32 FERTILIZATION 



the fertilizing capacity of spermatozoa after subjection to different 

 concentrations of multivalent and univalent fertilizin could be 

 quantitatively examined with advantage. 



Activation of spermatozoa by egg water. Egg water makes 

 homologous spermatozoa move more actively, respire at a greater 

 rate, and continue their movement, and therefore their respiration, 



o^ 



=1 

 I 



20 



40 



t (minJ 



FIG. 7. — Effect of egg secretions on the O, uptake of sea-urchin spermatozoa 

 {Psommechinus miliaris). •, with egg secretions; O, without egg secretions. 

 After Gray (1928). 



for longer than they do in ordinary sea water. The effect is rather 

 variable, though when it is present, there is no doubt about its 

 existence. Gray (1928) was the first to examine this phenomenon 

 quantitatively, using the spermatozoa of Psammechiniis miliaris 

 (Fig. 7). He found that in some cases, the initial rate of O2 uptake 

 was four times as great in egg water as in sea water. The pro- 

 longation of sperm movement has obvious advantages from the 

 point of view of fertilization, though without a detailed knowledge 



