358 CLASS CRUSTACEA. 



diminishes, the leaflets approximate one to the other, the for- 

 ceps is less defined and less sharp, and the first finger is 

 widened at the expence of its length, and rounded ; the two 

 anterior, much larger, in the form of oars, resemble ramified 

 antennae, and have been considered as such by some writers. 

 They present four setaceous filaments, composed of a great 

 number of articulations, and of which the two of the end (one 

 more especially), are much longer than the two others, which 

 are situated at the internal or anterior side. It is evident that 

 the two of the extremity are the analogues of the two fingers 

 of the forceps, and that the others also represent two of the 

 lateral leaflets. Of this we may be convinced, by comparing 

 these feet with their analogues, and the two or three follow- 

 ing in the young individuals. After the sixth or seventh 

 moulting, the latter much resemble the two anterior, and the 

 antennas are even proportionally longer than in the adult 

 state, and terminated by seta? or hairs. The eleventh pair 

 is very remarkable : the first articulation presents, behind the 

 vesicle, two circular valves, applied one upon the other, 

 formed by two leaflets, and enclosing the eggs, which re- 

 semble small grains of a very lively red. All the individuals 

 which have been studied up to the present day, having been 

 found provided with similar feet, it has been suspected that 

 they fecundate themselves, and that there are no males. 



These Crustacea inhabit ditches, pools, and dormant waters 

 of all kinds, and almost always in innumerable societies. 

 When thus assembled, they are swept up by very violent 

 winds, and have then been seen to fall like showers of rain. 

 They appear more commonly in spring, and at the commence- 

 ment of summer. Their food consists principally of tadpoles. 

 They swim very well on the back ; and when they sink into 

 the mud, they keep their tail elevated. When born, they 

 exhibit but one eye, and but four feet, in the form of arms or 

 oars, having aigrettes of hairs, and the second of which are 



