272 Studies in the Phxjaiohujtj of Fertilization 



2. The effect of extract on the eggs of Giona. 



The experiments described in the preceding section showed clearly 

 that treatment with egg-extract increases the fertilizing power of a 

 sperm-suspension. That is to say, such a suspension is capable of 

 fertilizing more eggs than sperm of equal concentration made up in 

 plain sea-water, other conditions remaining unchanged. This does not 

 prove, however, that the increased percentages of eggs which segmented 

 in the initial experiments when fertilized in the presence of extract, 

 over those fertilized in plain water with the same amount of sperm, 

 were to be attributed only to the action of the extract on the sperma- 

 tozoa. The substances in the egg-juice might also have influenced the 

 eggs, making them more receptive to spermatozoa. In the experiment 

 to be described next, the action of the extract on the spermatozoa was 

 as far as possible eliminated. Eggs were treated with extract, and the 

 proportion subsequently fertilized by the addition of a given amount of 

 sperm was compared with that in eggs not previously so treated. 



The eggs of an individual were divided into two lots and placed 

 in (1) water, and (2) ovary-extract, and left for 43 minutes. After 

 this interval, approximately equal numbers of eggs were tried out as 

 follows : 



((') Eggs in 1 cc. water, from (1). 



(6) Egg.s in 1 cc. extract, from (2). 

 (c) Eggs in 1 cc. extract, from (2). 



Immediately before fertilization a sperm-suspension was made up, 

 and equal amounts were dropj^ed into («) 80 cc. water; {^) 30 cc. water; 

 (7) 30 cc. extract. Fertilizations were effected by pouring (a) on to (a) ; 

 (/3) on to (6) ; and (7) on to (c). The large amount of water (30 cc.) 

 added to the eggs with the sperm was to dilute the extract in (h) as 

 much as possible, in order to prevent action on the sperm. 



The experiment was made double, the fir.st series being when 

 three drops of sperm were added to (a), (/S), and (7), and the second 

 when ten drops were added to each. 



TABLE XI. 



The comparison of the percentages of eggs fertilized in I and II in 

 the Table shows whether or not the extract had affected the eggs, which 



