Shinkishi Hatai 429 
the variation in the character under consideration. Therefore the greater 
values obtained for the male means simply that the characters in question 
vary more in the male than in the female. 
The absolute value of the standard deviation is widely different 
throughout the table. This is due to the fact that in these cases the 
standard deviation is a concrete number and therefore the variabilities 
can not be directly compared with one another since the magnitude of 
the characters as well as the unit taken for grouping is never the same. 
The coefficient of variation, however, enables us to compare the relative 
amount of variability of the characters measured in different units since 
it is one hundred times the quotient of the standard deviation divided by 
the means. From Table I it was found that the values of the coefficients 
of variation in the male are always greater than that in the female, except 
in the case of the squamosal distance in which the reverse is true." Here 
also the length of the nasal bone shows the greatest variation and the 
zygomatic width comes next while the least variation is found in the 
width of the cranium. Brewster, 97, also noticed a greater variation in 
both the length of the nasal bones and zygomatic width than in any 
other measurements made on the different parts of the skull. His studies 
were made on the lynx (Lynx canadensis) ; cat (Felis domesticus) ; and 
red fox (Vulpes fulvis). The methods employed by Brewster for deter- 
mining his coefficients of variation are so different from those used in the 
present investigation that two sets of figures can not be directly com- 
pared. Except the length of the cranium, the remaining characters tend 
to show the existence of a sexual difference as to the relative variability, 
that is the male tends to vary more than in the female. 
The mean values obtained from the cranial capacity, body-weight, and 
cube root of the product of the height, length and width of the cranium 
are also greater in the male than in the female. The standard deviations 
as well as the coefficients of variation indicates a relation similar to that 
found in the skull measurements, that is, the male tends to show in these 
characters a greater variability than the female. 
(c) Coefficients of variation in man and rat.—The following table was 
compiled in order to show the variation in the human skull as compared 
with that for the skull of the albino rat: 
1Slightly greater variability in the female is also found in the cranial 
capacity, nevertheless the result is insignificant owing to the greater probable 
errors in this case. 
