296 E. E. JUST. 



tilization capacity of butyric acid treated eggs show three physio- 

 logically distinct classes : under-exposed inactivated eggs whose 

 fertilizability the acid treatment prolongs; activated eggs, with 

 membranes, rendered incapable of fertilization at the instant of 

 activation ; and over-exposed inactivated eggs whose capacity for 

 fertilization is cut short by the excessive action of the acid which 

 initiates destructive changes. 



IV. GENERAL DISCUSSION. 



1. The activation of the egg whether produced through sperm 

 or butyric acid renders the egg incapable of insemination. Thus, 

 Moore found Arbacia eggs following the successful production 

 of membranes with butyric acid refractory to fertilization. In 

 Echinarachnius (Just, 'i9c) subsequent to membrane formation 

 with butyric acid the egg cannot be fertilized though the mem- 

 brane be removed as soon as formed. Likewise, sperm activation 

 renders the egg immune to the entry of any other sperm. The 

 test, therefore, of complete activation is the response to insemi- 

 nation. 



2. In Echinarachnius one may readily follow the changes lead- 

 ing to membrane production consequent on insemination : In the 

 cortex beginning at the site of sperm entry droplets escaping 

 push the membrane off. These droplets are discrete bodies that 

 squeezed out of the cortex may cross the perivitelline space and 

 reach the membrane before they go into solution. In other 

 words, the underlying process of membrane formation is a secre- 

 tion or liquefaction of the cortex. The result of this liquefaction 

 is the wide perivitelline space and the diminution in the size of 

 the egg. This process easily followed in Echinarachnius lends 

 support to Loeb's suspicion that " the membrane formation is the 

 result of a process of secretion of a liquid from the egg" (Loeb, 

 13, page 216). It also suggests the cortical secretion in the eggs 

 of Nereis and Platynereis. 



While we may say that in Echinarachnius certainly membrane 

 lifting is not the cause but rather the result of activation, at least 

 in sperm activation since the egg becomes immune to the entry 

 of any other sperm before the membrane lifts (Just, 'ipa), yet 

 membrane lifting is an important easily visible sign of complete 

 activation. 



