632 



CUTTLE-FISH 



colour for which the cephalopoda as a whole are so 

 remarkable. 



The head is broad, and contains a cartilage of 

 complex shape which protects the central nervous 

 system, and forms a socket on either side for the 

 large eye ; this has a bright green lustre during 

 life, the black pupil is shaped like the Greek letter 

 w, and there are two eyelids, the upper coloured, 

 the lower white. The front of the head is occu- 

 pied entirely by the bases of the arms and the 

 mouth. The former are ten in number, eight of 



1, Sepia officinalis from the dorsal aspect ; 2, view of the 

 Mouth, showing its Lip and the bases of the Arms and 

 Tentacles ; 3, the Shell seen from the ventral surface ; 

 4, the same in lateral view ; 5, the Animal with the 

 Mantle divided in the middle line to expose the 

 Branchial Cavity : 



s, siphon; i, its valve; c, pit in the base of the siphon ; c', pro- 

 minence on the mantle which fits into it ; TO, muscle pass- 

 ing backwards from the siphon to the mantle ; a, termina- 

 tion of the intestine ; Br, gill ; r, renal opening ; g, genital 

 opening ; i. s., ink sac. At the base of the right gill a portion of 

 the membrane has been removed to show the branchial heart. 



them being alike, oblong in transverse section and 

 tapering off to slender extremities ; they have the 

 surface which is turned towards the mouth covered 

 with suckers in four longitudinal rows. The suckers 

 consist of a muscular periphery, strengthened by a 

 horny ring ; a fleshy pad acts like a piston in the 

 base of this latter. Each sucker is mounted on a 

 short flexible stalk. The two remaining arms, 

 known as 'tentacles,' occupy the interspaces 

 between the ventral arms and those next to them. 

 They are twice as long as the others, and have a 

 cylindrical stem, slightly expanded at the extremity 

 into a club furnished with larger and smaller 

 suckers. They can be withdrawn into pockets 

 situated beneath the eyes, and are carried in this 

 position when not in use. The mouth (fig. 2), 

 situated in the centre of the roots of the arms, is 

 surrounded by a lip with seven prominent angles, 

 which bear small suckers in some species, and have 

 been compared to rudimentary arms. Projecting 

 from it may be seen the two black horny mandibles, 

 shaped like those of a parrot, but with the lower 

 overlapping the upper. 



On the lower aspect of the animal, between the 

 muscular sac and the body proper which contains 

 the viscera, is a hollow space, the ' branchial ' or 



'mantle-cavity.' When this is opened by a longi- 

 tudinal incision it is seen to contain the following 

 structures (fig. 5). Anteriorly is the base of the 

 'siphon,' or 'funnel,' s, a conical tube containing 

 a valve, i, through which water can be forcibly ex- 

 pelled by the contraction of the mantle. At its 

 posterior margin on either side is an almond-shaped 

 depression, lined with cartilage, c, into which fits 

 a prominence on the inner surface of the mantle, c', 

 an arrangement which largely contributes to the 

 solidarity of the body as a whole. Lying along the 

 middle line is the terminal portion of the intestine, 

 a, furnished with two small flap-like appendages 

 of uncertain function, and on either side, a little 

 farther back, is a small papilla, r, upon which the 

 kidney opens, and on the left side only, the genital 

 orifice, g. Two large gills, Br, are situated in the 

 lateral recesses of the mantle-cavity, each consisting 

 of an arterial stem running up the attached side, 

 and a venous stem passing down the other aspect, 

 the bulk of the organ being made up of a series of 

 folds passing transversely from one to the other, and 

 richly supplied with vessels containing the blood to 

 be aerated. Respiration is carried on by rhythmic 

 contractions of. the mantle, in consequence of which 

 water enters at either side, passes over the gills, 

 and is expelled by the siphon ; this takes place 

 about seventy times in a minute. 



On the dorsal side of the animal, immediately 

 beneath the integument, is a closed sac which con- 

 tains the internal shell (cuttle-bone, sepiostare, figs. 

 3, 4). Speaking generally, this may be said to be 

 of an elongated spoon or boat shape ; it consists of 

 a horny lamina, which gives it its characteristic 

 outline, extending also into the small cone at the 

 back, which in many species is much larger than 

 in the one now under consideration, and has been 

 compared with the guard of the Belemnites (q.v.). 

 On the dorsal surface is a granular calcareous 

 deposit ; while the concave ventral aspect of the 

 spoon is occupied by a series of layers of calcareous 

 matter, which are deposited in succession and do 

 not entirely cover each other, so that the hinder 

 portion of this surface presents a striated appear- 

 ance due to their parallel margins. This part of 

 the shell is porous and extremely light, the inter- 

 stices being filled with air. These shells are im- 

 ported into Liverpool in some quantity, and ground 

 into fine powder to form a dentifrice. 



The Digestive Organs. Within the beak above 

 alluded to is a solid muscular mass (buccal cone), 

 part of which is devoted to its movements. Through 

 its centre passes the gullet, the lower wall of 

 which bears a most remarkable organ, the tooth- 

 strap or ' radula ; ' this consists of seven longi- 

 tudinal rows of horny teeth, which are secreted by 

 certain special cells of the epithelium, and whose 

 apices are directed backwards. They can be moved 

 to and fro by appropriate muscles. Behind the 

 buccal cone the oesophagus bears the salivary 

 glands, and still farther back it opens into a round 

 saccular stomach with muscular walls. A large bi- 

 lobed gland, commonly called ' liver,' but having 

 the functions of a pancreas, is situated on the 

 oesophagus. Lying parallel to the terminal portion 

 of the intestine is the 'ink-bag,' i. s., a hollow 

 gland opening near the anus, and furnishing a deep- 

 brown fluid, which is ejected by the animal when 

 alarmed in order to conceal its retreat. When 

 genuine, the pigment known as ' sepia ' is prepared 

 from it. 



The Circulatory Organs. The heart is situated 

 posteriorly, and consists of a pear-shaped gac which 

 receives on either side a vein from the gills, dilated 

 just before its termination into a muscular con- 

 tractile antechamber or auricle. It gives off', an 

 artery anteriorly to supply the head and arms, and 

 one posteriorly to the abdominal organs. The 



