EGG SECRETIONS OF ARBACIA AND ASTERIAS 487 



cleavage in 21 per cent, the indication is that the sperm does not 

 activate the fertihzin. Of course, this is not conclusive, since 

 the temperature which kills the sperm may also destroy the 

 'activated' fertilizin, and unless this is broken down into the un- 

 activated form, we should expect fertilizin treated with sperm 

 to be markedly weakened. Since this is not the case, we shall 

 have to conclude that an activating effect on the ovophile group, 

 or lipolysin, is undemonstrable. But why should we expect 

 activation? The 'ovophile' and ' spermophile' groups are two 

 independent substances. Such being the case, it is not surprising 

 that a reaction involving one does not 'activate' the other. 



Since Lillie's idea of activation cannot be accepted, we are 

 brought back to superficial cytolysis and its connection with the 

 activation of the egg. It is quite natural that superficial cytol- 

 ysis should have been considered a cause of activation. On 

 this assumption, the search for a modus operandi has been carried 

 on by several investigators. Loeb himself suggests that cytol- 

 ysis removes an obstacle to development. R. S. Lillie ('11) be- 

 lieved the obstacle might be CO2. Loeb proved that this was 

 impossible by using sea- water charged with CO 2 as a partheno- 

 genetic agent. Glaser suggested that the obstacle might be anti- 

 fertilizin. Both R. S. Lillie and Glaser postulated that the 

 removal of these obstacles was due to the increased permeability 

 of the egg resulting from cytolysis. 



But suppose that cytolysis is not the cause of activation, but an 

 effect (of minor significance) of other processes which produce 

 development? From this standpoint we get a different view of 

 the situation. 



The egg has been found to contain a considerable amount of 

 lipoid, about 30 per cent of which is an unsaturated fatty acid. 

 Overton and others ha^'e shown that this lipoid must be more 

 concentrated at the surface than in the interior. According to 

 Jobling, an unsaturated fatty acid inhibits enzyme action. 

 We know that the egg contains a quantity of enzymes — catalase 

 and oxidase, for instance — which control metabolism. Let us 

 assume that the acti\'ity of the enzyme is decreased by the pres- 

 ence of the unsaturated fatty acid. Removal of this fatty acid, 



THE JOLEXAL OF EXPERIMENTAL ZOOLOGY, VOL. 26, XO. 3 



