THE PROBLEM OF ACTIVATION 237 



bind the egg receptors (as shown by failure of activa- 

 tion) in the absence of the fertilizin. 



Let us return to the fact that fertilized eggs produce 

 no more fertilizin. This is certainly a very remarkable 

 circumstance, because prior to fertilization in the case 

 of the sea urchin they produce it in such abundance 

 as to charge many hundreds of times their own bulk 

 of sea-water with easily detectable quantities. Imme- 

 diately after fertilization this ceases, and the eggs no 

 longer react to spermatozoa. Are we to conceive that 

 the eggs excrete it all in connection with the cortical 

 changes that take place at the same time ? Or is it in 

 some way combined so as to be no longer active ? In 

 favor of the latter point of view is the fact that the 

 internal substance of the eggs is capable of neutralizing 

 the sperm-agglutinating action of fertilizin (Lillie, 1914). 

 This can be shown by cytolyzing eggs deprived of their 

 jelly in distilled water and thus extracting the interior 

 substances; the aqueous extract has at first a powerful 

 agglutinating effect, which, however, disappears entirely 

 in the course of a few hours, whereas the fertilizin se- 

 creted by living eggs may last for months. Again, if 

 eggs are repeatedly washed for about forty-eight hours 

 until their production of fertilizin is very much reduced, 

 and are then shaken to pieces in the sea-water contain- 

 ing the fertilizin which they themselves have secreted, 

 the fertilizin present before the shaking is neutralized. 

 I explained this by supposing that eggs contain in their 

 interior a substance capable of combining with the 

 agglutinating group of the fertilizin, but which is sepa- 

 rate from it as long as the egg is inactive; this sub- 

 stance I called anti-fertilizin. I therefore proposed the 



