ACTION OF THE SPERMATOZOON UPON THE EGG Zol 
Godlewski! found recently that the eggs of sea-urchins can 
be fertilized with the sperm of Chaetopterus, an annelid. All the 
eggs form the fertilization membrane, but 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 f. Entwicklungsmechanitk, XXXI‘I, 196, 1911. 
