148 Francis B. Sumner 
greater, since the northern animals are of larger size. Indeed, the 
authors cited dwell with equal emphasis upon the Jarger size of 
the northern representatives (individuals or varieties) of species, 
both of birds and mammals, as compared with the’ southern. 
Previously, Allen tells us, Baird had “explicitly announced a 
general law of geographical variation in size; namely a gradual 
decrease in size in individuals of the same species with the decrease 
in the latitude and altitude of their birthplaces.*® And Allen 
further affirms that “this is true not only of the individual repre- 
sentatives of each species, but generally the largest species of eacn 
genus and family are northern.‘ 
The foregoing statements were made before the days of exact 
biometry, and an examination of the tables of measurements 
offered us shows that in most cases they comprise relatively few 
individuals and that the material used was not homogeneous, 
i. e., it includes alcoholic and fresh specimens, as well as dried 
skins. For this reason most of these tables are not likely to be 
of very great use to the modern student of variation. In more 
recent years, a very extensive mass of similar measurements has 
been gathered by a considerable number of naturalists, but, so 
far as the writer has been able to discover few if any of these have 
been subjected to statistical treatment with reference to testing 
the generalizations of Baird, Allen and Coues.*! It would seem 
overskeptical, however, to reject the emphatic opinions of a num- 
ber of able naturalists upon these matters, particularly as we have 
no more satisfactory data at our disposal. 
Regarding the pelage, there can be little doubt that this likewise 
responds directly or indirectly to climatic conditions. “At the 
northward, in individuals of the same species, the hairs are longer 
and softer, the under fur more abundant, and the ears and the 
soles of the feet better clothed. This is not only true of individ- 
uals of the same species, but of northern species collectively, as 
compared with their nearest southern allies.”*? Both Coues 
39 Op. cit., 1871, p. 230. 
40 1905, p. 378. 
417 state this on the authority of several of our leading students of mammalian distribution to 
whom I have appealed for information. 
# Allen, 1905, p. 382. 
