EGG-SECRETIONS OF ARBACIA AND ASTERIAS. 383 



must be permeable to it before impregnation, and consequently 

 there can be no accumulation that could be relieved as the result 

 of the increase in permeability associated with fertilization. 



However two possibilities remain; either the quantitative 

 difference in the rate of secretion between unfertilized ova and 

 ova undergoing fertilization is significant, or there is a qualitative 

 difference as yet undetected between the secretions from the 

 two kinds of eggs. Since "the velocity of segmentation in eggs 

 fertilized by two spermatozoa is identical with that found in 

 eggs fertilized by one. . . . ," we must believe, according to 

 Loeb ('i3 6 , p. 13) "that the spermatozoan causes development 

 ... by removing an obstacle to development." 



Certain facts and considerations to be dealt with in a later 

 paper, seem to point to the possibility that in addition to the 

 quantitative difference, the secretion at the moment of fertiliza- 

 tion differs from the secretion of uninseminated eggs, qualitatively 

 as well. Should further experimentation establish the correct- 

 ness of this suspicion, then since the rate of oxidation in fertilized 

 eggs is greater than in unfertilized, we could still say, "substances 

 antagonistic to oxidation are eliminated at fertilization" although 

 these substances may be neither CO 2 nor any of the constituents 

 of the secretion from unfertilized eggs. Furthermore their action 

 may be indirect through the inhibition of processes which when 

 set going by their removal allow oxidation to proceed at the 

 heightened rate normal for the fertilized egg. Whatever the 

 final solution of these problems may be, it seems altogether likely 

 that the initiation of development, and with it, the initiation of 

 the processes leading to cell division, are in some way significantly 

 related to the momentary increase in the permeability of the 

 ovum, accompanying the process of fertilization. 



VI. SUMMARY. 



1. In corroboration of F. R. Lillie, it was found that the egg- 

 secretions of Arbacia punctulata exert a chemotactic effect on 

 sperm, and activate, agglutinate, and paralyze them. 



2. The egg secretions of Asterias forbesii behave in a similar 

 manner toward Asterias sperm. 



3. Arbacia secretion activates, agglutinates, and paralyzes 



