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 set® 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 
