460 CHARLOTTE HAYWOOD. 



TABLE III. 



THE DELAY IN 50 PER CENT. CLEAVAGE CAUSED BY VARIOUS EXPOSURES 



TO 8O PER CENT. CO . 



(Experiment illustrated in Fig. 2.) 



Exposure Time Delay in 50 per cent. Cleavage 

 (in Minutes). (in Minutes). 

 



5' 5' 



10' 12' 



20' 18' 



35' (?) 34' 



80' 86' 



160' 186' 



370' 



640' 



It will be observed that with the shorter exposures the recovery 

 of the cleavage process may occur with great rapidity, the delay 

 being but little more than the time corresponding to the period of 

 exposure. Consequently, it has very often been found possible, 

 in performing experiments, to predict the beginning of cleavage 

 with a fair degree of accuracy simply by adding the exposure time 

 to that required for the beginning of cleavage in the normal. As 

 exposures become longer, the greater discrepancy between the 

 exposure time and the delay of cleavage is wholly in one direction 

 that of prolonging the cleavage time. A further analysis of 

 the data shows even in this respect a simple relation which may 

 best be brought out by plotting the time required for 50 per cent, 

 cleavage against the time of exposure, as has been done in Fig. 3. 

 It will be noticed that straight lines may be drawn through the 

 points representing any given experiment. Those indicated in 

 the figure have been calculated by the method of least squares, 

 with the result that the slopes of all the lines are approximately 

 equal. All may be represented fairly accurately by the equation 



2 > 



where a = the cleavage time of the eggs in the absence of CO 

 .tr = the time of exposure, and y-= the cleavage time of the ex- 

 posed eggs. Further data are given in Table IV. 



