ACTION OF THE SPERMATOZOON UPON THE EGG 231 



Godlewski 1 found recently that the eggs of sea-urchins can 

 he fertilized with the sperm of Chaetopterus, an annelid. All the 

 eggs form the fertilization membrane, bat they sooner or later 

 begin to disintegrate without segmenting. When he submitted 

 such eggs to hypertonic sea-water for 22 minutes, they developed 

 into larvae. The eggs behave as if the foreign sperm had only 

 acted through the membrane-forming agency. 



The interesting fact about these experiments was that the 

 spermatozoa entered the eggs and even fused with the egg- 

 nucleus. The eggs therefore received the second factor con- 

 tained in the spermatozoon, and yet they did not develop. 

 This seems to indicate that this second factor carried by the 

 spermatozoon is much more specific than the first membrane- 

 forming factor. This specificity is perhaps also the reason 

 that the sea-urchin eggs fertilized with starfish or any other 

 foreign sperm die in such large numbers in the gastrula stage. 



1 Godlewski, Archiv /. Entwicklungsmechanik, XXXIII, 196, 1911* 



