456 CHARLOTTE HAYWOOD. 



the foregoing the cleavage process is seen to be but little affected 

 by oxygen deficiency over a wide range, the more striking effects 

 observed with CO 2 , about to be described in more detail, may 

 justly be attributed to an action of carbon dioxide in which inci- 

 dental oxygen lack plays little or no part. 



Such being the case, the solutions used in the subsequent ex- 

 periments were simply mixed in a large graduated cylinder and 

 immediately added to the eggs. Siphons were not used nor were 

 Winkler determinations made. Speed in setting up the experi- 

 ment was important, and in cases where a considerable number of 

 'bottles were to be filled, this method had the advantage of expe- 

 diency. Where the sea water used was saturated with CO 2 (i.e. 

 " 100 - " per cent. CO 2 , with a trace of oxygen) it seems probable 

 that sufficient oxygen must have entered the solution from the air 

 to prevent any retardation of cleavage from oxygen lack, since 

 a 4 : i mixture of CO 2 -saturated and oxygen-saturated sea water 

 (i.e. 80 per cent. CO 2 and 20 per cent, oxygen) gave practically 

 the same result. In fact, the results following " 100 " per 

 cent. CO 2 were very similar to those of various tensions down to as 

 low as about 30 or 40 per cent. CO 2 . Inasmuch as most of the 

 work here reported is not concerned with more than a semi-quan- 

 titative estimate of the gases, it is believed that the method is 

 sufficiently accurate. 



In striking contrast to the extensive diminution in available 

 oxygen which the eggs seem to tolerate is the effect upon cleavage 

 of even very small amounts of carbon dioxide. The repression 

 of cleavage which occurs when, in the laboratory, the eggs are 

 subjected to overcrowding is a familiar example of the effects 

 which may be produced simply by the CO 2 which arises from the 

 metabolism of the cells themselves. Experimentally, sea water 

 containing as little CO 2 as 10 per cent, of saturation value was 

 found, after an exposure of twenty minutes to delay cleavage 

 twelve and one half minutes, while exposures of equal length to 

 30 per cent, and 40 per cent. CO 2 were found to delay cleavage 

 a longer time about twenty-three minutes. Apparently this latter 

 value of 40 per cent, saturation or 300 mm. fig represents prac- 

 tically a complete suppression of cleavage since it is approximately 

 the same value as is obtained with higher tensions. 



