STUDIES OF FERTILIZATION. 15 



i 



sticky (adhesive), as an important factor at least. It is obvious 

 that the reaction will detect only such changes in the individual 

 spermatozoa as will cause them to adhere to one another; and 

 that below this threshold the individual spermatozoa are prob- 

 ably affected to some extent ; this consideration is important for 

 the theoretical deductions. 



I found also that the egg-water of the Annelid Nereis simi- 

 larly agglutinates Nereis spermatozoa. But the agglutinating 

 substances of Arbacia and of Nereis are without effect on the 

 heterologous sperm. The reaction is thus specific between these 

 forms. The egg-water of Arbacia, however, contains a sub- 

 stance toxic to the spermatozoa of Nereis and causing a coagula- 

 tion of Nereis sperm suspensions that is rather deceptive at first 

 sight. It is possible to remove this substance by treatment of the 

 egg-water with Nereis sperm and leave the full complement of 

 specific agglutinating substance, which can then be shown to be 

 without visible action on Nereis sperm. The Nereis egg-water 

 contains nothing that acts on Arbacia, sperm. 



Just (''19) subsequently showed that similar specific relations 

 of agglutination obtained between Arbacia and Echinarachnius: 

 " Echinarachnius egg-water activates but does not agglutinate 

 Arbacia sperm. Arbacia egg-water agglutinates Echinarachnius 

 sperm. This is a ' hetero-agglutination ' by a substance in Ar- 

 bacia egg-water separate from Arbacia fertilizin because it may 

 be removed from the egg-water by dilution, by repeatedly wash- 

 ing the eggs and by precipitating it with Echinarachnius sperm. 

 It is found in Arbacia blood. The microscopic appearance of 

 this toxic heteroagglutination of Echinarachnius sperm is dif- 

 ferent from that of the iso-agglutination." 



It was of considerable interest to discover how specific this 

 agglutinating reaction really is. If the reaction indicates a sub- 

 stance contained in the eggs that is of fundamental significance 

 in fertilization, as I believe, then it should be highly specific, like 

 the fertilization reaction itself ; and so it turns out, as the follow- 

 ing data show. 



The egg-waters of both species have strong agglutinating ac- 

 tion, each on the sperm of its own species, which is quite similar 



