STUDIES OF FERTILIZATION. 23 1 



pretation, quantitative questions may be of serious significance. 

 It would seem to be a perfectly simple matter to determine 

 the greatest dilution of sperm at which any fertilization takes 

 place, and to express in the form of a curve, from percentages of 

 eggs fertilized, the rate of loss of fertilizing power due to dilution. 

 This was the very simple problem with which the present investi- 

 gation began. However the results were in the highest degree 

 contradictory; the same lot of sperm might vary in a period of 

 half an hour from 1/1,024 to 1/9,000,000 (or less) of i per cent, 

 dilution in its power to fertilize the same percentage of a single 

 lot of eggs. The investigation, therefore, turned to the problem 

 of such variations and their cause. 



II. Experiments. 

 I. Methods. 



Quantitative methods cannot possibly be as rigorous in a 

 problem of this kind as in a purely chemical problem. In the 

 first place we have to deal with variable reagents in the ova and 

 sperm of Arhacia; and in the second place the initial measure- 

 ments must be made rather hurriedly, so as to ensure freshness of 

 the reagents, and under conditions that do not injure their 

 vitality; the available quantities of material also limit the 

 methods of measurement. 



Sperm. — The standard for measurements of sperm dilutions 

 is the "dry sperm"; i. e., the thick creamy mass that exudes 

 from ripe testes of Arhacia. If a ripe male be opened and in- 

 verted in a dry Syracuse watch crystal a certain amount entirely 

 free from foreign admixture usually flows from the genital pores 

 and collects in a mass in the crystal. While this may in certain 

 cases be as much as 2 c.c, usually it is a much smaller quantity. 

 It is quite impracticable to measure this by graduated pipettes; 

 I have therefore used a drop of this dry sperm from bulb pipettes 

 of fairly uniform openings as a standard, and, reckoning 30 such 

 drops to the cubic centimeter, have made "i per cent, sperm 

 suspensions" by the addition of such a drop to 3.3 c.c. of sea 

 water. This is the standard suspension from which most of 

 the experiments proceed, and all sperm suspensions are expressed 

 in fractions of such a i per cent, suspension. Given perfectly 



