282 Studies in the Phjisiolorjii of Fertilization 



Given amounts of sperm-suspension (see Table XX) were added to 

 (1)5 cc. water, and (2)5 cc. egg-extract. To each was then added 5 cc 

 of water and they were poured on to separate lots of eggs. The experi- 

 ment was made with two different amounts of sperm. Table XX gives 



the result. 



TABLE XX. (42.4.7.) 



Cross: .///; 



VII. Influence of Egg-waters and Egg-extracts of Other 

 Animals ox the Fertilizing Power of Cioxa Sperm. 



The reason why eggs can, in general, only be fertilized by sperm of 

 the same species has always been a puzzle to physiologists. The 

 experiments on egg-secretions suggest that the action on the .spermato- 

 zoon of a substance given off by the egg is a necessary- preliminary to 

 fertilization. Now, if the secretions of the eggs only affected the sperm 

 of the same species, but had no action on the spei'm of other species, 

 this might be an explanation of the specificity of the fertilization process. 

 To te.st thi.s hypothe.si.s, the actions of the egg-extracts and egg-waters of 

 Phallusia, Arbacia and Strongylocentrotus on Giona sperm used to 

 cross-fertilize Giona eggs were tried. 



1. Phallusia egg-extract. 



This experiment was made before it had been settled that the 

 action of extracts was on the sperm and not on the eggs. In consequence 

 the eggs of Giona (A) were allowed to stand in five dishes, the first of 

 which contained 16 cc. of sea-water, and each of the others IG cc. of 

 different concentrations of Phallusia egg-extract, f<ir 'M^ minutes. After 

 this interval a drop of Giona sperm-suspension {b) was added to each of 

 the dishes. The result was as follows : 



TABLE XXI. (21.6.2.) 



Co. sea-water 



Cc. Phallusia egg-extract 



Cross: Cionii A/t> 



2. Arbacia egg-extract. 



In the next series of three experiments, the Giona sperm was treated 

 with Arbacia egg-extract before being used to cross-fertilize Giona eggs. 



