XXX 
ON ARTIFICIAL PARTHENOGENESIS IN SEA-URCHINS' 
In the last October number of the American Journal of 
Physiology I published a preliminary note on the artificial 
production of larve 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, 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 
1Science, Vol. XI (April 20, 1900), p. 612. 
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