Toxic AND ANTITOXIC Errects or Ions’ 713 
stages of segmentation, but dies when it reaches the thirty- 
two- or sixty-four cell stage. The concentration of a 3m 
sodium-chloride solution is indeed so high above the point 
of the fatal concentration of sodium chloride that a slight 
decrease in the degree of dissociation of the NaCl solution 
brought about through the addition of a small amount of 
another salt having a common ion, could be entirely dis- 
regarded. In the following experiments, however, salts with 
different ions were combined, wherever this was possible. 
If to a pure sodium-chloride solution a trace of a 
calcium salt is added, as many eggs develop as in ordi- 
nary sea-water, as shown by Table I. 
TABLE I 
7 Percentage of 
Solution Eggs Aiciding 
Mmbryos 
100 c.c. §m NaCl 0 
100 oe “ +4 e.c. 7 CaSO, 3 
100 6c “ + 1 66 6 3 
100 &e “ + 9 6 “c 20 
100 ee it + 4 rT “ 75 
100 6 6“ + 8 be 73 70 
This series of experiments does not show whether it is 
the Ca or the SO, ion that has the antitoxic effect. To 
determine this point the same series of experiments was 
twice repeated with certain modifications. In the first of 
these Ca(NO,), was added to the 3 NaCl solution instead of 
CaSO,. The result was practically that given in Table I. 
In the second Na,SO, was added to the sodium-chloride 
solution. The addition of Na,SO, did not inhibit the toxic 
action of the sodium chloride, and the eggs developed no better 
than in the pure sodium-chloride solution. We shall return 
to this point later. However, in order to eliminate entirely 
the effect of the anions in the antitoxic effects produced, a 
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