284 Studies in tjic Phiisioloyn of Fertilization 



possibility was this. The comparatively small \iil\iiiic of water in which 

 the Arhacia eggs had stooil for a relatively long time may have become 

 acid enough to inhibit the fertilizing power of the spermatozoa (see 

 p. 294). The acidity of this egg-water was not tested when it was used 

 for the experiment, but 1| hours afterwards it gave a pink colour with 

 a-Naphtholphthalein, whereas normal sea-water gives gi-een. 



Owing to these two possibilities of error, the experiment w;is 

 repeated. After remt)val from the ovary, the Arbacia eggs were washed 

 by allowing them to settle twice in finger-bowls of water. They were 

 then placed in 3 — 4 times their volume of water for 55 minutes only. 

 When this egg-water was di-awn ott' the eggs, it was still green to 

 a-Naphtholphthalein. 



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

 to (1)3 cc. plain sea- water, and (2) 3 cc. Arbacia egg- water, which was 

 quite free from Arbacia eggs. 10 cc. of water was added to each, after 

 which they were poured on to sejjarate equal quantities of eggs. The 

 experiment was double as last time. 



TABLE XXIV. (39.6.5.) 



i 3 drops sperm ... 

 Cross, F/y ^ ,„ , „ 



(12 drops speiin ... 



The Table shows that, under the conditions of this experiment, the 

 Arbacia egg- water increased the fertilizing power of Ciona sperm in the 

 same way as the A rbacia egg-extract had don<' in the experiments of 

 Table XXII. 



4. Strong ylocentrotus egg-extract. 



The two experiments recorded in this .section were made to test the 

 action of Strongylocentrotus egg-extract on Ciona sperm, used to cross- 

 fertilize eggs of the same species. Definite amounts of Ciona sperm - 

 suspension (.see Table XXV) were added to (1) 10 cc. plain sea-water, 



Exp. 1. Bjc 



Exp. 2. (7(/ 



