568 JACQUES LOEB AND MARY M. CHAMBERLAIN 



that those eggs which segment first have a greater mass of fer- 

 ment than the others, fluctuating variabihty would in this case 

 be due to differences in the mass of ferment in the different eggs 

 of the same female. If this idea were correct, eggs with the 

 maximum and with the minimum amount of ferment should 

 differ in the rate of segmentation by an amount of time which 

 would vary in direct proportion to the temperature coefficient 

 for the process of segmentation. This theory was tested and 

 it was found that the observed values agree very closely with the 

 expected values; the slight variations found being in the direc- 

 tion of the possible source of error of the method of the experi- 

 ments. These experiments support therefore the idea that the 

 hereditary factor responsible for the rate of segmentation is a 

 determiner for a given mass of certain ferments, and that fluctu- 

 ating variability depends in this case upon slight but definite 

 variations in the mass of those ferments in different eggs. 



SUMMARY OF RESULTS 



1. It is shown that the temperature coefficient for the lati- 

 tude of variation of the segmentation of the egg of Arbacia 

 (i.e., the time between the segmentation of the first and last 

 egg of a group fertilized at the same time) is practically identi- 

 cal with the temperature coefficient for segmentation. 



2. It is shown that the fact is intelligible on the assumption 

 that the fluctuating variation in this case is due to a variation 

 in the mass of enzyme contained in the different eggs and sup- 

 posed to be responsible for the rate of segmentation. 



