The Influence of Environment 307 



for this purpose, namely, the eggs of the marine fish 

 Fundulus, gave altogether different results. The eggs 

 of this marine fish develop naturally in sea water but 

 they develop just as well in fresh or in distilled water, 

 and the young fish when they are made to hatch in 

 distilled water will continue to live in this medium. 

 This proves that these eggs require none of the salts 

 of the sea water for their development. When these 

 eggs are put immediately after fertilization into a pure 

 solution of NaCl of that concentration in which this 

 salt exists in the sea water practically all the eggs die 

 without forming an embryo; but if a small quantity 

 of CaCl 2 is added every egg is able to form one, 

 and these embryos will develop into fish and the latter 

 will hatch. This led the writer to the conclusion that 

 these fish (and perhaps marine animals in general) 

 need the Ca of the sea water only to counteract the 

 injurious effects which a pure NaCl solution has if it 

 is present in too high a concentration. 1 When we raise 

 the eggs in a pure NaCl solution of a concentration 

 ^fm/8 practically every egg will develop; and even in 

 a m/4 or 3/8 m many or some eggs will form embryos 

 without adding Ca ; it may be that a trace of Ca present 

 in the membrane of the egg may suffice to counter- 

 balance the injurious action of a weak salt solution. 



1 Loeb, J., "The Poisonous Character of a Pure NaCl Solution," 

 Am. Jour. PhysioL, 1900, iii., 329; Arch.f. d. ges. Physiol., 1901, Ixxxviii., 

 68; Am. Jour. PhysioL, 1902, vi., 411; Biochem. Ztschr., 1906, ii. f 8l. 



