MOLLUSCA. 



209 



acetabula. The adhesion of these suckers is so great 

 that it is easier to tear away a limb than to detach it. 

 Their mechanism may be understood from Fig. 1 14. 

 The mouth has a horny beak, like a parrot's bill, but the 

 jaws do not move vertically, like the bird's. A long 

 gullet ends in a muscular gizzard, resembling that of a 

 fowl. Below this is a cavity, the stomach or duodenum, 



FIG. 114. Suckers on the Tenta- 

 cles of a Cuttle-fish : a. Hollow axis 

 of the arm, containing nerve and ar- 

 tery, c. Cellular tissue, d. Radi- 

 ating fibers, h. Raised margin of 

 the disk around the aperture f, g^ 

 which contains a retractile mem- 

 brane, or " piston," z". 



FIG. 115. Morphology of 

 Cephalopoda. Sepia oflkina- 

 hs, laid open to show viscera, 

 etc. a. Foot. b. Horny jaws. 

 c. Principal ganglion, d. Sal- 

 ivary gland, e. OZsophagus. 

 f. Liver, g. Stomach, h. Py- 

 loric caecum. i. Ink bag. 

 k. Ovary. /. Aperture of 

 atrial system, m. Branchiae. 

 n. Oviduct, o. Cuttle-bone. 



which receives the bile from a large liver. The intes- 

 tine is a tube of uniform size, which, after one or two 

 slight curves, bends up, and opens into the " funnel " 

 near the mouth. (Fig. 115.) The head is set off from 

 the body by a slight constriction, and is furnished with 



a pair of large, staring eyes, which are constructed like 



18* 



