veloped lateral hoofs in
the broader foot of palaeotherium.

Other missing links of this series of species have also been supplied.

How then is the origin of these intermediate gradations to be
interpreted? If the alternative--species by miracle or by law--be
applied to palaeotherium, paloplotherium, anchitherium, hipparion, equus,
I accept the latter without misgiving, and recognise such law as
continuously operative throughout tertiary time.

In respect to its law of operation we may suppose Lamarck to say, "as
the surface of the earth consolidated, the larger and more produced
mid-hoof of the old three-toed pachyderius took a greater share in
sustaining the animal's weight; and more blood being required to meet
the greater demand of the more active mid-toe, it grew; whilst, the
side-toes, losing their share of nourishment and becoming more and more
withdrawn from use, shrank"--and so on. Mr. Darwin, I conceive, would
modify this by saying that some individuals of palaeotherium happening to
be born with a larger and longer middle toe, and with shorter and
smaller side-toes, such variety was better adapted to prevailing altered
conditions of the earth's surface than the parental form; and so on,
until finally the extreme equine modifications of foot came to be
"naturally selected." But the hypothesis of appetency and volition, as
of natural selection, are less applicable, less intelligible, in
connection with the changes in the teeth.

I must further observe that to say the palaeotherium has graduated into
equus by "natural selection" is an explanation of the process of the
same kind and value as that by which the secretion of bile was
attributed to the "appetency" of the liver for the elements of bile.
One's surprise is that such explanatory devices should not have died out
with the "archeus faber," the "nisus formations," and other
self-deceiving, world-beguiling simulacra of science, with the last
century; and that a resuscitation should have had any success in the
present.

What, then, are the facts on which any reasonable or intelligible
conception can be formed of the mode of operation of the derivative law
exemplified in the series linking on palaeotherium to equus? A very
significant one is the following. A modern horse occasionally comes into
the world with the supplementary ancestral hoofs. From Valerius Maximus,
who attributes the variety to Bucephalus downwards, such "polydactyle"
horses have been no