CHAPTER XI 

 SIZE OF NUCLEUS 



T^\ata upon the modifications of size of various por- 

 ■*-^ tions of the unicellular body are, in the nature of 

 the organisms, very few. For that reason this chapter 

 will include nothing upon the less visibly differentiated 

 kinds such as bacteria and yeasts. Some of the studies 

 which have been already reviewed contained informa- 

 tion upon the variability and growth of the several 

 dimensions of the body. But, morphologically speak- 

 ing, almost the only distinct region or portion of the 

 body which has received study is the nucleus. 



1. Some Internal Factors 



It was a natural expectation, supported by general 

 observation, that various intracellular structures are 

 proportionate in bulk to the whole body. The analogy 

 of these structures to the organs of the metazoan body 

 made this assumption more than gratuitous. But it 

 could be tested only by actual measurements. Two 

 questions had to be investigated; first, did such pro- 

 portionality hold within a species, and second, did it 

 hold upon comparing different species? 



Relative size. The first measurements of nuclei 

 and of the bodies to which they belonged were made 

 upon a wild population of Paramecium by Hertwig 

 ('89). He ascertained upon each individual the two 

 linear dimensions, length and breadth; and drew the 

 conclusions that length and breadth varied in propor- 

 tion to one another. He gathered that each of the two 

 dimensions was correlated between the body and its 

 nucleus. When the relative volumes are calculated 



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