ARTIFICIAL PARTHENOGENESIS 639 



cause the egg to go through a few segmentations, but cannot 

 cause the parthenogenetic production of a blastula or a later 

 stage of development. The increase in the osmotic pressure 

 of the solution is therefore an essential condition for arti- 

 ficial parthenogenesis. As the season was at an end, it was 

 not possible for me to decide last autumn whether the other 

 two above-mentioned conditions are equally essential. 

 Through the aid of the Elizabeth Thompson Fund I was 

 enabled to carry on experiments in co-operation with Dr. W. 

 E. Garrey at Pacific Grove during the spring, 1 and I have 

 since had a chance to continue this work at Woods Hole. 

 My new results enable me to give a more definite answer to 

 the question of the nature of the process of fertilization. 

 I first tried to ascertain whether the MgCl 2 plays a specific 

 r6le in artificial parthenogenesis, or whether its place may 

 be taken by some other salt. I found that the latter is the 

 case. 2 A mixture of equal parts of a *- n NaCl solution and 

 sea-water, or of equal parts of a J n KC1 solution and sea- 

 water, is just as effective as, if not more so than, a 2 -^ n 

 MgCl 3 solution. Unfertilized eggs of Strongylocentrotus, 

 if left for seventy minutes in any of these solutions, devel- 

 oped, and some of them reached the pluteus stage. Such 

 eggs remained alive as long as ten days. Even a mixture 

 of equal parts of a 2 ^ n CaCl 2 solution and sea-water 

 brought about the development of the eggs, but it was 

 necessary to take the eggs out in about forty to fifty 

 minutes, as otherwise the solution killed them. None of 

 the eggs treated with the CaCl 2 solution developed beyond 

 the blastula stage, or lived longer than one day. 



1 noticed that in these experiments with a y n NaCl or 



i 1 wish to express my thanks to Professor Jenkins, of Stanford University, for 

 kindly allowing me the use of the Hopkins Laboratory. 



2 I had been misled in my original experiments of 1899 through the fact that 

 the solutions which I considered as isosmotic differed in their concentration, owing 

 to an error in their preparation. When I resumed the experiments in 1900 I dis- 

 covered the error and corrected it. [1903] 



