THE PROBLEM OF ACTIVATION 235 



zoon with the egg. It is a useful indicator that enables 

 us to make certain analyses, but the same principle of 

 fertilization may hold in the entire absence of sperm 

 agglutination. The spermatozoon is modified in the 

 presence of egg secretions of the same species, by union 

 of a substance in the spermatozoon (agglutinable sub- 

 stance) with a substance in the egg secretion (aggluti- 

 nating substance or fertilizin). If this union renders 

 the sperm heads adhesive, and if the spermatozoa are 

 sufficiently concentrated and motile, they will aggluti- 

 nate together, otherwise not. But a degree of adhesive- 

 ness insufficient for sperm agglutination may be quite 

 adequate for agglutination of the sperm to the egg. As 

 pointed out in chapter vi the quantitative aspect of 

 specificity in fertilization requires much more study, 

 and Loeb has given no quantitative data for the hybrid 

 fertilization in question. 



Loeb (1915, p. 279) misrepresents the view here 

 developed when he says that the writer has called the 

 egg an antigen, the spermatozoon a complement, and 

 the fertilizin an amboceptor. Such a view is not even 

 implied in anything I have ever written. What I did 

 was to utilize Ehrlich's method of formulating such a 

 three-body reaction for a pictorial representation of 

 what happens in the fertilization of the egg. The infer- 

 ence from the diagram given (Lillie, 1914, p. 579), on 

 a strict comparison with Ehrlich's conception of hae- 

 molysis, would be that a substance borne by the sperm 

 corresponds to the antigen, the fertilizin to the ambo- 

 ceptor, and a substance contained in the egg corre- 

 sponds to the complement. But it was not suggested 

 that these relations were established by an immunity 



