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 Chetopterus 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.’ 
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 Winkler’s experiment, I am not yet certain that these 
1 WINKLER, Nachrichten der kiniglichen Gesellschaft der Wissenschaften, Got- 
tingen, 1200. 
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