ARTIFICIAL PRODUCTION OF NORMAL LARVAE 605 



about how long the eggs must remain in this solution. I 

 now desired to verify these results and in addition find out 

 accurately how far the proportions between sea-water and 

 the 2 -^ n MgCl 3 solution might vary without interfering with 

 the results. The unfertilized eggs of one female were dis- 

 tributed in the following solutions : 



(1) 60 c.c. a a n MgCl 2 +40 c.c. sea-water 



(2) 30 +70 " 



(3) Normal sea-water 



At five different periods (one hour, one hour and forty 

 minutes, one hour and fifty-five minutes, two hours and 

 twenty minutes, two hours and forty-five minutes) portions 

 of the eggs in solutions 1 and 2 were brought back into 

 normal sea-water. After all that has been said, it seems 

 superfluous to give all the details as explicitly as in the pre- 

 ceding experiments, and I shall therefore confine myself to 

 a description of the main results as they appeared next 

 morning. The eggs in solution 3 (normal sea- water) had no 

 membranes nor had any egg segmented. It is obvious that 

 unfertilized eggs do not always undergo a beginning of seg- 

 mentation in normal sea-water after twenty or twenty-four 

 hours. Of the eggs that had been in solution 1 for one 

 hour and fifty-five minutes, about 25 per cent, had developed 

 into a blastula which swam about. About the same result 

 was obtained in the lot that had been for two hours and 

 twenty minutes in solution 1. The appearance of these 

 blastulas was the same as in the previous experiments. Most 

 of them were only fractions of one egg, and it was not 

 uncommon to see four smaller blastulse swim together, each 

 apparently having developed from one of the blastomeres of 

 the four-cell stage. In the other lots which were taken from 

 solution 1 a few blastulae were formed. The eggs that had 

 been in this solution for one hour were practically all 

 undivided, except that one in a thousand had segmented into 



