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SUPPLEMENT 
the threads which terminate the antenna and feet ; but M. 
Straus has proved that they are in the form of pectinated 
laminae, annexed to the base of the two pairs of jaws. Finally, 
in apus, branchipes, and limnadia, 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 known, 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 gf 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 squill®, 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 w r ell 
known, couple after the manner of insects. Some isopods, in 
