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 

 interioi*, 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. 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. 8 



