482 ALVALYN E. WOODWARD 



repeatedly with sea- water and inseminated. In one case the 

 control showed 79 per cent cleavages and the experimental eggs 

 12 per cent. In another case the cleavages were 40 per cent and 

 0, respectively. In both dishes the sperm appeared active and 

 normal. 



There seems to be no definite proof concerning the mode of 

 action of this inhibitor. Since mammalian blood contains specific 

 substances which prevent autolysis, we might expect echinoderm 

 serum to contain similar substances. These should, theoretically, 

 prevent the action of the egg enzymes and might or might not 

 resemble the fatty inhibitor already in the egg. If they are fatty, 

 they would probably combine with lipolysin as Lillie suggested, 

 otherwise they might not. 



TABLE 10 

 Inhibition of cleavage in Asterias by Asterias and Arbacia sera 



The fact that Arbacia serum inhibits sperm fertilization in 

 eggs of the same species suggested trying it with Asterias eggs, 

 and also suggested that Asterias serum might likewise contain an 

 inhibitor. The experiments shown in table 10 prove the sugges- 

 tion correct. 



o. Combination with egg receptors. 'Purple x', discovered by 

 GLiser ('14 c), is a purple compound which appears when 

 Arbacia sperm or egg secretion are boiled. He found that the 

 material prevents both normal fertilization and autoparthenogen- 

 esis. Since it does not prevent the agglutination reaction of 

 fertilizin, Glaser inferred that it did not act by combining with 

 sperm receptors or with agglutinin. It might, however, combine 

 with either the lipolysin or the egg. No decisive experiments 

 have been performed as yet. Sinc^ the jelly surrounding the egg 

 becomes swollen and sticky, sperm fertilization may be prevented 



