ARTIFICIAL PRODUCTION OF NORMAL LARV.E 583 



V 1 n CaCl 2 with 10 c.c. of distilled water I occasionally saw 

 an egg in the two-cell stage. In more dilute CaCl 2 

 solutions no trace of a segmentation occurred. Hence Mg 

 and K were more favorable than Na and Ca ions for the con- 

 centration used in the experiments. It is very evident from 

 these experiments that the optimum concentration for each 

 of these four chlorides is different. 



In a -| LiCl solution the majority of eggs remained un- 

 segmented, and only very few reached the two-cell stage. 

 Mixtures of LiCl with sugar were no more advantageous. 

 In pure glycerin and sugar solutions of the same osmotic 

 pressure as that of a -| NaCl solution no egg segmented. 

 It is evident that the quality of the ions is of more impor- 

 tance in these experiments than the osmotic pressure, and 

 that NaCl is not an indifferent substance. 



Two chlorides in solution. In a solution of one chloride 

 the eggs of Arbacia cannot reach the blastula stage. Are 

 mixtures of two chlorides more favorable for segmentation 9 



O 



Among the possible mixtures of the two chloride solutions 

 of the same osmotic pressure as the sea-water I found those 

 between yn MgCl 2 and y n CaCl 2 the most favorable. 

 The following twelve mixtures were prepared : ' 



(1) 100 c.c. YwMgCl 2 + Oc.c. V-HCaCl 2 



(2) 95 + 5 " 



(3) 90 " + 10 



(4) 80 " + 20 



(5) 70 " + 30 " 



(6) 60 + 40 " 



(7) 50 " 4- 50 " 



(8) 40 + 60 



(9) 30 + 70 



(10) 20 " + 80 " 



(11) 10 + 90 



(12) + 100 



lit will save repeating these figures if I may state here that the same twelve 

 proportions were used in all the following experiments with two chlorides in 



solution. 



