STUDIES OF FERTILIZATION 563 



July 28, 1912. a. A suspension of active Arbacia sperm was made at 



11.23 A.M. 



b. A suspension of active Nereis sperm was made at 11.24 1/2. 



The two suspensions were made of equal density as far as possible. 



Part of each suspension was then mounted on a slide beneath a raised 

 cover-slip. 



A drop of the Nereis sperm was then injected into the Arbacia slide 

 (slide 1) and a drop of Arbacia sperm into the Nereis slide (slide 2). 



Slide 1 gave a very faint reaction ; only slight evidence of a ring for- 

 mation at the margin of the Nereis drop. 



Slide 2, on the other hand, gave a very pronounced reaction due to 

 inwandering of the Nereis sperm into the Arbacia drop, followed by 

 agglutination of the inwandering sperm. 



The difference in reaction is due to two circumstances: (1) The 

 Nereis sperm exhibit a more pronounced chemotaxis than the 

 Arbacia sperm, hence they tend to enter the drop of Arbacia 

 sperm, whereas on the other slide the Nereis sperm tend to diffuse 

 from the drop into the Arbacia suspension. (2) The Nereis 

 sperm that wander into the drop of Arbacia sperm are agglutin- 

 ated, but there is no reciprocal reaction of the Nereis sperm on any 

 inwandering Arbacia spermatozoa. 



It is demonstrated, therefore, first that Arbacia fluids in general 

 are toxic for Nereis spermatozoa to the extent, at least, that they 

 cause agglutination; but on the other hand, that no secretion of 

 Nereis appears to cause agglutination of Arbacia spermatozoa; 

 and second that the eggs of each species produce an agglutinin for 

 the sperm of its own species. 



Agglutination is not in itself a specific process; it may take place 

 spontaneously to a certain extent under some conditions; it is 

 caused by increase of alkalinity of the sea-water in the case of 

 Nereis and Arbacia, or by the action of certain foreign sera as in 

 the case of the action of Arbacia fluids on Mereis sperm. On the 

 other hand, the class of specific immune agglutinins, character- 

 ized by limitation of their action to the specific form of blood or 

 sperm used as antigen is well known. The question naturally 

 arises, therefore, to which class the iso-agglutinating substances 

 produced by ova of Arbacia and Nereis belong.^ 



* In the latter case, fertilization itself would have to be regarded as an immuniz- 

 ing process, the sperm acting as antigen after entrance into the egg. It seems, in 



THE JOURNAL OF EXPERIMENTAL ZOOLOGT, VOL. 14, NO. 4 



