556 FRANK R. LILLIE 



demonstrates some change in the membrane that renders them 

 sticky. The cells are so minute that it is difficult to observe 

 any microscopical change in the case of Arbacia; in Nereis the 

 spermatozoa are larger, and it can be seen that in agglutinated 

 masses the heads of many of the spermatozoa are swollen into 

 spherical form and have lost the normal strong refringibility. 

 The change is in this case a very characteristic one, indicating a 

 great increase in permeabihty. The spermatozoa which have 

 undergone this change are usually motionless, and, when not 

 fused with one another, appear to be glued to the slide or cover 

 slip, never freely suspended. 



Agglutination in itself is in no sense a specific reaction, but one 

 that may be expected to accompany certain superficial changes 

 of the spermatozoa, however caused, under conditions that bring 

 the spermatozoa into contact. It occurs, to a limited extent, 

 spontaneously in sperm suspensions that have stood for some time. 

 It is particularly noticeable in Nereis under the following con- 

 ditions: A fresh sperm suspension is allowed to aggregate on a 

 slide beneath a raised cover slip and the aggregations remain 

 undisturbed. In the course of ten or fifteen minutes small agglu- 

 tinated masses may form around the margins of the aggregations 

 or beneath the aggregations in contact with the shde. There 

 may be twenty to fifty or more such masses associated with a 

 single aggregation, and they are quite similar in their general 

 appearance, to those produced suddenly by the agglutinin of the 

 egg, though much smaller, on the average. 



It is not probable that the agglutination is in any real sense toxic 

 or cytolytic. It is true that the agglutinin inhibits movement 

 after a few minutes, and it certainly lessens the fertilizing power of 

 the sperm. But if an agglutinated mass of spermatozoa of Nereis 

 be crushed under the microscope many of those liberated are 

 active. Moreover, if a small quantity of an agglutinated suspen- 

 sion of spermatozoa be added to a relatively large quantity of 

 sea-water fertilizing power is partially regained. This might be 

 either because some of the spermatozoa of the agglutinated sus- 

 pension had escaped combination with the agglutinin and were 

 alone concerned in the actual fertilization, or because of recovery 



