236 PROBLEMS OF FERTILIZATION 



reaction. Only once, and then in a footnote of a paper 

 of earlier date than the one dealing with the mechanism 

 of fertilization, have I alluded to the question whether 

 fertilization may be regarded as involving an immunity 

 reaction (1913, p. 563); the footnote follows: "In the 

 latter case, fertilization itself would have to be regarded 

 as an immunizing process, the sperm acting as anti- 

 gen after entrance with the egg. It seems, in fact, an 

 almost necessary conception of the general principles 

 of immunity phenomena that the sperm should so act. 

 The question would be, of course, whether there is a 

 connection between any antibodies so formed and the 

 sperm iso-agglutinins produced by the next generation 

 of ova." 



Loeb has reversed these relations. However, I 

 would point out again that no comparison to immunity 

 phenomena was made in the fertilizin hypothesis: an 

 analogous pictorial method of representation was 

 adopted, and only that. 



Another misunderstanding on Loeb's part is to 

 regard the theory as dealing with the egg and sperma- 

 tozoon as cells, which, as he well says, are not simple 

 organic compounds. I was always careful to speak of 

 " sperm receptors" borne by the spermatozoon and "egg 

 receptors" borne by the egg as the substances, not 

 otherwise known, concerned in the activation of the 

 egg, together with the fertilizin. They are linked in 

 line thus: sperm receptors-fertilizin-egg receptors, and 



not directly, as sperm receptors^ lzm , because 



\egg receptors 



the sperm receptors are able to bind the fertilizin in 

 the absence of the egg receptors but are unable to 



