INITIATION OF DEVELOPMENT IN CH/ETOPTERl^. 5! 



seem that the development of the swimmers, then, was entirely 

 due to the potassium chloride, but hindered by the low tempera- 

 ture. Cold alone, as noted earlier in the paper, may under 

 favorable conditions lead to the formation of swimmers. 



5. De-aerated Sea-water and Potassium Chloride. Two sets of 

 experiments were performed, to test the effect of potassium 

 chloride in connection with de-aerated si-a-water, one set using 

 the potassium chloride before, the other at the same time with, 

 de-aerated sea-water. The results were not very different from 

 those with potassium chloride alone. The percentage of eggs 

 forming polar bodies under either treatment was about equal to 

 that obtained with potassium chloride alone. No swimmers 

 were formed as a result of the potassium chloride alone in this 

 case, and none with the use of the combination, except in two 

 cases, namely, 0.5 per cent, swimmers were formed in a lot of 

 eggs left I ]/z hours in de-aerated sea-water + 2 per cent. 2^ M 

 KC1, and 3 per cent, swimmers were formed in a lot left over 

 night in de-aerated sea-water after being in 2 per cent. 2^2 M KC1 

 3 minutes. The swimmers were unsegmented. 



6. Potassium Chloride and Sea-water De-oxygenated by a Stream 

 of Hydrogen. A stream of hydrogen was run through a flask or 

 bottle of sea-water to remove the oxygen. A small amount of 

 oxygen was doubtless present, however, entering with the eggs, 

 etc. The eggs were placed in 3.5 per cent, of 2^2 M KC1 in 

 sea-water, 45 minutes to one hour, where many formed either one 

 or both polar bodies. They were then removed to the hydrogen 

 sea-water, and remained there from 8 minutes to 3 hours, with a 

 constant stream of hydrogen bubbling through the water. A 

 very few looked suggestive of first or second cleavage. Next 

 morning swimmers were found in all lots, particularly the three 

 hour one. Some appeared abnormally segmented. Sections, 

 however, show practically no normal cleavage, but one or two 

 ciliated larvae were found which were very abnormally cut up 

 into cells. The rest were much like ordinary KC1 material. 



7. Potassium Cyanide and Potassium Chloride. Many com- 

 binations of potassium cyanide and potassium chloride were tried. 

 In these experiments the differentiation was in general poorer 

 than with potassium chloride alone. A great deal of breaking 



