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‘pool Marine Biology Committee,

: oo MEMOIRS
“epirep BY Wx A; HEDMAN Dts ERS.

XVIII.

/ ELEDONE

BY

ANNIE ISGROVE, M.Sc.

(With to Plates)

4
“

Price Four SHILLINGS AND SIXPENCE

LONDON

— Wirrirams & Norcatr

Jury, 1909

aim |” Dibiion: Of Mots

GAs.

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: ey

EX LIBRIS

William Healey Dall

Division of Mollusks
Sectional Library

q

EVR MEMOTRS.

———EEE

VILE.

ELEDONE.

NOTICE.

Tue Comittee desire to intimate that no copies of these
Memoirs will be presented or exchanged, as the prices
have been fixed on such a scale that most of the copies will
have to be sold to meet the cost of production.

The Memoirs may be obtained at the nett prices stated,
from Messrs. Williams and Norgate, 14, Henrietta Stree,
Covent Garden, London.

Memow I.

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Snide
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XV.
OV:

Ascidia— published in October, 1899, GO pp.
and five plates, price 2s.
Cardium—published in December, 1899,
92 pp., six plates and a map, price 2s. 6d.
Kehinus—published in February, 1900,
36 pp. and five plates, price 2s.
Codium—published in April, 1909, 26 pp.
and three plates, price Ls. 6d.
Alcyonium—published in January, 1901,
30 pp. and three plates, price Is. 6d.
Lepeophtheirus and Lernea—published in
March, 1901, 62 pp. and five plates,
price Xs.
Lineus— published in April, 1901, 40 pp. and
four plates, price Ys.
Pleuronectes—published in December, 1901,
260 pp. and eleven plates, price 7s.
Chondrus—published in July, 1902, 50 pp.
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Patella—published in May, 1903, 84 pp. and
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Arenicola—published in March, 1904, 126
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Gammarus—published in July, 1904, 55 pp.
and four plates, price 2s.
Anurida— published in October, 1906, 105 pp.
and seven plates, price 4s.
Tigia—published in January, 1907, 45 pp.
and four plates, price 2s.
Antedon—published in June, 1907, 55 pp.
and seven plates, price 2s. Gd.
Cancer—published in June, 1908, 217 pp.
and thirteen plates, price 6s. 6d.

»,XVIT. Pecten—published in January, 1909, 144 pp.

and nine plates, price 4s. 6d.

» XVIII. Hledone—published im July, 1909, 118 pp.

and ten plates, price 4s. 6d.

Liverpool Marine Biology Committee.
ii (ede
Va tee VM eVrOH i S

ON TYPICAL BRITISH MARINE PLANTS & ANIMALS

EDITED BY W. Ao HHRDITAN D.Sc, FURS.

XVIII.

EKLEDONE

BY

ANNIES ISG ROW Be Msc.

(With to Plates)

y

Price Four SHILLINGS AND SIXPENCE

LONDON
Wicittams & NorGaTr

JuLy, 1909

MAY 1 2 1958
LIBRARY

rT. 56

a 79
Molt,

EDITOR’S PREFACE.

Tue Liverpool Marine Biology Committee was constituted
in 1885, with the object of investigating the Fauna and
Flora of the Irish Sea.

The dredging, trawling, and other collecting expeditions
organised by the Committee have been carried on inter-
mittently since that time, and a considerable amount of
material, both published and unpublished, has been aceu-
mulated. Twenty-two Annual Reports of the Committee
and five volumes dealing with the ‘“ Fauna and Flora”
have been issued. At an early stage of the investigations
it became evident that a Biological Station or Laboratory
on the sea-shore nearer the usual collecting grounds than
Liverpool would be a material assistance in the work.
Consequently the Committee, in 1887, established the
Puffin Island Biological Station on the North Coast of
Anglesey, and later on, in 1892, moved to the more
commodious and accessible Station at Port Krin in the
centre of the rich collecting grounds of the south end of
the Isle of Man. A larger Biological Station and Fish
Hatchery, on a more convenient site at Port Erin, has
since been erected, and was opened for work in July, 1902.

In these twenty-two years’ experience of a Biological
Station (five years at Puffin Island and seventeen at Port
Kirin), where College students and young amateurs form a
large proportion of the workers, the want has been fre-
quently felt of a series of detailed descriptions of the
structure of certain common typical animals and plants,
chosen as representatives of their groups, and dealt with
by specialists. The same want has probably been felt in

other similar institutions and in many College laboratories.

vl.

The objects of the Committee and of the workers at the
Biological Station were at first chiefly faunistic and
speciographic. The work must necessarily be so when
opening up a new district. Some of the workers have
published papers on morphological points, or on embry-
ology and observations on life-histories and habits; but
the majority of the papers in the volumes on the “* Fauna
and Flora of Liverpool Bay ” have been, as was intended
from the first, occupied with the names and characteristics
and distribution of the many different kinds of marine
plants and animals in our district. And this faunistic
work will still go on. It is far from finished, and the
Committee hope in the future to add still further to the
records of the Fauna and Flora. But the papers in the
present series, started in 1899, are quite distinct from these
previous publications in name, in treatment, and in pur-
pose. They are called ‘ L.M.B.C. Memoirs,” each treats
of one type, and they are issued separately as they are
ready, and will be obtainable Memoir by Memoir as they
appear, or later bound up in convenient volumes. It is
hoped that such a series of special studies, written by
those who are thoroughly familiar with the forms of which
they treat, will be found of value by students of Biology
in laboratories and in Marine Stations, and will be
welcomed by many others working privately at Marine
Natural History,

The forms selected are, as far as possible, common
L.M.B.C. (Irish Sea) animals and plants of which no
adequate account already exists in the text-books.
Probably most of the specialists who have taken part in
the L.M.B.C. work in the past will prepare accounts of one
or more representatives of their groups. The following
list shows those who have either performed or promised.

Memoirs from I. to XVIII. have now been published.

vil.

The next, on Polychaet Larve, by Mr. F. H. Gravely,
is now in the press; Doris, by Sir C. Eliot, is far advanced
and ought to be out during 1909. It is heaped that

Cucumaria, Buccinum, and the Oyster will follow soon.

Memoir I.

eel.
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9 V
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Ascip1a, W. A. Herdman, 60 pp., 5 Pls., 2s.
Carpivum, J. Johnstone, 92 pp., 7 Pls., 2s. 6d.
icHinus, H. C. Chadwick, 36 pp., 5 Pls., 2s.

. Copium, R. J. H. Gibson and Helen Auld,

26 pp., 0.Pls:, Is. 6d.

. Atcyonivum, 8. J. Hickson, 30 pp., 3 Pls., 1s. 6d.
. LerrorurHeirus AND Lernaca, Andrew Scott,

G2ppsoEls.,..2s%

. Linevs, R. C. Punnett, 40 pp., 4 Pls., 2s.
. Praicr, F. J. Cole and J. Johnstone, 260 pp.,

1 2a recs

. Cuonprus, O. V. Darbishire, 50 pp., 7 Pls.,

as. Od.

, Apia, 2. A Davisvand: Het. Klewre;

84 pp., 4 Pls., 2s. 6d.

_ ARENICOLA, J. Hi. Ashworth, 126 pps 6 Pils:

4s. Od.
Gammarus, M. Cussans, 55 pp., 4 Pls., 2s.
Anuripa, A. D. Imms, 107 pp., 8 Pls., 4s.
Lieta, OC. G. Hewitt, 45 pp., 4 Pls., 2s.
ANtTEDON, Hl. C. Chadwick, 55 pp.,7 Pls., 2s. 6d.
Cancer, J. Pearson ,217 pp., 18 Pls., 6s. 6d.
Pucren, W. J. Dakin; 144 pp., 9 Pls., 4s. 6d.

,, XVIII. Eepone, A. Isgrove, 113 pp., 10 Pls., 4s. 6d.

Bee)

Potycuarr Larva, I’. H. Gravely.

Doris, Sir Charles Eliot.

Cucumaria, EH. Hindle.

Oyster, W. A. Herdman and J. T. Jenkins.
Ostracop (CyrnEert), Andrew Scott.
Buccinum, W. B. Randles.

vill.
Buauna, Laura ht. Thornely.
Sacirra, H. J.. W. Harvey.
Zosters, R. J. Harvey Gibson.
Timantuaria, F. J. Lewis.
Draroms, F. EK. Weiss.
Fucus, J. B. Farmer.
Borryiiomes, W. A. Herdman.
Acrinia, J. A. Clubb.
Hyproip, EK. T. Browne.
TlanicuonpRiA and Sycon, A. Dendy.
SaBELLARIA, A. T. Watson.

In addition to these, other Memoirs will be arranged
for, on suitable types, such as Pagurus, Pontobdella, a
Cestode and a Pyenogonid.

As announced in the preface to Ascipia, a donation
from the late Mr. F. H. Gossage, of Woolton, met the
expense of preparing the plates im illustration of the first
few Memoirs, and so enabled the Committee to commence
the publication of the series sooner than would otherwise
have been possible. Other donations received since from
Mrs. ILlolt, Sir John Brunner, and others, are regarded by
the Committee as a welcome encouragement, and have

been a great help in carrying on the work.

W. A. Uerpman.

University of Liverpool,

June, 1909.

LM:.B.C: MEMOIRS.

No. XVIII. ELEDONE.

(THe Ocrorvop CuUrrLEFIsH.)

BY

ANNIE ISGROVE, M.Sc.

PREFACE.

The greater part of the work for this Memoir has
been done in the Zoological Research Laboratory of the
Manchester University. I take this opportunity of
thanking Professor Hickson and Mr. Hewitt, of that
University, for their helpful suggestions. Dr. Hoyle, of
the Manchester Museum, also kindly lent me much of the
literature of the subject, and assisted me in various ways.
My thanks are due to the Council of the Marine Biological
Association of Great Britain for the use of a table at the
Plymouth Laboratory, during the Easter vacation, 1908,
and also to Mr. Chadwick of the Port Erin Biological
Station, for several useful notes with which he supplied
me as to the occurrence of Vledone cirrosa in that district,

its habits, method of capture and other details.

»)

ai

INTRODUCTION.

EKledone cirrosa (Lamarck, 1798), or Moschites cirrosa,
as it should be called according to the rules of the
International Zoological Congress, belongs to one of the
two genera of British Cephalopoda Octopoda. The
following table, showing the classification adopted in
Pelseneer’s Text Book, illustrates the relation in which
Kledone stands to other groups of Cephalopoda :—

Class C&PHALOPODA.

1. Sub-class Tetrabranchia, e.g. Nautilus.

2. Sub-class Dibranchia.

Order 1. Decapoda, e.g. Sepia.
Order IL. Octopoda.
Family Octopodidae—Genus KLEDONE.*

All Cephalopoda are aquatic marine animals. The
genus Lledone occurs in the Mediterranean, round the
Atlantic coasts of Hurope, and elsewhere. Hledone
cirrosa is the species confined to British waters, and is the
only British representative of the genus. To the other
British genus Octopus, belong O. vulgaris the common
“ Octopus,” and O. arcticus a smaller deep-sea form.

Kledone cirrosa has been chosen for this Memoir
because it is a convenient type for dissection, and may be
fairly easily obtained at the Plymouth and Port Erin
Biological Stations. It has also a certain economic
importance, feeding on crabs and lobsters, and often
extracting them from the crab and lobster pots put out
by the fishermen. Popularly /. cirrosa is known as “ the

* As shown by Dr. Hoyle (Manchester Memoirs, Vol. XLV, No. 3,
1901, the correct generic names for ‘‘ Octopus’’ and ‘‘ Hledone’’ are
Polypus and Moschites respectively. Hence the true title of Hledone
cirrosa is Moschites cirrosa. Yet, as the names Octopus and Hledone

have been in general use for 100 years or more, I think it on the
whole better to continue to use them.

5)

lesser Octopus,’ as 1t never attains the size of the common
Octopus. It is also distinguishable by the single row of
suckers on each arm.

OccURRENCE.

During the spring, Eledone is brought in from depths
of 30 to 35 fathoms, at Plymouth and Port Erin, by
trawlers and other fishermen. At this season, young
specimens have also been taken occasionally in a few
inches of water, at low water of spring tides, at Port
Krin. The Eledones brought up in the trawl are probably
caught while adhering to or creeping over stones and
rocks, or while swimming near the sea bottom. ‘They
seem to occur im smali groups of two to six in number.
At Port Erin and Plymouth they are also taken in crab
and lobster pots. These, at Port Erin, are put out at
depths of from six fathoms inside the bay to twelve
fathoms outside it. Although Kledone is always fed on
Crustacea, when kept in captivity, and careful examina-
tion of about fifty specimens has shown no other than
Crustacean food in the gut, yet occasionally at Port Erin,
the fishermen have taken Hledone on hand lines baited
with pieces of herrmg and mackerel. The mouths and
oral surfaces of such specimens are lacerated by the hook,
showing that the Kledones actually attack the bait.

During the winter Eledone leaves the shallow water,
round the South coast of Devonshire, and seeks the
warmer and deeper water in the centre of the channel.
Specimens taken in this season, from deep water,
generally die before the trawlers get back, probably from
cold. With the warmer months Eledone comes further
in, and so from May to September it is taken in
Plymouth Sound, at an average depth of eight fathoms;

and in a hot summer it is unusually abundant. Some-

4

times it is found stranded at low tide, in the rock pools
on various parts of the coast. Curiously enough, the
Eledones obtained are almost always females. The
relative abundance of the sexes appears to be fifty
females toone male. ‘This disparity in proportion is also
noticeable to a greater or less degree in all Cephalopods.
Possibly the males, besides being fewer in number,
remain in deeper water, the females alone coming in with
the warmer weather to spawn, or, again, the males may
have a different method of concealment.

HABITS.

Eledone cannot be called an active animal. When
kept in a tank, if undisturbed, it passes most of its time
resting. Its attitude is often, as Text fig. 1 shows, with
the arms bent at an acute angle to the body, and adhering
to the floor of the tank by the suckers on the proximal regions
ot the arms. The visceral dome also rests postero-ventrally
on the ground, and the eyes are more or less closed. At
other times it rests with the tentacles folded together so as
to form an oval dise of attachment by which it clings to
the wall of the tank, the body hanging downwards in the
water.

When disturbed, Mledone seeks to escape by
swimming rapidly backwards, the motion being obtained
by ejecting powerful jets of water forward from the
anterior opening of the funnel. When swimming, the
arms are stretched out horizontally in a straight line
with the rest of the body, while the visceral dome points
forwards. The eight arms lie closely together, and
looking down on the animal from above, six arms may be
seen. Of these the outermost pair—II ventral—are
curved outwardly in the middle region. Thus Kledone

does not use the web when swimming, but only when

5

sinking downwards through the water. Then the tps
of the arms separate radially like the ribs of an umbrella,
so as to stretch out the triangular pieces of web between
the arms.

Eledone has another mode of progression—creeping.
This it does with a gliding motion, sometimes slowly, at
other times more rapidly particularly when in pursuit of
food. When creeping, the body is raised from the floor
of the tank, and the animal advances somewhat in the
posture of the Text fig. I, creeping by means of the
suckers on the middle region of the arms. Sometimes

Fia. I.—Hledone cirrosa, at rest.

the suckers further down are used, and consequently the
body is raised higher, while the animal appears to
advance on tip-toe. Eledone generally creeps thus when
stalking prey. Often when creeping up the wall of the
tank, the arms are well separated, so that the web is
half extended. Apparently, Eledone only swims when
seeking to escape. Possibly when not in captivity it
may have nocturnal periods of activity, when swimming
takes place. Careful watching of active specimens has
not, however, revealed this habit, but that may be
explained, perhaps, as due to artificial conditions.

6

During the night Kledones will sometimes escape by
climbing over the walls, if in an uncovered tank.

The shape of the visceral dome varies considerably.
When resting, the body is shortish, and forms a bluntly
rounded stout sac, and the arms may be coiled up or
stretched out, and are often waved gently about; while at
other times they are passed over the surface of the body,
seeming to brush it, or are passed down into the mantle
cavity and then out again. When swimming, however,
the shape of the body alters. It becomes stretched out
antero-posteriorly, and so assumes a form very like that
of Sepia, while a lateral fold of skin becomes prominent,
which marks off the dorsal from the ventral surface, and
forms a delicate fin, very similar again to that found in
Sepia. Wave-like undulations, beginning at the front
and passing backward, pass along this temporary
balancing organ, which helps to support the body. With
the return to rest or creeping the fin is lost again,
becoming indistinguishable from the general body
surface. Also when swimming, a longitudinal median
depression on the ventral surface of the mantle indicates
the line of insertion of the vertical septum, on its inner
surface.

Kledone is often found in the morning adhering
halfway up the glass front of the tank, nearest the light.
At other times it hides in dark corners, and if stones are
provided, will heap these into a rough mound in a
corner of the tank and hide behind this. It was, no
doubt, this desire for dim seclusion that often led one to
rest with the cephalopedal mass inside a jam jar, which
was in one corner of the tank. Kledone, apparently,
dislikes a strong light, in which it seems quite incapable
of opening its eyes. If a light is brought near during

the night, the eye contracts and the animal retreats.

7

How long Eledone lives is not known. However,
from the fact that during the early spring quite young
specimens occur—probably hatched from the previous
summer's spawn—together with many stages between half
and full grown specimens, they probably live several
years under natural conditions. At present nothing 1s
known as to their rate of growth, or the size at which
sexual maturity is reached. Hledone is an extremely
delicate animal, and rapidly suffers if the tank in which
it is placed has not a good and constant supply of sea
water. Hence it is practically impossible to observe it
alive elsewhere than at the Marie Biological stations.
Confinement affects it in various ways. For instance,
although it was found, on dissecting several Hledones
which had been kept in captivity for some weeks, that
the ink sac was full of ink; yet after the violent ejection
of ink which occurred when the animals were first caught,
and one or two very slight subsequent discharges, no ink
was ever again poured out. Hven when being killed, no
ink was ejected, although the body was convulsed, and
the animal appeared to make a great effort to discharge
the secretion.

Foon.

As Eledone is taken in both crab and lobster pots,
probably it eats both these Crustaceans. However, when
kept in tanks, it is generally fed on crabs, and crab
remains alone were found in the gut of numerous
specimens which were examined. It has been known to
attack and devour the Norway lobster, and will take
prawns or shrimps when they are placed in the same tank.
Preferably it takes the Edible Crab, Cancer pagurus, but
Portunus depurator is also taken, and Carcinus moenas.

Eledone sometimes stalks its food, creeping after the

8

scuttling crabs in the posture previously described. With
a quick rush it generally reaches its prey and renders
it incapable of motion by spreading its arms over the crab.
Sometimes it gathers up several crabs simultaneously in

this way—taking an armful as it were. These are then
consumed one by one. At other times it secures its prey
by quickly swooping down upon it from the water above,
with the arms outstretched.

How, exactly, Kledone opens the crab cannot be seen,
as the arms cover over and so hide the prey from view
when it is being consumed. If, however, the dorsal
carapace is removed from a crab in the easiest way
possible, beginning at the posterior edge, and simply
pulling the shell away, the portion which comes away is
exactly similar in shape to that which Eledone leaves.
Hence probably it adopts this method of removing the
carapace with its beak, and then eats the soft body of
the crab. Usually the ventral exoskeleton and limbs of
the victim are left attached to one another, or the limbs
may be broken away. While feeding, Eledone curls its
arms about in the water, as though with pleasurable
excitement. No accurate observations have been made as
to the amount of food consumed in any given time. They
have been known to attack and eat one another, the arms
only of the victim, which is not necessarily killed, being
generally devoured. Only two records have been made
of the occurrence of /. cirrosa in the stomach of British
fish (the Angler and the Ling—see list below). It is not
improbable that dolphins and porpoises prey on the large
Kledones, while the young and therefore small and feeble
ones probably form food for various marine animals.
When they attain some size, the suckers and beak will
render them decidedly uninviting. Possibly their sinister
attitude and bright colour also protect them. Congers

9

will take pieces of the flesh when given as food, but other
fish refuse it altogether. Crabs will take it as food only
reluctantly, although they will readily eat weak or dead
Sepia.

Cephalopods have been recorded as follows from the
stomachs of British fishes :-

Loligo, in Cod, Whiting, Gurnard, Plaice, Skate.

Octopus, in Haddock, Ling, Whiting, Plaice.

Eledone, in Ling and Angler. (Two isolated cases
only.)

Rossia, in Haddock, Whiting, Cod, Gurnard, Dab,
and Longe Rough Dab.

Sepiola, in Whiting, Cod, Gurnard, Tope, Thorn-

back, Dab, and Pout.

EXTERNAL FEATURES.
Skin.

The skin of Eledone has a smooth external surface.
It is soft and slimy to the touch, and contains numerous
gland cells. These secrete an opaline mucus, which is
especially noticed while killing the animal, say, with
chloroform, when the body becomes coated with this
secretion. It is, however, by no means as thick or sticky
or as abundant as that secreted by Archzdoris, or the
common garden slugs, under similar conditions. In
appearance the skin is smooth and velvety, and reminds
one of a peach. It is also tough and elastic. . When
Eledone is quiet it may be noticed that the skin is finely
eranulated all over the body. In addition to these
eranulations, there are also larger conical processes or
cirri, on the head and back, of 6 to 12 mm. in height.

10

On the head there is a single pair of these cirri,
which remind one of slight horns, over the eyes (PI. I,
fig. 1, /.d.e.), and down the back there are about seven
rather irregular rows of five or six papillae. However,
when Eledone is agitated or moving about, the skin
appears to become tightened over the surface of the body,
and this stretching causes the granules and cirri to flatten
down, and become indistinguishable from the rest of the
surface. After a short period of rest, the slackening of
the skin causes the granules and cirri to reappear. These
processes are not visible after death, and so a true idea
of the skin of Hledone can only be gained by watching the
living animal.

The colouration of the body is due to the
chromatophores which lie in the dermis, and are only
absent from (1) the oral surface of the web, and (2) the
suckers and the oral surface of the basal parts of the
arms. Hence these parts are white, but when the web is
stretched open, the chromatophores on its aboral side may
be seen through as greenish dots, by transparency. The
following notes were made as to the colouration of
Kledones kept in the tanks of the Plymouth aquarium,
when undisturbed : —

1. Lower or ventral aboral surface of web hight buff,
with a pale green metallic tinge.

2. Dorsal aboral surface of web butt mainly, with
flecks of cream scattered in between the predominating
patches of buff; aboral surface of arms similar.

3. Funnel light and _— practically — colourless
posteriorly, with yellowish-brown colouration anteriorly.
The colour is deeper on the dorsal than on the ventral
surface of the funnel, where there is also some indication
of the metallic green tinge which is found on the ventral

surface of the web, and of the mantle sac.

al

4. On the ventral surface of the mantle sae the
brownish chromatophores are larger than in other parts
of the mantle, and situated further apart. The prevailing
colour here is white, with a ight, metallic green cast.

5. The dorsal surface of the visceral dome, lke that
of the web and head, shows patches of cream in between
large flecks of a reddish-buff colour. From the eyes two
oblique lines of cream colour slant inwards and meet,
forming a light-coloured V on the dorsal surface of the
head. The iris of the eye is deep orange in colour. The
chromatophores are continued over the free edge of the
mantle, for about half an inch inside the pallial cavity.
The marbling of the skin is most distinct when the
animal is recovering from excitement. When quiet the
cream and buff flecks fade into one another rather
indistinctly, while the intense blush caused by excitement
spreads all over the skin and temporarily eliminates the
marbling, but when recovering again, the cream flecks
show up well against the terra-cotta patches. When the
animal is excited the skin becomes of a very dark reddish
terra-cotta tinge. After death the eyes become dull, and
the skin loses its velvety gloss and beautiful colouration
utterly, and becomes overcast with a dull grey tinge.
When Hledone is frightened in any way, the skin changes
colour, and an intense pallor spreads over it, causing it to
become quite ghostly in appearance. At this time the
eye stands out very prominently, because the iris remains
dark orange, as does the eyelid surrounding it, and thus an
orange circular patch marks out the eye, on a whitened
body. However, under normal conditions this patch does
not stand outin any way. At the same time that the pallor
is seen the animal tries to escape by rapidly swimming
backwards, and attempts to eject ink. Almost
immediately the pallor is replaced by an_ intense

12

darkening or blush of deep terra-cotta colour over the
whole body. If allowed to come to rest again now, the
colour gradually lightens until the normal condition is
reached. If the animal is stimulated several times in
succession say by poking with a glass rod, or by bringing
a brightly coloured bottle near—it becomes exhausted,
the pallor becomes less intense, and the consequent
darkening less noticeable; also efforts to escape cease.
At night the colour is like that of the resting condition.
Structure of the Skin—The skin consists of a
columnar epidermis, and a subjacent and much thicker
dermis (Text fig. IT). It may easily be detached from the
muscular body wall, thus destroying the deeper layers of
the dermis. ‘lhe epidermal cells secrete a thin cuticular
protective layer externally, while internally they are each
produced into several fine processes which attach the
epidermis closely to the dermis.
The dermis is divisible into four layers, as follows :—
1. External fibrous layer (Text fig. II, H#.C.L.).
2. Layer with chromatophores (Text fig. II, Chr.).
3. Layer containing iridocysts (Text fig. II, Zrid.).
4. Internal fibrous layer. This is the thickest layer,
and connects the skin to the underlying muscles of the
body wall. It contains the vessels and nerves of the skin,
and also feeble muscular strands (Text fig. II, /.C.Z.).
Chromatophores.—These are extensible pigment-
containing vesicles, occurring in the external part of the
dermis (Text fig. II, Chr.). Their expansion and con-
traction cause the changes of colour so characteristic of
all Dibranchiate Cephalopoda. The origin, structure and
movements of the vesicles have been studied by many
people, and much variation of opinion exists on all three
poimts. The views of Rabl, Miiller, Klemensiewicz,
Frédéricq and Kolliker may be briefly summarised thus :

13

1. The central spherical cell, which contains
pigment granules, is a uninucleate cell which originates
in the epidermis and later sinks down into the dermis.
The cell wall is a tough elastic membrane, and the
pigment granules are arranged round the periphery of the
cell, leaving the central protoplasm clear.

2. A girdle of about 18 mesodermal cells becomes
grouped round the equatorial region of the pigmented
cell, in a plane parallel to the epidermis. These cells

Rr =
AM Ranate : sual
li 2 PAMwuli ne
Pe sd a
So unues CTS 4 .
arms eee
‘ - Pagrs( MMleme A
< Lot me . ity a-
D----- Bane : : tan -Srutdy,
. (ody iron zB V
: ; os S

i) ee Sales

Fic. 11.—Section of the skin. Highly magnified.

finally become differentiated into triangular muscular
bands of fibrous tissue, the basal side of the triangle
adhering to the wall of the vesicle, and the long thin
apical region being lost amid the surrounding tissue of
the dermis. A basal nucleus shows in each fibre.

3. The elasticity of the vesicle wall opposes the
contractile tendency of the radial fibres. When the latter
contract, and the wall relaxes, the vesicle becomes

stretched out and flattened in a plane parallel to the

14

epidermis. When the chromatophores are thus expanded,
the colour of the animal is very deep—this occurs when
Eledone is excited in some way. When the radial
muscles relax, the chromatophore contracts and the
animal becomes pale, as when frightened. In _ the
normally quiet state the chromatophore is in a state of
tension, and is shaped like a biconvex dise (II, Chr.). In
this stage it is in a semi-expanded condition, the
contractile tendency of the two elements being equally
balanced. However, the cell is constantly varying
slightly in shape, as one or the other of the forces gets
the upper hand; and so the chromatophore exhibits
incessant slight tremulous movements. Hence when
watching Eledone in an aquarium, one is struck by the
constantly varying colour of the skin.

Harting, Blanchard and Girod agree that the vesicle
is of ectodermal, and the girdle of mesodermal origin, but
they consider that all motion on the part of the
chromatophore is due to the amoeboid movements of the
vesicle itself, while the radial fibres are connective tissue
only.

Again Chun, who worked on the chromatophores of
Bolitaena, a deep sea form, disagrees with both these
views. In Bolitaena the chromatophore arises as a single
ectodermal cell which sinks down into the dermis. The
nucleus now divides repeatedly, while the cell throws out
about 18 pseudopodial processes, in the equatorial plane
parallel to the epidermis. At the base of each process is
found a corresponding nucleus, which has originated as
above. Later it is found that this girdle of processes has
become differentiated into a ring of triangular muscular
strands, whose contraction serves to expand the
chromatophore. A second muscular region becomes
differentiated round the periphery of the cell, and this

opposes the radial tracks, tending to contract the

15

chromatophore. Hence Chun in Bolitaena derives the
vesicle and the contractile apparatus wholly from one
ectodermal cell. He has also traced the nerve supply of
the chromatophores. For instance, the pallial nerve has
several purely chromato-motor strands which run
outwards to the external epithelium of the mantle, and
there divide up ultimately into fine terminal nerves, one
of which supplies each radial muscular strand, entering
it at the narrow distal end. These nerves control the
movements of the chromatophores, and therefore if the
pallial nerve be severed the movements of the chromato-
phores on the corresponding side of the mantle cease.
This method of origin, which Chun has described, may be
peculiar to the chromatophores of Bolttaena, and is
difficult to reconcile with the account given by Rabl and
others.

In Eledone the pigment granules are very minute
and of a reddish-buff colour. As in all Cephalopods, the
motion of the chromatophores continues some time after
death.

Iridocysts.— These are light-reflecting cells embedded
in the dermis below the chromatophore layer. ‘They are
uninucleate flattened cells, each of which contains two
rows of thin fibrillar laminae arranged parallel to one
another and reflecting the light, and so giving rise to the
peculiar metallic iridescence noticed in the integument.

TT.—ExtTEerRnAL ORGANISATION.

The body may be divided into two regions—an
anterior cephalopedal mass, and a posterior mass, or
visceral dome, covered by the mantle.

As in other Octopoda these two regions are united
dorsally by a thin superficial sheet of muscles.
Externally the two regions of the body cannot be

16

definitely marked off, but merge gradually into one
another. When touched with the hand, the body feels
soft and slimy and of about the consistency of a firm jelly.
The flesh retains its elasticity for some hours after death.
The following are the dimensions of a probably full-grown
Kledone, immediately after death :—

Length of arm ... ae hs «860mm.
Length of visceral dome et <> 160-mm:
Length of head ae ma . 28 So min
Total length ... af ny ... oo8 mm.
Width of head .. ie “te 8 is amt
Width of body at widest part i, 140mm:

(A, Cephalopedal Mass.—This mass, which forms the
greater part of the body of Kledone, as regards length,
consists, as the name implies, of the head and foot.

(1) Head.—The head is a solid oval mass, behind the
arms and anterior to the visceral dome. The anterior part
or buccal mass is hidden away inside the bases of the
arms, and hence only the posterior portion shows
externally. Laterally it bears the eyes, while the central
portion consists of the muscles which cover the brain
cartilage, ventrally and dorsally. To the ventral surface
of the head is attached the funnel (Pl. III, fig. 11, /.).

Cephalic Cartilage.—It is convenient to describe the
structure of the Cephalic and Orbital Cartilage here.
They are both built up of oval cells surrounded by a clear
matrix (Pl. VI, fig. 66a, C. cell and Matr.). These cells
have large oval nuclei, and are connected by fine
cytoplasmic processes one with another. Hence the
spaces occupied by the cartilage cells also intercommuni-
cate by canals down which these cell processes run.

(2) The Foot is divided into eight equal muscular
processes, or arms. In the female these are all similar,

but in the male the third right arm is hectocotylised

Lia,

counting ventrally from the dorsal surface. ‘The arms are
long, flexible tapering cones, slightly compressed
laterally, and closely connected at their bases, to form a
circular circumoral crown round the Buccal Mass (PI. I,
fig. 1, Br. app.). ‘The bases of the arms are connected by
a membranous semi-transparent web which extends for
about one-fifth of the length of the arm, as an inter-
brachial membrane. Further along it 1s continued as
lateral wings—one on each side of each arm—which
evadually diminish in size, and towards the distal end of
the arm can no longer be distinguished (PI. I, fig. 1, HW’.).
This web is characteristic of the family Octopodidae, to
which Octopus and Kledoue both belong. Measuring the
two dorsal arms and the body of half a dozen specimens of
Kledone, it is found that the relative length of the arm,
to the head and body, is 229 mm. to 113 mm. or roughly
2 to 1. There are about eighty suckers on each arm,
arranged in a single row. They have no horny ring, and
thus differ from the suckers in the Decapoda. Also they
are much shallower, and none are modified into hooks.
The suckers in Kledone are sessile, but the surface of the
arm which supports them is raised up beneath each sucker
into a flexible cylinder which really acts as a stalk, and

allows it to move freely about. Successive suckers are
separated from one another by a slight space. It is

noticeable that when these suckers are applied to any
surface, they do not keep in one straight row, but become
displaced laterally so as to give the effect of several
irregular rows of suckers on the arm. The sucker nearest
to the mouth is about 3mm. in diameter in a large
specimen, and equals in size those about half-way down
the arm. At first they increase in size working from the
mouth towards the tip of the arm, and the fifth and sixth
suckers are the largest which occur—about 12 mm. to

B

18

18mm. in diameter. From here they steadily decrease
again, towards the tip becoming almost too small for the
naked eye to distinguish. ‘The pressure they exert is very
great, and must render the prey completely helpless.
Even when only clinging to the hand with one tentacle,
Kledone can hold on firmly enough by sucker action to
enable one to lift the creature bodily out of the water.
Frequently the skin is shed from the surface of application
of the sucker.

Sph.
Sph.
St Pp
Arm.
> Mus. Fic. 111d.
SIE E IN : ;
Fig. 111 (a) Trans. sect. distal
part of arm showing relation
of sucker (S).
Ari. V: :
; Fia. III (6) Sagittal sect. of
sucker of Argonauta.
Ss. Aus

ince lolli

Text fig. III a, shows a diagram of a transverse
section through the arm, indicating the relation of the
sucker to the remaining muscles. III 6, is a modification
of Niemiec’s figure of the sucker of Argonauta. The
outer surface of the sucker is covered by the general skin
of the arm. ‘The inner lining is a much folded
epithelium, which covers the inner and outer divisions of
the adhesive cup (III a, If and I). A sphincter muscle
(Sph.) tends to close the upper and lower cups off from
one another, and this muscle is opposed by the vertical

extensor muscle (III 4, eat.). When the sucker is applied

19

to any object, the extensor relaxes, the sphincter
contracts, and the massive muscular base of the inner
chamber is elevated to meet the sphincter. Thus we have
a shallow flattened disc-like surface pressed closely
against the object to be held. Now the extensor contracts
and the sphincter relaxes a little, and the floor of the
inner chamber is drawn away from the object, producing
the desired vacuum.

All Cephalopods have power to regenerate injured
arms. Frequently specimens of Eledone have been seen
with several arms in process of regeneration. When an
arm is first injured, it is curled up spirally towards the

mouth so as to protect the injured part.

b.

ad.

Fie. 1V.—(a) Hectocotylised arm and (0) ordinary arm of male
H. aldrovandt. x 2.

Hectocotylisation.—The third right arm of the male
Kledone is hectocotylised, i.e, it is modified for the
purpose of transferring the spermatophores expelled from
the anterior opening of the funnel into the oviduct of the
female. As no male ZH. cirrosa could be obtained, Text
fig. IV a, shows the hectocotyhsed arm of a young
male H. aldrovandi, which is very similar. Some
Cephalopods have an autotomous hectocotylised arm, e.g.
Argonauta and Tremoctopus, and in these hectocotylisa-
tion reaches its extreme state of specialisation.
Spermatophores having been expelled from the funnel of

20

the male, are stored in this arm, which, when packed with
them, becomes detached and in some way enters the mantle
cavity of the female. The arm of Eledone, however, is
less specialised and not autotomous, and the chief
modification is at the tip, as in Octopus. Probably then
the tip of this arm is inserted in the terminal part of the
oviduct of the female, after the manner actually watched
and figured by Racovitza in the case of Octopus. The
hectocotylised arm of Hledone is somewhat shorter than
the others—-about 15 mm. less in the small specimen
examined of 4. aldrovandt. Mxamining the ventral sur-
face, it may be seen that the third right arm—counting
ventrally from the dorsal pair—bears a groove on its
ventral aspect (IV, gr.). ‘This is formed by a narrow fold
of skin, and runs from the base to the tip of the arm,
where the groove is enlarged to form an oval depression
on the oral surface of the arm tip (IV, depr.)

/

Moreover,
the other seven arms of the genus Hledone are somewhat
modified in the male. The suckers at the tip are set more
closely together than in the female, and are shallower
(IV 6, S). The sixth and seventh suckers from the tip
have practically no cavity at all, and the remaining ones
are represented by tiny flat pads (IV 6, P).

(b) Visceral dome.—'This is the name given to the
mass formed by the principal viscera of the body.
Externally it is enclosed by the thick muscular mantle.
It is oval in shape, being longer than it is broad, and
bluntly rounded posteriorly. Anteriorly the visceral
dome is marked off from the head by a slight constriction
or neck. The dorsal surface is more convex than the
ventral, and lies uppermost during creeping and
swimming. As the shell is greatly reduced in Eledone,
the visceral dome is unprotected save by the skin and
muscular mantle,

MANTLE.

The mantle encloses the visceral mass, forming a sac
with thick muscular walls, which extends from the
posterior end of the body as far as the posterior border
of the head dorsally and of the funnel ventrally (PI. I,
fig. 1; Pl. II, fig. 8; ,). Morphologically it is an out-
growth of the posterior part of the visceral envelope, and
hence its inner wall is continuous with the outer wall of
the visceral sac. The space between these two walls is
the mantle cavity. The anterior edge of this sac is fused
with the head dorsally, but ventrally and laterally it is
free, so that a wide entrance to the mantle cavity is thus
left.

The Mantle Cavity may best be studied by cutting
the mantle down from the free edge on each side
of the mid ventral line, so as to expose the organs
contained therein. It is a deep cavity, as in Sepia
and most Cephalopods, and is more spacious ventrally
and laterally than dorsally, in order to enclose the
important pallial complex. The body is bound to the
enveloping mantle by:—(1) The above-mentioned dorsal
fusion of head and mantle; (2) the shallow siphono-pallhial
articulation; (3) a vertical muscular septum running out
from the median ventral line of the inner surface of the
mantle to the visceral mass and dividing the mantle cavity
into symmetrical halves; (4) the posterior continuity of
the inner surface of the mantle with the external
epithelium of the visceral mass; (5) two pairs of
muscular bands running out from the afferent and efferent
axes respectively of the gills—the band running along the
outer surface of the efferent vessel is inserted on the inner
ventral surface of the mantle, posterior to the insertion of
the vertical septum, and that running along the inner

19)

at el

edge of the afferent vessel is inserted on the upper end of
the mantle cartilage, near the insertion of the funnel
retractor; (6) the depressor muscle of the funnel,
running out from the funnel to the mantle, near the
branchial heart (fig. 8, ”.D.); and (7) the great lateral
muscle running out from the cephalopedal mass to the
mantle (fig. 8, L.d/.).

The epithelium lining the mantle cavity is the
internal continuation, over the free border of the mantle,
of the outer skin of this structure, which here becomes
much thinner and loses its chromatophores, and hence is
transparent and colourless. [fowever, the epithelium
covering the dorsal side of the visceral sac bears large
chromatophores, which show through the mantle during
life on account of the transparency of this structure.

Stylets. On removing the genital gland and the
posterior portion of the alimentary canal, the dorsal
portion of the mantle is exposed, internally. ‘Two curved
tracks can be seen, roughly forming a V-shape, posterior
to the depressors of the funnel (Pl. III, fig. 13). By
dissecting away these muscles, and the great lateral
muscles, just at their bases, and then removing the inner
epithelium of the mantle, two colourless, semi-transparent
rods are exposed (Pl. III, fig. 18, C.S.). These are
chitinous rods, oval in section and tapering at both ends,
which reach down almost to the posterior end of the
mantle, and are embedded in its substance (PI. ITI,
fig. 16, a and 6). At the point of insertion of the funnel
depressor the rods are thickest. Pl. III, fig. 16,
represents a transverse section through the stylet, an stu
in the mantle. Hach stylet is enclosed in and secreted by
the walls of an epithelial sac, one cell thick only. These
cells are columnar, and are rather longer at the two ends
of the sac than in the central region (fig. 15, Hp.S.). This

figure also shows that the rods are built up of concentric
layers of chitin, the innermost, and therefore oldest,
layers staining most deeply. Among the chitinous layers
may be noticed a few cells with deeply staining nuclei.
These are probably degenerate cells from the epithelial
sac, which have become surrounded by chitin. Round
the sac is a layer of connective tissue, outside which can
be seen the muscles of the mantle (fig. 15, 1/,J/.).
According to Appelléf, the epithelial sacs in Octopus, and
therefore probably in Eledone, are formed by the shell
gland. This gland, after closing and sinking below the
external surface of the mantle, divides into two halves,
each of which takes up a lateral position and secretes the
stylet of its side. Hence these stylets represent the shell
in Eledone, i.e., they are the homologues of the shell of
other Mollusca, although much reduced in size and
importance. The fact that the great muscles of the
funnel, cephalopedal mass, and the muscles of the mantle
radiate from these stylets, also gives support to this view.
Possibly this degeneration of the shell in Eledone, as in
other Octopoda, may be explained by the fact that it is no
longer needed as a means of protection. For we must
recognise that the means of offence and defence that
Eledone still has are most efficient—powerful suckers,
ereat biting jaws, immense bodily strength, together with
the ink sac and large far-seeing eyes.

Dorsal fusion of head and mantle.—In the Decapoda
the head and visceral dome are not as a general rule
united dorsally. However, in Sepiola there is a narrow
connection between the two. Eledone, like Octopus,
shows this dorsal fusion in a more complete stage. A thin
sheet of muscle is continued anteriorly from the dorsal
edge of the mantle over the region of the eyes, and fuses
with the muscular bases of the arms, thus forming a firm
dorsal union between the head and visceral dome.

24

a

Siphono-pallial articulation—This is very weak in
Eledone, as in all Octopoda. It consists of two shallow
ridges on the postero-ventral edge of the funnel, which
fit in two corresponding shallow grooves of the anterior
and inner ventral surface of the mantle (Pl. IT, fig. 9a,
Lf. gulm.gP2):

Vertical muscular septum.—This consists of two
symmetrical triangular sheets of muscle, which run out
from the mantle to the body and enclose the anus between
their anterior edges (Pl. II, fig. 8; Pl. III, fig. 11, m.s.,
m,s, and an.). The septum is covered by the general
epithelium of the mantle cavity. The shortest side of
each sheet is anterior, while the longest runs from the
base of the mantle out obliquely to the visceral mass.
The vertical line of attachment of the septum extends
from the ventral posterior extremity of the mantle to
within half an inch of its anterior edge (figs. 8 and 11,
m.s.a.). By referring to fig. 11 it will be seen that after
the septum enters the mantle cavity (e.m.), it is free for
some distance from the visceral mass, and hence adheres
only to the mantle. About half-way up the length of the
oviduct, it becomes attached to the visceral mass. Hence
there is free communication, posteriorly, between the
right and left halves of the mantle cavity (fig 11, P.C.).
Each of the two halves of the septum consists of two
rather thin sheets of muscle— (1) an upper sheet sloping
from the mantle, obliquely inwards and downwards, to
the body (figs. 8 and 11, m,); and (2)a lower sheet sloping
from the mantle, obliquely inwards and upwards, to the
body (figs. Sand 11, m..).

The lower strands of the upper sheet and the outer
strands of the lower sheet run towards one another, and
form a superficial sheet which runs along with the funnel
retractor muscle, down to the mantle (fig. 11, mL,

mp. ew., F'.).). The upper strands of the upper sheet,
and the inner strands of the lower sheet, after a superficial
course run together, and sinking deeper join in with the
great lateral muscle.

Muscles attaching gills to mantle.—The narrow
muscular band which runs along the external surface of
the efferent vessel of the gill, from the tip downwards,
after leaving this artery at the base of the gill, runs
obliquely inwards over the ventral surface of the kidney
to meet its fellow in the middle line (Pl. V, fig. 57,
Br.M.). The common strand now runs posteriorly, over
the ventral surface of the genital capsule, and is inserted
on the inner face of the mantle, just posterior to the
vertical septum. Possibly this strand affords additional
support to the genital gland, when it is enlarged at the
time of sexual activity, as well as serving to deflect the
ell.

FUNNEL.

This may well be studied along with the mantle
cavity, as it is closely related thereto. It is a hollow
conical structure, truncated anteriorly (PI. II, fig. 8, F.),
which is attached to the ventral surface of the head, and
is free laterally and ventrally, and for about the anterior
third of its dorsal wall (fig. 11, #.). The anterior and
external opening of the funnel is about 13mm. in
diameter, in a large specimen, while the posterior internal
opening is very much larger and forms the base of the
cone. At the posterior end, the ventral edge of the
funnel is recurved, ventrally and anteriorly. This forms
a ridge, which is more pronounced at the sides than in the
centre, and forms part of the funnel articulation (Pl. 11,
fie. 9a, l.f.r.). The weak locking apparatus is in strong

contrast with the firm one found in Sepia, Loligo and

26

other Decapods, and this means of locking the mantle
seems to have weakened as the dorsal fusion formed, and
so rendered it less necessary. Also, as Eledone is a much
less powerful swimmer than the Decapods, the need of a
strong funnel articulation is lessened. The funnel cavity
is three-chambered. ‘The central largest chamber alone
opens to the exterior, while the lateral chambers are blind
anteriorly. All three, however, open into the mantle
cavity. The central chamber is cut off laterally from the
side chambers by the great depressor or retractor muscle
of the funnel. This forms the ventral and ventro-lateral
wall of its own side of the funnel, and then runs out to

its insertion on the anterior border of the mantle cartilage

of its side. Two other pairs of muscular bands, which
are narrow and rather short, run in from the dorsal
surface of the funnel to the cephalopedal mass. They

act as protractors of the funnel, and are exposed by
cutting through the skin behind the funnel, as in PI. IT,
fig. 9, sk., and turning the funnel ventrally. The
protractors form a letter W, the external pair being
inserted above the inner pair, on the funnel wall. The
external pair run outwards and dorsally, to join in with
the capito-pedal muscles just below the eyes. The
internal pair run inwards to the ventral surface of the
cranial cartilage, and are attached there. The dorsal wall
of the funnel is formed by a broad pair of muscles which
then run outwards from the posterior lateral region of the
funnel to the top of the mantle. Thus with the depressor,
these two nuchal or collar muscles bound the lateral
funnel chamber. Hence the funnel muscles are arranged
in three sets: -

(a) One pair of depressors (fig. 9a,, /.D.),

(6) One pair of nuchal muscles (fig. 9, eo//.), and

tan)

(c) Two pairs of protractors (fig. 9, L.F.Pr., L.F.P1).

27

From the above description it can be seen that,
although water may enter the mantle cavity all along the
external opening of the mantle, yet when the funnel is
locked the only way out for the contents of the mantle
cavity—excretory or genital products, water, &c.—1s
through the central funnel chamber. As in other
Octopods, Eledone has no valve in the funnel. It has,
however, a large and elaborate mucous gland—Miiller’s
eland (PI. I, fig. 10, f.o.). This is four-lobed, and is an
elaboration of the internal epithelium of the funnel, and
may best be seen by opening the funnel ventrally, as in
Pl. II, fig. 15. It serves to lubricate the internal surface
of the funnel, which consequently is generally coated over
with opaline viscous mucus, rendering the e@land itself
rather obscure in fresh specimens. It may be seen, how-
ever, on scraping the mucus away.

Pallial Complex (figs. 8 and 11).—Under this general
term may be included those important organs situated in
the mantle cavity, together with the external apertures
of certain internal organs. Kledone, like other Cephalo-
pods, in spite of its high specialisation along certain lines,
has yet retained its primitive symmetry in certain
features, including the pallial complex. The organs of
the pallial complex are :—

(1) A pair of Gills, one on each side of the visceral
mass, and attached to it by muscles, vessels, &e.
(tig LE g.).

(2) The Anus, situated anteriorly, between the left
and right halves of the vertical septum (fig. 11, an.) ;

(8) The Urinary papillae—one pair, protruding for
about 12 mm. in a large specimen into the mantle cavity,
just in the angle between the base of the gill and the
visceral mass (fig. 11, Ur. p.). The urinary aperture is a
small hole at the tip of this papilla;

28

(4) Genital ducts. In the female these are a pair of
equally developed oviducts, which may be seen running
below the visceral epithelium from the urinary papilla
upwards for 12 to 24 mm., according to the size of
the specimen. The tip of the oviduct is alone free, and
protrudes for a short distance out from the visceral mass
into the mantle cavity, bearing the oviducal aperture at
its end, somewhat below the anterior end of the gill
(fig. 11, od. ap.). In the male (fig. 8), there is a single
genital duct—the penis situated similarly to the left
oviduct in the female (pen.).

Other organs exposed on opening the mantle cavity. —
After removing the vertical septum the following are
seen :—

(1) The intestine, running vertically up in the
median line, over the liver to the anus, with the anterior
vena cava lying on its left side ;

(2) The ventral surface of the liver, covered by the
visceral envelope; and

(3) The two kidney sacs, posterior to the liver.

Visceral envelope.—On removing the epithelium and
the septal muscle, which envelop the visceral mass of
Eledone, a muscular envelope external to this visceral
mass is exposed. Over it ventrally run the visceral nerves
(Pl. IX, fig. 69, V2se.N.). This envelope, dorsally, runs
from the posterior border of the cerebral cartilage, to
which it is attached, down to the level of the branchial
hearts, where it becomes adherent to the muscular mantle.
The dorsal region of the envelope is stouter than the
ventral, and contains large widely separated chromato-
phores, which probably show through the mantle during
life. The thin ventral region covers over the liver and
ink sac, but is dorsal to the rectum. It runs back from
the ventral posterior edge of the cranial cartilage to the

99

ae

anterior edge of the posterior division of the great venous
smus.(Pl, VII, fig. 53, S,V,), to the wall of which it is
attached by connective tissue. Ventrolaterally the
envelope is reinforced by the depressor muscles of the
funnel. Dorsolaterally it is similarly strengthened by
the great lateral cephalopedal muscles.

General conclusions.— Considering Hledone as a type
of the Cephalopod organisation, the following characters
are noticed :—

1. It retains the primitive bilateral symmetry of the
Phylum, and hence in this respect is less specialised than
many Gastropods such as Helix.

2. On comparison with more primitive members of
the Phylum, e.g. Chiton, it is seen that profound changes
have evidently occurred in the inter-relations of the head,
foot and visceral dome. The alimentary canal has turned
forward posteriorly, so becoming U-shaped. The anus
has been ventrally approximated to the mouth, the free
ends of the gills point anteriorly, the true morphologically
ventral surface of the body has been greatly abbreviated,
and the dorsal correspondingly lengthened. The mantle
now has the form of a pouch or sac, enclosing the visceral
dome. Simultaneously with these changes the foot ceased
to be used merely as a ventral creeping organ, and was
transformed into a circumoral mass. Probably this was
effected by the lateral regions of the foot growing up
dorsally, on each side of the head, and finally fusing above
it, the anterior edge meanwhile growing out into long

flexible processes.

30

DIGESTIVE SYSTEM.

The following is the best method of dissecting out the
alimentary canal :—

1. Remove the funnel from the ventral surface of
the head.

2. Cut down the web between the two ventral arms,
beginning anteriorly, and continue the cut down along
the ventral surface of the head, thus exposing the Buccal
bulb and the cartilage surrounding the brain.

3. Loosen the intestine from the liver, dissecting
out the ink sac from its place on the latter, so as to
enable the intestine to be turned back.

4. Loosen the liver at the sides, where it is connected
to the cephalopedal muscles, by cutting through the
visceral envelope, and then turn the liver forwards
(Pl. V, fig. 58a). The organs enclosed in the visceral sac
are now exposed. Pl. LV, fig. 17, represents the alimentary
canal, entirely dissected away from the surrounding
tissues, to give a clear representation of the relations of
the various parts. The alimentary canal is essentially a
U-shaped tube, the ventral limb of the U being the
shorter, and the anus being approximated to the mouth.

The Mouth is situated in the centre of the oral and
anterior surface of the arms (Pl. II, fig. 5). It is
circular, about 12 mm. to 22 mm. in diameter in large
specimens, and is surrounded by a circular lp the edge
of which is furnished with short finger-like papillae
(Pl. TV, fie. 17,.m23 Pl. UE stigs 6, 7 )s ee Uberextemnal
surface of the lip is continuous with that of the web, and
only marked off from it by a deep groove (fig. 6, g7,).
This edge of the web forms a kind of contractile outer lip.
The mouth leads imto a cavity with very thick and
muscular walls. ‘This is the Pharynx and the oval

ol

muscular mass enclosing it is known as the Buecal Mass
(fig. 17, B.ML.). The buccal mass is surrounded, and
therefore concealed, by the muscular bases of the arms
(Pl. III, fig. 14, B.W., arm). The pharynx is furnished
with two powerful chitinous jaws, whose shape curiously
resembles that of a parrot’s beak, and which are placed
dorsally and ventrally. Unlike the parrot, however, the
ventral jaw of Eledone, which bites outside the dorsal, is
the larger and wider (PI. IV, fig. 27, J, and J.). These
jaws bite vertically with great force, tearing up the food
captured and held by the suckers before it is passed on to
the rasping action of the radula. The anterior edge of
each jaw is thick, and dark brown in colour. The
trenchant border is sharp, and a raised ridge some
distance behind this gives attachment to the muscles
working the jaws (fig. 27, r.). This part of the jaw is
exposed by cutting away the lp (PI. IV, fig. 24).
Further in, they decrease in thickness, and their colour
lightens, and posteriorly they are thin, colourless, and
semi-transparent. On the floor of the pharynx, slightly
anterior to the middle point, is a muscular outerowth—
the tongue (fig. 24, ¢.). This forms the anterior wall of
the Radula sac, at the base of which is the growing point
of the radula (fig. 24, rad.). The Radula is a broad
chitinous ribbon which, issuing out of its sac, runs over
the upper and anterior surface of the tongue, which 1s
responsible for the rasping action of the radula, as it
works forwards, backwards and laterally. The tongue is
strengthened internally by two small cartilaginous strips,
which give it rigidity and also provide attachment for its
motor muscles. Here, then, the food cut up by the jaws
is further triturated. The teeth of the radula are large,
and each row consists of three on each side of a central
large tooth. The innermost of the three is the smallest,

and the outermost has a broad basal attaching portion (PI.
LV, fig. 25, Ce., 1, 2and 3). The radula, when removed
from its sac, is about 50 mm. long. In front of the
tongue is another outgrowth, the Sub-Radular organ, on
the tip of which opens the duct from the posterior salivary
glands. Thus the secretion from these glands is poured
on to the food before it is acted on by the radula (fig. 24,
s.r.0., 5,9,¢,). This duct enters the buccal mass below the
radular sac, after running above the sub-lingual gland
which is on the ventral surface of the bulb (fig. 24, s./..).
The paired ducts from the anterior salivary glands open
into the pharynx laterally and posteriorly (fig. 24, s.g.d.).
Thus it will be seen that the massive muscular wall of
the buccal bulb is formed chiefly by the muscles working
the jaws and the radula. Anteriorly it is attached to the
bases of the arms by a circular muscle band (Pl. III,
fig. 14, and PL. IV, fig. 20, ezre. m.), and posteriorly by two
ligaments (Pl. VII, fig. 53). Posteriorly the pharynx is
continued into the oesophagus.

The Oesophagus is a narrow tube running down
posteriorly to the stomach (fig. 17, oes.), dorsal to the
hepatic gland (Pl. V, fig. 38a). Its posterior end marks
the limit of the stomodaeum, the stomach, spiral caecum
and intestine being hypoblastic in origin in all Cephalo-
pods, while that part of the rectum posterior to the
aperture of the ink duct represents the very small
proctodaeum (Korschelt and Heider).

The internal surface of the oesophageal wall is thrown
into numerous longitudinal ridges (Pl. IV, fig. 18, and
Pl. V, fig. 33). Internally it is coated by a thin
chitinous layer, ridged correspondingly, which is
continued posteriorly as the chitinous lining of the
stomach (fig. 33, Cut. L.). About half-way down, the

b

oesophagus bears a large pouch-lke non-glandular

Bo

dilation or crop. ‘This is also lined with chitin, and
folded, and serves as a food reservoir when the stomach
is full (fig. 18, er.). At the base the oesophagus dilates,
and its wall and chitinous lining become smooth. (To
expose the anterior part of the oesophagus it will be
necessary to remove the ventral wall of the cranial
cartilage and the sub-oesophageal ganglia.)

Salivary Glands.—EHledone has five salivary glands:

1. Anterior salivary glands, 1 pair, closely applied
to the external surface of the buccal mass, posteriorly
Giga igs 88-92).

2. Posterior salivary glands, 1 pair, situated at the
side of the crop (fig. 17, 7.s, g,, and fig. 38a, s, g,).

3. One sub-lingual and median salivary gland,
situated in the ventral wall of the buccal mass (fig. 24,
$.b.G:.

These glands are granular in appearance, soft and
spongy in texture, and of a translucent whitish colour.
The anterior pair is much smaller than the posterior, and
is attached in the angle between the oesophagus and
buccal mass (PI. IV, fig. 20, s.g.). They are flattened oval
elands, bilobed posteriorly, and are about 16 x 12 mm. in
large specimens. The duct leads from a slightly elevated
ridge on the internal surface, inwards to the pharynx,
and is very short. Along with the duct, the artery and
nerve of the gland enter by this ridge (Pl. IV, fig. 22).

The posterior glands are large and flattened, and the
crop must be turned aside to expose them fully. They
are attached to the visceral sac by a suspensory ligament.
The duct leaves the anterior internal region where there
isa shght depression. Here also enters the artery of the
gland (Pl. IV, fig. 21, s, g, d,). They measure about
32 mm. X 25 mm., and the duct after a short course joins
its fellow to form an unpaired median ‘
c

‘posterior salivary

B4

duct,” which runs forward alongside the oesophagus to
the buccal mass (fig. 17).

The sub-lingual gland is oval, and_ thickened
posteriorly (Pl. IV, fig. 23, s./.g.). In those Cephalopods
whose development has been studied, it arises as an
infolding of the ventral wall of the pharynx of the
embryo, below and anterior to the sub-radular organ.
This infolded region then gives rise to many tubular
caeca, each of which opens independently by a minute
opening into the buccal cavity. These tubules, connected
together by indifferent tissue, thus form the compact
sub-lingual gland. The three salivary glands all consist
of glandular secretory tubules, embedded in a stroma of
connective tissue (Pl. V, figs. 34 and 35, Tw., Sér.).
These tubules are closely adpressed in the anterior glands,
but much further apart in the posterior glands, and
branch dichotomously here (figs. 35 and 34). The
secretory cells of the three glands are all similar, and are
columnar with a basal nucleus. The secretion forms in
globules in the anterior portion of the cell, and then falls
into the lumen of the tubule (Pl. V, fig. 36). The
secretion of these glands is a kind of mucus only, and
contains no ferment whatever (Frédéricq and Bourquelot).
The venous blood, collecting in the sinuses occurring in
the stroma of connective tissue which binds the secretory
tubules together, passes out directly into the perivisceral
venous sinus.

Stomach.—This is a very muscular grinding organ,
reminding one of the gizzard of a bird. Its ventral and
dorsal walls are thickened anteriorly into grinding pads.
These are thick and stout, and ridged internally. The
posterior and lateral walls are, however, thinner. The
oesophagus opens into the stomach at its right anterior
angle, and the origin of the spiral caecum and intestine

35

is quite near this point (figs. 17 and 18). In size the
stomach is rather less than the crop, and lke the
oesophagus is lined by an easily detachable layer of chitin.
This lining is specially thick where it covers the grinding
pads (figs. 18 and 19, ch,, pad.). Where it covers the
posterior wall of the stomach, however, it is smooth and
thin. At the exit of the spiral caecum and intestine the
cuticle ends, thus leaving a circular orifice through which
food passes onwards from the stomach (PI. V, fig. 38, or.).
The food is ground in the stomach, and also well mixed
up with the digestive fluid which enters from the spiral
caecum (Bourquelot), so that here digestion takes place.

Spiral Caecum.— A narrow passage leading out from
the stomach, soon bifurcates, and so gives rise to the spiral
caecum on the one hand and the intestine on the other
(Pl. V, fig. 38, Iné. ap.).

The spiral caecum is in reality a long narrow sac,
e.g., caecum in Loligo, which in the Octopodidae and
others becomes curled in a spiral of one and a half turns.
It is thin walled, and the internal septa are seen faintly
from outside (PI. IV, fig. 28). The columella of the spiral
is on the side opposite to the intestine (fig. 38). On
cutting open the caecum along the columellar edge, and
pinning it out, it will be seen that there is a series of
delicate folded valves, running transversely to its length
(fig. 38, v., v,). Cuvier described a spiral valve running
down the caecum in Octopus, but in Eledone there is a
series of short transverse valves instead, closely set. They
are widest centrally, and taper at their two ends, which
are attached to the columellar region of the wall. Along
this columellar region also runs a longitudinal fold, at
the side of which enters the common hepatic duct, some
distance from the anterior end of the caecum (fig. 38,
h.ap.). Probably this fold guides the digestive secretion

56

into the stomach and also into the intestine. Like the
intestine, the inner wall of the caecum is not covered by
any chitinous lining. It acts as a reservoir simply for the
hepato-pancreatic secretion, and no food of any kind was
recognised therein.

The Intestine.—Leaving the stomach, this long,
thin-walled, and slender organ, after running between
the two hepatic ducts, before their fusion, curves ventrally
upwards over the liver, over the ventral surface of which
it runs, curving first to the right, then in again to the
left, and then anteriorly to the anus. Just before it
reaches the anus, the ink duct enters the rectum by an
aperture at the tip of a small papilla on its dorsal wall.
The anus has a dorsal and a ventral lip, and bears two
small leaf-shaped appendages or “ ears’ laterally (PI. IV,
fig. 29). The internal wall of the intestine is ridged, the
two most prominent ridges being continued up from the
columellar ridge of the spiral caecum. In the initial
part of the intestine, the food which has been in great
part digested in the stomach is mixed with that portion
of the hepato-pancreatic fluid which enters this organ.
Hence digestion is completed here. The chief process,
however, occurring in the intestine is absorption of the
now digested food. Towards the rectal end of the
intestine, waste matter of a dull orange tinge collects.

Digestive Gland.—This large oval gland, although
often called the liver, does not secrete a fluid at all
comparable to the bile secreted by the liver of vertebrates.
It occupies almost the whole of the visceral sac, and lies
ventral to the crop and oesophagus. Although in Eledone it
consists of one lobe only, the paired duets and the analogy
with the Decapods indicate a fusion of two originally
distinct glands, which were situated laterally to the gut.
The ink sac lies in a deep groove excavated on the ventral

surface of the liver (fig. 17), and the two organs are sur-
rounded by a common iridescent membranous envelope,
outside and in addition to their individual coverings.
In a freshly obtained Eledone a bilobed oval whitish
region can be distinguished round the origin of the two
hepatic ducts (P]. VIII, fig. 32, P.). This is the so-called
pancreas, and shows up distinctly against the yellowish
green liver. The digestive gland as a whole is soft and
spongy, and enclosed in a very delicate membranous
envelope. It is built up of branching secretory tubules
which open into the hepatic ducts. The pancreatic
tubules likewise open into these ducts, further down.

According to Bourquelot, the digestive hepato-
pancreatic fluid poured into the spiral caecum is
colourless before digestion, and brownish after it. The
hepatic secretion consists of diastase, trypsin and pepsin,
while the pancreas secretes diastase also.

The opaque rather thick-walled hepatic ducts run
posteriorly, and after embracing the intestine unite to a
common channel which enters into the spiral caecum
(fig. 28). Hence the order of events in the digestive
economy of Eledone is as follows :—

(1) Food seized by the suckers is torn up by the jaws
and passed into the mouth.

(2) Here it is mixed with the mucous secretion of the
sub-lingual and posterior salivary glands.

(3) Next the radula rasps it and further breaks it up.

(4) As it passes into the oesophagus the secretion of
the anterior salivary glands is poured over it.

(5) Now it passes to the stomach. Here the food is
ground and mixed well. The hepato-pancreatic ferments
enter from the caecum or reservoir, and become mixed
with the food, and so digestion takes place.

(6) Next the food passes on out of the stomach into

38

the intestine, being prevented from entering into the
spiral caecum by the folds of the wall in this region.

(7) In the intestine digestion is finished, as some
proportion of the digestive fluid enters here. This region
is, however, chiefly that of absorption. After this, the
waste matter passes up to the anus and is ejected.

The Ink Sac, or anal gland of Eledone is a long,
somewhat pear-shaped gland, which opens into the dorsal
wall of the rectum, on a slight papilla, very near the
anus (Pl. IV, fig. 30, Z. p.). It is a much less developed
structure than the ink sac of the Decapoda, and, unlike
the latter, lies embedded in a groove on the ventral surface
of the liver, in a median position (Pl. VIII, fig. 32). To
expose it, the visceral envelope, and then the common
iridescent membrane round the liver and ink sac, must
be removed. Its dorsal wall lies in close contact with the
ventral epithelial wall of the liver. When the enveloping
membranes have been removed, the ink sac shows as a
dull metallic dark-blue organ. Great care must be
taken not to cut the wall, for the thick viscous
secretion is exceedingly hard to get rid of, and stains the
dissection deeply. The nerves should be traced before
removing the visceral envelope. ‘They come from two
sources in Sepia, and probably also in Eledone (Girod).
However, only those from one source have been followed
out, i.e. :—

(1) The visceral nerves running over the liver, in the
neighbourhood of the ink sac, send several branches
inwards, which end in its walls (Pl. VIII, fig. 31,
I,S, N,). Near the posterior end of the sac. a specially
large nerve runs in from each visceral trunk, and this,
after pursuing a downward course until it meets the
artery and vein of the ink sac, enters the gland along
with them (fig. 31, 7.S..).

Bh)

(2) In Sepia a branch from the gastric ganglion may
be followed up the wall of the intestine to its tip. At the
point where the ink duct joims the intestine this nerve
gives off a very fine branch which runs down the wall of
the duct and gland to the posterior end. This nerve
regulates the secretion of pigment, while the visceral
nerve branches control the muscular contraction of the
ink sae (Girod).

The ink sac has rather an elaborate vascular system.
The abdominal aorta, running up from the heart to the
intestine, gives off a vessel to the ink sac (Pl. VI, fig. 49,
I.S.A.). This enters at its base, first giving off at each
side a spirally curved vessel to the corresponding lobe of
the pancreas (fig. 32, P.A.). Then it divides into four
vessels, which become embedded in the wall of the ink
sac and send branches to the internal glandular
trabeculae. The ink duct also receives a small artery
from the terminal portion of the intestinal vessel.

The vein runs from the sac into the posterior part of
the anterior vena cava (posterior hepatic vein). It is
formed by the union of two vessels which run one on
either side of the ink sac and unite at its base. On their
way these receive branches from the sac, and much longer
ones from the liver and pancreas (fig. 32, Z.S.V.).

Structure.—Cutting a sagittal section of the gland,
the following portions may be seen:—(1) The basal
glandular part (Pl. IV, fig. 26, I. gid.); (2) the reservoir
above this (fig. 26, Res.) ; and (3) the duct, of about equal
length with the gland. Its terminal portion hes external
to the visceral envelope (fig. 32), and bears two internal
valves, just near the anterior end.

The glandular part, after being well washed, will be
seen to consist of numerous trabeculae, which branch and
run into one another (fig. 26, tr.). These are membranous,

10

perforated by small holes, and consist of a thin layer of
connective tissue covered on either side by the secretory
columnar epithelium. An oblique diaphragm limits the
region of the gland, and is perforated by a hole for the
passage of the ink. At the base of the gland is found a
whitish mass of round non-glandular cells (fig. 26, g/d,).
This is the formative region where the trabeculae
originate. The initially indifferent cells become differen-
tiated into either the connective tissue or the secretory
cells of the trabeculae. These trabeculae are constantly
being formed and travelling forwards to the anterior end
of the glandular region. ‘Tracing their course and
structure as they go, it is found that the young cells
gradually accumulate pigment granules, and when they
are full burst. Thus the ink is freed and the secretory
cells destroyed. Towards the anterior end of the gland,
then, the trabeculae disintegrate, and are constantly
replaced by the younger ones behind (Girod). The
secretion is a thick dark-brown liquid, and a few drops
will colour a large volume of water. On drying, a dark-
brown powder is obtained. ‘I'he liquid consists of a
colourless transparent plasma, having minute dark-
brown pigment granules in suspension. On analysis it
is found to contain both copper and iron, extracted from
the blood (Girod). Although the actual secretion of the
ink is continuous, its passage to the exterior is
intermittent and voluntary. After expulsion from the
anus, the ink is discharged, along with a jet of water,
through the funnel.

41

CIRCULATORY SYSTEM.

In order to dissect the vascular system of Eledone
adequately, it is necessary to inject the vessels. The
venous system is best injected from the anterior vena
cava, and the arterial system from the base of the efferent
blood vessel of one side. As the veins lie more
superficially than do the arteries, it is best to follow them
out first. If dissecting one specimen only for all the
systems, only the main blood vessels, e.g., the anterior,
abdominal, genital and efferent arteries, the three venae
cavae, and the veins of the arms, can be followed

satisfactorily.
The circulatory system will be described under the
following headings :— (1) Blood, (2) Heart, (3) Arterial

system, (4) Venous system.

The course which the blood follows in the body may
be briefly summarised as follows :——Blood which has been
aerated in the gills returns by means of the two efferent
vessels to the auricles, and thence into the ventricle of
the heart. From there it passes out to the body by the
anterior, posterior and genital aortae, and ultimately
reaches the arterial capillaries. Thence passing into the
veins, it finally enters the lateral venae cavae, which take
it back to the gill, thus completing the circulation.

Buioop.

The blood of Eledone is a clear limpid fluid, of very
pale blue colour. For examination it may be easily
obtained by opening the efferent artery, at the base of the
gill, or the anterior aorta, or again the anterior vena cava.
In contact with the oxygen of the air the blue colour soon
deepens. The various constituents of the blood are :—

(1) Small colourless amoeboid and very granular

42

corpuscles of 15 « diameter (PI. VI, fig. 44), with rounded
or slightly curved nuclei. After a lapse of several
minutes, these corpuscles are seen—if the blood is placed
in a watch-glass after withdrawal from the body—to
congregate together in large clusters.

(2) A quid medium, in which the above corpuscles
float, containing :—(1) Mineral salts (including iron in
small quantity, Girod); (2) slight traces of organic
compounds; and (35) 9 per cent. of the substance
Haemocyanin, an albuminous compound containing
copper. According to Cuénot, it is the great quantity of
copper present which gives the blue tinge to the blood.
This darkens when exposed to air, because of the oxidation
of the copper. The blood of Eledone, like that of all
Cephalopods, contains no fibrin. The analysis of the
contents of the blood plasma has not been made for
Ii. cirrosa, but Frédéricq and Cuénot made it for Octopus
and Sepia respectively. Two glands have been suggested
as the seat of origin of the blood corpuscles:— (1) The
branchial gland (Joubin), and (2) the white body
(Faussek).

Heart.

In Kledone the heart is situated just behind and to
the right of the stomach (PI. VI, fig. 42, V.). It is,
however, rather ventral to this organ, but dorsal to, and
therefore concealed by, the kidneys

The heart is rather smaller than the stomach, and
consists of three chambers, two auricles and a central
ventricle, into which the auricles open laterally, one at
each side. The two auricles are essentially the dilated
and slightly muscular basal portions of the efferent
branchial vessels, and may be defined as the portion of
these vessels lying between the posterior end of the gill
and: the ventricle (fig. 42, aw.). The auricles are
symmetrical, but the thicker walled, more fleshy ventricle

43

is asymmetrical in shape. The walls of this chamber are
muscular and, unlike the dark coloured branchial hearts,
of a whitish colour. The inner surface is produced into
numerous branching and interlacing fleshy pillars, which
are bathed in arterial blood (Pl. VI, fig. 45). The cavity
of the ventricle is incompletely divided into two chambers
by a fleshy partition which probably aids in ensuring the
distribution of blood through all three aortae during the
period of systole. This is triangular in shape, and as
the dorsal and anterior edges are attached to the
corresponding walls of the heart, while the basal side
hangs free, an incomplete vertical septum is thus formed.
(Pl. VI, figs. 47 @ and 3, tr. s., and fig. 45). The right
auricle leads into the right chamber, and the left auricle
similarly into the left chamber of the ventricle. The
anterior aorta is given off from the right anterior dorsal
corner of the heart, while the abdominal aorta leads out
of the ventral surface of the left chamber and the genital]
aorta from the posterior dorsal wall of the same (figs.
45, 46 and 47). Two semi-lunar valves guard the entrance
of each auricle into the ventricle. The free edge of each
is directed inwards into the ventricle (fig. 48, aw. v. and
au,v,). Consequently, at the moment of diastole they
open and allow blood to enter the ventricle from the
auricles, and at this time the blood in the two chambers
of the ventricle can mix freely. However, at the moment
of systole the valves close and prevent the reflux of blood
into the auricles. The ventricle is now completely
divided into two chambers by the partition, and the
blood from the right chamber is forced up the anterior
aorta, while the blood in the left flows into the abdominal
and genital aortae. ‘The anterior aorta also has two
smaller semi-lunar valves at its base. These have their
free edges turned towards the aorta. ‘They close during
diastole, and open during systole.

44

ARTERIAL SYSTEM.

The arterial blood in Eledone, as in Octopus, is
wholly enclosed in definite vessels. ‘These have muscular
walls, which are consequently stronger and thicker than
the membranous walls of the veins. The pressure of the
blood in the arteries is very great indeed, but is slight in
the veins (Frédérieq). As mentioned previously, the
arteries of Hledone radiate from three main trunks :—
(1) Anterior aorta, carrying blood to the cephalopedal
mass, the mantle and anterior portion of the alimentary
canal; (2) abdominal aorta, carrying blood to the
intestine and ink sac; and (3) genital artery, running
direct to the genital gland.

The anterior aorta is a large vessel which, leaving
the heart, runs forwards, and curving round the liver
runs dorsal to this organ, and then lying to the right of
the stomach follows its outline for a time. Then, entering
the large venous sinus surrounding the oesophagus, it
runs alongside and to the right of the latter almost as far
as the cranial cartilage (fig. 42, Ant. A.). Soon after its
origin, the anterior aorta gives off a large branch which
immediately bifurcates into the right and left pallial
arteries (fig. 42, LZ. Pall. A.). The right vessel curves
round dorsal to the aorta, and then runs internal to the
visceral envelope, towards the funnel retractor. Just
interior to this it gives off a vessel which runs up
anteriorly, on the inner side of the visceral envelope,
giving off several small branches during its course
(fig. 42, V,H,A,). This artery, after furnishing several
small branches to the retractor infundibuli, ends in the
base of the funnel. The main pallial vessel now runs
below the posterior part of this funnel retractor muscle,
and so gains the inner face of the ventral part of the
mantle, and then runs obliquely to the stellate ganglion

45

(fig. 42, St. G.). On its way it gives off several branches
to the right and left, which end in the substance of the
mantle. Running below the stellate ganglion, the pallial
artery ends in several branches which divide up in the
mantle substance.

The left pallial artery runs just internal to the
visceral envelope, dorsal to the stomach, where it gives off
a posterior branch to the visceral envelope. Then, running
almost transversely to the left, it gains the left depressor
of the funnel, after giving off an anterior branch. From
this point its course is similar to that of the right pallial

artery (fig. 42, 1. Pall. A.). Entering the venous sinus,

the aorta gives off a second large branch, the visceral
artery, which immediately gives off a branch ending in
small arteries on the right side of the stomach. Next it
gives off a large hepatic artery, which enters the liver
dorsally and posteriorly, and breaks up in its substance
(fig. 42, Hep. A.). Then, running down the groove
between the oesophagus and the stomach, it gives an
anterior branching artery to the lower part of the
oesophagus (fig. 42), an artery to the left wall of the
stomach, a branch to the intestine, and ends in many
branches to the spiral caecum. The aorta is hidden
anteriorly by the crop and salivary glands; when these
are turned aside it may be seen to give off a branch at the
level of the crop to the alimentary canal (fig. 42, Oes. A.),
and this branch gives off an anterior and a posterior fork
to the corresponding parts of the oesophagus, and several
branches to the walls of the crop. Near the anterior end
of the visceral envelope, the aorta gives off a small dorsal
artery to the muscles of the neck (fig. 42, V.A.), and then
divides into two smaller forks which run one on each side
of the oesophagus. An aperture on the ventral surface
of the brain, between the anterior infundibular nerves,

46

allows these two arteries to leave the central cavity of the
brain, through which they pass posteriorly, and gain the
ventral surface of the buccal mass, over which they run
obliquely (fig. 42, C.A.). At the anterior end of this
mass, each cephalic artery divides again. <A _— second
division of these four branches now gives the eight
brachial arteries (fig. 42, Arm. A.) which supply the
arms.

Each brachial artery runs down the centre of the arm,
external and closely applied to the brachial nerve
(Pl. VIII, fig. 80). Externally it gives off a series of
small arteries all along the arm, to the muscles and skin
of the external surface of the arm, and to the web
(Pl. VII, fig. 79). Internally the brachial artery
furnishes two branches to each sucker (fig. 79, S. a.).
These run up one on each side of the corresponding nerve
ganglion, and penetrating the muscles of the arm, end in
superficial small branches on the sucker and internal
surface of the arm. The brachial artery extends to the
tip of the arm, its size decreasing with the corresponding
lessening of that organ towards the tip.

Although the anterior and posterior salivary glands
are widely separated from one another, yet their arteries
have a common origin. Soon after its bifurcation, the
anterior aorta gives off two branches, one from each fork
(fig. 42). Each branch immediately divides again, one
artery running posteriorly to the corresponding posterior
salivary gland, which it enters anteriorly (fig. 42, S, A,),
and one branch (the pharyngeal artery, fig. 42, PA. A.)
running anteriorly to the buccal mass.

The pharyngeal arteries run forwards, one on each
side of the oesophagus, through the cranial cavity, and
emerging with the oesophagus reach the buccal mass.
Here each artery runs below the sub-oesophageal

47

ganglion, but internal to the neurilemma of this ganghon,
Le., between the neurilemma and the ganglionic
substance, and then divides into three branches. One of
these supplies the anterior salivary gland (Pl. VI, fig. 50,
S.A.), the anterior branch supplies the anterior lateral
wall of the buccal mass, and a third branch runs
ventrally, to supply the ventral posterior portion of the
buccal mass (fig. 50, B,A,, B.A.). Small arteries
accompany several of the nerves given off by the sub-
oesophageal ganglion. Anterior to the salivary and
pharyngeal arteries a second branch is given off which
divides into several arteries:—(1) an artery giving off a
branch to the funnel (fig. 42, /. A.), and then running
down on the inner side of the visceral envelope, to end
there by splitting up into many smaller branches (fig. 42,
V.H.A.); (2) a branch which follows the course of the
accessory pallial nerve, and so supplies the muscles of the
head, and the lateral chamber of the funnel; (5) a branch
to the eye (fig. 42, O. A.); and (4) a short branch running
inwards to the statocyst. The next branch given off by
these forks is a second artery to the eye (fig. 42, O. A.).
A second very fine branch to the anterior part of the
funnel is the last branch given off by the two forks of this
aorta (fig. 42, #, A,).

The Abdominal Aorta is much more slender and less
important than the anterior aorta. It arises anteriorly
from the ventral wall of the left chamber of the heart,
and runs forwards and ventrally. Soon after its origin it
gives off a left and right branchial artery. Each of these
runs transversely across to the corresponding gill, just
dorsal to the kidney sac, and ventral to the auricles
(fig. 42, Bl. A.). Further along, the abdominal aorta
gives off the artery of the ink sac, which runs inwards
and forwards to the base of that organ, giving off two

48

branches to the intestine on its way (PI. VI, fig. 49,
I. S. A., Int. A.). The abdominal aorta now curves
ventrally, and can be seen on the ventral surface of the
visceral mass, between the two diverging anterior ends of
the kidneys (Pl. V, fig. 87, Abd. A.). After giving off a
fairly large branch to the septal muscle (fig. 42, Sept. A.),
the abdominal aorta runs up alongside the intestine, to
end in fine branches on the rectum. In its course it gives
off several small intestinal branches, and also a second
septal branch (fig. 42, Sept, A,). To the left of this is
an important branch which terminates on the rectum,
after giving off several ramifying branches to the surface
of the liver, and a branch to the duct of the ink gland.

The right branchial artery, soon after its origin,
wives off a coronary artery to the walls of the
ventricle. The left branchial artery, running
behind the left kidney sac, soon bifureates (Pl. VI,
fig. 51, L. Bl. A.). One of the two forks running
along to the oviduct, gives off one or two small branches
to the auricle, and at the level of the oviducal gland
sends off a recurrent branch which runs down between
the water canal and the oviduct, to end in fine branches
on the wall of the genital capsule (fig. 51, /',, Fee.).
Other branches given off by this fork run to the flask-
like portion of the coelom, to the anterior part of the
oviduct (fig. 51, od.), and to the oviducal gland. The
other fork (fig. 51, /’,), after giving off a branch to the
genital capsule, runs over and feeds the branchial heart,
sends a second branch to the gonad, and ends in a vessel
running to the gill tip—alongside the branchial nerve
—and supplying each leaflet with nutrient vessels (fig. 51,
BISA)

The Genital aorta is an independent artery, given
off by the postero-dorsal wall of the left chamber of the

49)

ventricle. It runs posteriorly to the genital gland, and
ends in several ramifying branches to this organ (fig.

42, G.A.).
VENOUS SYSTEM.

The blood which has been carried to all parts of the
body by the arteries, ultimately passes from the
arterial to the venous capillaries, and then flows into a
system of veins with definite walls, which carry the
de-oxygenated blood back to the gills for aeration. Hence
in Eledone, as in most Cephalopods, the circulatory
system is highly organised. But still there is one large
venous sinus through which blood flows on its return to
the gills.

The blood from the arms is collected into two rather
wide, superficial vessels, which run one on each side of
the arm (Pl. VII, fig. 54, Arm V,, Arm V,, and

fig. 52). These lateral veins, externally or aborally

receive branches from the aboral part of the arm, and
from the web. Orally they receive a series of vessels
which alternate with the suckers (Pl. VII, fig. 58). All
these veins are superficial. The alternating vessels of
one side of the arm anastomose at their origin with those
of the other side of that arm (fig. 58). Towards the
bases of the arms, these brachial veins join in pairs
(figs. 52 and 54), each pair being formed by the neigh-
bouring veins of any two successive arms. Thus eight
vessels are formed, which run in the grooves between the
arms down to the level of the anterior border of the head
(fig. 52, Br. V.). On the way they receive numerous
branches from the surface of the arms and the web. The
posterior ends of these eight vessels are united by a
circular vessel of similar width, which embraces the head
superficially, just anterior to the eyes. Ventrally this

D

50

cephalic vessel joins the anterior vena cava, a wide vessel
running over the ventral wall of the cranial cartilage and
the liver, down to the kidneys. At the anterior end of
these it bifurcates, and each half runs behind the
corresponding kidney and soon meets a vessel running in
from the middle region of the venous sinus (fig. 52,
Abd. V.). These two vessels join to form the Lateral
Vena Cava of that side, which slants outwards and down-
wards to the branchial heart, behind the kidney (fig. 52,
L.V.C.). From the antero-external angle of this heart
the blood is led by the afferent branchial vessel to the
eill, and is distributed to branches which feed each
filament, and becoming aerated as it passes through the
thin gill laminae, is collected again into the efferent vessel
of the gill. The circular cephalic vessel also receives the
venous blood from the superficial muscles of the head and
neck by means of small branches which run into its
aboral wall (fig. 52, Ceph. V. and Sup. V.). The ventral-
most of the eight interbrachial vessels appears to run into
the cephalic vein sometimes to the right and sometimes
to the left of the origin of the anterior vena cava. Some
superficial muscles must be dissected away to expose the
circular vessel fully.

Below the origin of the second ventral interbrachial
vessel on each side, a large vessel runs in from the
surface of the mantle and the eye (fig. 52, J7.V’.). The
origin of this vessel is in the mantle. The whole of the
anterior part of the mantle is drained (Pl. VII, fig. 57) by
a series of vessels of which only (1) is on the internal
surface, while (2, 3 and 4) are external. These four
vessels unite to form one, which then receives a branch
from the postero-dorsal surface of the eyeball, and one
from the corresponding lateral wall of the funnel
(fig. 52, #,V,). Running up the ventral surface of the

51

eyeball, just below the skin, this vessel, after receiving
small branches on its way, joins the cephalic vessel. The
posterior part of the mantle is drained by veins
which radiate from a vessel running through the
substance of the mantle from its internal surface (figs. 52
and 57, M,V,). Here it is joined by the pallial vein,
and a vein from the so-called branchial * blood-making
oland.”” The large vessel formed by the union of these
three enters the lateral vena cava ventrally just before
the latter enters the branchial heart.

The pallial vein runs ventral to the corresponding
pallial artery, down from the stellate ganglion towards
the branchial heart. It is formed by the union of an
anastomosing network of vessels over the ventral surface
of the stellate ganglion, a branch from the great lateral
muscle, and several branches from the mantle, and on its
course receives several small pallial veins (fig. 52,
Pall. V.):

The Anterior Vena Cava lies cn the median ventral
surface of the visceral mass and is exposed at the same
time as the visceral nerves, by removing the septal muscle
and the epithelium covering the visceral mass. It lies
to the left of the rectum. Its walls are membranous and
semi-transparent. Posteriorly, as mentioned, it ends in
two forks which help to form the lateral venae cavae, and
anteriorly it originates in a vessel given off from the
ventro-posterior wall of the anterior division of the great
venous sinus (figs. 52 and 53, S,V,). Soon after its
origin it bifurcates, and the two halves run round the
origin of the internal funnel protractors, and join again
below it (fig. 52). Hach of these halves receives a vessel
which comes from the venous sinus surrounding the white
body, optic ganglion, &c., of the eye, pierces the ventral
eranial wall obliquely, and then enters the vena cava (fig.

52

52, Orb.V.). Just behind the origin of the funnel pro-
tractors are seen tyvo veins from the muscles of the head,
and a single ventral vein formed by the union of two
running down the back of the funnel (fig. 52, #.J’.). At
the level of the posterior edge of the funnel another branch
enters, which is formed by the union of branches from the
anterior surface of the visceral envelope and the posterior
dorsal funnel wall (fig. 52). Further back the anterior
vena cava receives a vessel dorsally from the antero-
ventral surface of the liver. This vessel also receives a
vein from the wall of the rectum. Ventrally, about the
same level, a pair of veins comes in from the funnel
depressors, receiving small branches from the visceral
envelope on their way. The next branch is from the
septal muscle, and is succeeded by another large vein
from the liver, entering dorsally, and draining the pos-
terior part of this organ. The final vessel which enters,
just before bifurcation, is from the intestine. The small
side fig. in fig. 52 illustrates the two valves at the anterior
end of the vena cava.

The Lateral Venae Cavae, and the two vessels which
run into them from the venous sinus, bear the so-called
venous appendages on their posterior walls (fig. 52,
Abd.V.and L.V.C.). These appendages are club-shaped
outgrowths of the vessel wall, arranged in five or six
irregular rows, the narrow end being that by which they
open into the veins. On opening up the lateral vena cava
(fig. 56) and examining the posterior internal wall, one
sees the circular aperture leading into each venous
appendage. This aperture opens into a short vessel whose
walls are again pierced by other smaller apertures leading
into a smaller series of vessels similarly pierced, and so
on, so that each appendage contains in its interior a
system of radiating vessels which ultimately opens into

53

the great vena cava; and the blood in the vena cava thus
penetrates into this intricate system in the appendages on
its way to the gill. Now externally these appendages are
covered by the glandular wall of the kidney, as they
encroach on the cavity of the kidney sac. ‘They show
many furrows and minute holes on their external surface,
which are lined by the glandular kidney epithelium.
Hence the blood contained in the vascular network in the
appendages comes into intimate connection with the
glandular cells of the kidney, and is deprived of its
excretory products. The appendages are spongy and
yellowish im colour, and show through the ventral
transparent wall of the fresh kidney. The two vessels
running to the venae cavae from the venous sinus each
give oft a small branch to the ventricle near their ventral
ends (fig. 53, Cor.V.). Into the right abdominal vein
opens a large vein formed by the union of many branches
from the genital gland. Half way along its course this
vein receives two lesser vessels from the dorsal region of
the visceral envelope, and a branch from the spiral section
of the sinus (fig. 53, V.#.V.).

The Branchial hearts are purplish glandular organs
at the base of each gill, into which the lateral venae
cavae open, one at each side (Pl. VII, figs. 52 and 55). This
round opening is guarded by two semi-lunar valves which
open into the afferent vessel, and prevent the reflux of
blood from the gill (Pl. VII, fig. 56). The branchial
heart is an organ with very thick spongy walls, composed
of soft cellular tissue. The central lumen, however,
which these walls enclose is very small. On the internal
surface of the wall numerous large and small holes may
be seen, which lead into short canals (Pl. VII, fig. 56),
from which other smaller passages lead off, and a third
series from the second, and so on, the ultimate apertures

54

leading into small caeca. Hence the wall of the branchial
heart is penetrated in every direction by a system of short
vessels, which lead ultimately into the lumen of the
heart. Therefore venous blood, on entering the organ,
penetrates into this system of vessels before it passes on
into the afferent vessel which is given off at the antero-
external angle of the heart. Cuénot considers that the
purplish colour of the branchial heart is due to the
purplish concretions found in the cells of which it is
composed. By experiment he has proved that these cells
are excretory, and therefore that the branchial heart is a
glandular organ. ‘The venae cavae, branchial hearts and
vessels, and main aortae, as well as the heart, are all
rhythmically contractile.

The Venous Sinus extends from behind the mouth to
the posterior edge of the stomach, and is divided into three
cavities—anterior, central and posterior, the first two of
which communicate by important vessels with the large
veins. The wall of the sinus is a tough transparent
membrane.

1. The anterior division is small and is joined to the
middle division by a narrow region, which runs with the
oesophagus through the cavity of the ring-lke central
nervous system (fig. 53). The thin wall becomes adherent
to the buccal mass about half-way down its length
(fig. 53, B.M.), thus forming the anterior boundary of
the sinus. Hence the posterior portion of the buccal
mass, the anterior salivary glands, and the anterior
portion of the oesophagus, are bathed in the blood
contained in this division of the venous sinus.

2. The central division is much larger, and
narrower in the middle region than at its two extremities,
and contains the oesophagus, crop, posterior salivary

glands and stomach. However, the liver and ink sae,

55

enclosed in their common envelope, lie wholly outside and
ventral to the sinus (fig. 53, S,V.,). The anterior aorta
penetrates into the latter at the anterior end of the
stomach, and runs therein, leaving it only after its
anterior bifurcation. Several small infoldings of skin
attach the stomach to the wall of the sinus, forming small
mesenteries (fig. 53, JMJes.). The two abdominal veins
running from this cavity to the venae cavae, leave it
dorsally, one at each side, towards the anterior end of
the stomach (fig. 53, Abd.V.). Thus the blood from the
sinus is drained oft by these, and passes direct to the
lateral venae cavae, and thence to the gills.

3. The posterior division contains the spiral caecum,
which is attached to its wall by several small mesenteries.
The anterior wall of this region is common to it and the
middle division, but forms only an incomplete septum,
allowing free passage of blood, as it is pierced dorsally and
ventrally by a row of rather large holes (fig. 53, Lac.).
The intestine soon after its origin pierces the wall of the
middle region, and then bending up over the ventral
surface of the liver, lies wholly outside the sinus (fig. 53).
The two hepatic ducts pierce the wall of the posterior
region, and uniting inside this part of the sinus, enter the
spiral caecum. Into the adjacent portions of the venous
sinus open small veins from the buccal region, lips,
surface of the brain, and the different organs of the
alimentary canal which float freely in the sinus.

RESPIRATORY SYSTEM.
(1) Resprration.

The respiration of Eledone appears to agitate the
whole of the trunk. Water enters the mantle cavity by the
anterior opening during the period of inspiration, when
the sides of the body may be seen to swell outwards. At

56

this time the anterior edge of the funnel curves inwards,
and so causes the funnel aperture to become almost
completely closed (Pl. II, fig. Ta, f. cd.) In this sketch
it will also be seen that the anterior mantle slit is now
widely opened, to allow the water to pass inward (m.op.).
Inspiration is accompanied by a shght movement upwards
and backwards of the whole body. During expiration,
the walls of the body contract again, as the amount of
water contained in the mantle cavity becomes greatly
diminished. This water is, however, bound to go out by
the anterior funnel aperture (fig. 7b, f.op.), for this is
now wide open while the mantle sht is tightly closed by
the locking apparatus (fig. 7), m.cd.). With expiration
the body moves slightly downwards and forwards. When
a stream of borax carmine was passed in at the mantle
aperture, during inspiration, it was passed out again as a
red jet, from the anterior funnel opening, during
expiration. Thus the way the respiratory water passes
was indicated. The stream of water thus ejected is sent
out with great force, and disturbs the surrounding water
for a considerable distance. There appears to be no
constant rate of respiration. After a period of rest, say
in the early morning in an aquarium, the rate is some-
times as low as six per minute, while after agitation it
increases to sixteen per minute. During the daytime it
averaged twelve to fourteen. Smaller specimens appear to
breathe rather more rapidly than larger ones. While
resting, the tip of the funnel is generally seen protruding
either from below the right or the left side of the
body (Text fig. I). Hvery now and then Hledone
changes the funnel over from one side to the other, and
while so doing the respiratory movements slacken
considerably. Often the body will be noticed to heave

convulsively, and the respiration to quicken greatly, for a

Di
short time, when there is no apparent cause for

disturbance.
(II) Resprrarory Mrcuanism.

1. Gills—Eledone, in common with all the hving
Cephalopods except Nautilus, is Dibranchiate, i.e., it has
a single pair of gills. Morphologically these gills
represent part of the inner surface of the mantle, which
has been specialised for respiratory purposes. They are
situated in the mantle cavity, laterally to the visceral
mass. When the mantle is cut open, and turned back (as
in fig. 11), they may be seen slanting obliquely outwards
and upwards from the posterior end of the visceral mass.
In fig. 8, which shows the left division of the mantle
cavity, only one may be seen. ‘They are attached both to
the mantle and to the visceral mass. The gill may be
considered as a slender hollow cone, with the apex
pointing upwards and outwards. The hollow which forms
the base leads into the cavity of the cone, whose walls are
formed by the branchial leaflets. The cone is, however,
laterally compressed, and is attached to the mantle
dorsally, but free ventrally. Along this dorsal attached
axis of the gill runs the afferent vessel, while along the
free one runs the efferent vessel, so that the plane joining
these two axes bisects the gill, and is at right angles to
the plane of the mantle. The tip of the cone is situated
just posterior to the level of the anus, while the base is
slightly behind the urinary papilla. Below this may be
seen the branchial heart, which, receiving blood from the
body, pumps it on through the afferent vessel to the gill
for aeration. Posteriorly the gill is bound to the visceral
mass by—(1) The two muscular bands, mentioned in the
description of the mantle cavity. The first runs down the
ventral side of the efferent vessel, from its tip, and then,

58

leaving this vessel at the base of the gill, is continued in
towards its fellow over the ventral side of the visceral
mass. The second, running along the inner side of the
afferent vessel from its tip, is inserted with the depressor
infundibuli into the mantle, at the anterior end of the
mantle cartilage of its side. These two bands of muscle
probably serve to deflect the gill, and also by their
contraction help the circulation of blood in the vessel
each respectively covers. (2) The afferent and efferent
vessels, which are continued from the gill into the visceral
mass, help to bind them.

The septum which joins the mantle and gill together
is triangular in shape. The apex of the triangle points
posteriorly, and the base, which is the shortest side,
anteriorly. This side is free, and allows the gill to be
deflected laterally. That side of the triangle which joins
on to the mantle is the longest (Pl. V, fig. 59, Br. mem.).
The dorsal part of the septum is thin, membranous and
transparent in a fresh specimen, but along the edge
attached to the gill runs a broad fleshy band, the so-called
spleen,” which hes dorsal to the afferent vessel (fig. 59,
Br.gid.). During life the gills are exceedingly graceful
objects, semi-transparent and colourless, and are deflected
laterally to and fro in the mantle cavity.

The structure of the gill is exceedingly complex,
much more so than the gill of Sepia and other Decapods.
The walls of the hollow gill cone are formed by pillars of
connective tissue penetrated by blood vessels, and bearing
the aerating filaments on their outer surface (Pl. V, fig.
60). There are eleven to thirteen pairs of leaflets in
Eledone, the number varying slightly with the size of the
specimen. ‘These are arranged in alternate pairs, 1.e. the
supporting pillars on the external side of the gill
alternate with those on the internal surface. Counting

Sh)

towards the tip, from the base of the gill, the leaflets at
first increase in size, the third pair being the largest, and
from here they gradually decrease towards the tip. The
aerating filaments stretch from the afferent to the efferent
vessels, and each leaflet is separated from its neighbours
by a slit. Hence water can pass in and out of the cavity
of the gill either by the hole at the base, or by the shits
between the gill leaflets. Looking through these slits on
the external side of the gill, the leaflet of the other side
may be seen (fig. 60, Z. and L,). This sketch shows a
part of the gill from the internal side. At the bottom is
the branchial gland, and from it three gill leaflets may be
seen running ventrally to the efferent axis of the gill.
The centre leaflet has been taken away except for a part
at the base, in order to show more clearly the two
alternating ones on the opposite side. Posteriorly, these
leaflets are attached to the outer side of the afferent vessel
which runs up the gill on the inner side of the spleen
(Pl. VIII, fig. 63), lessening in size as the gill narrows
to the tip. Thus the afferent vessel, covered over by the
general lining of the mantle cavity, forms the dorsal wall
of the cavity of the gill. Similarly on the outer edge of
the gill, the efferent vessel runs from its tip downwards,
but a thin sheet of connective tissue (fig. 60, C.7.),
running inwards into the gill cavity from the efferent
axis, along the median plane, separates the efferent vessel
from the cavity of the gill, and forms the ventral
boundary of the latter (figs. 60 and 63).

The complex gill-leaflets are attached ventrally to
this sheet of tissue. First considering each leaflet as a
single sheet, it is seen that the aerating portion or
filament is on the external side of the attaching pillar,
and is consequently bathed in the water of the mantle
cavity. Hence blood brought into these filaments for

60

aeration comes into contact with the constantly changing
water supply of the mantle cavity, and 1s only separated
therefrom by the very delicate tissue of the gill tilaments.
Now, each filament is not a plain sheet, but is crinkled
or folded in such a way as to form half cylinders, which
alternate with one another as do the leaflets themselves,
on each side of the tissue which forms the axis of the
filament. ‘This may be understood from the figure
where the crinkled filament is shown from the external
surface (fig. 62, 7,, f., f,). This sheet of alternating
semicylindrical folds does not extend along the full
length of the supporting pillar, but only along the
anterior two-thirds in the case of all the filaments on the
internal side of the gill, while those on the external side
bear the aerating folds all along their length, and
consequently there are more of these folds here (fig. 60,
L,). The number of aerating folds also varies, of course,
with the size of the leaflet.

Now, if we consider each filament as an element
of the first order, each of these is crinkled into
alternating elements of the second order, these again, in
the same way, into elements of the third order, and so on
until the eighth series of elements is reached, these
ultimate folds being microscopic. Accessory gill leaflets
are situated on the vertical septum interior to the efferent
vessel, and occur in pairs between successive leaflets (fig.
60, L.acc.) all along the gill. Probably they originally
were attached to these leaflets, and now have moved
shghtly away. They equal one of the folds of the true
leaflets in size. In shape they are triangular, the apex
of the leaflet pointing downwards. Hach is crinkled into
five or six pairs of secondary elements, whose further
structure exactly resembles that of the ordinary secondary
element of the gill.

61

The afferent vessel of the gill runs along the dorsal
wall of the branchial cone (PI. VIII, fig. 63), ventral to
the spleen, giving off alternate branches on its way, to the
alternating internal and external gill leaflets. Narrowing
down with the gill, it runs to its tip. The branch to the
leaflet runs in the supporting pillar, and, therefore, on
the side next to the gill cavity. Running along to the
ventral side of this cavity, it joins another venous vessel,
parallel to the main afferent vessel, and forming the
ventral wall of the gill cone (fig. 63). Again, each of
these vessels to the leaflets or primary elements of the
gill, gives off similarly alternating vessels to the
secondary elements of the gill (fig. 65, V,, V,,), and so
on. However, these vessels run along the outer edge of
the secondary, tertiary, &c., elements (fig. 62). On the
internal surface of the gill, where the leaflets do not
bear secondary elements all along their axis, the four
lowest folds receive blood from a common vessel (fig. 6:3).
The secondary vessels running up along the outer edge
of the corresponding folds, decrease in size and end on
the external surface of the gill, at the tip of the fold
(fig. 62). As there are eight series of gill elements, and
consequently eight series of vessels, the ultimate ones
are extremely fine. They open into a venous lacuna in
the gill filaments, and the blood which by now is in
ereat part aerated and arterial, is gathered up again into
a network of arterial capillaries. | Each accessory leaflet
receives blood from a vessel given off by the vein parallel
to the main afferent vessel, and described above. This
vessel runs along the outer surface of the accessory leaflet
and divides up exactly as do the branches to the secondary
elements of the gill (fig. 63).

The finest arterial capillaries of the efferent vessels
are situated in the eighth elements of the gill. © Mach

62

fold here sends off rather larger vessels, that form a some-
what coarser meshwork in the seventh element, and so
on, till the secondary elements are reached. Now, in
the axis of each gill filament, about halfway between
the internal and external surfaces, runs the artery from
this leaflet, out to the efferent gill vessel (fig. 61, A,).
It originates in branches from the network of vessels in
the secondary elements of the gill, and the latter must
be turned aside to disclose both the artery and the
network (fig. 61, /V.).

The efferent vessels of the accessory leaflets also
originate in a network of capillaries. ©The meshwork
of arteries increases in size in succeeding elements of the
eill. Ultimately they open into two vessels:—(a) A
sinuous vessel common to, and between the two leaflets,
and opening into the efferent vessel of the true leaflet
between them, but on the opposite side of the gill (fig. 63,
and (b) A sinuous vessel on the other side of each
accessory leaflet, running into the efferent vessel of the
leaflet adjacent (fig. 63, 2).

The so-called Spleen or branchial gland of the
Cephalopods, would appear to have some intimate con-
nection with the blood,’ as it is irrigated by both arterial
and venous blood, and is placed close to the gill. It is
built up of polygonal cells, separated by lacunae of
various sizes containing blood (Pl. VI, fig. 68a; 6.s. and
/.b.s.). There are no true capillary vessels whatsoever.
Tt receives blood: (1) from branches which, coming
from the afferent vessel, furnish venous blood (fig.
63, Aff); and (2) from arteries running down
the supporting pillars of the branchial leaflets. These
arteries originate in a network formed by the arteries
of the accessory gills (fig. 63). This blood mixes
in the intercellular lacunae of the branchial gland,

63

and passing off in the vessel on its inner side, 1s carried
back by a vein to the lateral vena cava (fig. 65, Br. gld.
V.). This it enters just external to the branchial heart.
Probably this gland is connected with the manufacture
of the corpuscles of the blood of Kledone—and other

Cephalopods.
2. Skin.— As the skin of Eledone is very plentifully

supphed with capillaries, especially from the venous

system (fies. 57 and 58), it is possible that there is also a
certain amount of cutaneous respiration.

COKLOM.

All Molluses have a reduced coelom, and a corre-
spondingly dilated haemocoel. Although this pheno-
menon of ‘ phleboedesis’ has not been carried so far as
in the Arthropoda, still (1) the coelom has ceased to be
a true perivisceral cavity and its main remnants are the
pericardium and the genital cavity, which still communi-
cate with one another; and (2) large venous sinuses occur,
forming a secondary body cavity.

Whereas in Sepia the pericardium and genital
cavity are both well developed, and are only separated
from one another by an incomplete dorsal septum, in
Hledone and other Octopoda the pericardial division is
greatly modified and reduced. It is represented by a pair
of thin-walled, semi-transparent, flask-shaped pouches
(Pl. V, fig. 40, Coel.), situated laterally, dorsal and
posterior to the base of the ureters. Posteriorly each pouch
contains the corresponding branchial-heart-appendage,
or pericardial gland (fig. 40, Br. app.), while anteriorly
it opens into the corresponding ureter, by an oval reno-
pericardial aperture in the dorsal wall (fig. 40, PR. Pe. ap.).
The genital division of the coelom is well developed in

64

Kledone, and communicates with the exterior directly by
means of the genital ducts and indirectly by means of the
so-called ** Water Vascular Canals.” These are two long
slender ducts leading from the genital gland into the
pericardium. The right duct is partly shown (fig. 40,
W.V.C.) where the canal runs dorsal to the right kidney
and pericardium, and opens into the latter dorsally, just
behind the reno-pericardial opening. In the female there
are two symmetrical canals which are long, slender and
thick-walled, and open posteriorly into the genital capsule
(Pl. V, fig. 39, W.V.C. and ap. int.) - These internal
apertures are just exterior to the internal apertures of the
oviduct (fig. 39, 2. od. ap. int.). In the male, however,
the right canal alone resembles that of the female in width
and position, while the left is much wider—particularly
in the region near the genital gland—and opens into the
genital capsule quite anteriorly (Text fig. VII, A.p. 90).
In both sexes the pericardial pouches and the water canals
are lined by ciliated epithelium, and as shown (PI. VI,
fie. 51), the water canal follows the course of the sexual
duct for the greater part of its length.

EXCRETORY SYSTEM.

The Kidneys—a single pair of large transparent sacs

are exposed by stripping off the epithelium which covers
the visceral mass. ‘They lie on the postero-ventral surface
of the visceral mass, ventral to the heart and posterior
to the greater part of the alimentary canal (Pl. V, fig. 37,
R.K.). The left kidney stretches a httle further forward
than the right. In young females these sacs may cover
the whole postero-ventral surface of the body, but in older
females and all males the genital gland pushes them
anteriorly and laterally, by its ventral protrusion (fig. 37,

65

(’.). Henee the kidneys tend to diverge posteriorly.
They are triangular in shape, the longest side being
external. As they are wholly independent of one another,
they differ from the kidneys of Sepia, where the two are
in direct communication. The ureter is situated half way
down the external side of the sac, and bears the urinary
aperture at the tip (fig. 37, Ur. p.). When fresh, the
intestine, heart, liver, etc., may be seen through the
transparent walls of the urinary sacs. On opening the
kidney it is found to contain a thick colourless liquid in
which may be seen yellowish accretions of guanin—hboth
the liquid and the guanin being excretory products
eliminated from the blood by the glandular cells of the
kidney. Roundish colourless corpuscles are found floating
in the kidney fluid, and also numbers of the small
Mesozoan parasite, Vicyema miilleri, in various stages of
development (Pl. X, fig. 81). Behind the kidney run the
lateral venae cavae, and the two abdominal veins, and
where these vessels touch the kidney wall they are
produced into the club-shaped venous appendages. The
kidney wall, which elsewhere is quite smooth, membranous
and non-glandular, is composed of columnar glandular
cells where it covers these appendages. As shown (PI.
VII, fig. 56), these “ spongy bodies’ have their surfaces
furrowed by numerous folds and grooves, lined also by
the glandular excretory epithelium of the kidney. The
visceral mass dorsal to the kidney also protrudes into,
and so encroaches on, the cavity of the sac. The ureters
are canals about 12 mm. long, and are furrowed
longitudinally on their inner surface.

The Pericardial gland is a white gland of somewhat
depressed oval form, situated on the inner anterior wall of
the branchial heart, and enclosed in the pericardium
(fig. 40, Br. app.). Numerous folds run inwards from the

E

66

free surface of the gland, and in eross section appear as
narrow passages. From these passages secondary canals
run into the substance of the gland, and end in rounded
chambers. Into these chambers open minute caeca,
whose walls consist of the glandular excretory cells of the
organ. All the above passages are lined with non-
glandular cells. Blood entering the branchial heart,
fills the passages excavated in its walls, some of which
extend into the substance of the adjacent pericardial
gland. The blood thus comes into contact with the
excretory cells of the branchial heart appendage, and is
there deprived of waste matter.

NERVOUS SYSTEM,

All Cephalopods have a highly concentrated nervous
system, which reaches its maximum in Argonauta,
Octopus and then~//edone ranking next in the series.
The typical molluscan ganglia are so closely approxi-
mated, and so intimately connected, as to form a
peri-oesophageal nerve collar, just behind the buccal mass,
and between the eyes (Pl. TX, figs. 70 and 76). In
Eledone, this collar or “ brain” is enclosed in a tubular
cartilaginous capsule, the anterior and posterior ends of
which are closed by tough membranes. ‘These are
pierced for the passage of the oesophagus, posterior
salivary duct, pharyngeal arteries, &c. (Pl. X, figs. 85a
and 6, and 82, P.M/.). Round the brain, and separating
it from the cranial walls, is found a kind of gelatinous
transparent tissue.

Four pairs of ganglia, the cerebral, the brachial, the
pedal, and the visceral ganglia, form the brain of Hledone.
These pairs of ganglia are, however, very intimately

fused together, and although the supra-oesophageal or

67

cerebral gangha are distinguishable from the remaining,
sub-oesophageal ganglia, yet the three pairs which build
up this latter mass cannot be definitely marked off
externally one from another. Similarly any two ganglia
of a pair are intimately fused, so as to appear like one
mass only. The ganglion cells in these ganglia form
an external layer round a central fibrous mass.

The Cerebral ganglia form a supra-oesophageal mass
oval in dorsal view, triangular when seen laterally
(Pl. IX, figs. 76 and 70, C.G.). Three transverse grooves
mark the ganglionic mass externally into four divisions
which increase in size from the front, backwards. The
last and largest division is marked with longitudinal
alternating bands of white and grey matter, and the
regions of the above grooves are also grey. The anterior
division of this mass also bears a groove running antero-
posteriorly, along its dorsal middle line.

The Brachial ganglia form the anterior third of the
sub-oesophageal mass. They exceed in size the pedal
eangha, and together with these form a mass which is
morphologically equivalent to the pedal ganglia of other
Molluses (fig. 70, Br. G.). As the arms are so greatly
developed, while the remaining portion of the foot, the
funnel, is comparatively small, so the brachial gangha
exceed the pedal ganglia in size. The former are also
connected above the oesophagus by a slender supra-
oesophageal commissure.

The Pedal ganglia form the central and smallest
portion of the sub-oesophageal mass, and innervate the
funnel (epipodium) (fig. 70, Ped. G.).

The Visceral ganglia lie behind the pedal. Accord-
ing to Pelseneer, there are really two pairs of visceral
ganglia—an anterior pair (the pleural ganglia) lying
dorsally and giving off the pallial nerves, and a more

68

ventral pair posterior to these, which give off the visceral
nerves (fig. 70, Ant. Vise. G. and Vise. G.).

Commissures.—Short stout commissures connect the
sub- and supra-oesophageal nerve masses. ‘There are two
such pairs, the posterior being the broader:—(1) the
anterior pair, uniting the cerebral and brachial gangha,
and (2) the posterior pair, uniting the cerebral and
viscero-pedal masses.

NERVES.

From the brain are given off numerous pairs of
nerves, which innervate the different regions of the body.

A. The nerves given off from the cerebral gangha
are:—(1) Optic, (2) olfactory, (5) labial (4 pairs), (4)
buccal, (5) anterior superior ophthalmic nérves, and the
motor nerves of the eyeball.

B. The nerves given off from the sub-oesophageal
mass are:——(1) Posterior superior ophthalmic, (2) inferior
ophthalmic, and the motor nerves of the eyeball, (8)
anterior infundibular, (4) posterior infundibular, (6)
visceral, (6) pallial, (7) accessory pallial, (8) anterior
vena caval, (9) auditory, (10) brachial, (11) interbrachial,
and (12) the nerves of the head.

A. (1) The Optic nerves are stout, rather short
nerves running straight out from the lateral region of the
cerebral ganglion at the level of the posterior groove
(fig. 70, Opt..V.). In section the optic nerve is oval,
and piercing the cranial cartilage it enters the orbit
and there expands into a large oval optic ganglion from
which are given off nerves to the retina (PI. IX, fig. 71,
R.N.). These optic ganglia are each greater in bulk
than the two supra-oesophageal ganglia, and are about
twice as long as they are thick. Internal to the optic

ganglion, on the dorsal side of the aptic nerve, is a much

69

smaller oval ganglion (fig. 71, 0.g.). Chéron termed
this the olfactory ganglion, but Zernoff denies its
connection with the olfactory organ.

A. (2) The Olfactory nerves.—The strands of the
olfactory nerve are, at their origin, indistinguishable from
those of the optic nerve. They he ventral to these,
however, and run along with them to the optic ganglion.
Here they separate, and run on as a separate nerve, which
is absolutely independent of and unconnected with
Chéron’s olfactory ganglion (fig. 71, olf. N.). Beyond
the separation from the optic nerve it may be seen,
running external to the white body, on the internal wall
of the orbit (fig. 71, «.), where it pierces the wall of
the eyeball and then runs over the dorsal posterior wall
of the eye to the olfactory pit, which it innervates
(PlIX, fig. 74, olf. N. and-olf. P.).

A. (3) Labial nerves.—These are four pairs of fine
nerves, which run out from the anterior edge of the
cerebral ganglion and innervate the lip (fig. 76, a, 4, ¢,
and d). Leaving the cranial cavity, they pierce the
membranous wall which closes this cavity anteriorly, and
then run over the outer wall of the sinus venosus, which
here surrounds the buccal mass, anterior salivary glands,
and oesophagus (fig. 76, S.V.). Anterior to the sinus
venosus, they run over the outer wall of the buccal mass,
and so finally reach the lip, where they end in fine
branches. The innermost pair of labial nerves (fig. 76, @)
leave the cerebral ganglion one on each side of the
middle line, and running along the outer wall of the
sinus venosus, each soon divides into two. branches.
Reaching the anterior limit of the sinus venosus, each
half again gives off several small branches, which end
finally in the lip. The second and third pairs have a
similar course, the third pair being rather stouter than

70

the second (fig. 76, 6 and ¢). The fourth pair run
forwards and outwards over the wall of the sinus. Thus
they cross over the buccal nerves which run forwards and
inwards (fig. 76, d, and B. V.). Each of the two gives off
two branches, an inner and an outer. The three branches
thus obtained now run over the wall of the sinus to end
in the lip.

A. (4) Buccal Nerves.—These are two nerves much
stouter than the labial. Running from the outer anterior
angle of the cerebral ganglion each nerve pierces the
anterior cranial wall, and then runs inwards towards the
sub-oesophageal ganglion (Pl. VIII, fig. 72, B.Y.).
Arriving at the posterior lateral wall of the buccal mass,
this nerve divides into three branches (fig. 72, D., J/. and
V.). Of these, the most dorsal runs up to the sub-
oesophageal ganglion, the median ends in branches in
the buccal wall, while the ventral one curves downwards,
and ends similarly im the wall of the buccal mass. The
innermost branch given off from this ventral nerve runs
towards its fellow from the other side and meets it
just below the initial part of the radula sac, swelling
here to form a small, oval sub-radular ganglion (fig. 72,
ca

Ophthalmic Nerves..To <ee these it is best to
expose the eyes from the dorsal surface by dissecting
away the skin and superficial muscles from the back of
the head (Pl. IX, fig. 74, /.). Thus the muscles which
dorsally cover the brain case and the bases of the arms
are also exposed (fig. 74, 6, and a). There are three
groups of ophthalmic nerves on each side:—(1) three
anterior superior, (2) one posterior superior, and (3) three
inferior.

A. (5) The Anterior Superior Ophthalmic are three
fine nerves, which arise dorsal to the origin of the optic

el

nerve of the corresponding side (fig. 70 Ant. Sup. oph.).
The most anterior of these pierces the cranial cartilage and
so enters the orbit, and runs for a short time along its
inner wall. Then, piercing the muscles of the eyeball, it
runs external to this out to the eyelid, where it ends in
several fine branches (fig. 74, Ant. Sup. oph.). The two
posterior nerves are motor only. Piercing the cramial
wall, and entering the orbit, they are distributed to the
dorsal region of the muscles of the eyeball.

B. (1) The Posterior Superior Ophthalmic (fig. 74,
Post. Sup. oph.) is a rather stout nerve, arising from the
postero-dorsal angle of the visceral ganghon, anterior
to the pallial nerve (fig. 70). Running outwards, this
nerve penetrates the cranial wall and so enters the orbit.
Here it runs internally to the wall of the orbit, and
external to the white body for a short time, and soon
expands into a small oval ganglion. Piercing the
muscular wall of the eyeball, it runs over its outer surface
(fig. 74, Post. Swp.oph.), and finally ends in several
branches which are distributed to the eyelid.

B. (2) The Inferior Ophthalmic are three nerves
on each side, of which the posterior is the least and is
purely motor, being distributed to the inferior muscular
wall of the eyeball. All three nerves, arising from the
lateral face of the sub-oesophageal ganglionic mass, rather
in front of the median line, run outwards and enter the
orbit after piercing the cranial wall. The anterior nerve,
after running for a time on the inner wall of the orbit,
pierces this, and then runs along its outer wall to the
eyelid, where it ends in several fine branches. The
median nerve of the three is the largest and has a course
sunilar to that of the posterior superior nerve. Like this,
it bears a ganglion, but runs over the antero-inferior

surface of the eyeball (fig. 75, Inf. oph. N.).

72

B. (3) The Anterior Infundibular Nerve is given
off from the ventral surface of the brain, at about its
median point (fig. 70, Ant. Mun. N.). It is exterior to
the nerve of the anterior vena cava and ventral to the
auditory nerve. This nerve pierces the ventral wall of
the cramial cartilage (fig. 69) anterior to the statocysts.
Between the two anterior infundibular nerves is an oval
aperture, through which the two forks of the anterior
aorta leave the central cavity of the brain, and
reach its ventral surface (see arterial system in
Section IV). Just before the nerve leaves the
cranial cavity it gives off a fine branch which
leaves this cavity by an independent hole, and runs
to the protractors of the funnel on that side. After
leaving the cranial cavity the anterior infundibular nerve
gives off a second branch which supplies the posterior
dorsal wali of the funnel. Some of its branches run to
the wall of the lateral funnel chamber. Soon after, the
nerve gives off a third branch to the funnel. This ends
in several branches which run to the median wall of the
funnel. The anterior infundibular nerve runs on
anteriorly, and soon bifurcates, both halves entering the
funnel wall, and both supplying eventually the dorsal
wall of the funnel. The lower of these two branches
soon swells into an oval ganglion, which is about as large
as the smaller of the two ganglia on the course of the
visceral nerve. From the anterior end of this ganglion
several branches run, with the strands from the upper
branch, to the dorsal wall of the funnel. The ultimate
fine branches in which all these infundibular nerves end
form a complete anastomosinge network which quite
surrounds the funnel walls.

B. (4) The Posterior Infundibular Nerve runs out
from the brain just exterior to the corresponding visceral

73

nerve of that side (fig. 70, Post. Fun. N.). It is not so
stout a nerve as the visceral. Piercing the posterior
wall of the cranial cavity, external to this nerve, it runs
out to the postero-dorsal wall of the funnel (fig. 69, Post.
Fun. N.). Next it penetrates the visceral envelope, and
runs for a short time on the inner wall of this structure,
and then returns to its outer side (Pl. X, fig. 82). Then
it runs out to the funnel and innervates its posterior
region, splitting into three main forks (fig. 69):—(1) A
fine anterior strand which running forwards sphts up
into several branches innervating the funnel wall; (2) a
stouter median branch which ends similarly, just behind
the above; and (3) a posterior strand, which innervates
the depressor muscle of the funnel.

B. (5) The Visceral Nerves are very long and
stout. Much of their course may be followed by removing
the septal muscle, and also the epithelial cover of the
visceral mass, as they run over the ventral surface of the
liver. The visceral nerve is given off from the posterior
surface of the visceral ganglion, at its external and ventral
angle (fig. 70, Vese. V.). Piercing the membranous
posterior wall of the cranium, it reaches the inner surface
of the visceral envelope (fig. 82, dsc. V.), courses along
the inner surface of the visceral envelope, just to one side
of the median line, runs over the anterior surface of the
liver, and gains its ventral surface. In fig. 69, Vase. V.,
it may be seen on the ventral side of the visceral envelope,
which it has pierced. It is now separated from its fellow
by the anterior vena cava, alongside which the visceral
nerve runs for some time. Further back the visceral
nerves are also separated by the rectum, which les on the
right side of the vena cava (fig. 69, P.). At the level of
the anterior edge of the kidney, the visceral nerves begin
to slope away from one another, each running out towards

74

the branchial heart of its side. This slanting course at
first causes them to run external to the kidneys, but more
posteriorly they run over the kidney sac (fig. 69), and
then passing between the ureter and the oviduct—or
penis-—they gain the branchial heart, and finally end in
the branchial nerve which runs up the fleshy axis of the
gill (fig. 69, Bl. V.). The visceral nerve swells during its
course into two ganglia, of which the second is the larger.
The first is a small oval ganglion, just anterior to the
ureter. From it radiate fine nerves to the oviduct,
coelomic canal, flask-like division of the coelom, and the
aorta (fig. 69, g'). Two other fine nerves are given off,
one running down the surface of the kidney to the wall of
the genital capsule, while the outer and smaller nerve ends
in the kidney wall (fig. 69). The second ganglion is
larger, and is about 3 mm. across (fig. 69, g"). It is
attached to the cord dorsally, and adheres to the wall of
the branchial heart. Branches radiate out from its free
edge, to the walls of the lateral venae cavae, and the
efferent artery. Several branches are also given oft to the
substance of the branchial heart, and there is a small
anterior branch which runs to the muscles of the back.
Two longer branches sink down dorsal to the kidney, and
end in the back and the genital capsule respectively.
Beyond this ganglion the nerve may be called the
branchial nerve. Jt runs along that side of the gill
nearest to the visceral mass, just lateral to the afferent
blood vessel (fig. 69, Bl. V.). It gradually narrows down
with the decreasing size of the gill, and swells to a
ganglion at the level of each internal lamella of this organ
(fig. 69, Bl. g.). Kach ganglion gives off a nerve which
runs down the gill lamella to which it corresponds, and
also a second nerve which runs dorsal to the afferent

vessel, and so reaching the external side of the gill feeds

’
Th

the lamella alternating with the internal one. Soon after
attaining the ventral surface of the liver, the visceral
nerve gives off a large, much-branched nerve to the
anterior vena cava. This runs down along the wall of the
vessel to about the level where the ink duct enters the
visceral mass (fig. 69). A second branch runs out from
the main nerve, over the visceral envelope, and ends in
small branches to the depressor of the funnel. On its
way, this nerve gives off several branches to the visceral
envelope, and while that of the right side furnishes a long
branch to the bent region of the intestine, that of the left
sends a fine branch to the rectum (fig. 69). The visceral
nerve, during its course over the liver, gives off many fine
branches to that organ, to the ink sac, to the kidney wall,
&e. Nerves may also be seen running to the rectum and
the septal muscle.

B. (6) The Pallial Nerve is a broad flat nerve
eiven off from the posterior dorsal angle of the anterior
visceral ganglion (fig. 70, Pall. V.). Running posteriorly
and outwards, it pierces the membranous posterior
cranial wall, and so enters the visceral sac (fig. 82).
On entering the visceral sac it runs outwards and
posteriorly alone the inner wall of the visceral envelope,
towards the great lateral muscle, giving several branches
to the envelope in its course. Then it runs obliquely
through the lateral muscle, to terminate in a large flat
triangular star-shaped mass just exterior to this muscle.
This “stellate ganglion ”’ controls the movements of the
mantle, on the inner surface of which it lies, covered by
the internal epithelium of the mantle. In an adult
Medone the ganglion is about 6 mm. across, and _ its
surface is smooth. It gives off a radiating series of nerves
to the mantle. These nerves are all stout, and after
running for part of their course on the internal wall of

76

the mantle enter its substance, and divide up into smaller
branches, which end there, forming a network of nerves
throughout this organ. There are about fourteen of these
large branches, and also several short nerves which run
directly inwards into the mantle substance from that
surface of the stellate ganglion which is applied thereto.
The two longest radiating branches run down towards the
base of the gill, and innervate the posterior part of the
mantle (fig. 69). Internal to these longer nerves are
two shorter ones which run below the lateral muscle, and
then enter the mantle.

B. (7) The Accessory Pallial is a rather more
slender nerve, given off just dorsal to the pallial (figs. 69
and 70, Acc. Pall. N.). It pierces the cranial wall
dorsal to the pallial nerve, and runs alongside this for a
short time, on the inner surface of the visceral envelope.
Next it runs inwards and becomes embedded in the
muscles of the head. Here its fibres may be traced to the
lateral wall of the funnel and also to the great lateral]
muscle.

B. (8) The Nerve of the Anterior Vena Cava
arises just exterior to and behind the anterior funnel
nerve (fig. 70, Ant.V.N.). It is a fine nerve which,
after piercing the ventral wall of the cranial capsule,
curves ventrally round the wall of the anterior vena cava
(fig. 69), and ends in several fine branches.

B. (9) The Auditory Nerve is short and slender,
and runs to the auditory organ or statocyst, from its
point of origin, just above the anterior funnel nerve
(fie. 70, Aud. N.). Each auditory nerve running
posteriorly enters the statocyst at its interior and dorsal
angle, and then runs to the membranous vesicle, ending
in two branches, one to the sensory pad and the other to
the sensory ridge in that organ. In reality the fibres of

17
the auditory nerve arise from the cerebral ganglion
(Pelseneer).

B. (10) There are eight Brachial Nerves given off
from the anterior edge of the brachial ganglion (fig. 70,
Br. N.) which run forwards over the buccal mass, towards
the bases of the arms. ‘They run on the outer side of
the wall of the sinus venosus and may be seen there as
broad flat bands. Between the above wall and these
brachial nerves le the labial nerves, dorsally. Hach
brachial nerve runs up the centre of an arm, internal to
the corresponding brachial artery, and lessening towards
the tip of the tapering arm (PI. IX, fig. 69, and Pl. VIII,
fig. 80, Br. V.). At the base of the arms, im the region
where they are joined on to the cephale mass, a circular
nerve cord joins the eight brachial nerves together
(figs. 69 and 80, V.Cire.). This cord is of very peculiar
structure. Between the nerves it is single, but in the
region of the nerves it splits into two cords, of which the
anterior joins on to the brachial nerve, while the posterior
runs below it (fig. 69). Running up the arm the brachial
nerve bears a series of long elliptical ganglia on its oral
surface (PI. LX, fig. 77, S.@.). Mach ganglion corresponds
to a sucker, and gives oft two rows of small nerves which
run up to innervate these structures (fig. 77, S. WV.) and
also the muscles of the arm. A gelatinous transparent
tissue fills the space between the nerve cord and the walls
of the cavity containing it.

B. (11) Interbrachial Nerves.—Several small nerves
given off between the ventralmost brachial nerve and the
one above this run out and innervate the bases of the
arms. Also between the second and third, and the third
and fourth brachial nerve, counting upwards from below,
a fine nerve runs out to these muscles (fig. 70, Z.br.).

B. (12) Nerves of the Head.—J ust above the dorsal-

78

most brachial nerve, at its origin, a fine nerve on each
side runs outwards to innervate the muscles of the head

(fig. 70, H,).

Visceral Nervous System.

Kledone, like all other Cephalopods, possesses a
visceral nervous system. There are two ganglia, one
situated near the anterior end of the alimentary canal,
and one near the stomach. The two are united by a long
nerve which runs down the wall of the oesophagus. EKach
of them gives off several nerves to the neighbouring parts
of the alimentary canal. This system is connected with
the central nervous system by means of the buccal nerve
only.

The Sub-oesophageal Ganglion represents the
anterior centre of the visceral system (fig. 72, Oes. g.). It
is a fairly large, bilaterally symmetrical, flattened
ganglion, situated in the acute angle between the buccal
mass and the oesophagus. To expose it properly, the
anterior salivary gland must be turned forward (P]l. VIII,
fig. 72, s.g.). Looked at laterally, the ganglion is
roughly triangular. ‘The buccal nerves enter it at its
posterior external angles (fig. 72, B.N.). From the
anterior angle the ganglion gives off several nerves. Of
these, the lowest enters the buccal mass, the next runs to
the anterior salivary gland (fig. 72, a and 6 resp.), the
third enters the buccal mass (fig. 72, ¢.), the uppermost
(fig. 72, d.) runs up to the oesophagus, and then
anteriorly along its wall to the buccal mass. The
posterior edge of the sub-oesophageal ganglion gives off
two nerves to the oesophagus. The anterior one is short
(fig.
the side of the oesophagus as far as the crop (fig. 72, ¢).

72, f), but the posterior one is long and runs down

Posterior to the crop the left and right nerves of this pair

79

join, and then this nerve runs along the ventral side of
the oesophagus down to the gastric ganghon. These two
nerves give off branches to the oesophagus all along
their course, and specially important ones alongside the
crop.

The Gastric Ganglion is the posterior centre of
the visceral nervous system, and les on the ventral
surface of the alimentary canal, just where the intestine
and spiral caecum lead out of the stomach. It is
triangular, about the size of a wheat grain, and is exposed
on turning forward the liver (Pl. V, fig. 38 a, and Pl. IX,
fo ta Gg: )-

A. From its right upper corner it gives off:—(1) A
large nerve which runs up over the ventral surface of the

riving off several

posterior part of the oesophagus, g

branches to the wall on its way (fig. 73, a), continues its
course along the oesophagus, and ends in the sub-
oesophageal ganglion as previously described: (2) several
short branching nerves to the base of the oesophagus, and
to the ventral wall of the stomach (fig. 75, 6); (3) a large
nerve which runs along the groove marking the division
between oesophagus and stomach, and gives off small
branches on its way, ending by running round the right
side of the stomach to its dorsal border (fig. 75, ©).

B. From the left upper corner are given off: ——(1) A
large intestinal nerve which runs along to the anus
(fig. 73, €); (2) several small nerves which end in the
walls of the initial part of the intestine (fig. 75, /).

C. From the third and lowest angle of the gastric
ganglion are given off:—(1) Several branching nerves to
the spiral caecum (fig. 73, g); (2) two large and several
smaller nerves to the paired hepatic ducts (fig. 78, A).
These run upwards into the liver.

The large intestinal nerve, from analogy with Sepia,

80

gives off a fine branch to the ink gland at the level where
the ink duct enters the intestine. It has not, however,
been followed in Hledone. From the posterior edge of the
gastric ganglion are given off several small nerves to the
initial part of the intestine and spiral caecum, and also a
large branching nerve to the postero-ventral wall of the
stomach (fig. 73, d).

SENSE ORGANS.

The general surface of the body of Eledone is sensory,
the arms in particular forming slender sensory organs.
There are, in addition, well developed eyes, organs of
equilibration—the statocysts, and the olfactory organs
which probably function also as taste organs.

THe Eve.

Hledone has a pair of prominent eyes, situated one
on each side of the head (PI. I, fig. 1, #.). As in the case
of most Cephalopods, they are sessile. In large specimens
of /. cerrosa the diameter of the eye is about 25 mm.
Although it much resembles the vertebrate eye in several
respects, Le., both are vesiculate and both are very
complex and remarkably perfect in structure, yet there
are many profound differences. The eye of Kledone has
no anterior or aqueous chamber, no choroid, and the cells
of the retina are different from those of the vertebrate
retina. Again, while the Vertebrate has a cerebral eye,
that of Kledone originates as an invagination of the
epidermis, which later becomes elaborated into retina,
iris, &c. Another important point upon which they differ
is that while in vertebrates the optic nerve penetrates
the retina and enters the retinal cells from the front, in

81

the Cephalopod the fibres of the optic nerve enter the
retinal cells from behind and do not pierce the retina.
The circular external orifice of the eye is small, only
about 6°5 mm. in diameter, and is surrounded by the skin
of the head, and the muscular sheet which binds the
cephalopedal mass together and to the mantle, super-
ficially (Pl. X, figs. 83 and 84, eat. or.). This circular
rim round the eye forms an eyelid which can completely
close over that organ by radial contraction. Dorsally
this eyelid is continued over the aperture of the eye as a
membranous semilunar transparent fold (Pl. X, figs. 88
and 84, ps. ewt.). Ventrally another fold is continuous
with the eyelid, this fold also being transparent, but lying
below the dorsal one mentioned above, and extending
further over the eye (figs. 83 and 84, ps.int.). These
two membranes appear to be only slghtly if at all
moveable, and through them may be seen the pupil of
the eye (Pl. X, fig. 78, ps. mem.). Possibly water may
penetrate between them and so bathe the lens directly, as
in the Vegopsida. These two membranes may be called
the external and internal pseudocorneal membranes, the
internal being the thinner. Cutting away these two
membranes, the metallic deeply pigmented iris is
exposed; this iris bounding an oval pupil (fig. 78, Zris)
which it opens and closes by a dorso-ventral expansion or
contraction. Text fig. V shows the various stages of
contraction and expansion which occur in the eye of
Eledone. When resting, the eye seems to vary from (a)
to (d) without apparent cause. Stage (a), however, seems
to occur after a rest of long duration, i.e., it is noticed
when examining Eledone early in the morning. Stage (e)
shows the eye opened much more widely, as it is when
the animal is disturbed, and (f/f) shows the condition
during periods of great fright or agitation.
F

82

Looking into the pupil the lens can be seen. This is
a spherical ball, built up of concentric layers of a non-
cellular, transparent, cuticular, crystalline substance (fig.
78, L). Looking down into the pupil the eye appears
black, because the dark retina shows through the lens,
from behind.

a b c d e /
Fic. VY. Eye of E.ciwrrosa, showing various stages of dilatation of
pupil. x 2,

The eye is enclosed in a cartilaginous cup, that
adheres internally to the “skull.” This cup is thickest
at the base but much thinner at its external edge, which
reaches about half-way round the eye (fig. 85 a, orb. C.).
External to the capsule a strong muscular coat is attached
which surrounds the eye and extends as far as the hd
(fig. 78, Mat. Muse.). Internal to the capsule is a second
muscular coat, which extends to the border of the pupil,
and is more delicate than the first (fig. 78, Znt. M/usc.).
The retina, sclerotic, &c., form a roundish, rather
depressed chamber that only occupies about one-third of
the whole volume of the eye. Behind this chamber is a
second much larger one that contains the optic ganglion,
which gives off from its external surface a great number
of nervous strands to the retina, and the white body
(fig. 78, Opt. G. and W. B..).

The white body is a glandular mass surrounding the
optic ganglion, and consists of three lobes—one large
dorsal and two smaller ventral (Text fig. VI). This
body has been shown to be the remains of a
degenerate portion of the embryonic nervous system,

83

and possibly is the seat of formation of the blood
corpuscles. This, however, is doubtful, as its blood
supply, from the arteries of the eye, is very limited.
The skin which covers the eyelid, after being reflected
over the pseudo-corneal membranes, is continued down
the inner surface of the external muscular coat of the eye
(fig. 78, Conjunct.). Just anterior to the cartilaginous
capsule it is reflected on to the globe of the eye, and
running up clothes the iris as far as the pupil. Here it
is again reflected internally and runs down on the internal
surface of the iris, and then over the ciliary body, and
then is continued as the external layer of the true cornea.

This outer layer of the two-layered cornea thus arises

Vi
Fia. VI. Diagram showing relation -- Opt.G
of white body to eye and optic
ganglion. x 1.
ET TV i

from the infolded external skin of the head, while the
internal layer is the external part of the wall of the optic
vesicle, of which the internal part forms the retina.
Hence the internal layer of the cornea and the retina are
continuous. ‘The two corneal membranes secrete the lens
which thus is in two segments, an external smaller one
and a larger internal. The external division is a
seoment of a much larger sphere than is the internal, but
the two themselves are of equal area where they adjoin
the cornea. ‘They readily separate. The internal
segment alone corresponds morphologically with the
Gastropod lens. The rest of the ocular cavity is occupied
by the vitreous body—a thick, perfectly clear and
transparent fluid, contained in a thin membranous sac

84

(fig. 78, Vitr.). The white body and optic ganglion are
also contained in a thin-walled sac, which encloses a venous
blood sinus—this blood, therefore, bathing these organs.

The optic vesicle is covered posteriorly by a
tough semi-cartilaginous sclerotic (fig. 78, Sc/.). This is
iridescent, and reaches to the external border of the ciliary
body, which supports the lens. Posteriorly it is pierced
by numerous fine holes, which allow the passage of optic
nerve strands to the retina. ‘The internal wall of the iris
is very darkly pigmented, and raised anteriorly into a
circular ridge. While arterial blood is supphed to the
eye by two arteries which are given off by the anterior
aorta soon after bifurcation, the venous blood is drained
off into the above-mentioned venous sinus, and thence
passes by a vein through the ventral wall of the skull to
the anterior vena cava. As in all Cephalopods, the eye
may be adapted for near and distant vision by variation
of the distance between the lens and the retina.

The Retina is the most complex part of the eye
of Kledone. Anteriorly it is continuous with the ciliary
body and internal layer of the cornea, and it forms the
posterior wall of the optic vesicle. It is very deeply
pigmented with a dark brown retinal pigment. Grenacher
and Hesse made very careful examinations of the retina
of FE. moschata. ‘The structure (as given by Hesse) of this
retina appears to agree with that of H. cirrosa, except in
one point, which will be mentioned below. The retina
consists of a single layer of cells (see Pl. X, fig. 86),
which are of two kinds, retinal and limiting cells. The
former are long slender cells, alternating in position with
the rather shorter limiting cells (Pl. X, fig. 86, Ret. C.;
Lim.C.). There are three regions in the retinal cell :—
(1) The innermost and longest region, where the rods are
situated (fig. 86, Rod.); (2) the central shortest region,

85

where most of the characteristic dark brown retinal
pigment is collected (fig. 86, Pig.); and (3) the basal
region, which is external to the basal membrane, and
is continued outwards into fine nerve fibres continuous
with the nerve cells of the optic ganghon. The nucleus
also is found in this region (fig. 85, Opt. V. f.; Ret. N.).

There are two long slender cuticular rods in each
retinal cell. These are crescentic in cross section, and
enclose between them the cytoplasm of the cell. By
making a cross section of the retina, 1.e., at right angles
to the length of the cells, it will be seen that the rods
are arranged in groups of four, all four belonging to
adjacent but separate cells. Hence the two rods of any
cell belong to adjacent groups of four rhabdomes.

The limiting cells lie between the visual or retinal
cells. They are broadest at the base, and the roundish
nucleus is situated here. Also in this region there is an
accumulation of pigment granules, corresponding to that
wyeacn retinal, cell (Ply x. fig. 86, Lam.iV.). The
limiting cells are shorter than the visual cells, and end
just internal to the basal membrane (fig. 86, B,J/,).
This is a membrane of connective tissue, external to the
limiting cells therefore, but pierced by the retinal cells.
The region below this membrane and between the basal
part of the visual cells is occupied by connective tissue
and blood vessels (fig. 86, C. 7’.). In the region where
the rods are found the limiting cells extend forward only
as very fine protoplasmic processes (fig. 86, Liam, C,),
which are continued as far as, and secrete, the membrana
limitans, which covers the internal surface of the retina
(fig. 86, M. L.).

Hesse has observed in /. moschata a fine, somewhat
sinuous fibre which runs centrally down each retinal cell,
from the basal region, and ends in a minute knob at the

86

tip. ‘This fibre and knob he considers to be the termina-
tion of the nerve in the retinal cell. This continuity has,
however, not yet been seen in /. cirrosa.

There is in both species a second region where
pigment accumulates, towards the internal end of the
retinal cell (fig. 86, Pig,). The pigment here is connected
with the larger basal accumulation by a long slender
track. This track and internal accumulation surround
the nerve fibre and knob, according to Hesse.

In the dark, e.g., at night, the pigment all collects
at the base of the cells, but during the daylight much
flows up from here, and collects at the apex of the cells,
and so protects the delicate visual cells from excess of

hght.
THE OLFAcrory ORGAN.

Eledone has one pair of olfactory pits. These are
round, of about 3 mm. diameter, and situated just inside
the mantle cavity, in the angle between the postero-lateral
wall of the funnel and the mantle. Hence they cannot
easily be seen in the living specimens. They are shallow
pits, lined by horizontally folded epithelhum (Pl. X,
fee G6, 0l7. 22):

The epithelial lining consists of two kinds of tall
slender cells:_(1) Spindle shaped cells with large
nuclei, which are the true olfactory cells, each bearing
externally a stiff fine process, while internally they are
continued into fibres which run from the olfactory nerve,
and having, external to the nucleus, an oval, finely
eranulated body (Pl. VI, fig. 65, Olf. cell). (2) Mpithelial
cells, of long cylindrical form, which are interspersed
among the sensory cells (fig. 65, Mp. cell), and have their
internal ends drawn out into fine branching processes.

We have no evidence that this organ is really

S7

olfactory in function. More probably it is some kind of
taste organ. Its function may be the testing of the water

which enters the branchial cavity.

Tur AUDITORY ORGAN.

Kledone has one pair of statocysts, embedded in the
ventral wall of the cranial cartilage, and therefore just
below the sub-oesophageal nervous mass, between the
pedal and visceral gangha. ‘The membranous statocyst is
spherical, with a diameter of 6 mm., and lies in a
spherical cavity of somewhat larger dimensions. The
organ is attached to its cartilaginous capsule by a network
of fine arterial vessels, running to the wall of the vesicle
(Pl. VIII, fig. 68, Aud.caps., Aud.ves.). The venous
blood collects in the cavity of the capsule, and thence
passes out to the anterior vena cava, along with the blood
from the eye. Dorsally the smooth cartilaginous wall is
pierced by the auditory nerve and artery. Internally a
thin wall separates the two capsular cavities.

The Statocyst itself is a spherical transparent
structure, lined with a flattened epithelium. Its antero-
dorsal wall is thickened into an oval pad, whose internal
wall is covered with columnar cells, bearing numerous
short cilia (fig. 67, s.d.). Besides this sensory pad, there
is also a sensory ridge, which runs from the former round
the dorsal wall of the vesicle, then over the ventral, and
finally ends on the dorsal surface (fig. 67, s.r.). Between
these two sensory regions is a low conical ridge which
projects inwards from the wall of the vesicle (fig. 67, pr.).

The auditory nerve originates in the cerebral
ganglion, runs downwards, and leaving the pedal enters
the statocyst dorsally, and bifureates. One branch ends in
the pad, whereas the other supplies the ridge, which is

88

composed of two longitudinal rows of columnar ciliated
cells.

The cavity of the vesicle is filled by a clear trans-
parent fluid. Fitting on the pad internally is a small
conical calcareous statolith (fig. 67a, and 67, WStat.),
which is probably secreted by the cells of the pad.

The function of the statocyst is that of equilibration.
Experiments in cther Cephalopods have shown that
destruction of one or both statocysts causes loss of power
to balance properly in the water. ‘The description given
by Owsjannikow and Kowalevsky of the statocyst of
Octopus agrees with this organ in Kledone. Kolliker has
shown that the short blind finger-like canal, running
outwards from the wall of the vesicle near the
sensory ridge (fig. 67, A.C.), is the ciliated remnant of
the invagination which gives rise to the auditory pit, seen
in the embryos of Cephalopods.

REPRODUCTIVE SYSTEM.

I. FEMALE.

The Ovary occupies the posterior end of the visceral
dome. It is a large organ, the size varying with the
season, and with the maturity of the specimen. When
enlarged, the ovary pushes the kidneys which before
partially overlaid it forwards and to one side, thus
separating them posteriorly (Pl. V, fig. 37, G. and R. K.).

The gonad is a whitish oval gland, with a thick tough
wall. The ventral region of this wall alone bears the ova,
which are suspended from it in racemes. Hence the
germinal epithelium of the ovary is confined to this
ventral region. There are from 30 to 40 racemes of ova
(PIV, fiea95 005). Elsewhere the wall of the ovary is

smooth, with the exception of a much folded and twisted

89

patch, situated in the middle hne (fig. 39, gldr. p.).
Here there is a thickened region, intersected by many
sinuous lines. Above the oviducal apertures the patch is
trilobed, while below them it is bilobed and much larger.
This raised and folded region forms a frill round each
oviducal aperture, the two being separated by a folded
ridge (fig. 39, ¢.r.). There are two symmetrical, equally
developed oviducts, through which the ova pass from the
genital gland to the exterior. They open into the dorsal
wall of the genital gland by two closely approximated
apertures, one on each side of the middle line (Pl. V,
fig. 39, 2. od. ap. int.). The initial part of their course is
best followed by turning aside the ventral wall of the
ovary, together with the ova. The oviducts are embedded
in the substance of the dorsal wall of the ovary for some
distance beyond their origin, and are hence obscured ex-
ternally (fig. 39, emb,). It will be seen that the water
vascular canals are similarly embedded in the wall of the
ovary for the first part of their course. On reaching the
lateral wall of the ovary the two pairs of tubes become
free and run round the side of the genital gland to its
ventral surface. From this point the oviduct slants
obliquely forwards and outwards, dorsal to the kidney,
and at the level of the ureter reaches the ventral surface
of the visceral mass. About half-way down the duct
occurs a whitish oval swelling—the oviducal gland. As
shown in fig. 8, the terminal third of the oviduct is visible
from the mantle cavity, being only covered by the
epithelium of the visceral mass.

All the eggs in any given ovary are at the same stage
of maturity. The origin of the ova has not been followed
in Eledone, and the youngest specimens examined already
show the eggs well developed, and surrounded by a
nourishing egg follicle. In other Cephalopods the ova

90

are cells of the germinal wall, which sink below the
general epithelium, and then protrude into the ovary,
pushing the wall before them until they are completely
surrounded by an epithelial layer, several cells thick.
The egg itself becomes surrounded by a special nourishing
or follicular layer, at the expense of the surrounding cells.
With the growth of the ovum, this layer becomes actually
folded into the egg substance (Pl. IX, fig. 674, foll.), to
increase its surface of contact with the ovum. Further
protrusion and folding of the germinal wall gives rise to
the characteristic racemes (Pl. V, fig. 41, egg. R.).
Finally the follicle secretes the chorion round the mature
ovum, which now escapes, bursting through the covering
layers (fig. 676, C. 7.), and then passing out by the

oviduct.

Fie. VIL.—A. Bie. ViIT-—B. Fic. VII.—C.

Fic. VII.—Male reproductive organs of young E. aldrovandi. A, from
ventral side; B, genital duct as in situ, dorsal view; C, genital duct unravelled
to show various regions ; x 2.

Il. Mate.

It is not proposed to give a detailed account of the
male genital organs of Mledone, as no male specimen of
I). cirrosa could be obtained. However, the following
description of an immature male KH. aldrovandi will

91

probably resemble //. cirrosa in its general outlines. As
in the female, the genital gland is situated posterior to
the alimentary canal, at the extreme end of the visceral
dome. It is rounded in shape and opens to the exterior
by :—(1) Two coelomic canals, right and left, which open
anteriorly into the testes (Text fig. VIIa, W. V. C.); and
(2) one sexual duct, which is the left, the right being
atrophied. The binder portion of this duct 1s coiled into
a spiral mass lying on the left antero-dorsal wall of the
genital gland (Text figs. VIIa and s.). The different
regions into which it is divided when spread out are shown
in Text fig. VIIc. Much of this duct is ciliated internally.
The part visible from the mantle cavity resembles in
position and appearance the left oviduct of the female
(Pile dies,’ pen.)

A narrow winding vas deferens leads off the sperma-
tozoa from the testes (Text fig. VIIc, V.D.), and then
widens to form the vesicula seminalis. This region and
the prostate and accessory glands are concerned in the
formation of the spermatophores, 1.e., they form a tube
round the spermatozoa (Text fig. VIIc, V.S., Pr.).
Needham’s sac (Text fig. VIIc, N,), into which the
spermatophores now pass by a short thin vas efferens, is a
store, where they are arranged side by side longitudinally,
to await expulsion through the penis. As in the ovary of
the female, the ventral wall of the testis is alone

verminal.
SPAWNING.

The eggs examined were spawned by a specimen of
ii. cirrosa in a tank at Plymouth in July, 1903. Since
the crabs placed in the tank as food for the Kledones
attacked the ova, only two bunches were saved. The

ova have not, as yet, been dredged, or taken in the

92

trawl—possibly they are fastened by the mother amongst
rocks in inaccessible places.

The ova of H. ctrrosa are grouped in characteristic
strings during the spawning (PI. I, fig. 2). One female
deposits about 30 of these racemes, each consisting
of 25 to 30 eggs, so that the total number spawned
is about 800. The whole process of spawning lasts over
several days, the racemes being produced at intervals
during this time. According to Joubin, /. aldrovandi
will devour its own spawn if disturbed during the laying
process.

The spawn will now be described, so that the order of
events in spawning may be understood. The egg itself
is enclosed in a semi-transparent horny egg case (fig. 2,
h.c.), which is secreted by the follicular epithelium before
the expulsion of the ovum. Anteriorly this egg case is
drawn out into a string for attachment (egg. st.). These
strings seem first io be twisted together in groups
of four to six, and then the latter become intertwisted,
thus forming a main central horny axis, which is coated
externally by a thin dark layer of horn, and ends in a
flat disc which adheres to the glass front of the tank
(fig. 2, A.D.). The strings of ova are generally attached
on or near the glass front of the tank, about a foot from
the surface. The actual deposition of the eggs has been
observed at the Port Erin Biological Station by Mr.
Gravely, of Manchester University, who has kindly
furnished me with notes on the process for this Memoir.

For about two hours before the eggs were spawned,
the Eledone was seen clinging to the glass front of the
tank, with the small suckers on the proximal part of the
arm extended. Several very violent waves of contraction
passed over the body from behind forwards, and several

jets of water were directed by the funnel over the

93

proximal region of the arms and the mouth. The dorsal-
most pair of arms was loosely thrown back over the head,
and while the ventralmost was pressed against the ventral
posterior part of the body, the lateral pairs were thrust
into the mantle cavity, and appeared to press vigorously
against the visceral mass. Then the arms were all
twisted about in the water in an extraordinary spiral
manner. After these preliminary indications of great
excitement, and preparation for spawning, the Hledone
seemed to settle down, the small circumoral suckers were
approximated and extended so as to form a closed chamber
over the region of the mouth. Then the siphon was
inserted into this chamber, and a number of eggs passed
in. Next the circumoral suckers began to press
the very sticky glutinous substance which accompanied
the ova against the glass.

The proximal part of the bunch of eggs, together
with the adhesive disc, could now be seen, but the distal
part of the bunch was still hidden by the bases of the
arms. Next the suckers in this region moved the eggs
about and appeared to arrange them in their final con-
dition as described above. When first spawned the eggs
have no definite central cord, but appear to be held
together merely by the glutinous mass which accompanies
them. Then the two ventral arms press the bunch firmly
against the glass, and seem to test the firmness of the
adhesion. ‘The whole process, after the Mledone comes to
rest before spawning, occupies from fifteen to twenty
minutes.

Kledone very rarely spawns when in captivity—
possibly as a result of living under artificial conditions.
Hence the fact that it is never kept in aquaria throughout
the winter may possibly be explained as the result of
becoming egg-bound, as well as of too low a temperature.

94

At Port Erin, Eledone frequently appears to make
unsuccessful attempts to spawn, and in the late summer
the body swells up greatly and then begins to degenerate,
causing death. Possibly this may be due to the absence
of males.

The large ova of H. cirrosa are oval, and slightly
narrower at the tip than at the base, measuring about
19 x 65 mm. A large amount of yolk is present, in
fine granules. The only egg envelope, or chorion, 1s
transparent and horny, being drawn out into the attaching
string anteriorly. At this end also it is pierced by the
fine micropyle. The ovum is surrounded by a clear fluid,
and the formative protoplasm is aggregated at the anterior
end, and round the circumference of the ege cell. No
vitelline membrane is present, the follicular epithelium
in the ovary secreting the chorion.

During fertilisation it is probable that the male, as
in Octopus, deposits the spermatophores by means of the
hectocotylised arm, in the anterior end of the oviducts.
When these spermatophores burst, the free spermatozoa
enter the eggs by means of the micropyle. As Lledone
has no nidamental glands, the egg is not covered by any
capsule such as occurs in the case of Sepia, or jelly mass
as in the egg of Loligo. Since in KF. cirrosa the egg is
even larger and more yolk-laden than in Sepia, possibly
the development may be along similar lines.

No account of the development of /. cirrosa can be
civen, as no living material was obtained, nor has the
development of any member of the genus H/edone yet been
followed out. Drawings of two embryonic stages of
FE. aldrovandi are shown on Plate I. Figure 3 is that of
a rather younger embryo than is fig. 4 (after Korschelt),
and is drawn from some half-developed embryos kindly
given by Mr. HK. 5. Russell, of Glasgow University.

Je)
i

LITERATURE.

Brock. Geschlechtsorg. der Cephalop. Zeitschr. wiss. Zool.,
Vol. XXXII., pp. 1-108, pls. 1-4, 1879.

Brock. Phylogenie der Dibranch. Cephalop. Morph. Jahrb.,
Vol. VI., pp. 185-293, pls. 11-12, 1880. ;

Brock. Anatomie und Systematik der Cephalop. Zeitschr.
wiss. Zool., Vol. XXXVI., pp. 543-606, pls. 34-37, 1882.

BourqueLot. Recherches sur. la Digestion chez les Céphalop.
Arch. Zool. Exp. (2), Vol. TIL., pp. 1-73, pls. 1-3, 1885.

(HfRoN. Systeme nerveux des (éphalopodes dibranchieux.
Ann. Sci. Nat. (5), Vol. V., pp. 1-116, pls. 1-5, 1866.

Cuenor. Etudes sur le sang, &e. Arch. Zool. Exp. (2), Vol. IX.,
pp. 19-28, pl. 1, 1891.

Cuvier. Mémoires, &c., des Mollusques, pp. 1-54, pls. 1-4, Paris,
1817.

Freperrca. Recherches sur la physiologie du Poulpe. Arch.
Zool. Exp., Vol. VII, pp. 535-583, 1879.

Crop. Recherches sur la poche du noir des Céphalopodes.
Arch. Zool. Exp., Vol. X., pp. 1-98, pls. 1-5, 1882.

(irrop. Recherches sur la peau des Céphalopodes. Arch. Zool.
Kxp. (2), Vol. L., pp. 225-266, pl. 14, 1883.

GropsBeN. Morpholog. Studien itiber den Harn-und Gesch-
lechtsapparat, &c. Arb. Zool. Inst. Wien, Vol. V., pp. 179-252,
pls. 1-3, 1883-1884.

CGropsBen. Zur Kenntniss der Morphologie, &c., der Cephalopoden.
Arch. Zool. Inst. Wien, Vol. VII., pp. 61-82, 1886-1888.

Hesse. Untersuchungen tiber die Organe der Lichtempfindung.
Zeitschr. wiss. Zool., Vol. LXVIII., pp. 379-469, pls. 25-32, 1900.

Hoyze. ‘On the generic names Octopus, Eledone, and Histiop-
sis.’ Manchester Memoirs (3), Vol. XLV, No. 9; pp. 1-7, 1901.

Jupria, H. v. Ueber die Verwandtschaftsbeziehungen der Cepha-
lopoden. Zeitschr. wiss. Zool., Vol. XX XV, pp. 1-22, 1881.

JouBIN. Structure et développement de la branchie, &c. Areh.
Zool. Exp. (2), Vol. U1., pp. 75-150, pls. 4-6, 1885.

KEFERSTEIN. Kopfiisser, in: Klassen und Ordnungen des
Thierreichs, Vol. III., pp. 1307-1484, pls. 110-129, 1862-66.

Korscuett AND Herprr. Text-book of the Embryology of
Invertebrates, Part 4, pp. 235-310, 1900.

OwsJANNIKOW UND Kowatrvsky. Ueber das Centralnerven-
system, &e. Mém. Acad. Sci. St. Petersburg. Series 7, Vol. XI. (3),
pp. 1-36, pls. 1-5, 1867.

PreLSENEER. Sur la valeur morphologique des bras, Xe. Arch,
Biol., Vol. VIII., pp. 723-752, pls. 37-38, 1888.

PrISENEER. A Treatise on Zoology (Lankester), Vol. V., Mollusca.

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Dansk. Vidensk. Selskabs Skrifter, 1856. English translation: Ann.
and Mag. Nat. Hist. (2), Vol. XX, pp. 81-114, 2. pls., 1857.

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Nat., Vol. XVIL., pp. 147-185, pls. 6-9, 1852.

96

EXPLANATION
REFERENCE

= Base of arm.
a, = Arm tip.
an. = Anus.
an. l. = Anal appendage.
ap. int. = Opening of water canal.
au. = Auricle.
au. V., AU, V;= Semilunar valves.
A, = Artery of Br. filament.
As, Ayo A, — Arms,
A and D. = Anterior and dorsal.
A, D. = Adhesive disc.
A. V. C. = Anterior Vena Cava.
Abd. A. = Abdominal Aorta.

Abd. V. = Abdominal Vein.

Ac. Gl. = Accessory gland.

Acc. Pall. N. = Access. Pallial nerve.
Aff. v. = Afferent Branchial vessel.
Ant. A. = Anterior Aorta.

= Ant. Infundib. nerve.
= Ant. Sup. Ophth.

Ant. Fun. N.

Ant. Swp. oph.
nerve.

Ant. V. N. = Nerve of Ant. Vena Cava.

Ant. Vise. G. = Pleural ganglia.

Arm. A. = Brachial artery.

Arm V,, Arm V5. = Brachial veins.

Aud. caps. = Auditory capsule.

Aud. N. = Auditory nerve.

Aud. ves. = Auditory vesicle.

b. = Degenerate ovum.

b, = Muscles over Cranial Cartilage.

b. s. = Blood sinus.

Br. app. 3. v. r. = Brachial appendage.

Br. mem. = Branchial membrane.

B. A. = Buccal artery.

B, M,= Basal membrane.

B. M. = Buccal mass.

B. N. = Buccal nerve.

B. V. = Blood vessel.

Bl. A. = Branchial artery.

Bl. N. = Branchial nerve.

Bl.g. = Branchial ganglion.

Br. A. = Brachial artery.
Br. app. = Pericardial gland.
Br. G. = Brachial ganglion.
Br. gld. = Branchial gland.

gid.V. = Vein of Bran. gland.

Br. ht. = Branchial heart.

Br. M. = Branchial muscle, attaching
gill to mantle.

Br. N. = Brachial nerve.

Br. V. = Interbrachial vein.

Br.

OF PLATES.

LETTERS.

a = Cuticular layer.
= Cephalic artery.
6 = Cerebral ganglion.
N. S. = Central nervous system.
S. = Cartilaginous Stylet.
eee Cartilage cell.
ee = Central tooth of radula.
Ceph. V. = Cephalic vein.
circ. m. = Circular muscle.
Conjunct. = Conjunctiva.
Cor. V. = Coronary veins.
C. T. = Connective tissue.
Cr. C. = Cranial Cartilage.
c. r. = Ridge betw. oviducal. apert.
ch. = Chitinous lining.
Chr. = Chromatophores in dermis.
Cil. B. = Ciliary body.
circ. lid. = Circular eyelid.
Coel. = Pericardial coelom.
coll. = Collar muscle.
cr. = Crop.
Cor. A. = Coronary artery.
Cpdl. mass. = Cephalopedal mass.
Cut. L. = Cuticular lining of oesophagus.
depr. = Depression for spermatophores.
D,. = Dermis.
D, = Dorsum of heart.
D. M. and V. = Buccal nerve branches.
Du. = Salivary ductule.

ee

a ye

Eff. A. = Efferent artery.
egg. R. = Egg raceme.
egg. st. = Egg stalk.

emb. = Embryo.

emb,. = Part of oviduct.

e. m. = Muscular septum.

ep. = Epipodium.

Ep. cell. = Epithelial cell.

Ep. = Epidermis.

Ep. S. = Stylet sac.

Ex. C. L. = Ext. fibrous layer.

Ext. = Ext. muse. of sucker.

Ext. Musc. = Ext. musc. coat of eye.

ext. or. = Ext. orifice of eye.
f. = Foot.

hy fo fe = Folds of gill fila’ts.
f. ant. = Ant. funnel opening.

f. cl. = Closed funnel (inspiration).
f.o. = Funnel organ.

. op. = Open Funnel (expiration).
foll. = Follicular layer.

2,

x

Ce
2

Funnel.
Ovidueal artery.
= Infundibular artery.
= Depressor muscle of funnel.
= Infundibular veins.
= Folded wall, olf. pit.

-

2° Sass

= ae for spermatophores.
Ge; 9”. = Ganglia on Visceral nerve.
gr = Groove betw. web and lip.

= Genital gland.

_ A. = Genital aorta.

G. g. = Gastric ganglion.

gidr. p. = Glandular region

Rs

G. V. = Genital vein.
gid, = Indifterent cells.
h =

h. ae Sas -pancreatic aperture.

h. ©. = Horny egg-case.

H. H. = Epithelial covering of hepatic
gland.

Dp. fe Hepatic artery.

Nerves to head.

Heart.

= Hepatic vein.

= Common Hepatic duct.

}. d. = Ink duct.

int. = Intestine.

. 8 = Ink sac.

br. = Interbrachial nerves.

3 Ge

Pp

Hep

L. = Internal fibrous layer.

. = Ink duct papilla.

id. = Lridocysts in dermis.

S. A. = Artery to Ink sac.

S. Gr. = Ink sac groove.

S. N. = Nerve to Ink sac.

S. V. = Vein to Ink sac.

. oph. N. = infer. Ophth. nerve.
f A. = Intestinal artery.

. ap. = First part of intestine.

. Musc. = Inter. muse. of eye.
Int. V. = Intestinal veins.

I. £. = Jridescent envelope.

t. ep. = Inter. epith. of oesoph.

I. gid. = Ink gland.

J, and J. = Ventral and dorsal jaws.
K. C. = Kolliker’s canal.

= Lip.

E iol lip.

.c. = Left dorsal cirrus.

. S. = Larger blood sinus.

r. = Left funnel ridge.
ad,

nC eee
&

and 1. h. d. = Hepatic ducts.
= Hye lid.

SS SQ ann

&;

n. gr. = Left mantle groove.
od. ap. int. = Int. apert. of]. oviduct.
= Lens.

Sao

a

L, = Branchial leaflets.

Lac. = Apertures in wall betw. S, V5
and S; V5.

Liv. = Liver.

L. ace. = Accessory gill leaflets,

L. Au; R. Au. = L. and R. auricles.

L. Bl. A. = Left Branchial artery.

L. F. D. = Left Funnel depressor.

L. F. Pr. = Left Funnel protractor.

L. M. = Lateral muscle.

L. Pall..A. = Left Pallial artery.

L. V. C, = Lateral Vena Cava.
Lim. C. = Limiting cell.

Lim. N. = Nucleus of
m. = Mouth.
m,, m.l., m.p., m.p. ex.=nuscular

ditto.

sheets.
m. cl. = Mantle closed (expiration).
m. op. = Mantle open (inspiration).
m. 8. = Muscular septum.
m. 8. a. = Attachment of septum.
M, = Mantle.
M. C. = Mantle cavity.
M. L. = Limiting membrane.
M,M. = Muscular mantle.
M.V. = Mantle Veins.
M. W. = Oesophagus wall.
M. ep. = Inner Mantle epithelium.
Matr. = Cartilaginous matrix.

Mem. = Membranous sac.

Mes. = Mesentery.

Mus. = Muscular part of arm.

N, = Needham’s pouch.

N. = Arterial network in folds of gill

filament.
N. A. = Nuchal artery.
N. Cire. = Circular Brachial nerve.

Nuch. M. = Nuchal muscle.

Od. = Oviduct.

od. ap. = Aperture of oviduct.

od. gl. = Oviducal gland.

oes. = Oesophagus.

Oes. g. = Sub-oesophageal ganglion.
Oi, = = Oval g ganglion.

Olf. cell. = Olfactory cell.

ON — Olfactory nerve.

olf. P. = Olfactory pit.

Opt. G. = Optic ganglion.

Opt. N. = Optic nerve.

Opt. N. f. = Fibres from optic nerve.
opt. N, = Nerves to retina.

ov. = Ova.

ov. w. = Wall of ovary.

O.A. = Optic artery.

Oes. A. = Oesophageal artery.

or. = Pyloric aperture.

orb. C. = Orbital cartilage.

98

orb. V.
p. ¢.

= Vein to orbital sinus.

= Polygonal cell.

pad. = Muscular stomach pad.
peh. = Pouch-like dilatation.
pen. = Penis.

ps. ext, = Ext. pseudocorneal memb.

ps. int. = Int. pseudocorneal memb.

ps. mem. = Pseudocorneal membrane.

P. = Pancreas.

P, = Terminal suckers of male.

P. C. = Post. communication between
mantle cavities.

P. A. = Pancreatic artery.

Pp. = Pupil of eye.

P. M. = Post. membranous wall of
brain capsule.

Pall. N. = Pallial nerve.

Pall. V. = Pallial vein.

Ped. G. = Pedal ganglion.

Ph. A. = Pharyngeal artery.

Pig. = Retinal pigment.

Post. Fun. N.= Post. Infundib. nerve.

Post. Sup. oph. = Post. Sup. Ophthal-

mic nerve.

pr. = Prostate.

r. = Ridge for jaw muscles.

r. b. = Base of radular sac.

r. m. gr. = Right mantle groove.

rad. = Radula.

R. = Rectum.

R. K. = Right Kidney.

R. N. = Retinal nerves.

R. Pall. A.= Right Pallial artery.

R. Pe. ap. = BR. reno-pericardial aper-
ture.

R. 8S. = Radula sac.

R. wall. = Inner wall of oesophagus.

Rec. = Recurrent artery.

Res. = Reservoir.

Ret. = Retina.

Ret. C. = Retinal cell.

ee N. = Nucleus of ditto.

S. A. = Salivary artery.

Ss. ri = Sensory pad.

8. 9.5 8, 9) = Salivary glands.

s.g. d. = Salivary ducts.

sh. = Shell.

s. 1. g. = Sub-lingual salivary gland.

sk, = Kdge of integument.

Ss. ¥. = Sensory ridge.

s. 7. 0. = Sub-radular organ.

S. = Sucker.

S. a. = Sucker artery.

S. G. = Ganglion supplying suckers.
S. N. = Nerves to sucker.

S. V. = Venous Sinus.

8,V,, S2Vz, S3Vs.=Divisions of ditto.

S. Vess. = Vein running between
successive suckers.

Sept. A.= Septal artery.

Sept. V. = Septal vein.

Sph. = Sphincter of sucker.

St. G. = Stellate ganglion.

scl. = Sclerotic.

Sp. Coe. = Spiral caecum.

St. = Stomach.

Stat. By ee
Str, = Conn. tiss. Stroma.
Sup. V. = Superficial veins of head.

t. = Tongue.

tr. = Secretory trabeculae of Ink gland.
tr. s. = Triangular septum in heart.
Ti — estes:

Tu. = Secretory tubule.

Ur. = Ureter.

Ur. p. = Urinary papilla.

V. = Ventricle.

v. = Trans. valves in spiral caecum.
V. D. = Vas deferens.

V,, Vi,. = Secondary Branchial veins.
V,. = Semilunar valves.

V. app. = Venous appendages.

Visc. A. = Visceral artery.

visc. d. = Visceral dome.

Vise. G. = Visceral ganglia.

Vitr. = Vitreous body.

V. #. = Visceral envelope.

V. Lf. = Vas efferens.

Vasc. N. = Vascular network.

Visc. N. = Visceral nerve.

V. B. A.= Artery to visceral envelope.

V. BE. V. = Vein from visceral envelope.
V. 8. = Vesicula seminalis.

V, 8, = Sac of vitreous fluid.

W. = Web.

W. B. = White body.

W. V. C. = Water vascular canal.
W.V.C. ap. = Opening of water canal

into pericardium.

3h

9a.

10.

Le,

12.

15.

=

Prats I.

Dorsal view of adult female 1. cirrosa; spirit
specimen. x 32.
Ova of EL. cirrosa; in formalin. x 3.
Unhatched embryo of H. aldrovandi, right
side: in formalin. x 2.

Older unhatched embryo of 4. aldrovandi, left
side. x 4. (After Korschelt.)

Puate II.

Oral view of web of adult L. cirrosa; spirit

specimen. x 3.

Mouth and initial sucker of arms, showing
internal and external ips. x 1.

(a) Eledone from left side, during inspiration ;
and (6) Hledone from left side, during expira-
tion. x 3.

FE. aldrovandi, male; left half of mantle cavity.
Young specimen. x 1.

Funnel, showing muscles; integument cut

along line (sk.), and funnel turned forward
vel

ventrally. x 4.

Ventral view of anterior part of mantle cavity ;

to show the locking apparatus. x 4.

Funnel opened to show funnel organ. x $.

Prarie

Mantle cavity from ventral side; showing
pallial complex and vertical septum. x 32.
Visceral mass from ventral side, kidneys
removed and ink sac dissected away from liver,
and turned forward. x 4.

Postero-dorsal region of mantle, inner surface ;
viscera removed, and the funnel depressor and
lateral muscles partially dissected away, to
show the cartilaginous stylets in © situ.

Diagrammatic. x 4.

Vig.

Fig.

fo)

Fi

Fig.

IS

100

Cephalopedal mass, dissected to show relation
of buccal mass to bases of the arms—from
ventral surface. x 3.

Transverse section of mantle in region of
cartilaginous stylet. Highly magnified.
Right stylet (a) dorsal view; (6) from right

side. x 3.

Prate IY.

Alimentary canal, dissected out from body, to
show relations of various parts; crop turned to
the right, buccal mass to the left, and liver
forwards. x #4.

Oesophagus with crop, and stomach; slit open
to show ridged chitinous lining of all three
regions. Muscular walls of stomach turned
back from the chitinous lining. x 1.

T. S. stomach, showing thickened grinding
pads, and corresponding thickened cuticle.

Buccal mass, from right side. x 1.
Right posterior salivary gland; inner surface.
Right anterior salivary gland; inner surface.

Ventral surface of buccal mass, showing sub-
lingual salivary gland. x 1.

Sagittal section through buccal mass, and
anterior portion of oesophagus. x 1.

Two rows of teeth from radula; much enlarged.
Sagittal section of ink sac. x 2.

Jaws, from left side. x 1.

Spiral caecum; ventral view, showing entrance
of hepato-pancreatic duct. x 1.

Anal ear (enlarged).

Inner wall of terminal part rectum, showing
aperture of ink duet on dorsal papilla. x 2.

38.

58a.

39.

40.

41.

59.
60.

101

Pirate VY.

Transverse section of oesophagus (enlarged).

Transverse section of tubules of posterior
salivary gland.

Transverse section of tubules of anterior
salivary gland.

Transverse section of secretory tubule of
salivary gland, showing secretory cells.
Kidneys, seen from ventral surface, after
removal of visceral envelope. Female. ~ I.

Spiral caecum, opened along columellar edge
of spiral, and walls pinned back. The series
of transverse valves may be seen, and the
internal aperture of the hepato-pancreatic
duct. x ¥.

View of viscera, after removing kidney and
heart, and turning liver forward—from

ventral surface. x i

Ovary, and female genital ducts. The ventral
germinal wall has been turned forward
anteriorly. xe ili,

Sketch showing relation of pericardial division
of coelom to water vascular canal and ureter.
Reno-pericardial aperture seen at base of
opened ureter. x 2.

View of portion of germinal wall of ovary, from
inner surface, showing attachment of the eges

im racemes. x q,

Right gill—ventral view. x 1.

Portion of gill, from inner surface, showing
alternating arrangement of inner and outer
leaflets : ihe ceutanl inner leaflet removed.

(Enlarged. )

Pratt VI.

Injection of arterial system, showing the dis-
tribution of the main brachial, cephalic,
palhal, genital and visceral branches. From

ventral surface- partly diagrammatic. x 2.

44,

102

Amoeboid colourless blood corpuscles.

45 & 46. Heart bisected in median antero-posterior

48.

49,

50.

O6a.

D2.

plane. Fig. 45 shows dorsal portion from inner
surface, and entrance of anterior and genital
aortae; also triangular septum. Fig. 46
shows ventral portion from inner surface, with
openings of auricles and abdominal aorta. x 1.
Ileart bisected in median dorso-ventral plane,
and viewed from cut surface. (a) Left half
of heart—inner surface, showing triangular
septum. (b) Right half. x 1.

Semi-lunar auriculo-ventricular valves, looked
at from ventricle. x 1.

Diagram showing relation of inferior intestinal
arteries, and abdominal aorta, to artery of the
ink sae. 4.

Buccal mass from left side, showing distribu-
tion of left pharyngeal artery and branches.
aed I

Sketch showing distribution of left branchial
artery, and its oviducal branch. x .
Sketch showing polygonal cells of branchial
gland, and the intercellular blood sinuses.

Epithelial and olfactory cells lining the
olfactory pit. (After Zernoft.)

Portion of cartilage, showing branching and
anastomosing processes of cartilage cells.

Puate VII.
Figure of venous system, from ventral surface,
partly diagr ammatic, showing — principal

cephalic, and pallial veins, and three venae
cavae. X 2.
Large perivisceral blood sinus and its connec-

tien with the lateral and anterior venae cavae.
Ventral surface. Xx 4. Partly diagrammatic.

Di

Two adjacent arms, showing venous vessels and
common interbrachial vein. x 4.

=
10 Je)

Fig.

56.

on
co |

31.

1038

Left branchial heart, showing the branchial
appendage or pericardial gland. From ventral
surface. x

Distal portion of lateral vena cava, showing
two semi-lunar valves at entrance to branchial
heart, and also apertures leading into venous
appendages, and into the network of vessels
occurring in the spongy wall of the branchial
heart. x 1.

Mantle cut down ventral median line, and
opened out flat. The left half is seen from
the dorsal surface, after removing the skin.

M.V. and M.V, represent the two main

pallial veins. x 1}.
Portion of arm, showing relation of main veins

to the network which drains the arm. x 2.

Puate VIII.

Ventral view of ink sac, after removal of

epithelium covering visceral sac, showing

visceral nerves, and nerve artery and vein of
3

mk sac. x 3.

Ventral view of ink sac, showing veins and
eRe. a ae
arteries injected. ‘The visceral and iridescent
envelopes cut open and turned back. x 1.
Heart from ventral surface, showing paired
coronary veins. x 1.
Gill leaflet, showing network of arteries
flowing into the main axial vessel which leads
into the efferent artery. x 1.
Portion of gill filament from external surface,
showing terminations of venous vessels of the
second order. x 1.
Portion of gill, from inner surface, showing
main arteries and veins injected—-second inner
filament cut away. Much enlarged.

Right statocyst, from ventral surface. x 3.
Statolhth, from free surface. Much enlarged.

Auditory capsules opened to show the statocyst
attached to capsule by vascular network. x 1.

Fig.

80.

DuL

TO.

“I
\

~

104

Buccal bulb from left side. The sub-
oesophageal ganglion and its branches (a—g),
and the buccal nerve are shown. x 1.
Longitudinal median vertical section of arm,
showing brachial artery and nerve, nerve
gangha corresponding to the suckers, and net-
work of fine arteries and veins which surrounds
them, 2x Ie

Dissection of dorsal surface of head, eee
the circular nerve which unites the brachia

nerves, at the bases of the arms. x 4.

Pirate IX.

Ventral dissection of nervous system, partly
diagrammatic. Funnel cut open and turned
aside, muscular septum removed; the branches
from ganglia on visceral nerves are shown
only on the right side. x 2.

Central nervous system, from left side. Slightly
enlarged.

Left optic ganglion and nerve from dorsal
surface. x

Dissection of gastric ganglion and its branches
(a—h). The alimentary canal is seen from
the ventral surface.

Dissection of the superior ophthalmic nerves,
and the olfactory nerves from the dorsal
surface. The skin and superficial muscles
have been dissected away and turned back,
showing the muscular coat of the eye, the
bases of the arms, and the muscles covering

the cranial cartilage. x 2.

Lateral view of right eye, after dissecting away

the superficial muscles and skin. Shows
anterior superior and inferior ophthalmic
1

nerves. x 9:

Buccal mass and central nervous system, dorsal
view. The course of the labial (a—d) and
buccal nerves may be seen. x 1.

105

7. Median vertical longitudinal section of arm,
showing the ganglion and group of nerves,

which supply each sucker.

Fig. 7

Fig. 676. Diagrammatic longitudinal section through
two ova, showing their mode of attachment to
the germinal wall, and also numerous folds of
the follicle, which nourishes the developing
ovum. In left hand corner is a diagram of
an ege in transverse section, showmg the
infolded follicular membrane.

Puats X.

-1
ioe

Diagram of median vertical section of eye. The
whole optic ganglion is drawn in order to show
the relation of the retinal nerves to the retina
and ganglion. ‘The small figure on the left
shows the outer segment ot the lens, from the
surface which rests on the cornea. x 2.

Fig.

Fig. 81. Diagram of the parasite Dicyema miilleri, found
in the kidney fluid of Hledone cirrosa. Much
enlarged.

Fig. 82. Anterior region of visceral envelope, from inner
surface, showing posterior membranous wall
of brain case, and various nerves. x 2.

Fig. 83. Kye from external surface, showing lid and
pseudocorneal membrane. x _ 1.

Fig. 84. Median dorso-ventral section through eyelid
and pseudocorneal membrane. x 1.

Fig. 85. (a) Cranial and orbital cartilages, from dorsal
surface. (b) The same, ventral view. x 1.

tol

Fig. 86. Vertical section through portion of the retina.

Fig. 64. Dorso-ventral section through olfactory pit,
much enlarged, showing the folded sensory
wall.

Fig. 66. Right olfactory pit; mantle turned back. x 1.

C. Tinling & Co., Ltd., Printers, 53, Victoria Street, Liverpool.

L.M. B. C. Memoir XVIIL PATEL

M‘Farlane & Erskine, Lith. Edin*

BLEDONE.

LM. B. C. Memoir XVIIL : PrateE IL

M‘Farlane & Erskine, Lith. Edint

L.M. B. C. Memorr XVIII. Prate Il

M‘Farlane & Ershine, Lith. Edin?

EK LEDONE.

L.M.B. C. Memoir XVIII. Puate IV.

2 5,9,
: ee A

cr. vA Oe

: ee

MiFarlane & Erskine, Lith. Edin®

ELEDONE.

L.M. B. C. Memoir XVIII

Lod. ap. int.
wr - Viapp. x: qj
RIE

M‘Farlene & Erskine, Lith.Edin™

ELEDONE.

L.M. B. C. Memorr XVIII. Prare Vi

Matr. Olf. cell.

Fig. 42.

we Seer

Fig oom PEE Rapes

A.1. del. M‘Farlane & Erskine, Lith Edin?

ELEDONE.

L.M. B. C. Memoir XVIII. Puate VII.

Arm Vo-\
Arm V;---

‘AREPaTLeT TARTS OT ESTER

Fig.58. ©

A.I. dey M‘Farlane & Erskine. Lith Edin™

ELEDONE.

L.M.B.C. Memorre XVIII. PLATE VIL

Br.gld.V.

M‘Farlene &Erskine. Lith. Edin™

Di, iON.

L.M. B.C. Memorr XVIII PLATE IX.
N. Cire. Ant Sup. oph.

i Ad a ee Cnt Not Sup. oph.

G ! Ace. Pall. W.

Ant Fun.N.---\-----S> A = Vt f Ane. Ve q = *. AREVM. 4 N.
Post. Fun.N. _ SS eee a Z Jisc. NV. : uN Aud... “Vise. N.
eS = 2 4 . | Ant Fun.N.
SN eer Ped. G.
Z Z Ty * Ope. G.
cor = —— a S i

MFarlane & Erskine, Lith Edin?

ELEDONE.

a a

L.M B.C. Memorr XVIIL

P ob. Coe

ps- Tree
‘

ee Pa

ld. Conjunct. ee ————
: ey Tris. spl ae Rome aplann Beeey bile

——

Conjunct.

---eet. C.

Muse. >

Fut Muse.

ae ey We ope.

Fig, 78.

Venous Blood Sinus.

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M&Farlane &Erakine, Lith. Edin?

A.I. dei. ELEDONE.

WM