232 HEPOET— 1880. 



inner surface of the ovisac to the internal branch of each of the four lobes 

 of the median membranous lamina of the caudal appendage. This fila- 

 ment exists when the embryos have only attained about three-fourths of 

 their development. 



If the young, continues M. Chantran, detach themselves before this 

 period, they cannot live separately ; but after the first nioulb they some- 

 times quit their mother and return to her again, up to the twentieth day, 

 at which period they can live independently. He .'=ays {Gomptes Rendus 

 for July 17, 1871) he has observed that the young not only feed, 

 while attached to the mother, upon the pellicle of the eggs, and the 

 exnvia of the early moults, but the stronger ones cat those individuals 

 whose development is rendered difficult by their agglomeration, and 

 whicli cannot moult. Those which in moulting break their limbs ai-e also 

 devoured by their companions. Thus the crayfish which are ten days 

 old eat each other, and this is moreover the case with those of any age 

 when they moult and are too numerous for the small space they occupy 

 beneath the pleon of the mother. 



M. Chantran also has observed that temperature exerts a marked in- 

 fluence upon the duration of incubation and the number of the periodical 

 moults between the exclusion of the young from the ovum and the adult 

 period. The male becomes ready for copulation on entering its third 

 year, and the female for fecundation at the commencement of the fourth 

 year. In relation to the reproduction of the lost appendages M. Chan- 

 tran's observations require confirmation, which he promised to make 

 known. He says that the antennae are reproduced during the period of a 

 single moult. The other limbs are reproduced more slowly, three moults 

 taking place during their regeneration. In the first year of their existence 

 seventy days suffice for the reproduction of these limbs, while in the adult 

 crayfish, the female requires three or four years to reproduce its limbs, 

 and the male from a year and a half to two years, for the adult male 

 moults twice a year and the female only once. 



M. Gerbe, who has given much attention to the development of Crus- 

 tacea, says, none of those that he has observed has its organisation complete 

 on its quitting the ovum as a hrephalus (or larva), or j^ossesses features iden- 

 tical with the parent, so that it might be referred to the species to whicli 

 it belongs. All are furnished with transitory appendages adapted for 

 natation, whicli give them a locomotion different from that of the adult 

 stage. These appendages, he states, remain until the fifth and sixth 

 moult, and become atrophied in position without falling off. It is not 

 until the fifth or sixth moult that the general form of the adult external 

 organs are complete. The brepJiali of various species, however they may 

 resemble each other in external form, show minor features of distinction, 

 such as a variation in the number and form of spots, and especially in 

 the number and conformation of the plumose hairs and spines which 

 fringe the extremity of the last segment of the pleon. These, he says, 

 present definite characters which enable us to say to what species any 

 particiilar brepbalus belongs. 



The stomach of the Crustacea in the zoasa stage presents, he says, no 

 solid pieces adapted for the grinding of food. It is furnished on its inner 

 surface with stiff siJinuIes arranged in rows, and with vibratile cilia like 

 those found in the stomachs of a great number of the lower animals. 

 These cilia communicate an incessant movement of rotation to the orgauic 

 molecules upon which the animals feed. 



