270 Studies in the Physiology of Fertilization 



The most important experiments in regard to this question, however, 

 are those to find the influence of egg-extracts, both from " own " and 

 '' foreign " eggs on self-fertilization itself Some such experiments have 

 been made already, but these must be extended and confirmed before 

 being published. 



IV. Does the Extract affect the Egos or the Sperm ? 



The experiments already described have shown that if a given 

 number of eggs be mixed with a certain concentration of sperm- 

 suspension in sea-water, fewer eggs segment than if approximately 

 the same number of eggs are inseminated by exactly the same con- 

 centration of sperm in egg- or ovary-extract, other factors remaining 

 the same. Now this result might be due to a " stimulating " effect 

 of the extract on the spermatozoa alone, or to some change brought 

 about in the eggs so that they can be more easily fertilized, or to a 

 combination of both causes. The experiments described in the following 

 sections were made to settle this question. 



1. Effect of extract on the sperm of Ciona. 



In each of the experiments recorded in Table IX, a sperm-suspension 

 was made up in the usual way. 5 cc. of this was mixed with 5 cc. of 

 water (= Sperm a), and at the same time 5 cc. was mixed with 5 cc. 



TABI.E IX. (23.10.2.) 



a=5 cc. sperm-susp< 



^ = .5 cc. sperm-suspeusion + .5 cc. extract. 



„ . , . ^ I a= 5 cc. sperm-suspension + 5 cc. water, 



Sperm in each experiment : < 



of the egg-extract (= Sperm /3), suspensions a and ^ being thus of 

 identical concentrations. The eggs to be fertilized were divided into 

 three equal lots, each in 16 cc. sea-water. Thirty minutes after the sperm 

 mixtures had been made up, fertilization of the three lots of eggs was 

 effected as follows : — (1) addition of one drop of Spi'i'ni a ; (2) addition 

 of one drop of Sperm a, and at the same time one drop of egg-extract; 

 (3) addition of one drop of Sperm /3. The fertilization (2) was made to 



