STUDIES OF FERTILIZATION. 133 



The data then give rise to the hypothesis that there is an 

 activable substance present in the cortex of the unfertilized egg 

 for which copper possesses special affinity. Copper thus prevents 

 the inception of activation when present before insemination; 

 during membrane formation it causes a quantitative reduction 

 of activation. Thereafter, this substance haying been consumed, 

 the specific copper effects are absent. 



Copper affects primarily the activation of this substance, and 

 presumably not its operation, or at least to a very much less 

 extent. The quantitative effects of the first two minutes can 

 be understood in terms of the respective amounts activated and 

 unactivated at the time of exposure to copper. 



Using our earlier term fertilizin for the activable substance of 

 the egg we may now attempt to form a picture of what actually 

 happens in the copper chloride sea-water. 



When a given lot of eggs is inseminated normally there is an 

 interval of time taken up by the meeting of the spermatozoa 

 and the eggs. The length of this interval will naturally vary 

 statistically for any given insemination, and will tend to be 

 inversely proportional on the average to sperm and egg concen- 

 tration. Fertilization proper begins after the actual aggluti- 

 nation of the spermatozoon to the surface of the egg, following a 

 latent period of variable duration. The activation of the 

 fertilizin is then begun and the egg becomes sterile to other 

 spermatozoa. As Just ('19) expresses it, a "wave of negativity' 

 sweeps over the surface of the egg from the point of attack of 

 the successful spermatozoon. Now the rate of this wave is 

 sufficiently rapid to prevent polyspermy even at high sperm 

 concentration where the eggs are in their best condition; the 

 wave must therefore be completed very rapidly. As a result of 

 activation the egg engulfs the spermatozoon within one minute 

 or less, and the fertilization membrane elevates beginning at 

 the point of entrance of the spermatozoon (cf. Just). Thus the 

 events are (i) agglutination of the spermatozoon to the egg, (2) 

 latent period, (3) activation and sterilization, (4) penetration 

 of the spermatozoon, (5) membrane formation. 



It does not necessarily follow that all of the fertilizin is acti- 



