162 The Mechanistic Conception of Life 



eight years ago that if we make the sea- water slightly more 

 alkaline than it naturally is the eggs of the sea-urchin can be 

 fertilized by the sperm of the star-fish. For the fertilization 

 of the Californian sea-urchin, Strongylocentrotus purpuratus, 

 with the sperm of Asterias, the best results were obtained when 

 0.6 c.c. of n/10 NaOH were added to 50 c.c. of sea-water. In 

 this case, with active sperm, in about fifty minutes all the eggs 

 form the typical fertilization membrane. 



If we watch the further development of sea-urchin eggs 

 fertilized by star-fish sperm we notice very soon that there are 

 two different kinds of eggs present; the one kind of eggs 

 behave as if they had been fertilized with sperm of their own 

 kind. That is to say, they segment regularly and develop into 

 swimming blastulae and gastrulae. The other kind of eggs, 

 however, act as if they had been treated with one of the agencies 

 which cause the membrane formation in the unfertilized sea- 

 urchin egg; these eggs begin to segment, but at room tempera- 

 ture they slowly perish by cytolysis. If, however, these eggs 

 are treated for half an hour with a hypertonic solution they 

 develop into larvae. 



If we examine the eggs of a sea-urchin which have been 

 treated in an alkaline medium with the sperm of the star-fish, 

 we find that only a certain percentage of these eggs contain 

 the sperm nucleus, and this percentage seems to be identical 

 with the percentage of the eggs which develop into larvae. 

 As far as the other eggs are concerned, which form only a 

 membrane and then disintegrate, no sperm nucleus can be 

 found inside of them. I am inclined to draw the following 

 conclusion from these observations: The spermatozoon of the 

 star-fish penetrates very slowly through the surface film of 

 the sea-urchin egg. When it lingers for some time partially 

 imbedded in the surface film, one of the substances of the 

 spermatozoon is dissolved in the superficial layer of the egg 

 and causes the membrane formation. Through the act of 



