304 E. E. JUST. 



In the egg, as a result of the activation of fertilizin, cortical 

 changes take place. These changes may be initiated through the 

 mere attachment of the sperm to the egg membrane, as in Nereis 

 and Platynereis where jelly secretion from the cortex takes place 

 before the penetration of the sperm. In Echinarachnius cortical 

 changes leading to the lifting of the membrane are induced by 

 the sperm or by proper exposure to butyric acid. 



Fertilizin likewise acts on the sperm ; as Lillie puts it, the 

 sperm itself needs to be fertilized. As a result of the union of 

 the sperm with fertilizin, the sperm head is made to swell. If 

 fertilizin be absent, as in immature eggs, in butyric acid mem- 

 brane eggs (Moore) or in stale eggs, the sperm head does not 

 swell. Spermatozoa may penetrate these three classes of eggs 

 but they undergo no change nor do the eggs develop. We have 

 thus two criteria of the sperm-f ertilizin-egg reaction : the cor- 

 tical changes in the egg and later the swelling of the sperm head. 

 But even before this the reaction is complete. It is not a reversible 

 destructive reaction in need of a "corrective factor" but a con- 

 structive, irreversible, practically instantaneous reaction setting 

 in motion the whole train of events, with accompanying changes 

 in oxidation, permeability, etc., leading to the cleavage of the egg. 



V. LITERATURE CITED. 

 Goldfarb, A. J. 



'18 Effect of Aging upon the Germ Cells and upon Early Development. 



Part III. BIOL. BULL., XXXV. 

 Heilbrunn, L. V. 



'15 Studies in Artificial Parthenogenesis. II. Physical Changes in the 



Egg of Arbacia. BIOL. BULL., XXIX. 

 Herlant, M. 



'17 Le mechanisme de la parthenogenese experimentale chez les amphibiens 

 et les echinodermes. Bull. Sci. de la France et de la Belgique, Ser. 7, 

 T. 50. 

 Just, E. E. 



'iga The Fertilization Reaction in Echinarachnius parma. I. Cortical Re- 

 sponse of the Egg to Insemination. BIOL. BULL., XXXVI. 

 'igb II. The Role of Fertilization in Straight and Cross Fertilization. Ibid. 

 'igc III. The Nature of the Activation of the Egg by Butyric Acid. Ibid. 

 Lillie, F. R. 



'ig Problems of Fertilization. University of Chicago Press. 



