124 JACQUES LOEB 



Lillie's theory of the phenomenon of agglutination is an appli- 

 cation of Ehrlich's side-chain theory, a fact which gives it addi- 

 tional interest. 



In previous papers I have described the secretion of a substance by 

 the ova of the sea urchin, Arhacia, in sea water, which causes aggluti- 

 nation of the sperm of the same species. The eggs of Nereis also secrete 

 a substance having a similar effect upon its sperm. I therefore named 

 these substances sperm-isoagglutinins. During the present summer I 

 have ascertained that in the case of Arhacia, and presumably also of 

 Nereis, the agglutinating substance is a necessary link in the fertilization 

 process and that it acts in the manner of an amboceptor, having one 

 side-chain for certain receptors in the sperm and another for certain 

 receptors in the egg. As this substance represents, presumably, a new 

 class of substances, analogous in some respects to cytolysins, and as the 

 term agglutinin defines only its action on sperm suspensions, I have 

 decided to name it fertilizin.^ 



The writer had for many years observed that when the eggs of 

 the Californian sea urchin Strongylocentrotus purpuratus, were 

 fertilized with sperm of their own species the spermatozoa would 

 not always scatter but would form small clusters which were 

 often visible with the naked eye. These clusters would disappear 

 in a few minutes. The whole phenomenon resembles strikingly 

 the phenomenon described by Lillie under the name of sperm 

 agglutination, and is possibly identical with it. 



The writer was interested to find out what the conditions of this 

 cluster formation of the sperm and its relation to the process of 

 fertilization were. Since he is not certain whether this cluster 

 formation observed by him on the Californian sea urchin is 

 identical with the observations of Lillie on the agglutination of 

 sperm in Arbacia, he will confine himself to a discussion of his own 

 experiments and observations, leaving it for future work to decide 

 to what extent they harmonize with Lillie 's observations and con- 

 clusions. 



2 Science, N.S., vol. 38, no. 980, p. 524, October 10, 1913. 



