Vol. XLIV. January, 1923. No. 1. 



BIOLOGICAL BULLETIN 



THE FERTILIZATION-REACTION IN ECHINA- 

 RACHNIUS PARMA. VI. 



The Necessity of the Egg Cortex for Fertilization. 



E. E. JUST,i 



ROSENWALD FELT.OW IN BlOLOGY, NATIONAL RESEARCH COUNCIL. 



If we define fertilization as an instantaneous irreversible reac- 

 tion at or in the cortex of the egg between an ovogenous substance, 

 fertilizin, and the spermatozoon, it must follow (1) that an egg, 

 once fertilized, is incapable of response to additional insemination, 

 and (2) that fragments of fertilized eggs are likewise incapable of 

 fertilization. If, moreover, the fertilization-reaction be limited to 

 the cortex, then it must likewise be shown (3) that uninseminated 

 eggs, or fragments thereof, devoid of cortex are not fertilizable. 

 The present paper aims to set forth certain observations made at 

 the Marine Biological Laboratory, Woods Hole, Mass., on the egg 

 of Echinarachnius parma which indicate that fertilized eggs, or 

 fragments thereof, are unf ertilizable ; and that uninseminated eggs, 

 or fragments thereof, devoid of cortex are likewise unfertilizable. 

 It is therefore concluded that the cortex of the uninseminated egg 

 is necessary for fertilization. 



II. 



The fertilized egg does not react to additional insemination; 

 sperm do not enter fertilized eggs. In order to test the validity 

 of this generally accepted statement, fertilized eggs after removal 

 of their membranes have been inseminated two, three, and four 

 minutes after insemination and at later stages during development 

 to gastrulation. Such eggs have been sectioned. 



In no case have sperm been found in the egg or blastomeres 

 after even the heaviest insemination. Rupture of the blastomeres 



1 Zoological Laboratory, Howard University. 



