604 STUDIES IN GENERAL PHYSIOLOGY 



no blastulse were left in lots 2 and 7, where they had at 

 most been very scarce. The next morning only a few larvse 

 were left in lots 3 to 6, and these died during the day. 



I stated at the beginning of my experiments that only a 

 part of the eggs of one female were put into the MgCl g 

 solution. The others were left in normal sea-water to serve 

 as control material. None of these eggs which were in the 

 same sea-water as that used for the eggs treated with the 

 MgCl 2 solution formed any membrane. After twenty-four 

 hours a few eggs were found divided into 2 cells. No egg 

 developed beyond this stage. 



This experiment shows that the time during which 

 unfertilized eggs must remain in contact with a mixture of 

 60 c.c. 2 -n MgCl 2 +40 c.c. sea- water in order to give rise 

 to blastulse is limited in two directions. If the eggs remain 

 only thirty minutes in such a solution, a few of them may 

 begin to develop, but none will reach the blastula stage. But 

 if the unfertilized eggs remain in this solution from one and 

 one-half to two hours, more than 20 per cent., and as many 

 as 50 per cent., may develop, and the solution then teems 

 with moving blastulse, which however remain at the bottom 

 of the dish. On the other hand the time limit will be 

 exceeded if the eggs are left in the solution more than two 

 and one-half or three hours. 



I tried another experiment in this series to see how soon 

 the unfertilized eggs would lose their power of being affected 

 by the MgCl 2 solution. The eggs were left in normal sea- 

 water for eighty minutes, then put in a solution of 60 c.c. 

 2 ^n MgCl 2 +40 c.c. sea-water for two hours. Two hours 

 later they were put back into normal sea-water. A large 

 number of eggs began to segment, but I did not find any 

 blastulse the next day. 



Third series. Thus far I had found the right solution 

 for producing blastulse from unfertilized eggs, and had found 



