572 STUDIES IN GENERAL PHYSIOLOGY 



would accelerate the disproportion between the Na and Ca 

 ions of the protoplasm. I tried y n Na g SO 4 solution. In 

 no experiment was a single embryo formed, and in each case 

 the development of the germ stopped in an earlier stage 

 than in the pure NaCl solution. This corroborates our 

 view that the poisonous character of the pure NaCl solution 

 is due to the fact that for the development of the egg the Na, 

 Ca, and K ions must exist in definite proportions in the 

 protoplasm. 



In a pure y n MgCl 2 solution no egg can develop. Even 

 in equal parts of y n MgCl 3 and distilled water only a small 

 proportion of eggs (20 per cent.) were able to form embryos, 

 none of which hatched. Mg ions behave toward the egg of 

 Funduhis very much like Ca and unlike K ions. In a solu- 

 tion of 98 c.c. -|tt NaCl + 2 c.c.y n MgCl 2 all the eggs form 

 embryos, although no fish hatch. But in larger quantities 

 the Mg ions are not so poisonous as the Ca ions. Even in a 

 mixture of equal parts of |n NaCl+ ^ n MgCl 2 as many as 

 75 per cent, of the eggs form embryos (although none of 

 the latter hatch). This behavior of the Mg ions is similar to 

 the one described in my paper oii-the absorption of liquids. 

 The above-mentioned experiments on the effects of K ions 

 show very clearly that the effect of these ions upon cell- 

 division is altogether different from their effect upon the 

 rhythmical contractions. This is not only true for the cells 

 of Fundulus, but also for the egg-cells of the sea-urchin. I 

 intend to discuss the effect of ions upon the cell-division in 

 the eggs of sea-urchins in the next paper. 



III. SOME GENERAL CONCLUSIONS 



1. The results of this paper bear upon several other 

 problems which we have thus far had no chance to discuss 

 sufficiently. There has been a controversy as to whether 

 the contractions of the heart are myogenic or neurogenic. 



