the common domestic cattle, as well as with one another. Perhaps all or
nearly all of the dozen or more "species" of the genus _Bos_ would thus
be included together. All of the dogs, wolves, and others of the
_Canidæ_ might thus be considered as fundamentally a unit. The cats
(_Felidæ_) are well known to breed freely together, Karl Hagënbeck of
Hamburg having crossed lions and tigers as well as others of the family.
Practically all of the bears have been crossed repeatedly, and the
progeny of these and other crosses are quite familiar sights at the
London Zoölogical Gardens. Among the lower forms of life even more
surprising results have been attained by Thomas Hunt Morgan and others.

[Footnote 16: "Mammals Living and Extinct," pp. 284-285.]

It would, however, be a very hasty conclusion to say on the basis of
these facts that there are no natural limitations to groups of animals
and plants. But we are entirely warranted in concluding from these facts
that in very many cases, perhaps in most, our system of taxonomic
classification of animals and plants has gone altogether too far, and
that scientists have erected specific distinctions which are wholly
uncalled for and which confuse and obscure the main issues of the
species problem. Among the workers in botany and in every department of
zoölogy there have always been the "splitters" and the "lumpers," as
they are familiarly called; the former insisting on the most minute
distinctions between their "species," thus multiplying them; the latter
being more liberal and tending to diminish the number of species in any
given group. For a generation or more in the recent past the "splitters"
had things pretty much their own way; but of late there is a growing
tendency to frown down the mania for creating new names. Even yet it is
with the utmost reluctance that long established specific distinctions
are surrendered, as is illustrated in the case of the mammoth, which is