582 STUDIES IN GENERAL PHYSIOLOGY 
of the eggs stopped developing at the two-cell stage. The 
size of the cells was as a rule unequal from the beginning. 
In a mixture of 90 cc. of this solution with 10 cc. of 
distilled water about 80 per cent. of the eggs developed, some 
of which even reached the thirty-two-cell stage. In making 
more dilute solutions fewer eggs segmented, and in solutions 
that were more dilute than a mixture of 70 c.c. $n NaCl + 40 
c.c. distilled water as a rule no eggs segmented. This was 
not due to the reduction in the osmotic pressure, for in a 
solution of 70 c.c. §n NaCl+ 30 c.c. of cane sugar of the 
same osmotic pressure but very few eggs began to segment. 
They did not develop beyond the four-cell stage. In equal 
parts of the NaCl and the sugar solution not an egg segmented. 
In a $n KCl solution about 70-80 per cent. of the eggs 
segmented, and many reached the eight-cell stage. A slight 
dilution of the KCl allowed the eggs to reach the thirty-two- 
cell stage. Even in a mixture of 60 c.c. KCl and 40 cae. 
distilled water about 5 per cent. of the eggs began to seg- 
ment, but reached only the two- or four-cell stage. In 
more dilute solutions no segmentation occurred. The 
cleavage cells were more equal in size than in the NaCl 
solutions. It is obvious that a pure KCl solution is more 
favorable for segmentation than the pure equimolecular NaCl 
solutions. In a former paper I published a similar observa- 
tion on the Fundulus egg. 
Ina 1'n MgCl, solution the eggs reached the thirty- 
two-cell stage, and in more diluted solutions, for instance 
50 c.c. MgCl, +50 c.c. of distilled water, the development 
went even farther (sixty-four cells or more). But the various 
experiments with a pure MgCl, solution varied somewhat in 
their results. On the whole, the MgCl, was more favorable 
than the KCl or NaCl. 
In a 1,'n CaCl, solution there was at the best only the 
beginning of a segmentation. In a mixture of 90 c.c. 
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