30 FERTILIZATION 



reaction between spermatozoa and egg water as a typical serological 

 reaction is plausible — fertilizin can even combine with comple- 

 ment (Tyler, 1942/^)— criticisms of the analogy have not been lack- 

 ing, while some of the difficulties will not have escaped the reader. 

 Rybak (1949), for example, said that reversal of agglutination was 

 not due to the splitting of fertilizin but to a change in the sperma- 

 tozoa. Popa made a similar claim as long ago as 1927 and more 

 recently, J. C. Dan (1952, 1955) has published electron micro- 

 graphs showing morphological changes which are believed to take 

 place after treatment of sea-urchin spermatozoa with egg water. 

 Rybak also disbelieves in univalent fertilizin, but his experiments 

 in support of this view are not convincing. A further difficulty is 

 the fact that fertilizin appears to impair the fertilizing capacity of 

 spermatozoa by masking some of the combining groups on the 

 sperm head surface. It seems curious that an unfertilized egg 

 should be normally surrounded by a substance which positively 

 interferes with fertilization. At the same time Tyler (i94i«) 

 showed that following complete removal of jelly from unfertilized 

 eggs of Strongylocentrotus purpuratiis, by methods which did not 

 harm the eggs from the point of view of subsequent development, 

 more spermatozoa were needed to achieve a particular percentage of 

 fertilized eggs than when the jelly was present. This observation 

 was confirmed and put on a quantitative basis, in terms of the 

 probability of successful sperm-egg collisions, by Rothschild & 

 Swann (1951). 



An interesting question has been raised by Monroy et al. (1954) 

 — whether the reaction between a spermatozoon and egg jelly in 

 solution in sea water, or between a spermatozoon and egg jelly 

 surrounding an egg, are necessarily the same, a subject which re- 

 quires further investigation. As regards the former reaction, these 

 workers, together with Hultin et al. (1952), have shown that living 

 spermotozoa of Arbacia lixula and Echinocardium cordatum remove 

 fucose from egg water (Table 4), which confirms that surface 

 groups on the spermatozoa react with and bind fertilizin. (Mudd 

 et al. (1929) found that the ^-potential of the spermatozoa of 

 Arbacia punctulata increased from —22 to —25 mV. in the presence 

 of homologous egg water.) Monroy, in the paper referred to above, 

 and Vasseur (1952) suggest that, as alkylation of amino groups on 

 spermatozoa inhibits agglutination (Metz & Donovan, 195 1), the 

 reaction given in Table 4 is between amino groups on sperm 



