xley will always be associated, is the most familiar of all
the instances taken from fossils in support of the evolution of
animals. This famous case is the pedigree of the horse. In 1870, in an
address delivered to the Geological Society of London, Huxley had
shewn that there was a series of animals leading backwards from the
modern horse to a more generalised creature called Anchitherium, and
found in the rocks of the Miocene period. He suggested that there
were, no doubt, similar fossils leading still further backwards
towards the common mammalian type of animal, with five fingers and
five toes, and went the length of suggesting one or two fossils which
might stand in the direct line of ancestry. But in 1876 he visited
America, and had the opportunity of consulting the marvellous series
of fossils which Professor Marsh had collected from American Tertiary
beds. Professor Marsh allowed him the freest use of his materials and
of his conclusions, and the credit of the final result is to be
shared at least equally between Marsh and Huxley. The final result was
a demonstrative proof of the possible course of evolution of the
horse, given in a lecture delivered by Huxley in New York on Sept. 22,
1876, and illustrated by drawings from specimens in Marsh's
collection. The matter of the lecture has become so important a part
of all descriptive writing on evolution, and the treatment is so
characteristic of Huxley's brilliant exposition, that it is worth
while to make some rather long quotations from it. The lecture was
published in the New York papers, and afterwards with other matter
formed a volume of _American Addresses_, published by Macmillan, in
London.

"In most quadrupeds, as in ourselves, the forearm contains
distinct bones called the radius and the ulna. The corresponding
region in the horse seems at first to possess but one bone.
Careful observation, however, enables us to distinguish in this
bone a part which clearly answers to the upper end of the ulna.
This is closely united with the chief mass of the bone which
represents the radius, and runs out into a slender shaft which
may be traced for some distance downwards on the back of the
radius, and then in most cases thins out and vanishes. It takes
still more trouble to make sure of what is nevertheless the fact,
that a small part of the lower end of the bone of the horse's
forearm, which is only distinc