The Influence of Environment 309 



square of the concentration of the NaCl solution.^ 

 The reader will notice that the eggs can survive and 

 develop in a solution of three times the concentration 

 of sea water, provided enough Ca is added. 



It was found also that not only Ca but a large num- 

 ber of other bivalent metals were able to counteract 

 the injurious action of an excessive NaCl solution; 

 namely Mg, Sr, Ba, Mn, Co, Zn, Pb, and Fe;^ only Hg 

 and Cu could not be used since they are themselves 

 too toxic. The antagonistic efficiency of the bivalent 

 cations other than Ca was, however, smaller than 

 that of Ca. The following table gives the high- 

 est concentration of NaCl solution in which the 

 newly fertilized eggs of Fundulus can still form an 

 embryo. 3 



50 CO. 10/8 m NaCl +4 c.c. m/i MgCU 

 50 c.c. 14/8 m NaCl+i c.c. m/i CaCU 

 50 c.c. 1 1/8 m NaCl + 1 c.c. m/i SrCU 

 50 c.c. 7/8 m NaCl+i c.c. m/i BaCla 



On the other hand it was seen that in all the chlorides 

 with a univalent cation, LiCl, KCl, RbCl, CsCl, 

 NH4CI, the eggs could form embryos up to a certain 

 concentration of the salt; but that this concentration 

 could be raised by the addition of Ca. 



^ Loeb, J., Jour. Biol. Chetn., 1915, xxiii., 423. 



* Loeb, J., "On the Physiological Effects of the Valency and Possibly 

 the Electrical Charges of Ions," Am. Jour. Physiol., 1902, vi., 411. 

 3 Loeb, J., Jour. Biol. Chem., 1914, xix., 431. 



