742 



ZOOLOGY 



SECT. 



opening the excretory aperture (neph.). On the left-hand side is 

 the opening of the sperm-duct or oviduct (ovid.) as the case may be. 

 In addition to the shell, which is an important protective 

 structure, and gives support to the muscles of the fins, Sepia also 

 has a remarkably well developed internal skeleton composed of 

 cartilage. An important part of this the cranial cartilage (Fig. 



665) protects the principal nerve- 

 centres, encloses the statocysts, and 

 gives support to the eyes. Other 

 cartilages support the bases of the 

 arms. A thin shield-shaped plate 

 the nuchal cartilage (Fig. 666) lies 

 on the posterior surface of the neck. 

 The pair of elevations on the pos- 

 terior wall of the funnel and the 

 corresponding depressions on the 

 anterior surface of the body are 

 borne each on a thin plate of carti- 



cranial 



FIG. 665. Sepia cultrata 



cartilage seen from the posterior aspect, 

 with the cavities of the statocysts ex- 

 posed, eye, position of eye indicated by 

 dotted line ; ot. statocyst ; pall. n. 

 pallial nerve ; vise. n. visceral nerves. 



, 



lage, and 



other thin cartilages 

 support the bases of the fins. 



Alimentary System. The 

 mouth is surrounded by a thin, 

 lobed peristomial membrane, within which is a circular lip (Figs. 

 669, 672, perist.) beset with numerous papilla?. Lodged within the 

 circular lip is a pair of powerful horny jaws (Fig. 668, Fig. 669, 

 jawl, jaw 2; Fig. 670, j. ; Fig. 672, jaw). These have somewhat 

 the appearance of the beak of a parrot, the posterior jaw being 

 larger and more strongly bent than the other, which it partly 

 encloses. The mouth leads into a thick-walled buccal cavity, which 

 contains an odontophore bearing numerous minute horny teeth. 

 The oesophagus (Figs. 669 and 670, 03 ; Fig. 672,'ces), 

 following on the buccal cavity, is a narrow straight 

 tube, which runs between the halves of the 

 ' liver " towards the aboral end of the body. It 

 opens into a rounded thick- walled stomach (st.), 

 and, close to the pyloric aperture leading from the 

 latter into the intestine, opens a wide ccecum (c.). 

 The alimentary canal at this point bends sharply 

 round upon itself, and the intestine runs nearly 

 parallel with the oasophagus to open into the 

 mantle-cavity as already described. 



A pair of glands (Fig. 670, s.g. ; Fig. 672, sal.), which are 

 commonly termed salivary, though their functional correspondence 

 with salivary glands has not been proved, are situated in the 

 head behind the cranial cartilage. The ducts of these two glands 

 run inwards and unite to form a median duct, which opens into 

 the buccal cavity. The name of " liver " (Fig. 670, 1, I. ; Fig. 671, 



FIG. 666. Sepia 

 cultrata, nuchal 

 cartilage. 



