394 OTTO GLASER. 



those experiments on normal fertilization in Arbacia which have 

 led him to propose the fertilizin theory, briefly outlined in his 

 paper "The Mechanism of Fertilization" ('i3 3 ). 



The facts on which this theory is based are dealt with in F. R. 

 Lillie's earlier papers, as well as in the one specifically referred 

 to. In my paper on "A Qualitative Analysis of the Egg-Secre- 

 tions and Extracts of Arbacia and Asterias" ('i4 2 ) will be found 

 certain verifications of Lillie's observations. It would take us 

 too far to go into the factual basis of the theory here, but briefly 

 it postulates as the essential point in fertilization a chain of 

 chemical reactions in which an amboceptor-like substance the 

 sperm-agglutinating agent present in the secretions from the 

 egg, unites by means of a spermophile side-chain with receptors 

 in the sperm, and by an ovophile side-chain with receptors in 

 the egg. 



If this chain of reactions indeed occurs and is related to fer- 

 tilization and the initiation of development in the significant 

 manner put forward by Lillie, it follows that there are theoretic- 

 ally at least five possibilities of blocking fertilization. Lillie 

 has listed these as follows: 



1 . Through loss of fertilizin by the egg. 



2. Through occupancy of the sperm receptors. 



3. Through occupancy of the egg receptors. 



4. Through occupancy of the ovophile side chain of the ambo- 

 ceptor (fertilizin). 



5. Through occupancy of the spermophile side-chain of the 

 amboceptor (fertilizin). 



Of these Lillie has proved possibility I, by washing the eggs; 

 4, by means of an inhibitor in the blood which prevented fer- 

 tilization, but not the sperm-agglutinin reaction; and 5, by 

 setting free from the egg itself an inhibitor, the anti-fertilizin 

 which obstructs the union of the sperm with the amboceptor by 

 occupying the spermophile side-chain. Since therefore the 

 presence of the agglutinating agent, and moreover its presence in 

 a state in which both spermophile and ovophile side-chains are 

 free to combine with their respective normal receptors in the 

 sperm and the egg, seems to be necessary for normal fertilization, 

 Lillie has called the substance in question, fertilizin. 



