ARTIFICIAL PRODUCTION OF NoRMAL Larva 623 
the egg, either by its carrying specific ions into the egg or 
by carrying enzymes, or in some other way which is as yet 
unknown to us. It is certainly remarkable that the sperma- 
tozoa contain a large amount of ash (5 per cent., according 
to Hammarsten). In the parthenogenetic egg the colloids 
are from the beginning in such a condition as to allow the 
development to proceed. In other animals it is perhaps 
solely the ion constitution of the sea-water or of the blood 
which prevents the eggs from developing parthenogenetic- 
ally. I shall discuss this point more fully in connection 
with further experiments on this subject. 
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