ARTIFICIAL PRODUCTION OF NoRMAL LaRv#® 585 
Mixtures of $n KCl with 1° CaCl, allowed only the be- 
ginning of the segmentation, and this only as long as CaCl, 
was used in very small quantities. In 96 cc. KCl+4 ce. 
CaCl, one egg in a thousand went into the two-cell stage, or 
formed two large cells with two micromeres; but in 90 c.c. 
KCl+ 10 c.c. CaCl, not one egg segmented, and the solu- 
tions with more Ca were not more favorable. 
A combination of $n NaCl with 1° CaCl, was equally 
poisonous. Even in 98c¢.c. NaCl+2c.c. CaCl, the eggs 
did not go beyond the beginning of the segmentation, and in 
96 cc. NaCl+4c¢.c. CaCl, the eggs died in the four-cell 
stage. It is worthy of mention that in these solutions the 
cleavage cells were very unequal in size. 
Mixtures of $n KCl and $n NaCl were, on the other 
hand, almost as favorable as the MgCl, solutions. In 98 c.c. 
NaCl+2c.c. KCl the eggs reached the sixty-four-cell 
stage or went even beyond this. It was the same in 96 c.c. 
NaCl+4c¢.c. KCl for almost every egg divided. With 
more KCl and less NaCl the results were less favorable. 
In a former paper we pointed out that the comparative 
harmlessness of K ions for the phenomena of cell-division 
is in striking contrast with the harmfulness of the same 
ions for the phenomena of muscular contraction. We thus 
see that the following two combinations of two chlorides 
in solution are the most favorable for development: (1) 
90 cc. 49n MgCl+10 cc. 49 CaCl,; and (2) 98 cc. 
an NaCl+ 2 c.c. $n KCL. 
Three chlorides in solution.— Neither with one nor with 
two chlorides in solution was it possible to obtain swimming 
blastule. From the experience with Fundulus’ I expected 
that a combination of three metal ions (especially NaCl, 
with small amounts of KCl and CaCl,) would allow the 
eges of the sea-urchin to complete their development. 
1 Part II, p. 544. 
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