230 FRANK R. LILLIE. 



alone, that is, of its capacity to "penetrate the ovum," there 

 could be no object in quantitative studies. But as it came to 

 be recognized that the fertilizing power of the spermatozoon is 

 associated with some definite substance that it bears, possibly 

 either a lysin (Loeb) or an activator (self), the problem assumes 

 a different aspect; for it is obvious that if the sperm should 

 lose such a substance in any way, its fertilizing power would be 

 lost even though its motility should be preserved unimpaired. 

 In such a case the relative fertilizing power of sperm suspensions 

 could not be measured either in terms of concentration or of 

 activity of the spermatozoa. Variations in the fertilizing power 

 of suspensions of known concentrations might, therefore, be a 

 measure of the loss of the postulated fertilizing substance. On 

 reflection it is obvious that the spermatic substance in question 

 must be loosely bound to the sperm, because it exerts its first 

 effect, that of inducing cortical changes in the egg, before pene- 

 tration, as I have shown for Nereis, and Loeb for certain hybrid 

 combinations; at this time, therefore, the spermatozoon must set 

 free its receptors^ (activators). 



Recently Glaser (1913 and 1915) has maintained that in 

 Arhacia more than one spermatozoon is needed for fertilization 

 of the egg, even though only one actually penetrates. The 

 observations on which this conclusion rests are no doubt correct, 

 under the given conditions, and I have made similar observations, 

 as will appear in the course of the present paper. But it by no 

 means follows from the observations that a single spermatozoon 

 may not be adequate under other conditions (and this can be 

 demonstrated). We cannot, however, deny a priori the possi- 

 bility that for the initial phases of fertilization a number of 

 spermatozoa may be of assistance though only one enters and 

 is concerned in later phases. If the phenomena of fertilization 

 are to receive a physiological, and ultimately a chemical, inter- 



1 In study VI. (1914), I propounded a theory of feitilization according to which 

 the initiation of development of the egg is due to activation of an ovogenous 

 substance, which I named fertilizin, contained in the cortex of the egg. In fer- 

 tihzation sucli activation is caused by a certain constituent of the sperm, which I 

 called the sperm receptors; and the action of the fertilizin thus aroused must be on 

 certain substances of the egg which I named in general egg-receptors. From a 

 chemical point of view therefore we must have an interaction of three substances 

 (or groups of substances), viz., sperm receptors, fertilizin, and egg receptors. 



