ON CRUSTACEA. 2G5 



the tail bears underneath two oval bodies, sufficiently distant 

 from each other, and which appear to give rise to two small 

 organs, which the elder M. Jurine presumes to be those of 

 generation. Each of them is composed of three rings, which 

 diminish in size. The second furnishes two or three threads ; 

 and the third is terminated in a point. 



With respect to the products of generation, the Crustacea 

 are either oviparous or ovo-viviparous. The eggs w^iich they 

 lay have a corneous envelope, solid, and usually transparent, 

 through which the gum may sometimes be perceived. These 

 eggs, developed in a liquid conduit, which in its bottom part 

 receives the name of ovary, and in its most external portion 

 that of oviduct, are small, often very numerous, of a spherical 

 or oval form, and present, according to the species, very vari- 

 ous colours. 



After they issue from the body, they are usually carried for 

 a longer or a shorter time by the females, sometimes under 

 the tail, attached by filaments, resembling, from the desicca- 

 tion of theViscous matter which invests them, two peculiar ap- 

 pendages, which have received the name of false feet, as is the 

 case with crabs and astaci; sometimes between leaflets, at the 

 base of which the gills are fixed, as in certain isopods ; 

 and sometimes, in fine, in an exterior membranaceous en- 

 lelope, forming an ovary or external matrix, as in cyclops 

 and branchipes, or in a dorsal cavity, as in daphnis and 

 [ynceus. 



In certain genera they disclose the young while yet con- 

 tained in the body of the animal, or in the doi'sal cavity which 

 tve have just mentioned, as is remarked in Argulus and Daph- 

 ais, which, in consequence of this phenomenon, are distin- 

 auished from the other Crustacea, as being ovo-viviparous. 



The little ones which issue from the eggs are, in the 

 oenerality of the Crustacea, altogether similar to their parents ; 

 V'et sometimes they differ so much from them, that they have 



