632 Wisconsin Academy of Sciences, Arts, and Letters. 
In a recent paper on “Racial Variations in Plants and Ani¬ 
mals with special reference to the Violets of Philadelphia and 
Vicinity/’ Witmer Stone says: “In birds and mammals the 
individual variation in size, after making due allowance for 
age and sex, is exceedingly slight, and the same may he said of 
color, provided the additional allowance for season is made, so 
that very slight differences in measurements or in shades of 
color, which might appear trivial, are really constant and per¬ 
fectly reliable as indications of the differentiation of a distinct 
form.” Pro. Acad, of Natl. Sci. of Philadelphia, Oct. 1903, 
p. 658. The italics are mine. 
The general truth of this statement I do not wish to dispute, 
hut it is a question whether zoologists possess sufficient data to 
enable them to determine the extent of these “very slight dif¬ 
ferences” in many species or groups of mammals; in other 
words, whether the range of individual variation in measure¬ 
ments has been sufficiently exactly determined for practical 
application. At all events any additional data, such as is here¬ 
with presented, can only serve as a farther aid towards the 
clearing up of this point which, to the best of my knowledge, 
requires still farther elucidation. 
The exact amount of variation in the measurement of any 
member in any of the species of bats here tabulated is readily 
obtained at the left margin of the tables. 
How near my localities represent the centers of habitat of the 
different species I am unable to say; though from the large 
numbers of some of the species resident in the localities where 
collections were made the presumption is that they were well 
within their proper territory. 
In order to facilitate comparisons between the different mem¬ 
bers of any individual or the measurements of any member 
between the different individuals of the same species, I have 
graphically plotted them in the manner I think best adapted for 
this purpose. Reading down from any individual, as noted by 
number and sex at the top of the diagram, we find in succession 
the measurements of the different parts, each of which can be 
read in millimeters by referring to the left margin where is 
noted the scale in millimeters for each member. 
At the right of the diagram showing the measurements of 
any member in all of the individuals of a species is a binomial 
curve which shows the number of individuals having a given 
