This indicates that the quantity of CaCl₂ required to counteract the injurious effects of a pure solution of NaCl increases approximately in proportion to the square of the concentration of the NaCl solution.[262] 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. [262] Loeb, J., _Jour. Biol. Chem._, 1915, xxiii., 423. It was found also that not only Ca but a large number 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;[263] 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 highest concentration of NaCl solution in which the newly fertilized eggs of _Fundulus_ can still form an embryo.[264] 50 c.c. 10/8 m NaCl+4 c.c. m/1 MgCl₂ 50 c.c. 14/8 m NaCl+1 c.c. m/1 CaCl₂ 50 c.c. 11/8 m NaCl+1 c.c. m/1 SrCl₂ 50 c.c. 7/8 m NaCl+1 c.c. m/1 BaCl₂ [263] Loeb, J., “On the Physiological Effects of the Valency and Possibly the Electrical Charges of Ions,” _Am. Jour. Physiol._, 1902, vi., 411. [264] Loeb, J., _Jour. Biol. Chem._, 1914, xix., 431. On the other hand it was seen that in all the chlorides with a univalent cation, LiCl, KCl, RbCl, CsCl, NH₄Cl, 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. TABLE XVII CONCENTRATIONS AT WHICH THE EGGS NO LONGER ARE ABLE TO FORM EMBRYOS -------------------+----------------------------- _In the | _In the Same Salts with the Pure Salts_ | Addition of 1 c.c. m CaCl₂ | to 50 c.c. Solution_ -------------------+----------------------------- LiCl about 6/32m | >5/8 m NaCl m/2 | >14/8 m KCl >11/16 m | >8/8 m <6/8 m | RbCl >8/8 m | >9/8 m <7/8 m | CsCl >3/8 m | >8/8 m <4/8 m | -------------------+----------------------------- In short it turned out that the injurious action of the pure solution of any chloride (or any other anion) with a univalent metal could be counteracted to a considerable extent by the addition of small quantities of a salt with a bivalent metal. It was also found in the early experiments of the writer _that the bivalent or polyvalent anions had no such antagonistic effect_ upon the injurious action of the salts with a univalent cation.