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 c.c. of this solution with 10 c.c. 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. -|nNaCl -f- 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. -- 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 KC1 solution about 70-80 per cent, of the eggs 

 segmented, and many reached the eight-cell stage. A slight 

 dilution of the KC1 allowed the eggs to reach the thirty-two- 

 cell stage. Even in a mixture of 60 c.c. KC1 and 40 c.c. 

 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 110 segmentation occurred. The 

 cleavage cells were more equal in size than in the NaCl 

 solutions. It is obvious that a pure KC1 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. 



In a y?i MgCl 2 solution the eggs reached the thirty- 

 two-cell stage, and in more diluted solutions, for instance 

 50 c.c. MgCl 2 +50 c.c. of distilled water, the development 

 went even farther (sixty-four cells or more). But the various 

 experiments with a pure MgCl 2 solution varied somewhat in 

 their results. On the whole, the MgCl 2 was more favorable 

 than the KC1 or NaCl. 



In a y n CaCl 2 solution there was at the best only the 

 beginning of a segmentation. In a mixture of 90 c.c. 



