SPKRM FILTRATES AND DIALYZATES. 



317 



Practically no heated sperm reach the surface of the filter 

 mantle as they do not pass through the Whatman filter paper. 

 This might appear to indicate that any active substance is 

 adherent to the heated. coagulated sperm and not readily given 

 off into sea-water. 



10 |L If It. is 



GRAPH VIII. Relation of the strength of the dialyzate to the percentage of 

 ova divided and cytolyzed -Arbacia punctulata. A = average of three experi- 

 ments with dialyzates from 50 per cent, sperm suspensions. B = average of three 

 experiments with dialyzates from 25 per cent, sperm suspensions. C = average of 

 six experiments with sea-water controls. Duration of dialj-sis = ten hours. 



Another filtrate was made by filtering a heated sperm sus- 

 pension directly through a Mandler filter. As a control part 

 of the same suspension, unheated, was passed through a second 

 filter. The effects of these two preparations are compared in 

 Table III. 



The filtrates of the heated sperm suspension have as great an 

 effect on unfertilized ova of the same species as filtrates of fresh 

 suspensions if the suspensions are filtered directly. 



The Effect of Boiled Filtrates of Arbacia Sperm. If the sub- 

 stance which so affects the eggs is an enzyme, heated filtrates 

 may be ineffective. A filtrate prepared from a five per cent, 

 sperm suspension was heated to boiling and then cooled rapidly. 



