568 STUDIES IN GENERAL PHYSIOLOGY 



such a solution. Their duration of life after hatching is, 

 however, very short. The fact that the eggs of Fundulus 

 are able to develop in sea- water to which as much as 5 per 

 cent. NaCl has been added shows that other constituents of 

 the sea-water are able to counteract the poisonous effects of 

 a pure NaCl solution. In a solution of 98 c.c. -f-n NaCl 

 + 2 c.c. |?i KC1 only a small number of embryos are formed. 

 They cannot be kept alive for more than a week. In a solu- 

 tion of 98 c.c. |w NaCl -|- 2 c.c. -|n CaCl 3 every egg devel- 

 ops, but only in exceptional cases does the fish hatch. Those 

 that hatch die immediately afterward. The addition of 

 even as little as ^ c.c. l - n CaCl 2 to 100 c.c. |NaCl causes 

 all the eggs to develop. A small amount of Ca ions counter- 

 acts the poisonous effect of a large quantity of Na ions 

 sufficiently to allow the development to go on, but not enough 

 to allow the embryos to hatch. In a solution of 96 c.c. f n 

 NaCl + 2 c.c. y>n CaCl 2 +2 c.c. |n KC1 not only all the 

 eggs develop, but the young fish hatch and live indefinitely. 



In distilled water all the eggs are able to develop, and 

 the young fish hatch in due time and live indefinitely. 

 Hence the Ca and K ions of the above-mentioned solution 

 are not directly necessary for the development of the fish. 

 They are only indirectly necessary to counteract the poisonous 

 effects of the Na ions in a solution of a Na salt. In a gly- 

 cerin solution of the same osmotic pressure as a-f-wNaCl 

 solution, no embryo was formed. In mixtures of glycerin 

 and sea-water embryos formed, but the glycerin acted as a 

 poison ; the more glycerin the solution contained, the quicker 

 it killed them. 



Thus far our results agree entirely with our previous 

 results on the poisonous character of a pure NaCl solution. 

 Such a solution has a poisonous effect on the germ of 

 Fundulus, and the Na ions are exclusively or mainly 

 responsible for the poisonous effect. But this poisonous 



