Errect 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 averystriking way: If we mix 75 c.c. 
of sea-water with 25 c.c. 42 CaCl,, 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 KCl, 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 + 25 c.c. 19 n 
CaCl,, while in 50 c.c. of sea-water + 25 cc. 1Pn CaCl, 
+25 cc. 8n KCl every egg formed an embryo. I have 
repeated this experiment very often, and in each case ob- 
tained similar results. But while the K tons 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. Asa tule, on the sixth day every egg was dead. 
In a pure 1 CaCl, 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 
embryoformed. Inasolution of 25c.c. 1° n CaCl, with 75 c.c. 
of distilled water embryos could be formed. In one case 
as many as 30 per cent. of the eggs contained embryos. 
This is the more remarkable as in a mixture of 75 c.c. of 
sea-water + 25 c.c. 42n CaCl, a much smaller percentage of 
eggs formed embryos. In a $n CaCl, 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 Nasalt 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 
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