FERTILIZATION-REACTION IN ECHINARACHNIUS PARMA. 29! 



cytolysis. But it is fallacious to argue that because the over- 

 exposed egg is a cytolyzing egg the properly exposed egg, because 

 of its membrane, is likewise a cytolyzing egg. That it cytolyzes 

 is true, but it is also true that the normal uninseminated egg in 

 normal sea-water cytolyzes. Instead, we might more logically 

 contend that since under-exposed eggs are resistant to cytolysis 

 that membrane formation protects against cytolysis for the un- 

 der-exposed egg is no farther below the proper exposure for 

 membrane production than the over-exposed egg is above it. 



III. OBSERVATIONS ON THE DURATION OF FERTILIZATION 



CAPACITY IN BUTYRIC ACID TREATED EGGS. 

 In Echinarachnius , membrane elevation is a sign of complete 

 activation whether the elevation is due to the agency of sperm or 

 of proper butyric acid treatment for in either case the egg does 

 not fertilize even after removal of the membrane. Activation is 

 an irreversible reaction. But, neither the under-exposed egg that 

 forms no membrane nor the over-exposed egg that likewise 

 forms no membrane but exhibits a jelly-like cortex is activated 

 since they are both capable of insemination; the former produc- 

 ing normal membrane, cleavage, and larva; the latter no mem- 

 brane, abnormal cleavage, and larva. Thus, the response to in- 

 semination constitutes a physiological criterion of activation no 

 less important than the striking morphological cortical changes. 

 Since, now, we know that in Echinarachnius the effect of mem- 

 brane production by butyric acid is the instant loss of fertiliza- 

 tion capacity (Just, 'IQC) it would seem to be important in the 

 analysis of the nature of butyric acid activation to know the 

 duration of the fertilization capacity of under-exposed and over- 

 exposed eggs. This section presents observations on this point 

 which prove that, as in the case of the rate of cytolysis, there exist 

 sharply defined differences among the three classes of eggs: 

 under-, over-exposed, and activated. 



A. The Method. 



The method used in these observations is very simple. Follow- 

 ing their exposure to butyric acid for varying lengths of time 

 eggs are transferred to dishes of 250 c.c. of sea-water from 



