STUDIES OF FERTILIZATION 565 



The experiment in detail was as follows: 



September 15, 1912. One small male Nereis available. Its sperm 

 is aggregative and very active. The Arbacia egg-extract was of August 

 29 and was made by cutting up ovaries and eggs of Arbacia in four times 

 their volume of sea-water. After settling of the eggs the supernatant 

 fluid was poured off, and had been kept in a stoppered vial since. 



1. A drop of the Nereis sperm and a drop of the egg-extract were 

 placed side by side on a slide and connected; the sperm diffused into the 

 egg-extract and swam around in it; no agglutination. 



2. A raised cover mount was made of the Nereis sperm and a drop of 

 the egg-extract injected. The sperm entering the drop swam around, 

 and were not agglutinated. 



Controls: 1. The sperm of Nereis was agglutinated immediately by 

 extract of Nereis eggs kept since September 8. 



2. The egg-extract of Arbacia agglutinated Arbacia spermatozoa with 

 no apparent diminution in the strength of the reaction. 



Conclusion: The nonspecific agglutinating substance has been de- 

 stroyed by the chemical changes in the extract in the course of seventeen 

 days; but the iso-agglutinating sperm substance still remains. 



This experiment does not demonstrate that the sperm iso-agglu- 

 tinin of Arbacia egg-extract is specific, but merely that it is with- 

 out effect on the Nereis sperm, just as the iso-agglutinin of Nereis 

 eggs is without effect on Arbacia sperm. It is of course still 

 possible that the iso-agglutinating substances might have an 

 agglutinating effect on some other varieties of sperm, and a crucial 

 test of specificity must await the securing of new material. 



However, it seems to me that the probabilities in the case lie 

 strongly on the side of specificity of these sperm iso-agglutinating 

 substances. Quite apart from the value of the evidence already 

 adduced, we must consider the general fact that ova and sperma- 

 tozoa of the same species do behave in a specific way with refer- 

 ence to one another in the process of fertilization. This must have 

 some chemical basis and on the chemical side the only reactions 

 that exhibit a corresponding degree of specificity are those between 

 antigens and anti-bodies in the field of immunity. We have two 

 parallel instances, therefore, and the slight evidence which I have 

 so far be'en able to bring forward in favor of the specificity of the 

 sperm iso-agglutinins of ova gains immensely in weight by its 

 association with the universal principle of specificity in fertili- 

 zation, and the known class of specificities in agglutination re- 

 actions. 



