494 ALVALYN E. WOODWARD 



will lie dormant. As the egg 'ripens/ however, it secretes more 

 and more lipolysin. If this accumulates within the egg to such 

 an extent that the inhibitor is relatively greatly reduced, the 

 metabolic enzymes become extremely active and development or 

 cytolysis results. Perhaps natural parthenogenesis, such as 

 occurs in Daphnia and aphids is the result of such conditions. 

 The membrane of starfish and sea-urchin eggs is easily perme- 

 able to lipolysin, so that it does not normally accumulate within 

 the egg. If, however, the eggs are crowded in a small amount 

 of sea-water or, which amounts to the same thing, are placed in a 

 bath of lipolysin, the loss of this substance from the egg is pre- 

 vented. It therefore reacts w !th the inhibitor, and the egg de- 

 velops — a case of autoparthenogenesis. 



Any other method which disturbs the ratio of activating 

 enzymes to fatty acid so that the proportion or effectiveness of 

 the enzymes is increased must lead to development or cytolysis. 

 As already stated, many chemicals have this effect, and produce 

 parthenogenesis. 



B. Activation hy sperm 



Can the action of the spermatozoon be explained along similar 

 lines? Its effect probably varies with the group of animals. 

 Ostwald ('07) measured the amount of peroxidase and catalase in 

 1) extracts of Amphibian eggs ; 2) extracts of sperm ; 3) a mixture of 

 the two extracts. He found that the mixture contained con- 

 siderably more enzyme than the sum of (1) and (2). Hence we 

 may conclude that in Amphibia the sperm carries into the egg 

 something which changes pro-enzymes into enzymes. It in- 

 creases the activator. On the other hand, Amberg and Winter- 

 nitz ('11) were unable to find any more oxidase or catalase in 

 echinoderm eggs laked after fertilization than in those laked be- 

 fore. Moreover, Warburg ('08) and Loeb and Wasteneys ('13) 

 found the same rate of oxidation in parthenogenetic as in fertilized 

 sea-urchin eggs. S nee, in this group, fertilization does not in- 

 crease the amount of oxidase in the egg, the spermatozoon may 

 act by reducing the amount or effect of the inhibitor. 



