CELL SIZE AND NUCLEAR SIZE Ba 
readily determined since the nuclei undergo several divisions, 
though the cell body does not divide. 
From these measurements it may be concluded that when cell 
division takes place at regular intervals the Kernplasma-Relation 
is fairly constant; when it takes place at irregular intervals this 
ratio is variable. The longer the resting period the larger the 
nucleus becomes, and in extremely long resting periods the greater 
part of the plasma may be taken up into the nucleus. 
These observations are in full agreement with experiments on 
the eggs of Crepidula which will be described later. They are 
not antagonistic to Boveri’s conclusions as to the correlation be- 
tween chromosome number and nuclear size; on the other hand 
my own experiments show that the size of the nucleus is depend- 
ent, in part, upon the number of chromosomes which enter into 
its formation. But in normal cells all of which contain the same 
number of chromosomes differences in nuclear size must be due 
to some other factor. 
The results of my measurements do not indicate that the Kern- 
plasma-Relation of Hertwig is either a constant or self regulating 
ratio in the blastomeres of these eggs; on the other hand it appears 
to be a result rather than a cause of the rate of cell division, and 
consequently it is a variable rather than a constant factor. 
Furthermore the size of the nucleus, in these eggs, is dependent 
upon at least three factors: (1) The initial quantity of chromatin 
(number of chromosomes) which enter into the formation of the 
nucleus (Boveri). (2) The volume of the protoplasm in which 
the nucleus lies. (8) The length of the resting period. 
ITI. Cell size and nuclear size in adult tissue cells 
It is generally believed that embryonic cells differ greatly from 
adult tissue cells in their ‘““Kernplasma-Relation.’’ In a series of 
thoughtful and suggestive works Minot (90, ’95, ’08) has main- 
tained that differentiation, senescence and finally death are the 
accompaniments, if not the results, of an increase of protoplasm 
as compared with nucleus. It is well known that embryonic 
cells of plants are more purely protoplasmic than adult cells, 
