104 Artificial Parthenogenesis 



the same species can induce membrane formation. 

 This might find its explanation on the assumption 

 that the active substance contained in the foreign 

 sperm or serum is water-soluble and a protein, while 

 the activating or membrane-forming substance in the 

 spermatozoon is insoluble in water but soluble in the 

 ^gg (or in lipoids). If this assumption is correct 

 the two substances are essentially different. 



Robertson' has succeeded in extracting a substance 

 from the sperm of the sea urchin which causes mem- 

 brane formation of the sea-urchin egg after the latter 

 has been sensitized by a treatment with SrClz. It 

 seems to the writer that if the substance extracted by 

 Robertson were the real fertilizing agent contained in 

 the spermatozoon it should fertilize the egg without a 

 previous sensitization of the egg with SrClz being 

 required. 



3. The action of acids in the mechanism of artificial 

 parthenogenesis provides some interesting physiological 

 problems. When unfertilized sea-urchin eggs are left 

 in sea water containing any of the lower fatty acids up 

 to capronic, the eggs will form no membranes, while 

 in such sea water, and they will show no outer signs of 

 cytolysis (swelling). When, however, the eggs are 

 left in sea water containing any of the fatty acids from 

 heptylic upward the eggs will form membranes while 

 in the acid sea water and soon afterward will cytolyze 



» Robertson, T. B., Arch.f. Entwcklngsmech., 1912, xxxv., 64. 



