breeding
and selection can produce any further advance. The race-horse is chosen
as an example. It is admitted that, with any ordinary lot of horses to
begin with, careful selection would in a few years make a great
improvement, and in a comparatively short time the standard of our best
racers might be reached. But that standard has not for many years been
materially raised, although unlimited wealth and energy are expended in
the attempt. This is held to prove that there are definite limits to
variation in any special direction, and that we have no reason to
suppose that mere time, and the selective process being carried on by
natural law, could make any material difference. But the writer does not
perceive that this argument fails to meet the real question, which is,
not whether indefinite and unlimited change in any or all directions is
possible, but whether such differences as do occur in nature could have
been produced by the accumulation of variations by selection. In the
matter of speed, a limit of a definite kind as regards land animals does
exist in nature. All the swiftest animals--deer, antelopes, hares,
foxes, lions, leopards, horses, zebras, and many others, have reached
very nearly the same degree of speed. Although the swiftest of each must
have been for ages preserved, and the slowest must have perished, we
have no reason to believe there is any advance of speed. The possible
limit under existing conditions, and perhaps under possible terrestrial
conditions, has been long ago reached. In cases, however, where this
limit had not been so nearly reached as in the horse, we have been
enabled to make a more marked advance and to produce a greater
difference of form. The wild dog is an animal that hunts much in
company, and trusts more to endurance than to speed. Man has produced
the greyhound, which differs much more from the wolf or the dingo than
the racer does from the wild Arabian. Domestic dogs, again, have varied
more in size and in form than the whole family of Canidae in a state of
nature. No wild dog, fox, or wolf, is either so small as some of the
smallest terriers and spaniels, or so large as the largest varieties of
hound or Newfoundland dog. And, certainly, no two wild animals of the
family differ so widely in form and proportions as the Chinese pug and
the Italian greyhound, or the bulldog and the common greyhound. The
known range of variation is, therefore, more than enough for the
derivation of