$$ 38, 39. THE POLYPI. + 47 
DIGESTIVE CAVITY OF BRYOZOA. 
§ 38. 7 
The very complicated digestive canal of the Bryozoa floats freely in the 
spacious cavity of their body. It is composed of an cesophagus which, at 
its lower extremity, dilates into a round or oval muscular crop ;” upon this 
immediately succeeds a ccecal stomach, from the upper portion of which a 
small intestine arises and passes upwards in front. This, after a course of 
-variable length, ends by a constriction in a short but large rectum, which 
-opens in the vicinity of the mouth, at the external side of the base of the 
tentacles.” The digestive canal here, therefore, is not in communication 
with the cavity of the body. Its whole inner surface is lined with very 
active, ciliated epithelium, which keeps its contents in motion, and especially 
the feeces of the rectum. The sides of the stomach are often colored brown, 
yellow or green, from the presence of hepatic cells.t 
CHAPTERS VI. AND VII. 
CIRCULATORY AND RESPIRATORY 
§ 39. 
A vascular system has yet been found only with a few Polyps; but there 
it is so apparent that its presence in others may be inferred. The blood- 
vessels exist upon both the sides of the body and of the stomach, and are 
in part longitudinal, in part circular, ending in a capillary net-work. They 
are not simple canals excavated in the parenchyma, but have proper walls, 
and circulate a liquid containing a great number of white (blood) globules.” 
SYSTEMS. 
juice of the Anthozoa must have a very great 
digestive power, since the Actinia eat hard-shelled 
crustacea, and even the soft Hydrae quickly dis- 
solve the larves of Nats and Chironomus. But 
the indigestible parts of these animals, such as epi- 
‘dermis, bristles, hooks and jaws, are afterwards 
ejected by the mouth. 
1In Bowerbankia (Farre, Phil. Trans. 1837, 
p. 392, Pl. XX. fig. 5; Pl. XXI. fig. 7) this crop 
is composed of pyramidal corpuscles, with the 
apices pointing inward, so as to act like teeth. I 
have observed avery similar structure in Alcyo- 
nella stagnorum. 
2In Bowerbankia and Vesicularia the small 
intestine is very long (Farre. loc. cit. Pl. XX. and 
XXII). I have observed it very short with Cris 
tatella mirabilis.* 
* (§ 88, note 2.] . According to Allman (Report 
Brit. Assoc. 1850, p. 310), the cesophagus succeeds 
the stomach without the intervention of any dis 
tinct crop with all the fresh-water Bryozoa. The 
‘stomach is large and thick-walled, and may be 
divided into a cardiac and a pyloric portion. The 
pylorus is distinctly valvular, and the intestine, 
1 Milne Edwards has perceived a vascular net» 
work of this kind in the sides of the body, with 
Alcyonidium elegans, and Alcyonium palma- 
tum and stellatum (Ann. d. Sc. Nat. IV. p. 
338). Quite recently, Will has described the vas- 
cular system of Alcyonium palmatum (Froriep’s 
neue Notizen, 1843, No. 599, p. 68). According to 
him, white vessels may be perceived, even with the 
naked eye, upon the longitudinal furrows of this 
animal. These enter the lobules on the border of 
the body, and there form a dense net-work, from 
which a branch is sent to each arm, and this last 
gives off laterally a twig to each tactile lobule. The 
principal trunk of the longitudinal vessels con- 
tinues upon the sides of the stomach to the base of 
the tentacles. At the point where the bodies of 
the Polyps continue with the corallum, there are 
wide at first, passes along the side of the cardiac 
cavity and cesophagus, and rapidly decreases in 
diameter, until it terminates in a distinct anus just 
below the mouth. — Ep. 
t [ Note at end of § 38.] Sec in this connection 
my note urder § 13, note 2.— Ep. 
