272 LIBBIE H. HYMAN. 



treatment with membrane-elevating solutions without cytolysis, 

 the membrane elevates without an accompanying cytoplasmic 

 gelation, it is evident that the egg is left without a resistant sur- 

 face. Consequently the surface of the egg after lifting of the 

 vitelline membrane is weak. The membrane-elevating substances 

 tend to induce the expansion of the egg in the same way as they 

 induce the expansion of the membrane (cf. further Heilbrunn, 

 '15) and as the egg is not protected by a resistant surface it 

 naturally ruptures by expansion. Such rupture causes coagula- 

 tion since it has been shown by the microdissectionists (Cham- 

 bers, '170, Seifriz, '20) that injury leads to coagulation. The 

 agents in question do not cause coagulation directly but act by 

 elevating the protective vitelline membrane from the egg, leaving 

 the cytoplasm without a sufficiently resistant surface. 



From these considerations it is highly questionable whether 

 the cytolytic action of parthenogenetic agents has any relation 

 whatever to their parthenogenetic power or whether any conclu- 

 sions can be drawn concerning the mechanism of normal activa- 

 tion from the cytolytic properties of such agents. A similar 

 conclusion as to the lack of relation between cytolysis and activa- 

 tion has been reached by Just ('20) from other lines of evidence. 

 It seems sufficiently evident that cytolysis is simply a death 

 change and has no bearing on activation. 



It occurred to me to determine whether artificial agents can 

 elevate membranes on eggs in which the sperm are not able to 

 do so. It is well known that after standing in sea-water for 

 twenty-fo.ur hours or more urchin eggs no longer elevate mem- 

 branes on fertilization although they are still capable of develop- 

 ment. The vitelline membrane probably loses its elasticity and 

 capacity for distension after a prolonged stay in sea-water. I 

 found a considerable degree of parallellism between the action 

 of sperm and of artificial agents on such eggs. It is much more 

 difficult and in some cases impossible to induce membrane eleva- 

 tion by agents in eggs which do not elevate membranes on in- 

 semination. In most cases, however, the artificial agents are 

 more or less effective in partially or completely elevating the 

 membrane. The action of these agents is thus more powerful 

 than that of the sperm and may possibly be of a different nature. 



