686 STUDIES IN GENERAL PHYSIOLOGY 



Another surprising fact in Viguier's paper is that he does 

 not mention whether or not his unfertilized eggs had a 

 membrane. In my researches on Arbacia I have considered 

 the lack or presence of a membrane the most important 

 criterion for deciding whether the development of the eggs 

 is due to the entrance of a spermatozoon or to the osmotic or 

 chemical treatment they have received. The fertilized eggs 

 form a thick membrane, while the unfertilized eggs generally 

 have no membrane (unless treated with certain salts in exces- 

 sive quantities and for a long time). The cleavage of the 

 parthenogenetic egg that has no membrane differs so radi- 

 cally from that of the fertilized egg within a membrane, that 

 it must arouse the interest or surprise of any morphologist. 

 These differences are most noticeable during the first hours 

 of the development. As soon as the egg approaches the 

 blastula stage the membrane very often begins to disintegrate. 

 I do not think that any experienced observer would have 

 dared to publish the statement that the unfertilized eggs of 

 Arbacia reach the pluteus stage, without having convinced 

 himself that the "unfertilized" eggs had no membranes. 1 



Mr. Viguier makes the statement that he tried to repeat 

 my experiments but was not able to confirm them. This 

 does not surprise me, as he had not read my papers, and as 

 he did not even know how my solutions had been prepared. 

 My experiments have been repeated and confirmed by the 

 following authors: Dr. C. Herbst (Naples), Professor E. B. 

 Wilson (Columbia University), Dr. Hans Winkler (Tubin- 

 gen), and Dr. S. Prowazek (Prague), and partly by Professor 

 A. Giard (Paris). In addition they were repeated with 

 success by all the members of the class in physiology and 

 embryolgy at Woods Hole last summer. As far as the state- 

 ment is concerned that the unfertilized eggs of Arbacia or 



1 Viguier's paper has been criticised by A. GIARD, Comptes rend us de la Soci6t 

 de Biologic, Vol. LII (1900), p. 761. 



