MASS PHYSIOLOGY OF SPERMATOZOA 



?73 



accompanying legend. The significance of the reaction to emana- 

 tions from a homotypic egg in relation to fertilization is obvious, but 

 does not constitute a part of our present problem. 



Lillie (192 1) studied the effect of copper chloride upon fertiliza- 

 tion in connection with his analysis of the fertilization reactions. 

 Briefly, he found that fertilization was markedly inhibited at as low 

 a concentration as i part of copper chloride in 2,500,000 parts of 

 sea-water, using a normal sperm suspension. Most of his experi- 



FiG. 29. — Reaction of a sperm suspension of Nereis to a drop of i per cent CO2 

 sea-water (natural size). The preparation (a) is mounted on a slide beneath a raised 

 cover slip, a, Showing the form of the reaction after 15 seconds; b, after 75 seconds; 

 c, after 105 seconds; and d, after 195 seconds. In d the general suspension has aggre- 

 gated. The drop to the right in a is a control drop of sea-water. Note that in a the 

 spermatozoa also withdraw from the margin of the preparation, thus mcreasing the 

 CO2 tension. (Figure and legend from Lillie, 1919.) 



ments were done at a copper concentration of 1/500,000 copper 

 chloride in sea-water, a concentration at which no eggs fertilize at 

 normal sperm concentrations. If much higher concentrations of 

 sperm are used, small percentages of fertilization are obtained, the 

 number varying somewhat in different similar experiments. Lillie 

 comments: "There is thus a certain virtue in mass action of the 

 sperm in the presence of this inhibitor of fertilization; this is some- 

 what difficult to understand, because only one spermatozoon pene- 

 trates normally." He suggests the possibility that an excess of 

 sperm protects the eggs to a certain extent by combining with the 

 copper and thus reducing the amount acting directly on the eggs, a 

 suggestion he and Just repeat (1924). 



