156 Bulletin American Museum of Natural History. [Vol. XXXIV, 
forms. This change of view at first made headway slowly abroad, but in 
the course of a few decades came to be almost universally accepted, finally 
taking form as a principle of nomenclature in all modern zodlogical codes. 
But these discoveries were, for a time, not unmixed with evil in their 
results, especially with respect to mammals, where so many points have to 
be considered, and where in general, until near the close of the nineteenth 
century, the amount of material from outside of the temperate portions of 
North America was very small and very defective in quality. In the case 
of the smaller, and especially the exotic, species, as late as 1877, the skulls 
were often left in the skins, there were rarely any trustworthy measurements, 
dates of collecting were often omitted, and the localities given were usually 
more or less indefinite. Mexico, Central America, New Granada, Brazil, 
South America, written on the label, gave no very definite clew to the actual 
locality and environment of the specimen. Such was the state of affairs 
when, at the height of the lumping craze in 1877, I ventured to publish my 
“Monograph of the American Sciuride.’ A system that worked well where 
material was fairly adequate proved, as already shown, woefully inade- 
quate when applied to little known faunal areas, like the American tropics. 
The viewpoint of 1878 is well indicated in the following extracts from the 
introduction to Mr. Alston’s paper ‘On the Squirrels of the Neotropical 
Region.’ He says: “No better example of a polymorphic genus can be 
found than the almost cosmopolitan Sciurus. Even our common European 
Squirrel assumes such phases of coloration in the north, in the east, and 
among the Alps that the extremes would undoubtedly be considered per- 
fectly distinct species if the intermediate links were not known.... 1 
“In facing the intricate and often baffling problem of distinguishing 
between ‘species’ and ‘ varieties’ in such a protean group, I have endeavored 
to act in harmony with Mr. Darwin’s directions: ‘When a naturalist can 
unite by means of intermediate links any two forms, he treats the one as a 
variety of the other.’ It must be remembered that many of these ‘ varieties’ 
apparently breed true and prevail in certain parts of the range; but all that 
are here brought together are united by such intergradations that a sufficient 
series at once convinces one of their identity. It is evident, however, that 
still more complete material will be required before every point can be 
regarded as definitely settled.””— Proc. Zool. Soc. London, 1878, pp. 656, 
658. : 
The viewpoint of twenty years later (1898) may be illustrated by Mr. 
KE. W. Nelson’s ‘Revision of the Squirrels of Mexico and Central America,’ 
1In 1912 Mr. Gerrit S. Miller, Jr., in his ‘Mammals of Western Europe’ (pp. 898-923) 
found it desirable to recognize 12 subspecies of the European Squirrel from western and 
central Europe. 
