328 EDWIN G. CONKLIN 



in artificial parthenogenesis, (1) an external factor, such as bu- 

 tyric acid, which causes a cytolysis of the cortical layer of the egg 

 followed by increased oxidation and which leads to the rapid 

 disintegration of the egg at normal temperatures, and (2) an 

 internal factor, such as hypertonic solutions, lack of oxygen, etc., 

 which inhibits this disintegration. Loeb concludes also that in 

 normal fertilization both of these factors are present and that 

 the spermatozoon carries substances into the egg which (1) 

 cause cytolysis of the cortical layer and increased oxidation and 

 (2) other substances which inhibit this cytolysis before it leads 

 to the disintegration of the egg. Godlewski ('11) also finds that 

 the cytolysis which is caused by fertilizing the eggs of sea ur- 

 chins by the sperm of Chaetopterus may be checked and arti- 

 ficial parthenogenesis induced by a brief treatment of such cross 

 fertilized eggs with hypertonic sea water. 



R. S. Lillie ('11) concludes that the cortical changes consist in 

 increased permeability of the cell membrane which tends "to de- 

 stroy the normal osmotic equilibrium and allow abnormal dif- 

 fusion of substances into and out of cells." The essential re- 

 sult of the after treatment of such eggs with hypertonic sea 

 water is to decrease the permeability of the cell membrane and 

 thus restore normal conditions. 



F. R. Lillie ('12) holds that ''the action of the spermatozoon 

 in fertilization involves two distinct phases, the first of which 

 may be effected before penetration and brings about a sudden 

 and marked increase in permeability of the egg membrane; the 

 second, which follows after penetration, consists essentially in 

 the establishment of normal interchange between nucleus and 

 cytoplasm, and consequently normal regulation of all the ac-. 

 tivities of the cell." More recently ('13) he has put forth a 

 new view based upon the reactions of spermatozoa to substances 

 secreted by the ova. He concludes that the ' lysin' which caue^es 

 cytolysis is contained in the egg, not in the sperm, as L^^eb 

 thought; "if cytolysis is involved it is a case of autocytolysif^." 



My experiments on the giant polar bodies of Crepidulae, show 

 that changes in the cortical layer which prevent the entrarf^ce of a 

 second spermatozoon take place very rapidly over th\Q entire 



