(ii.) Moreover, a very grave difficulty at once suggests itself, of which Professor Huxley makes no mention. The horse as we now have him, _Equus caballus_, is a native of the Old World, and has been introduced to America only since the time of Columbus. There had, it is true, been horses in America previously,--belonging to the genus _Equus_, perhaps even to the species _caballus_,--they had, however, been long extinct, and no memory of them remained. But, as will be noticed, the pedigree given by Professor Huxley consists almost entirely of American animals, to which category belong all whose names terminate in _-hippus_, and these cannot with any reason be assigned as progenitors to the European horse. As Sir J. W. Dawson observes:[281] In America a series of horse-like animals has been selected, beginning with the _Eohippus_ of the Eocene--an animal the size of a fox, and with four toes in front and three behind--and these have been marshalled as the ancestors of the fossil horses of America.... Yet all this is purely arbitrary, and dependent merely on a succession of genera more and more closely resembling the modern horse being procurable from successive Tertiary deposits often widely separated in time and place. In Europe, on the other hand, the ancestry of the horse has been traced back to _Palæotherium_--an entirely different form--by just as likely indications, the truth being that as the group to which the horse belongs culminated in the early Tertiary times, the animal has too many imaginary ancestors. Both genealogies can scarcely be true, and there is no actual proof of either. The existing American horses, which are of European origin, are, according to the theory, descendants of _Palæotherium_, not of _Eohippus_; but if we had not known this on historical evidence, there would have been nothing to prevent us from tracing them to the latter animal. This simple consideration alone is sufficient to show that such genealogies are not of the nature of scientific evidence. (iii.) Even apart from this fundamental difficulty, there is much diversity as to the precise genealogy. We may compare together the lines of ancestry favoured--(1) by Professor Huxley, (2) In a case exhibited in our Museum of Natural History to illustrate the subject, (3) By Mr. Mivart,[282] (4) By Mr. Lydekker,[283] (5) In The _Evolution of the Horse_, a pamphlet issued, January, 1903, by the American Museum. This last gives the very latest version of the pedigree, but, naturally, of the American Horse alone.