STUDIES OF FERTILIZATION 569 



4. The agglutinating substances are highly thermostable, but 

 are slowly destroyed by temperatures above 95°C. 



5. In the presence of excess of the agglutinating substance 

 spermatozoa of Arbacia lose their fertilizing power. 



6. Eggs of Arbacia give off the agglutinating substance in 

 the sea-water in large quantities prior to insemination; but eggs 

 of Nereis give off only small quantities until inseminated, or until 

 the cortical change analogous to membrane formation in the sea- 

 urchin egg is somehow produced. 



7. The egg-extract of Nereis does not agglutinate Arbacia 

 spermatozoa. 



8. The substance in the egg-extract of Arbacia that aggluti- 

 nates Nereis spermatozoa is distinct from the iso-agglutinating 

 substance. 



9. The coelomic fluid of Arbacia contains a substance which 

 agglutinates the spermatozoa of Nereis but not of Arbacia. Pre- 

 sumably this substance is the same as the hetero-agglutinating 

 substance of Arbacia egg-extract. 



10. Two arguments in favor of the specificity of the iso-agglu- 

 tinative reaction were brought forward, namely, (a) The fact 

 that the iso-agglutinin of Arbacia is distinct from the hetero- 

 agglutinin in the case of Arbacia and Nereis : (b) that fertilization 

 is fundamentally a specific reaction, and that the phenomena of 

 agglutination belong in a class of phenomena in which specificity 

 exists, and between elements which react specifically in fertiliza- 

 tion. ' While admittedly not demonstrative these arguments 

 appear to me to be cogent. 



V. DISCUSSION 



Since PfefTer's fundamental investigations concerning chemo- 

 taxis of spermatozoa of ferns and mosses with reference to the 

 secretion of the archegonia a similar explanation of the behavior 

 of animal spermatozoa with reference to the eggs of the same spe- 

 cies has been anticipated, and indeed has been postulated by 

 many writers without any other experimental basis. However 

 such actual experiments as have been performed have not been 

 favorable to such an interpretation. Thus Buller ('00) experi- 



