Artificial Parthenogenesis 109 



its osmotic pressure is higher than that of the colloidal 

 solution inside the membrane the latter will collapse. 



It should also be stated that the unfertilized eggs 

 of many marine animals are surrounded by a jelly 

 (chorion) which is dissolved when the egg is fertilized. " 

 The writer has shown that the same chemical substances' 

 which will induce membrane formation and artificial 

 parthenogenesis will as a rule also cause a swelling and 

 liquefaction of the chorion. 



We have devoted so much space to the mechanism 

 of membrane formation since it is likely to give a clearer 

 insight into the physicochemical nature of physiological 

 processes than the phenomena of muscular stimulation 

 and contraction or nerve stimulation, upon which the 

 majority of physiologists base their conclusions con- 

 cerning the mechanism of life phenomena. 



Before we come to the discussion of the second factor 

 in the activation of the egg it should be stated more 

 definitely that for the eggs of some forms the first 

 factor, the process underlying membrane formation, 

 suffices for the development of the egg into a larva and 

 that no second factor is required in these cases. This 

 is true for the eggs of starfish and certain annelids. 



1 It has been stated by several writers that the eggs of the sea urchin 

 can no longer form the fertilization membrane when the jelly surround- 

 ing the egg is dissolved. The writer has found that if the jelly sur- 

 rounding the eggs of Strongylocenirotus purpuratus is dissolved by acid 

 the eggs still form a fertilization membrane upon the entrance of a 

 spermatozoon. 



