THE TROBLEM OF ACTIVATION 243 



The fact that agents and conditions capable of 

 producing cytolysis may cause membrane formation in 

 the sea urchin egg merely shows that cytolysis may be 

 a subsidiary factor in the activation effect. But that 

 cytolysis is a more fundamental factor is proved, accord- 

 ing to Loeb, by the fact that the eggs exposed so as to 

 produce membranes die by cytolysis later, unless saved 

 by a second process. However, any activated egg not 

 developing normally cytolyzes sooner or later from 

 internal causes. Is the death of the eggs not given a 

 second treatment due to cytolytic action of the agent 

 or to some internal cause resulting from activation ? 



The latter alternative seems to be demonstrated by 

 the cytological examination of eggs treated according 

 to Loeb's method, which has been made especially by 

 Herlant (1917; see also Hindle, 1910). The eggs 

 treated by butyric acid alone live for from twelve 

 to twenty-four hours before cytolysis begins. What 

 happens during all this time ? After the formation of 

 the membrane and the appearance of the hyaline zone 

 at the cortex the cortical changes cease, and the nucleus 

 becomes the center of activity, increasing in size and 

 moving toward the center of the egg. The nuclear 

 membrane then disappears and a monaster develops 

 around the group of chromosomes formed from the 

 egg nucleus. But no amphiaster forms, and though 

 the chromosomes divide they do not separate in two 

 groups. This occurs in about if hours at 15° C, accord- 

 ing to Herlant. At the same time the cytoplasm 

 becomes active, but no division takes place. The 

 chromosomes return to the condition of a resting nu- 

 cleus; a second monaster then appears. This process 



