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 gizzard,* or when it is absent (which proves to be the case 
in many genera), 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 tinges 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 
vibrating 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 ring. 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- 
tile 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 placed in the genus Nemertes. Mag. of Zool. and Bot. Vol. i. p. 
530. pi. 17, fig. 5. 
