2G2 SUPPLEMENT 



the threads which terminate the antenna and feet ; but M. 

 Straus has proved that they are in the form of pectinated 

 laraina3, annexed to the base of the two pairs of jaws. Finally, 

 in apus, branchipes, and liranadia, they consist, in many 

 species, of membranaceous leaflets, the assemblage of which 

 composes the natatory feet of these animals. The name of 

 branchiopods, which has been particularly applied to them, is 

 derived from the alliance which has been remarked between 

 the organs of motion and the organs of respiration. 



The function of generation in most Crustacea is well known, 

 as is also the distinction of the sexes ; but in some of them, 

 naturalists have been as yet unable to distinguish the male sex. 

 All the individuals among these last lay eggs, from which 

 animals similar to themselves proceed, apparently without 

 any previous sexual intercourse. 



The decapods, stomapods, isopods, and amphipods, are 

 those in which the sexes are well know-n, and in which, in con- 

 sequence of their size, the organs have been better studied. 



In the crabs, astaci, and the Crustacea of the two families in 

 which these animals are ranged, the exterior organs of gene- 

 ration are very distinguishable; and in the interior of the body 

 the preparatory organs of this function are easily discovered. 

 These last are visible when the carapace is raised up on the 

 sides and in front of the heart, and they are more especially 

 apparent at the period of coupling or that of laying. The 

 sexual organs are double. 



Certain individuals of the genus squillas, presumed to be 

 males, have near the internal origin of each of their last am- 

 bulatory feet, a small, crustaceous, filiform appendage, arched 

 and not articulated, which is presumed to be a dependence of 

 the sexual organ of the male. 



The amphipods, whose organs of generation are not well 

 known, couple after the manner of insects. Some isopods, in 



