NUCLEAR VOLUME AND LIFE-CYCLE OF HYDATINA 



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upper curve of figure 1. Even if one might attribute the second 

 period of high male-production to the decrease in volume of 

 nuclei in the intestine, there would be no similar decrease of 

 nuclear volume coincident with the first period of high male- 

 production. 



Oocytes. Drawing conclusions from the nuclear volumes of 

 these cells must be done with caution for the reason that smaller 

 numbers of cells are available for measurement and that the cells 

 are of very different sizes correlated with stages in the growth 

 period. The former condition obviously causes high probable 



TABLE 3 



The relative nuclear volume of the cells of the stomach-intestine of Hydatina senta 



for each of nineteen generations of the same line as is 



represented in table 2 



errors of mean nuclear size, and, as pointed out below, the second 

 condition has a like effect. Disregarding the differences in size 

 and grouping all cells together, one obtains the relative nuclear 

 sizes shown in table 4. The graph of these sizes is given in figure 

 1, bottom curve. 



One might be tempted to see in the lower curve of this figure 

 three modes which correspond to the periods of high male-pro- 

 duction in generations 5 and 6 and 15 and 16, and to the much 

 less marked but isolated male-production in the ninth generation. 

 The rise of relative nuclear volume in. the eighth and two suc- 

 ceeding generations seems out of all proportion to the percentage 

 of male-producers occurring at that time, but were there no other 



