EFFECT OF IONS UPON TISSUE 571 



It has long been maintained that there is an antagonism 

 between Ca and K ions. The following experiment demon- 

 strates this relation in a very striking way : If we mix 75 c.c. 

 of sea-water with 25 c.c. y n CaCl 2 , as a rule only a very 

 small percentage of the eggs are able to form an embryo. 

 But if we add a large quantity of KC1, almost every egg 

 forms an embryo. In two experiments not a single embryo 

 was formed in a mixture of 75 c.c. of sea-water -f- 25 c.c. y n 

 CaCl 2 , while in 50 c.c. of sea-water + 25 c.c. * n CaCl s 

 4- 25 c.c. |- n KC1 every egg formed an embryo. I have 

 repeated this experiment very often, and in each case ob- 

 tained similar results. But while the K ions antagonized 

 the poisonous effects of the Ca ions upon the formation of the 

 embryo, the poisonous effects of the K ions upon the heart- 

 beat were not counteracted by the Ca ions. In none of the 

 embryos formed in this solution was the heart able to beat 

 sufficiently long to enable the embryo to complete its devel- 

 opment. As a rule, on the sixth day every egg was dead. 



In a pure y n CaCl 2 solution the germ died in the early 

 stages of segmentation (four- to eight-cell stages). It ap- 

 peared to be coagulated. Not even in a mixture of equal 

 parts of such a solution with distilled water was a single 

 embryo formed. In a solution of 25 c.c. y n CaCl 2 with 75 c.c. 

 of distilled water embryos could be formed. In one case 

 as many as 80 per cent, of the eggs contained embryos. 

 This is the more remarkable as in a mixture of 75 c.c. of 

 sea- water -f- 25 c.c. l ^n CaCl 3 a much smaller percentage of 

 eggs formed embryos. In a ^n CaCl 2 solution all the eggs 

 formed embryos whose development was normal. 



We should expect that if we put eggs immediately after 

 fertilization into a pure solution of a Na salt whose anion 

 precipitates calcium, the fatal effects of the Na ions upon the 

 development would be still more obvious than in a pure NaCl 

 solution. The precipitation of Ca ions in the protoplasm 



