ARTIFICIAL PRODUCTION OF NORMAL LARV.E 607 



osmotic pressure was not sufficient. Moreover I wished 

 once more to repeat the former experiments. The unfer- 

 tilized eggs of one female were distributed in the following 

 solutions ; 



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



(2) 100 c.c. sea-water + 3i gr. (wet) MgCl 2 



(3) 100 c.c. sea-water + 8 gr. (wet) MgCl 2 



(4) Normal sea-water 



At various intervals a lot of the eggs were taken out of 

 each of the four solutions and put into normal sea-water. 

 The eggs that had been in solution 1 from one and one-half 

 to two hours had developed into blastula3 the next norning. 

 The number of blastul* was comparatively larger than in 

 any of my previous experiments. The eggs that had been 

 in solutions 2 and 3 contained no blastulas. Solution 2 is, by 

 the way, the one Norman and Morgan had used in their ex- 

 periments. In solution 4 no egg was even segmented the 

 next day. In none of the four solutions had any egg formed 

 a membrane. These experiments show that the substitution 

 of a number of Mg ions for one-half of the ions naturally 

 contained in the sea- water is either necessary or more favor- 

 able than the mere addition of Mg ions. This experiment 

 explains why Morgan did not succeed in getting live larvse, 

 having treated the eggs with solution 2. But I intend to 

 determine in my future experiments whether the addition 

 of a little more than 3^ gr. of MgCl 2 and a little less than 

 8 gr. of the solution to 100 c.c. of sea-water may not give 

 more favorable results. 



Fifth series. I next wished to try whether it would not 

 be possible to carry the artificial development of the unfer- 

 tilized egg one step farther. The blastulas thus far obtained 

 were by no means healthy, and although some of them looked 

 normal, they died before they had time to reach the pluteus 

 stage. This latter result I was inclined to ascribe to the 



