274 SUPPLEMENT 



where these Crustacea are very common, that they were 

 derived. 



It is more especially to the decapods that the name of Crus- 

 tacea has been given. Of all the animals of this class, the 

 decapods are the most remarkable for their size, the complica- 

 tion of their organs, the solidity of their teguments, and their 

 longevity. They all possess a very carnivorous instinct. Some 

 travellers do, nevertheless, inform us, that certain species feed 

 on fruits ; but this appears to be doubtful. Some pass a very 

 considerable portion of their lives out of the water, and repair 

 thither only at the period of their amours, and for the purpose 

 of laying their eggs. They go in very numerous bands, always 

 pursuing the shortest and straightest direction, without em- 

 barrassing themselves with any obstacles in the way, and they 

 return in the same manner, after having fulfilled the decrees 

 of nature. The others scarcely ever, or at all events, but for 

 a very short time, abandon the element in which they were 

 born. Some among them live in the fresh waters ; but the 

 majority inhabit those which are salt or brackish, most fre- 

 quently near the shore, at depths and localities which vary 

 according to their means of subsistence, and the resources 

 with which nature has provided them, to escape from the 

 dangers by which they may be menaced. Thus the pin- 

 notheres withdraw themselves into bivalve shells. The 

 dromise form with alcyones a sort of mantle, which completely 

 covers them. Many apply, upon their back, the valve of a 

 shell, and on that account, these Crustacea, like dorippus, have 

 their four posterior feet recurved upwards, and adapted for re- 

 taining, with the strong hook that terminates them, and which 

 in some species, is even accompanied by another, but a smaller 

 one, the bodies which they think proper to appropriate. 



Many, such as the matuti, portuni, orithyiae, and the 

 macrouri in general, swim with facility. But the other 



