STUDIES IN ARTIFICIAL PARTHENOGENESIS. 321 



effect. If the reagent is just a little too strong it can not be 

 effectively employed. In many cases only a certain length of 

 exposure is suitable. Too long exposures generally produce 

 exovates. Formation of exovates is represented by the symbol 

 "e" in the table. 



With ether and chloroform it is particularly difficult to obtain 

 maturation. In both instances I at first despaired of success. 

 A 3 per cent, solution of ether in sea-water did not produce 

 maturation. With such a solution exovates generally appeared. 

 On the other hand 2.5 per cent, ether had no observable effect on 

 the eggs. With a concentration intermediate between 2.5 per 

 cent, and 3 per cent, success was attained. In the table are given 

 the figures for a representative experiment with ether. 



In the case of chloroform the range of effective solutions is 

 even narrower. In making up chloroform solutions very small 

 quantities of the liquid had to be measured out. This was done 

 by counting the drops from a small pipette which was calibrated 

 for the purpose. About 60 drops from this pipette constituted 

 i c.c. By placing 8 such drops into a 100 c.c. measuring flask 

 and diluting to the mark a 0.13 per cent, solution was obtained. 

 This solution produced but little effect upon the eggs. Exposures 

 of 3-5 minutes showed only 1-2 per cent, of polar body formation. 

 Thus a 0.13 per cent, solution was apparently too weak. On the 

 other hand, a 0.17 per cent, solution proved too strong. Such a 

 solution was prepared by diluting 15 drops of chloroform (from 

 the pipette mentioned above) up to 100 c.c. with sea-water. 

 A 0.25 per cent, solution was thus obtained and this was then 

 diluted to 0.17 per cent, by adding 5 c.c. of sea-water to 10 c.c. 

 of the solution. The resultant 0.17 per cent, solution was found 

 to be too strong, for it produced exovates. Moreover viscosity 

 tests with the centrifuge showed that it coagulated the egg cyto- 

 plasm. Although neither 0.13 per cent, nor 0.17 per cent, 

 chloroform produced maturation, a concentration slightly under 

 0.17 per cent. did. This solution was made by diluting 10 drops 

 from the pipette up to 100 c.c. Such a solution would ordinarily 

 give 0.17 per cent., but one particular solution was made on an 

 extremely hot day (when the room temperature was 27). No 

 doubt the drops from the pipette were smaller, owing to the 



