154 PROBLEMS OF FERTILIZATION 



inconsistent with the idea of a general gelation effect, 

 which is decidedly more pronounced in the region of 

 the aster. Karyokinesis is, according to Chambers, 

 essentially a reversible gelation effect. The gel area 

 represented by the sperm aster is a preparation for the 

 first cleavage of the egg. 



4. Chemical changes - -The initiation of development 

 which is associated with fertilization involves a progres- 

 sive chain of chemical changes, but it is obvious that 

 these lead us outside of the field of fertilization proper, 

 beyond the stage of indicia of fertilization. There is, 

 however, one very striking change occurring at the 

 very beginning of the fertilization reactions that de- 

 serves notice here. I allude to the complete loss of 

 sperm-agglutinating substance by the egg. This was 

 first observed by the writer in the case of Nereis, and 

 was subsequently more carefully studied in Arbacia 

 (1914-1 5) . As long as eggs of Arbacia retain capacity for 

 fertilization they produce this substance, which is read- 

 ily recognizable by its agglutinating action on sperm 

 suspensions of the same species. But if the adherent 

 jelly which also contains this substance is removed from 

 fertilized eggs and the substance present before fertili- 

 zation is washed off, not a trace of the agglutinating 

 substance can be derived from the fertilized eggs. 

 There is a complete loss of sperm-agglutinating sub- 

 stance and with it a loss of capacity for further fertili- 

 zation reaction at the moment of fertilization. This 

 determination has been confirmed by Glaser (1914), 

 by Just (1919), and by Moore (1916). The writer was 

 convinced by this and other data, discussed later, that 

 the agglutinating substance is necessary for fertilization. 



