274 Sfmlics ill lli( rinisliihiiiji <if Fertilization 



quantities ol' (1) plain sua-water and (2) egg-extract, and a <lit))) of 

 each compared under the microscope, the spermatozoa are very much 

 more active in the extract suspension. Moreover, if eggs be ])ut in 



TABLE XII. (1.26.1) 



Cross : A jc A egg-extract 



each of the ih-ops, the number of spermatozoa which collect round the 

 eggs is considerably greater in the latter suspension. These effects, 

 which are very obvious in Strongylocentrotus, are hardly noticeable in 

 Ciona, where the sperm is always much more sluggish in its movements. 



The greater activity of the spermatozoa of Stroiigylocentrotus in the 

 presence of egg-extract suggests that the greater proportion of eggs 

 fertilized by such suspension is due to UKjre spermatozoa coming into 

 contact with eggs, owing to their quicker movement. This is, however, 

 at all events not the whole explanation, since Lillie (3) has shown that 

 the egg-extracts have a positive chemotactic effect on the spei-matozoa. 

 as well as an activating influence. 



The following two experiments were made to determine the effect 

 on the fertilizing power of the sperm of treatment for varying lengths 

 of time with egg-extract. 



In each experiment a sjjerm-suspension was made in sea-water and 

 1 cc. was pipetted into each of (I) four dishes, each containing 5 cc. of 

 plain sea-water, and (2) four dishes, each containing 5 cc. of egg-extract. 

 These suspensions of equal concentration were used for fertilization 

 immediately and at ten minute intervals. At each fertilization, 5cc. 

 plain water was added to (1) a dish of water sperm-suspension, and 

 (2) a dish of extract sperm-suspension. After the usual thorough 



Exp. 1. Ajb 



Exp. 2. Ajr 



