THE MORPHOLOGY OF FERTILIZATION 7 



the cortical granules remain unchanged after fertilization; Both 

 phenomena occur and are intimately related to each other. The 

 disappearing cortical granules are concerned in the formation of a 

 structure which appears round some eggs after fertilization, the 

 Fertilization Membrane (q.v.). 



Fertilization cone. After attachment of the spermatozoon, a 

 conical hyaline protuberance, the fertilization or entrance cone, 

 appears at the egg surface. Fig. 2. In the eggs of Psammechiniis 

 miliaris (P. L. S. Muller), the fertilization cone disappears in less 



FIG. 2. 



Fertilization cone 



-Entry of the spermatozoon into the egg of Patiria pectinifer (J. 

 Muller & Troschel), after J. C. Dan (1950a). 



than 20 seconds at 18° C, but in other eggs it may persist for much 

 longer. In the case of the egg shown in Fig. 2, for example, the 

 fertilization cone is visible until the tail of the spermatozoon has 

 passed into the egg cytoplasm, after which it is more or less re- 

 sorbed into the egg. 



Sperm-egg filaments. In 1877 Fol reported that the starfish 

 spermatozoon became connected to the surface of the egg by a 

 long, exceedingly thin filament, which he believed was an extension 

 of the fertilization cone. This observation was confirmed by R. 

 Chambers in 1923, contradicted by Just in 1929 and reaffirmed by 

 Horstadius in 1939. Similar claims, that filaments derived from 



B 



