Miscellaneous. 1 73 



the so-called rivers of stone of the Falkland Islands, which attracted 

 the attention of Darwin during his cruise with Captain Fitzroy, and 

 Avhich have remained an enigma to this day. I believe it will not 

 be difficult to explain their origin in the light of the glacial theory ; 

 and I fancy now they may turn out to be nothing but ground mo- 

 raines, similar to the " Horsebacks " of Maine. 



You may ask what the question of drift has to do with deep-sea 

 dredging ? The connexion is closer than may at first appear. If 

 drift is not of glacial origin, but the product of marine currents, its 

 formation at once becomes a matter for the Coast Survey to investi- 

 gate ; and I believe it will be found in the end that, so far from 

 being accumulated by the sea, the drift of the lowlands of Patagonia 

 has been worn away to its present extent by the continued en- 

 croachment of the ocean in the same manner as the northern 

 shores of South America and of Brazil have been 



Hoping some, at least, of my anticipations may prove true, 

 I remain, ever truly yours, 



LoTJis Agasstz. 

 — Bulletin of the Museum of Comparative Zoology at Harvard College, 

 Cambridge, Mass., vol. iii. (Communicated by the Author.) 



On the Fecundation of the Crayfish. By M. S. Chantean. 



Hitherto we have been in uncertainty as to the question whether 

 in the crayfish the fecundation of the ova takes place in the interior 

 of the body of the female or on the outside of it, I think I have 

 determined that it is on the outside that this phenomenon takes 

 place ; ' and the following are the conditions. 



In my note read to the Academy on the 4th of July 1870 *, I 

 stated that the male deposited his fecundating material, in the form 

 of si:»ermatophora, upon the plates of the caudal fan and on the 

 plastron of the female, and that thB period of the oviposition varied 

 from the second to the forty-fifth day after the copulation. 



When the moment of oviposition arrives, the female raises herself 

 upon her feet, and then her abdominal appendages secrete for several 

 hours a very viscous greyish mucus ; then she lies upon her back, 

 and bends her tail towards the opening of the oviducts, so as to 

 form a sort of chamber, already noticed by Lereboullet, in which, 

 during the following night, the ova are collected as they are expelled 

 from the genital organs. In diff'erent 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 false legs and the margins and 

 extremity of the tail to the thorax, and which assists in bounding 

 the pouch or chamber above mentioned, in which a certain quantity 

 of water is enclosed with the oTa and the mucus. Immediately after 

 oviposition we may detect in this mucus and water the presence 

 of spermatozoids t precisely similar to those which are contained in 



* See Ann. & Mag. Nat. Hist. ser. 4. vol. vi. p. 265. 



t Here they are mixed with pale yellowish drops and a certain num- 



