XXX 



ON ARTIFICIAL PARTHENOGENESIS IN SEA-URCHINS 1 



IN the last October number of the American Journal of 

 Physiology I published a preliminary note on the artificial 

 production of larvae from the unfertilized eggs of the sea- 

 urchin. I mentioned that unfertilized eggs were able to 

 develop into normal plutei after having been in a solution of 

 equal parts of a 2 ^ n MgCl 2 solution and sea-water for about 

 two hours. The control experiments by which the possibility 

 of the fertilization of these eggs through spermatozoa had 

 been excluded were briefly mentioned. In the April num- 

 ber of the same journal a full description of my experiments 

 was published which I believe puts an end to any doubt con- 

 cerning the possibility of an error. Nevertheless, I decided 

 to repeat these same experiments with the additional precau- 

 tion of using sterilized sea-water. Through the kindness 

 of the board of trustees of the Elizabeth Thompson Fund I 

 was enabled to make further experiments on artificial par- 

 thenogenesis at the Pacific coast. These experiments have 

 led to a number of new results, which will be published in 

 the American Journal of Physiology. Here I will confine 

 myself to a description of the precautions which were taken in 

 these experiments to exclude the possibility of a fertilization 

 of the eggs through spermatozoa. 



The sea- water used for these experiments was heated the 

 day before, very slowly, to a temperature of from 50 to 70 

 C., and was kept at that temperature for about ten minutes 

 and allowed to cool very slowly. The control experiments 

 proved that, as was to be expected, the spermatozoa are 

 killed by this treatment. During the time the water was 

 heated no sea-urchin was opened in the laboratory or was even 



i Science, Vol. XI (April 20, 1900), p. 612. 



624 



