THE INTERPHASE NUCLEUS 



Their evidence for this is indirect, and is based on studies of the distribu- 

 tion of size of large numbers of nuclei. Thus, if the nuclei in a tissue 

 remain at one size for some time and then rapidly grow to another at 

 which they again halt, then the histogram of nuclear size will show 

 peaks corresponding to these values, provided that the errors involved 

 are not large enough to obscure the result. The best known of such 

 numerical investigations are those of Jacobj^^^ ^^^ who measured 

 nuclear diameters in a series of mammalian tissues, and displayed the 

 calculated volumes in this form; the peaks were identified as modal 

 values which, Jacobj claimed, bore to each other ratios of 1:2:4 ^^^ 



Time 



Figure 1 9 Nuclear area of a mouse spleen cell in tissue culture 

 during mitosis; (A) that of the parent cell in prophase, (B) 

 that of one daughter cell in telophase and early interphase. 

 From Fell and Hughes^*^ (By courtesy, Quart. J. micr. Sci.). ' 



so forth. Before discussing the author's conclusions, we must first 

 examine the evidence on which they are based. 



In the first place it is necessary to say that simple inspection of a 

 histogram is not adequate to decide whether or not a distribution is 

 discontinuous, for the irregularities may be due merely to sampling 

 errors. However, a simple test may be applied to Jacobj's data by 

 plotting his result on probability paper, in the manner described in a 

 recent paper by Harding.^ ^^ It is better to use the measured data for 



E 57 



