in the brain and the skul l
,and
in origin .
The statocyst arises from an i nvagination of the ectoderm which forms
laterallv on the posterior s ide of the embryo . The bottom of the invagination
becomes larg e and rounded and proj ects inward unti l i t reaches the middle of
the posterior part of the head and is separate d from its mate by a thin septum
only . The cavity Of the statocyst remain s for some time in communication with
the surface by a l ong,narrow duct which is attache d l ike the neck Of a retort
,
to the side of the cav ity and l eads to the posterior surface Of the embryo . In
the adul t the outer open ing seems to be closed but the canal remains as a
sl ender ci l iated duct which i s named from its discoverer,K oel liker
’s duct . I t
leads thru the skul l from its inner Opening at the front end of the statocystic
cavity j ust above the crista,downward and sl ightly backward to the lower sur
face O f the skul l . Here the duct seems to end but it is possibl e that i t l eads to
the surface .
T H E E YE . (Plate III figs . 20 The eye of the h igher Cephal opoda is very
similar to the vertebrate eye ; i n fact the two structures furnish a most remarkable
case of converg en t development , for while differing essential ly both in the origin
of their parts and in structure,the eyes are so similar that a larg e part of the
terminology of the vertebrate eye is appl icable to the Cephalopod eye . I n the
young embryo of the squid an oval area Of ectoderm at each side of the embryo
becomes differentiated from the surround ing fl at or cubical epithel ium and forms
the anlage of the retina . The cell s Of the anlage become greatly elongated
and the nuclei take up different posit ions at the middl e or at each end of the
cel ls so that,al though remain ing one layered the epithel ium appears to be several
layered . The cubical epi thel ium at the margin of each retinal p late forms a
circular ridge which gradual l y becomes a fold surrounding a pit and final ly the
outer wal l of a vesicle,the inner chamber of the eye . From the wal l s of the
Optic vesicl e the retina,the l ens
,and the inner port ion of the cil iary body are
formed . The outer wal l Of the vesicl e consists of two sheets of ectoderm separ
ated by a smal l amount of mesodermal t i ssue . The mesodermal tissue forms the
scleroti c coat and the suspensory l igarrren t of the lens , and the ectoderm produces
the lens which consists of two segments,one formed in the inner chamber by
the inner layer O f the ectodernr and one formed in the outer chamber by the
external sheet of ectoderm . T wo circular folds al so contai n ing both ectoderm and
m esoderm arise around the'
Optic vesicl e . The inner fold grows over the Optic
v esicle and forms the iris . The outer fold al so grows over the vesicl e and enclosing
the outer chamber forms the cornea and the capsule Of the eye . The outer
and radial fibres . The forme r enci rcl e the pup il and are i nserted in the v isor
l ikc fol d o f the i ri s . T he latter arise from the margin of the scl erotic cup and
i nterweave with the c irc ular fibres . T he contraction of the ci rcular fibres narrow s
the pupi l and draws the visor down into i t . while the contraction Of the ra dial
fibres di lates the pupi l and draws up the v rsor. The inner epithel ium is contin
u ous at the inner edge of the i ri s w ith the outer epithel ium and at i ts peri
phery w ith the outer layer of the ci l iary body . I ts cell s are cubical and are
fil led with black pigment .
The eyebal l i s held in place by nine muscles and by a somewhat cyl indr ical
fascia which stretches from the equator of the eye to the margins of the optic
cup of the skul l and so,with the eye
,encloses the optic ga ngl ion and the white
bod i es . The inner side Of this fascia is supported by the preorb ital cartilage
which proj ects from the pedal process of th e sku ll'
forward and sl ightly down
ward between the outer chamber and the eyebal l . The nine orbital musc les , how
ever,form the chief attachment of the eye . They l ie in the orbital fasc ia and
are attached w i th it to the eyebal l . The muscles arise from three points and so
natural ly fal l i nto three groups v iz . 1) two that arise from the cerebral process
of the sku l l : 2) three that ar ise from the lower part of the outer edge of the
skul l ; and 3 ) four that arise from the pedal process and the preorbital bar. One
of the two arising from the cerebra l process passes outward and downward to the
dorsal surface of the eye . The other passes downward between the muscl es of
thi s thi rd group and the eye , then outward to its l ower surface . Of the three
that arise from the outer edge of the sku ll ; one , a sl ender band ,passes upward
and is inserted upon the upper part Of the dorsal su rface Of the eye ; another,
a smal l short muscl e ,reaches d i rectly forward to the lower part of the dorsal
surface Of the eye ; the thi rd ,a strong muscle
,goes forward to the l ower sur
face O f the eye . The four remaining muscles arise from the pedal process or
from the preorbital bar . One passes from the former outward and dow nward to
the lower surface of the eye . A second arises from the same process and i s
i nserted upon the lower edge of the preorbital carti lage . A th ird muscle,appar
ently a continuation of the last,arises from the opposite edge of the carti lage
and from the pedal process near the base Of the preorbital ca rti lage and is in
serted upon the ventra l surface Of the eye . The remain ing muscl e is a pecul iar
digastric muscle which extends from eye to eye passing through a pull ey at the
ventral end of the pedal process . From this pul ley which may be considered
the origin of the muscl e a slender tendon passes outward and forward upon each
preorbital bar and then ends in a smal l triangular muscu lar bel l y that is attached
by a broad fascia to the ventral su rface of the eye .’
It is not probabl e that th is
83
extensive rrruscu latu re produces any considerabl e movement of the eyebal l i t i s
too firmly attached to the immovable optic cup but the muscles probab l y
adj ust the eye to the d isplacements produced by the flexures Of the arms and head .
The sclera i s a hemispherical cup Of carti lage whose margin is thick
ened and sl ightly incurved . This cartilage consists Of a single layer of flattened
cel l s ly ing between tw o sheets Of matrix . Toward the rim of the cup the ce l ls
b ecorrre cubical,then col umnar and i n the thickest part of the run
,they form
two or three lavers of angular ce l ls . T he portions O f the scl era that are not
covered or are only partial ly covered by the argentea of the . iris are coated
external ly by an argentea similar to that of the i ris whose fibres,however
,are
sinuous,longer and finer
The white bodies (see p . 65) are tw o i rregular masses Of problematical
t i ssue which are wedged in between the Optic gangl ion and the eye . The upper
white body l i es upon the antero -dorsal surface of the eye while the lower l ies
upon the postero - interrral surface so that they are upon opposite sides of the
bundle of nerve fibres which passes between the eye and the Optic gangl ion .
A falc iforrrr bar of carti lage,attached by a fascia to the pedal process
,l i es
between the upper white body and the eye,and helps both to support - the eye
and to protect the optic gangl ion . The fora mina in the scl era through which
the nerve fibres pass out from the retina are smal l,quite near together and
are si tuated in an el l iptical area on the dorso - internal surface of the eye . The
l onger axis of this area extends obliquely downward and forward .
A sheet of connective tissue,the suspensory ligament of the lens
,stretches
across the top of the sclerotic cup and supports both the ci l iary body and
the lens . The peripheral portion of this l igament has attached to i ts inner sur
face the fibres O f a ra dial muscle,the cil iary muscle (of L A N C E R ) w hich arises
from the rim of the scl era . The intermediate zone of thi s l igament supports
the inner and outer portions of the “ cil iary body or “ corpus ep itheliale which
produce the inner and outer portion s O f the l ens,respecti vely . The two portions
Of the cil iary body (Plate III ,Fig . 20) ari se from the inner and outer sheets of
ectoderm that form the outer wal l of the optic vescicle whil e the suspensory
l igament and c i lary muscle arise from the mesoderm enclosed between the
ectodermal sheets . T he cel ls of these sheets are at first cubical but those at the
center Of the inner sheet soon produce smal l , finger- l ike processes
,one for each
cel l,which extend into the posterior chamber and
,uniting
,form a smal l club ~
shaped body,the lens . T he cel l s of the zone immediately around the center
,
produce similar but longer processes which ,extending toward the lens
,unite
with one another and form one of the concentric laminae Of the lens . The
84 :
laminae,thus produced
,are added constantly to the lens unti l i t becomes a
spherical mass attached to the inner portion of the cil iary body by means O f
the stalks of the processes . As soon as the lens has become spherical , the
Outer part of the cil iary body begins to contribute to i ts growth,for further
growth by additions from the inner portion Of the cil iary body necessari ly
produces a l ens flattened on the side in contact with the suspensory l igament .
Hence,to maintain the spherical form Of the l ens ,
a plane - convex segment is
produced by the outer portion of the cil iary body . T hese cell s of the cil iary
body which are enclosed between the tw o segments of the l ens degenerate and
are absorbed,leaving on ly the su spensory l igament between the tw o segments .
T he constant grow th of the l ens and O f the ci l iary body necessitates the exis
tence of three zones i n the latter v iz . an i nner zone of degenerating ce l l s,a
middle zone of mature cel ls,and a marg inal zone of immature cel ls . The lens
forming processes of the immature cell s are relatively larg er and more conspicuous
than those of the mature cel l s and form a prom inent layer between the cil iary
body and the adjacent chamber of the eye . The large size and conspicuous
position of the processes have led some writers (FA U S S E K’96) to ascribe to them
the formation of the enti re l ens and to assert that the large mature ce l ls of the
cil iary body have some unknown physiological function . The mature cel ls of the
ci liarv body are oval,cubical or columnar and are attached by thei r bases to
the suspensory l igam ent . The free end of each cel l is drawn ou t into a long,
slender process which i s so smal l compared with the cel l and the corresponding
portion O f the lamina,that i t probably serves as a duct which carries the
secretion O f the cel l ' to the lamina . When isolated these cel l s are so S im ilar in
genera l appearance to unipolar nerve cel ls that the writer who has given the
best description of them (HOFFMANN) bel ieved them to be nerve cel ls . The cel l
body is larg e and stain s deeply with nuclear stains . The nucleus i s large and
the nucleolus conspicuous . While attain ing their mature condition,the cel ls of
the inner porti on of the cil iary . body grow so much that the epithel ium formed
by them is thrown into ra dial folds . The inner furrows of these folds are fi l l ed
by the cel l processes whil e the outer furrows are fil l ed by ridges Of the suspen
sory l igament . Thus this outer layer remai n s a simple palisadal epithel ium which ,
however,in section appears several cel ls thick . The outer layer of the ci l iary
body is l ess fol ded or remains plane . A pigmented membrane,the continuation
Of the supporting . layer of the retina , l i es upon the inner surface of the cil iary
body,and
,as HOFFMAN has Shown
,the cell s Of the inner part of the cil iary
body may be distinguished from those of the outer part by the presence of
pigment granules in or between the cel ls .
8 6
length of the entire cel l . T he nucl ear segments are supported by richly vascu lar
connective tissue . The proximal portions of these segments contai n the nucl ei,
which are arranged at various l evels so that they seemingly form two or three
The above description is genera l ly accepted,but the essential part of the
sensory cel l,
the pe rcipien t structure has been,and perhaps stil l is
,l ittl e
understood . HES SE (1900) finds that the neu rofibri llae which form the fibers of
the Optic nerve,and which seem to him the percip ient structures
,arise near
the di stal end of the rods and extend the entire l ength of the sensory cel l s .
MERTON however,
finds that the neu ro - fibri l,entering the nuclear seg
ni ent,broadens into an i rregular and often spl it lamella which extends to the
base of the rod stalk ; and that the'
red contai ns a cytoplasmic network
mistaken by HESSE for the continuation of the n eurofibri l which is the path
Of migration Of the pigment .
The pigment migration has been extensi vel y studi ed by BA e z,HES SE and
HESS,w ho have shown that the retina O f a Cephalopod which has been long
in the dark contai ns a singl e layer of pigment,
the external pigment layer,
and that in the l ight the pigment granules migrate inward from this layer and,
massing in the expanded inner ends of the rods,form the inner pigment layer
which l ies beneath the internal l im iting membra ne and which i s connected
w ith the external p igment layer by a smal l amount of pigment scattered along
the rods .
HESS finds that the fresh retina always appears dark brown or b lack and
that a red hue tends to predominate in the upper , a brown shade in the lower
hal f of the eye . On the contrary,a retina preserved after remain ing long in
the dark,appears gra y ; after exposure to l ight , dark brown or black ; while
after an exposure for one hour to changing l ight,there appears a horizontal
gray band about 4 mm . broad between the darker upper and lower hal ves of
the reti na. With increased l ight this band becomes narrower and final ly dissappears.
The dark color of the fresh retina i s due to i ts transparence,which al lows
the pigment to be seen at any depth ,whi le the Opaqueness of the preserved
retina does not al low the pigment to be seen unless i t l i es near the surface .
The retardation of the migration Of pigment to the d istal part of the rods
of the horizontal band seems to indicate that the cell s of this region are l ess
sensitive to an excess of l ight .
In addition to this merel y protective pigment,HESS finds that the Cephalo
pod reti na contains a purple pigment which is very S im i lar to,perhaps identical
w ith,visual purpl e .
8 7
BEER has described the mechanism of acconrodation and has shown that it is
rri neh the sari re as i n the eyes of Teleosts , al though there are important differences .
In both cases the eye is myOp ic ,the convexity Of the lens is unchangeable
,
and accorn odat iorr i s effected by drawing the lens toward the retina . In fish the
falc iform process,or muscu lus retractor lentis , draws the lens toward the retina
but in the Cephalopod eye,the cil iary muscle accompl ishes this . The outer sur
face of the eye is convex and the contract ion Of the cil iary muscle flattens the
outer wal l of the eye and draws the len s toward the retina . Moreover,the
more viol ent contraction Of one segment of the ci l iary muscle turns the lens so
that a ray ,which otherwise would not reach the retina
,strikes i t . Thus
,by
tnrn irrg the lens , a moving body may be watched without turning the eye or
the head .
90
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