334 CHI PING 
The smaller size of the cells in the inbreds and Norways is 
not related to pigmentation, for the inbreds with the smaller 
cells are not pigmented. It is not due to domestication, for 
both the standards and inbreds are domesticated. 
It would appear therefore to be a characteristic of this inbred 
strain, but without further evidence it cannot be said to be due 
to inbreeding. 
Since the differences according to strain are mainly in the cell, 
the nucleus-plasma ratios show the same relations as do the 
cell diameters, and the most striking feature is the small value. 
TABLE 13 
Giving the diameters and nucleus-plasma ratios of the standard, inbred and Norway 
rats according to body weight, based on previous tables. In each instance the 
values given are for the two sexes combined 
DIAMETERS 
STRAIN BODY WEIGHT piesa: 
Cells Nucleus 
grams Le M 
Stancarc seer ee 145 28.9 tee Ts (925 
Imbnedie <.nkensoe 144 24.5 13.2 Pp 534 
INOTwiiyeceee cece 146 28.0 1335 1b Sas 
Standard. f\\.0 <0. 200 34.1 (14.5 esdiead 
lhilomteclSkeaoe wooo 206 25.4 3.33 ts &8 
INOGWaynecnteie acre 203 28.0 Teel iTepctn cones 
for the ratios in the inbreds. The data for the heavier body 
weights show that in this group these cells in the inbreds have 
only half the volume of those in the standards. 
Perhaps the point of most general interest which is thus brought 
out is the plasticity or variability in the size of this group of 
cells according to strain. 
F. The rate of the formation of large from small cells 
As table 6 (Ping, ’21) shows, in the standards the number of 
large and advanced cells increases about thirteen-fold from one 
to twenty days. On the other hand, table 8 of this paper indi- 
