ON CRUSTACEA. 
257 
vessels, floating, undulated, of a yellow colour, altogether 
similar to the vessels considered as hepatic in the insects. 
Finally, in the entomostraca, we can admit as organs ana- 
logous to the liver, only the two small vessels which lead to 
the anterior part of the stomach in daphnis. 
We are not acquainted with any organ analogous to the 
pancreas in Crustacea. It nevertheless is possible that this 
viscus may be replaced by the coecum, of which we have 
spoken above, which admits no aliments in digestion into its 
interior, and which may be a gland intended to pour a pecu- 
liar fluid into the intestinal canal. 
There is no peritoneum ; the stomach, as we have seen, is 
supported by particular muscles. But the intestinal canal is 
supported only by the vessels, and by the compression of the 
surrounding parts. 
The heart, in the decapod Crustacea, is placed pretty nearly 
towards the middle of the body properly so called, in the rear 
of the stomach, and of a portion of the preparatory organs of 
generation, and between the gills. It is lodged in a sort of 
cavity, surrounded by solid partitions, to which are attached 
the muscles of the base of the feet, the assemblage of which 
forms two sorts of buttresses on each side, which sustain 
the upper part of the testa in the points where we see ex- 
ternally two small longitudinal impressions upon it. Its 
form is oval, a little depressed, its colour is whitish, and its 
parietes, which are semi-transparent, are yet tolerably thick. 
Its movements of dilatation and contraction are very apparent, 
and in general rather slow r . It has no auricles, and no val- 
vules are found in its interior. 
This heart, by its contractions, distributes the lymph to the 
gills, by the assistance of as many vessels as there are packets 
of branchial plates, and these vessels all proceed from one or 
two principal trunks. The lymph which has received the 
influence of respiration, issues from the gills through an equal 
VOL. XIII. S 
