THE PHYSIOLOGY OF CELL-DIVISION 707 
and D) left the great majority of the eggs practically unaltered, 
as shown by absence of change (no larvae) and by normal develop- 
ment on fertilization with sperm next day; eggs after-treated as 
above with hypertonic sea-water also remained unchanged for 
the most part, but a small proportion yielded larvae—smaller 
than in the experiments of table 1, a difference due probably to 
the higher calcium-content of the solutions. In another series 
of similar experiments, in which potassium iodide and potassium 
sulphocyanate were compared, the same result was obtained, In 
this series also the action of the sulphocyanate was less completely 
inhibited than that of the iodide by the presence of calcium. 
Treatment with hypertonic sea-water after the caletum-containing 
sulphocyanate solution gave a considerable number of larvae, 
though few compared with those obtained with the pure solution 
followed by hypertonic sea-water. 
Results similar to the above were obtained in ten other series 
of experiments with sulphocyanate and iodide solutions. With 
sodium and potassium nitrate and sodium chlorate a similar 
increase in the proportion of developing eggs followed after- 
treatment with hypertonic sea-water; but the effect was less pro- 
nounced, and the proportion of larvae was never high. Nitrate 
was more favorable than chlorate. Hypertonic sea-water thus 
has well-marked action only when the initial treatment with the 
isotonic salt solution has produced a decided change in the eggs. 
Time-relations of the above treatment. It was found that the 
after-treatment with hypertonic sea-water produced the most 
favorable results if the eggs were brought into this medium within 
a fairly definite interval—from ten to fifteen minutes—after the 
treatment with isotonic salt-solution. This is illustrated by 
table 2. 
These experiments indicate that the most favorable interval 
between the return from the salt solution to sea-water and the 
exposure to the hypertonic sea-water is from ten to fifteen minutes ; 
an interval of twenty minutes seems already above the optimum; 
other experiments in which the interval was shorter—five to seven 
minutes—gave somewhat fewer larvae than in Experiments 1 and 
