so 



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. 40 

 In the univalve Mollnsks, 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 mouth with powerful man- 

 dibles leads to a long gullet, w T hich ends in a strong mus- 

 cular gizzard resembling that of a fowl. 41 Below this is a 

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



the bile from a 



Fig. 44. — Alimentary Canal of the Oyster: a, stomach from tll6 intestine 

 laid open ; d, liver ; b, c, d,f, convolutions of the intes- 

 tine ; g, anal aperture; n, o, auricle and ventricle; I, by a nari'OW " py- 

 m, adductor muscle; h, Jc, lobes of mouth divided to , ' . ,, 



ifk intestine is a tube 



111 °^ uniform size, 



111 which, after one or 



Wm two slight curves, 



m bends up, and opens 



f into the "funnel" 

 near the mouth. 



Fishes have a 

 simple, short, and 

 wide alimentary 

 canal. The stom- 

 ach is separated 



large liver. The 



show the venous canals at the base of the gills. 



loric " orifice, or 



