THE FERTILIZATION REACTION IN ECHINARACH- 



NIUS PARMA. 



III. THE NATURE OF THE ACTIVATION OF THE EGG BY BUTYRIC 



ACID. 



E. E. JUST. 



CONTENTS. 

 I. Introduction 39 



II. Activation of Echinarachnius Eggs by Butyric Acid 40 



A. Optimum Exposure to Butyric acid 40 



B. Condition of the Egg as a factor in the Response to Activation by 



Butyric Acid 42 



1. Effect of Washing ". 43 



2. Effect of Body Fluid 44 



C. Summary of Part II 45 



III. Analysis of Butyric Acid Activation 45 



A. Action of Hypertonic Sea-water on Butyric Treated Eggs 45 



B. Effect of Insemination Following Butyric Acid Activation 46 



C. Summary of Part III 49 



IV. Discussion 49 



.V. Literature cited , 53 



I. INTRODUCTION. 



The egg of Echinarachnius as shown elsewhere (Just, '19^) 

 following engulfment of one sperm immediately becomes immune 

 to farther sperm entry. This change takes place in the cortex 

 before the membrane lifts off and probably represents the neutra- 

 lization of the fertilizin by the anti-fertilizin present in the egg. 

 This is the mechanism for the prevention of polyspermy, and 

 not the immediately succeeding membrane lifting. Loeb, 

 however, found that butyric acid, though it be capable of calling 

 out "fertilization membranes" in one hundred per cent, of the 

 eggs of the sea-urchin, is none the less incomplete in its action, 

 for if by shaking he removes these "fertilization membranes" 

 sperm penetrate the eggs, membranes form anew, and develop- 

 ment proceeds like the normal. This finding certainly does not 

 support his view that fertilization is a kind of artificial partheno- 

 genesis for after fertilization eggs or fragments thereof do not 



39 



