To inbreed them there is only one plan. Select your very best stallion and put him to a certain number of mares, and then put all the good fillies when three years old to their father; also, select your very best mare and put her to another stallion, and go on breeding from her to the same stallion until you have a colt, then put that colt to his mother, and use the produce to breed from with the produce obtained by putting the fillies above mentioned to their father.” A better plan for fixing the size could hardly be imagined. If followed for some years the size of the bones and muscles would doubtless be so effectively stereotyped that, however much their “memory” was jogged by “fresh fields and pastures new,” there would be little or no response. Although close in-and-in breeding was undoubtedly practised, the Shetland Pony Stud-Book indicates that the advice of the originator of the “Sir George” strain of hackney ponies was not literally followed. _The Ancestors of the Shetland Pony._—From pigmy horses it seems but a step to the little “fossil” horses of bygone days. It is hence not surprising that many are led to inquire to which particular branch of the equine family tree the Shetland pony belongs. Not many years ago it was said the horse tribe was at the start represented by a primitive race about the size of a fox but with as many hoofs as a tapir—four in front and three behind,—that in course of time a new race arose (with three hoofs in front as well as behind) which eventually gave rise to the one-toed ancestor of all the living Equidæ. Now, however, we know that in Eocene times there were several kinds or species of four-toed “horses” from which were derived, in the Oligocene and Miocene periods, numerous three-toed species, some of them doomed to early extinction, others to bring forth one-toed races which in due time produced the ancestors of the modern horses, asses, and zebras. Hence it is now admitted that, in the past as in the present, the horse tribe was always represented by several species, not a few of which at times occupied the same area. It is also now admitted that the modern domestic breeds include several wild prehistoric species among their ancestors. Is it possible to say which of the wild horses of prehistoric times contributed to the making of the Shetland pony? To be in a position to hazard an answer to this question it will be necessary to refer to the more important links which are believed to connect modern breeds with _Hyracotherium_, generally regarded as the remote polydactylous ancestor of the horse family.