80 



COMPARATIVE ZOOLOGY. 



the intestines end in a large bladder-like expansion; Scor- 

 pions have no stomachal cavity — a straight intestine passes 

 directly through the body. 



In bivalve Mollusks, like the Clam, the mouth opens 

 into a short oesophagus which leads into the stomach, 

 which lies imbedded in a large liver, and the intestine, 

 describing a few turns, passes directly through the heart." 

 In the univalve Mollusks, like the Snail, the gullet is long, 

 and frequently expands into a crop ; the stomach is often 

 double, the anterior being a gizzard provided with teeth 

 for mastication ; the intestine passes through the liver, 

 and ends in the fore-part of the body, usually on the right 

 side. 



The highest Mollusks, as the Cuttle-fish and Nautilus, 

 exhibit a marked advance. A month with powerful man- 

 dibles leads to a long gullet, which ends in a strong mus- 

 cular gizzard resembling that of a fowl." Below this is a 

 cavity, which is either a stomach or duodenum ; it receives 



the secretion froni 

 a large digestive 

 gland or pancreas. 

 The intestine is a 

 tube of uniform 

 size, which, after 

 one or two slight 

 curves, bends up, 

 and opens into the 

 "funnel" near the 

 mouth. 



Fishes have a 

 simple, short, and 

 wide alimentary 



Via. 44.— Alimentary Caual of the Oyster: a, stomach canal The stom 

 laid open ; d, liver : 6, c, d,/, convolntious of the iutes- 



tlue; g, anal aperture; n, o, auricle and ventricle; I, ach is Separated 



m, adductor muscle ; R, *, lobes of month divided to j; . , 



•how the venous canals at the base of the Riils. trom the intcstuie 



