688 STUDIES IN GENERAL PHYSIOLOGY 



Through these facts and conceptions the phenomena of 

 artificial parthenogenesis assume a different aspect. It 

 would be wrong to say that the K ions are the stimulus that 

 causes the developmental process. They merely act as 

 catalyzers, accelerating a process that would otherwise 

 proceed too slowly. The loss of water on the part of the egg 

 cell must have a similar effect, but possibly a less direct one. 

 It may be that the loss of water alters the chemical processes 

 in the egg in such a way as to give rise to the formation of 

 a substance which acts catalytically. 



Whether or not the catalytic substances introduced by 

 the spermatozoon are identical with those employed in my 

 experiments, I cannot say. I consider it probable that in 

 the case of Chsetopterus the natural fertilization is not 

 brought about by K ions, inasmuch as the normal develop- 

 ment does not show the characteristics of a treatment of the 

 eggs with K. 



I have made a series of experiments with various enzymes 

 to bring about the development of the unfertilized eggs of 

 Arbacia, thus far without any results. The only enzyme 

 that caused the egg to segment at all was papain. But 

 I cannot be certain whether this was not due to some acci- 

 dental constituent of the enzyme preparation used. The 

 other enzymes were absolutely without effect. If we wish to 

 find the active principle in the spermatozoon, we must make 

 experiments in the direction of those begun by Winkler. 1 

 This author used extracts of the spermatozoon, and found 

 that such extracts caused the eggs of sea-urchins to reach 

 the two- or four-cell stage. As such a result can be brought 

 about by slight alterations in the osmotic pressure or con- 

 stitution of the sea-water, and as such alterations occurred 

 in Wiiikler's experiment, I am not yet certain that these 



1 WINKLER, Nachrichten dt-r kSniglichen Gesellschaft der Wissenschaften, Got- 

 tingen, 1900. 



