Gametogenesis, Fertilization and Parthenogenesis 



191 



Upon extraction of antifertilizin by acidi- 

 fied sea water the head of the spermatozoon 

 is found to round up and the surface to 

 become diffuse in the region between the 

 acrosome and midpiece, while the latter 



of this agent are similar to those described 

 for the antifertilizin from sperm. In other 

 words, antifertilizin from within the egg 

 can react with fertilizin on the surface of 

 the same egg. The active agent appears to 



^^MiM 



Fig. 61. Electron micrographs of sperm of the sea urchin Lytecyinus pictus, showing changes upon ex- 

 traction of antifertilizin; X 30,000. a. Control, imextracted sperm, b, Extracted at pH 3.5. c. Extracted at 

 pH 3.0. d. Extracted at pH 2.8. (From Tyler, '49.) 



structures and tail are not visibly affected 

 (Fig. 61). Antifertilizin is, then, considered 

 to be located on the lateral surface of the 

 head between the acrosome and midpiece. 

 Antifertilizin from Eggs. Lillie ('14) had 

 postulated the presence of an antifertilizin 

 within the egg and Tyler ('40b) was able 

 to obtain such an agent by extraction of sea 

 urchin eggs that had been previously di- 

 vested of their gelatinous coat. The effects 



be a protein (Tyler, '40b, '48a). Injection 

 of the extracts into rabbits induces the pro- 

 duction of antibodies that not only pre- 

 cipitate the homologous antigen but also 

 agglutinate sperm of the same species, indi- 

 cating antigenic similarity to the antifer- 

 tilizin of sperm. 



Consideration of the finding that sub- 

 stances capable of interacting in antigen- 

 antibody-like manner can be obtained from 



