38 FERTILIZATION 



methanol (Runnstrom et al., 1944a). Whether this substance 

 normally diffuses out of sea-urchin spermatozoa and therefore has 

 a function in fertilization is much more debatable. According to 

 Hartmann et al. (1940), A.I. is responsible for the lack of sperm 

 movement in undiluted sea-urchin semen. This is wrong as the 

 lack of movement has been proved to be due to lack of oxygen ; 

 sea-urchin spermatozoa can be induced to move in undiluted 

 semen by increasing the oxygen tension, while the effect can be 

 reversed by replacing the oxygen with nitrogen (Rothschild, 1948). 

 Spermatozoa in salmon semen cannot be induced to move by in- 

 creasing the oxygen tension (Rothschild, 195 1); there is no doubt 

 that salmon semen contains an inhibitory substance and that it has 

 a genuine biological function (Runnstrom et al., 1944a). When 

 ejaculated salmon semen is diluted with water, the concentration 

 of the inhibitory substance, which is not a protein and diffuses 

 through cellophane, falls below the level at which it inhibits move- 

 ment, and the spermatozoa become motile. 



Although the systematic study of sperm-egg interacting sub- 

 stances was started by F. R. Lillie (1919) * and Just (1939),* in- 

 tensive investigations into their biological and chemical properties 

 only started in about 1939. Like all young subjects, this one is still 

 confused and therefore difficult to expound in an aesthetically 

 satisfying way. Some of the more 'straightforward' aspects are 

 discussed in the succeeding chapters. The reader may be surprised 

 that, apart from studies on hyaluronidase, so much of this work 

 has been done on marine invertebrates. Is there, for example, any 

 similarity between the causes of sperm inactivity in the mammalian 

 epididymis and the causes of sperm inactivity in undiluted salmon 

 semen? Apart from Glaser's preliminary observations (1921) on 

 frog spermatozoa, are there biological similarities between the jelly 

 round frogs' eggs, whose chemistry has been intensively studied 

 (Folkes et al., 1950), and fertilizin? Does it, for example, inhibit 

 the clotting of blood ? Such questions might repay investigation. 



* These contain references to early work on this subject. 



