132 ARTHUR W. GREELEY. 



PERIODS OF EXPOSURE TO SOLUTION. 



* 



3J/S hours. 5 hours. 



O O 



O O 



15 20 



.5 10 



The figures indicate the number of swimming blastulae formed 

 in 100 eggs. At a' temperature of 30 C. no development took 

 place as a result of the NaCl solution, except a few irregular 

 segmentations. At 11 C. a slightly longer residence in the so- 

 lution over that necessary at the room temperature (23 C.) was 

 required, although at periods of three to five hours a larger per- 

 centage of blastulae were formed than at the. room temperature. 

 At a temperature of 2 C. a still longer exposure to the solu- 

 tion was required to produce any effect. At this temperature 

 practically no development took place until the eggs were ex- 

 posed to the solution for five hours. At, 30 C. only a few 

 irregular segmentations occurred as a result of the NaCl solution. 



Experiment 3.-- Arbacia eggs were placed in the following 

 solution : 100 c.c. sea-water concentrated by evaporation to 

 three fourths its volume. This solution has the same relative 

 proportion of ions as normal sea-water, and hence its only effect 

 upon the egg can be the purely physical one of extracting water 

 from it. The same temperature and periods of exposure were 

 used as in experiments i and 2. The results will be presented 

 in tabulated form as in experiment 2. 



PERIODS OF EXPOSURE TO SOLUTION. 



i hour. 7 hours. 3* hours. 5 hours. 



30 o o o o 



23 04 .50 



11 O 15 25 20 



2 o -5-43 



Many more of these eggs segmented at the room temperature 

 (23 C.) than is indicated in the table, but the cells fell apart be- 

 fore complete blastulae were formed. Practically the same gen- 

 eral result is seen as in experiment 2. The optimum period of 

 exposure to the concentrated sea-water becomes increasingly 

 longer as you lower the temperature, but with these longer 



