228 Studies in the Phyaiologij of Fertilization 



thoroughly mixed by pouring from one dish to another. A sperm- 

 suspension was made and diluted down to the required amount, after 

 which it was thoroughly mixed by pouring it 20 times from one 

 dish to another. Two small glass dishes were then taken. Into the 

 first (1) was placed 10 cc. of normal sea- water, and into the second (2) 

 10 cc. of sea- water which had come through the filter-paper. This 

 paper had already been washed for 15 minutes in running sea-water 

 and the water which came through after this interval gave the same 

 reaction as normal sea-water with neutral red. To each of the dishes (1) 

 and (2) were added three drops of the sperm-suspension b, so that two 

 sperm-suspensions were obtained, (1) in normal sea-water, and (2) in 

 filter-paper water, and each of identical concentration. The liquid in 

 each dish was thoroughly mixed by pouring. Into each of two other 

 small dishes were then placed approximately equal quantities of A eggs 

 in three drops of water. The liquid in dish (1) was then poured on to 

 one of these lots of eggs, and that in (2) on to the other. By this means 

 fertilization was effected, and in order to ensure a quick and thorough 

 mixing of the eggs and sperm, the contents of the two dishes were each 

 poured backwards and forwards into two other dishes several times. 

 When the 4-cell stage was attained, the percentages of eggs which had 

 been fertilized in the two dishes were counted in the way described 

 above. 



The experiment was then repeated on exactly similar lines with 

 another cross, Ajc. The results are tabulated below. 



TABLE. To show the effect on the "fertilizing poiver " of a sperm-suspension 

 o/ water which has passed through a washed filter-paper. (44.26.6.) 



(1) Normal (2) Filter-paper 



water water 



Exp. 1, cross A/b 100 77 



Exp. 2, cross Ajr 95 31 



The Table shows that in each of the experiments fewer eggs were 

 fertilized by the sperm-suspension treated with water from the filter- 

 paper than by the sperm not so treated, although the two suspensions 

 were of identical concentrations. In the first case the decrease was 

 from 100% to 77%, and in the second from 95 7,, to 31%. This is 

 expressed by saying that the "fertilizing power" of the sperm-suspension 

 had been diminished by the treatment with filter-paper water. 



The foregoing remarks have emphasized enough the importance on 

 such work as this, where the validity of the results depends on numerical 



