240 ZOOPHYTA ASCIDIOIDA. 



considerable length, and studded, especially at the upper part, 

 with minute oval spots arranged in close contact with each other. 

 The whole tube appears to be highly irritable, and contracts 

 vigorously when food is introduced into it. "At the termi- 

 nation of the oesophagus is a distinct cardiac orifice (a, 2.) that 

 opens into a small globular cavity of singular construction, which 

 appears to perform the office of a gizzard, (a and b, 3.) The 

 parietes of this organ are thicker than in any other part of the 

 alimentary canal. They contain two dark round bodies placed 

 opposite to each other, from each of which dark lines are seen 

 radiating." In the space between these bodies may be seen a 

 number of scales grouped in a close, regularly tessulated man- 

 ner, which line the inner surface of the cavity, and probably 

 serve the office of gastric teeth, having their motions regulated 

 by the muscular fibres whose disposition is indicated by the dark 



radiating lines. 



The o-izzard,*or when it is absent (which proves to be the case 

 in many oenera), the oesophagus, opens downward into the true 

 digestive stomach, (a, 4.) from which it is separated only by the 

 contraction of the parietes. This stomach is usually of an ob- 

 long shape, and its walls are thickly studded with spots of a rich 

 brown colour, — apparently hepatic follicles that secrete a fluid 

 which often tino-es the whole organ, as well as its contents, of a 

 similar hue. — " From the upper part of the stomach, and by 

 the side of the entrance from the gizzard, arises the intestine 

 {a, 6.) by a distinct pyloric orifice (a, 5.) that is surrounded by 

 vibratino- cilia. The intestine passes up straight and narrow by 

 the side of the oesophagus, from which it is entirely separate and 

 free, and terminates by a distinct anal orifice {a, 7.) in the deli- 

 cate parietes of the body, close to the outer side of the tentacu- 

 lar rino-. The parietes of the intestine are marked with pale 

 spots, something like those of the pharynx, and the whole tube, 

 like the rest of the alimentary canal, possesses a high contrac- 

 tde power. Thus the alimentary canal consists of pharynx or 

 oesophagus, gizzard, stomach and intestine, with subsidiary se- 



* Compare this with a somewhat similar structure in the planarian worms 

 which I have phiced in the genus Nemertes. Mag. of Zool. and Bot. Vol. i. p. 

 530. pi. 17, fig. 5. 



