Shinkishi Hatai 4.37 
standard taken. This is due to the fact, as Tables [V.-VIII show, that 
the correlations is higher in male in some cases and in female in others. 
Five out of seven, characters in the male are absolutely greater than those 
in female even when the length of the entire skull in two sexes is equated. 
However the differences are too small to be significant, except in the case 
of the length of the nasal bone and perhaps the zygomatic width. The 
nasal bone is significantly longer in the male while the zygomatic width 
is slightly greater in the female. On the other hand if we equate the 
TABLE X. 
Probable values of male characters with Probable values of female characters with 
mean skull length equal to that of the mean skull length equal to that of the 
observed female. | observed male. 
| Ob- | Prob- Differ-| Differ-| Prob-| ob- | 
CS aa No. | served| able | ence | ence | able |served Characters and No. 
1i0ns. | | i 
q 9 al | 4, Ole ees, of equations. 
Fronto-occipital | Fronto-occipital 
length. 26.37 | 26.36 07 | —.89 | 27.51 | 27.26 length. 
af | as 
Squamosal distance. | 15.06 | 15.09  —.19 | 30 | 15.23 | 15.27 | Squamosal distance. 
IND | TAY 
Height of skull. 11.14 | 11.21 —.67 || 1.69 | 11.30 | 11.49 Height of skull. 
Vis | | Wale 
Length of nasal bone. | 15.69 16.12  —2.64 1.81 | 16.65 | 16.96 | Length of nasal bone. 
WAGE | | WITT: 
Cranial capacity. 10.37 | 10.42 —.50 | of =6| «610.86 | 10.90 Cranial capacity. 
Exes | aXe: 
Zygomatie width. 20.93 | 20.68 117 | —.80 | 21.92 | 21.75 Zygomatiec width. 
axel | XII. 
(Height x length (Height X length 
x width). 16.43 16.43 —.06 .53 | 16.79 | 16.88 x width)’. 
XIII. | | | | | XIV. 
- length of the female skull to that of the male then the greatest diflerence 
is noticed in the length of the nasal bone also and the height of the skull 
comes next. Besides these two the remaining characters give differences 
which are always less than 1 per cent. Taking all the results together, 
we reach to the conclusion that aside from the nasal bone, and perhaps 
the zygomatic width and height of skull too, the actual sexual differences 
in the remaining characters are inconsiderable, being less than 1 per cent. 
This suggests that the nasal bone in the rat may be considered as one of 
the secondary sexual characters. Consequently the female skull can not 
be considered as an undersized male skull nor the male skull an overgrown 
