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THE IMPROVED METHOD OF ARTIFICIAL PARTHENO- 
GENESIS IN THE SEA-URCHIN EGG 
The first method of producing larvae from the unfertilized 
egg of the sea-urchin by a mere increase of osmotic pressure 
only sufficed to show that the mysterious complex “living 
spermatozoon” might be replaced by well-known physico- 
chemical agencies. It did not lend itself well to a physico- 
chemical analysis, since the method was not always reliable. 
We have already mentioned that with the Californian sea- 
urchin S. purpuratus the method worked only with the eggs of 
a small percentage of females and even the eggs of different ~ 
females of Arbacia did not yield equally well to this method. 
For a further investigation of the nature of the process of 
fertilization this method was therefore very unsatisfactory. 
There were other reasons which indicated that a better 
method for artificial parthenogenesis was needed. The larvae 
of normally fertilized eggs rise to the surface of the water; they 
are pelagic. The larvae produced by means of a hypertonic 
solution rarely or never rose to the surface of the sea-water, 
but swam at the bottom of the dish. And finally, the eggs 
form, upon the entrance of a spermatozoon, the fertilization 
membrane. The unfertilized eggs which developed after treat- 
ment with a hypertonic solution never formed a characteristic 
fertilization membrane, but only a fine gelatinous film instead 
of the clear fertilization membrane. 
This led me to think that the osmotic activation of the egg 
was only an incomplete imitation of the fertilization process, 
and that the fertilization by the spermatozoon perhaps depend- 
ed not upon a single chemical agent, but upon a combination 
of two or more which were only fortuitously combined in the 
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