ORDER BRANCHIOPODA. 337 



According to the Genevese naturalist just cited, these ani- 

 mals, when they swim, move the two anterior feet with as much 

 rapidity as the antennae ; but they move them slowly when 

 they walk on the surface of marshy plants. These feet, con- 

 jointly with the two terminated by a long hook, or the penul- 

 timate feet, then support the body. He supposes that those 

 which, according to him, form the second pair, are intended 

 to produce an aqueous current, and direct it towards the 

 mouth. This would assimilate their functions to those of the 

 lower antennae, which he names antennula. The two fila- 

 ments composing the tail are united, and seem to form but 

 one, when they come forth from the testa. They answer the 

 purpose, as is presumed, of cleansing its interior. The female 

 deposits her eggs in a mass, fixing them, by means of a gluten, 

 on plants or mud. Hooked, at this time, with the aid of the 

 second feet, and so as not to fear the shocks of the water, she 

 employs almost twelve hours in this operation, which in the 

 larger species furnishes as many as four and twenty eggs. 

 M. Jurine has collected some of these packets of eggs, when 

 they came forth, and after having isolated them, he has seen 

 them disclose the young, and he has obtained another gene- 

 ration without the intervention of the males. A female which 

 had laid its eggs on the twelfth of April, up to the eighteenth 

 of May inclusive, changed skin six times. The twenty-seventh 

 of the same month she laid a second set, and two days after, 

 on the twenty-ninth, a third. He concludes from this, that 

 the number of moultings from infancy is in relation with the 

 gradual development of the individual ; that this development 

 cannot manifest itself but by the general separation of an 

 envelope become too small to lodge the animal ; and that 

 there is a determinate limit of size to W'hich the latter must 

 attain. 



The lophyropa of our third division, (our CladoceraJ or the 

 Daphnides of M. Straus, compose, in the history of the mono- 



VOL. XIII. Z 



