ARTIFICIAL PRODUCTION OF NORMAL LARV.E 599 



such precautions, the results obtained were of such a char- 

 acter as to absolutely exclude in themselves any idea of con- 

 tamination by spermatozoa. In all the successful experi- 

 ments the cultures of unfertilized eggs that had been treated 

 with the right MgCl 2 solution were teeming with blastulee 

 the next day. Twenty per cent. , in some cases even more, 

 almost 50 per cent, of the eggs, had developed. In former 

 experiments with unfertilized eggs where no such precautions 

 were taken, I never noticed that more than perhaps one egg 

 in a thousand developed. I shall describe each series of ex- 

 periments independently. TheMgCl 3 used in these experi- 

 ments was chemically pure, but had been dried by heating it. 

 First series. Unfertilized eggs of the same female were 

 divided into four lots and distributed into the following four 

 solutions : 



(1 ) 60 c.c. If- n MgCl 3 + 40 c.c. sea-water 



(2) 100 c.c. YrcMgCl 2 



(3) 100 c.c. Yw CaCl 2 



(4) 100 c.c. normal sea-water 



After the eggs had been in these solutions one and one- 

 half hours they were carefully examined. Not one had a 

 membrane and not one was segmented. Twenty minutes 

 later one part of the eggs of each of these four solutions 

 was transferred back into normal sea-water. The latter was the 

 same for all four solutions. This time I took special care to 

 see that each lot of eggs was given enough normal sea- water 

 (about 200 c.c.). After they had been back in the normal 

 sea-water for about two hours and fifty minutes, they were 

 examined again. The eggs that had been in solution 1 

 (60 c.c. ? g n MgCl 2 +40 c.c. sea-water) were all without a 

 membrane. About 20 per cent, of the eggs were segmented 

 into as many as 32 cells. The eggs that had been in solu- 

 tion 2 (100 c.c. y*n MgCl 2 ) were without any membrane 

 and unsegmented. Many of those that had been in solution 



