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,’ 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, plays a specific 
role in artificial parthenogenesis, or whether its place may 
be taken by some other salt. , I found that the latter is the 
case.” A mixture of equal parts of a 1,9 n NaCl solution and 
sea-water, or of equal parts of a 42 KCl solution and sea- 
water, is just as effective as, if not more so than, a 2,9 n 
MgCl, 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 %2n CaCl, 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, solution developed beyond 
the blastula stage, or lived longer than one day. 
I noticed that in these experiments with a 19 NaCl or 
1 I wish to express my thanks to Professor Jenkins, of Stanford University, for 
kindly allowing me the use of the Hopkins Laboratory. 
2I 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] 
Digitized by Microsoft® 
