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. 
Ido 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.! 
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 (Tibin- 
gen), and Dr. 8. 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 
1Viguier’s paper has been criticised by A. GIARD, Comptes rendus de la Société 
de Biologie, Vol. LII (1900), p. 761. 
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