230 REPOKT— 1880. 



Report on the Present State of our Knowledge of the Crustacea. 

 By C. Spexce Bate, F.R.S , c&c. 



Part V. — Ox Feccxdatiox, Eespiratiox, and the Green Gland. 



Copulation of the crayfish takes place, according to the observatious of 

 M. Chantran,' during a period which includes the months of November, 

 December, and Jannary. The male seizes the female with his large 

 nippers, turns her over, and whilst he holds her lying on her back, places 

 himself in such a manner as to pour out the fecundating material upon 

 the two outer lamelliB of the tail. After this first operation, which lasts 

 some minutes, he conveys her rapidly beneath his pleon, in order to effect 

 a second deposition of semen upon the plastron round the external open- 

 ing of the oviducts, by means of the curious mechanism so accurately 

 described by M. Coste, upon the plates of the caudal fan (Bipisura).^ 



According to the degree of the maturity of the ova at the time of the 

 union of the sexes, oviposition takes place at a period varying from ten 

 to foi'ty-five days after copulation. At the moment when this function 

 is about to be performed, the female raises herself upon her feet, and her 

 pleopoda secrete for several hours a very viscous greyish mucus ; and 

 then she lies upon her back and brings up her tail upon her plastron in 

 such a manner as to form with her pleon a chamber, as has also been ob- 

 served by Lereboullet, in which the ova are collected, enclosing the aper- 

 ture of the oviducts, the wall of which secretes a viscous fluid intended to 

 fasten the eggs to the pleopoda during incubation. When things are in 

 this state, the laying of the eggs takes place. It is efiected at once, 

 usually during the night, rarely during the day. ' In different females 

 this expulsion lasts from one to two hours. The ova, which are always 

 turned so as to present their whitish spot or cicatricula above, as if to 

 receive more easily the influence of fecundation, are thus immersed in the 

 greyish mucus, which in a manner binds the pleopoda and the margins 

 and extremity of the telson to the pereion, and which assists in bounding 

 the pouch or chamber so formed, in which a certain quantity of water is 

 enclosed with the ova and mucus. Immediately after the oviposition we 

 may detect in this mucus and water the presence of spermatozoids, pre- 

 cisely similar to those which are contained in the spermatophores attached 

 to the plastron, and derived from them. With them are mixed pale yellowish 

 drops and a certaia number of rounded gi^anulated globules, isolated or 

 united in little masses, which do not exist in the cavity of the spermato- 

 phores, when spermatozoids are to be found. These spermatozoids are 

 thus in direct contact with the ova, and in the midst of the vehicle which 

 facilitates their penetration. Fecundation, then, is accomplished in this 

 chamber — that is to say, outside of the genital organs of the female.' 



The observations of M. Chantran have been corroborated by M. C. 

 Robin, who has ' seen that the spermatozoids, which are found in contact 

 with the ova in the chamber I have just described, are similar to those 

 seen in the genital organs of the males, and to those in the spermatophores 



' Comptes B^ndus, July 4, 1870, tome Ixxi. pp. 42-45. Ann. Nat. Hist. 4th ser, 

 vol. 6, p. 265. 



^ 'Pixi'y, fan ; ovpd, tail (fantail). Telson and posterior pair of Pleopoda, 



