ARTIFICIAL PRODUCTION OF NORMAL LARV.E 587 



through the changes of cell-division and assimilation re- 

 quired for the process of development. I next tried whether 

 it was necessary that the Ca and K ions be added in equal 

 proportions to the NaCl. Table II gives the results of such 

 experiments. 



It is obvious that the proportion of K and Ca ions may 

 vary within certain limits as long as they are present in 

 sufficient quantity. I will add that I have not yet found any 

 other combination of three chlorides that yields swimming 

 blastulse. In the foregoing papers I mentioned that the 

 anions are not indifferent, and that in a NaBr solution the 

 rhythmical contractions of a muscle begin even sooner than 

 in an equimolecular NaCl solution. I made some experi- 

 ments on the effect of bromides on development. In a solu- 

 tion of 96 c.c. %n NaBr + 2 c.c. ^n KCl + 2 c.c. ^n KCl 

 the eggs developed into normal blastulce. In a solution of 

 96 c.c. LiBr + 2 c.c. CaCl 2 + 2 c.c. KCl the eggs reached 

 the sixteen-cell stage, while in the corresponding LiCl solu- 

 tion practically no segmentation took place. All these ex- 



TABLE II 



periments together give us the impression that different com- 

 binations of ions may exist which all have the same effect. 



