10 Proceedings of Royal Society of Edinburgh. [sess. 
made to determine from which of the ancestral forms the various 
domesticated breeds have inherited their more striking characters, 
i.e. to ascertain to which ancestral types the Shire, Clydesdale, 
Percheron, and other heavy breeds, the Barb, Arab, Thoroughbred, 
Kattiawar, and other slender-limbed breeds, are indebted for their 
chief peculiarities. 
In this paper I shall not attempt to show that either Prejvalsky’s 
horse, the Celtic pony, or the Libyan variety recently described 
by Professor Bidgeway 1 is genetically related to pre-glacial species, 
or entitled to be regarded as an ancestor of one or more domestic 
breeds. 
Sufficient data for a discussion of this kind is not yet available. 
1 propose now, by way of clearing the ground for the investiga- 
tions mentioned above, to enquire whether the Tarpan (long 
regarded as the wild progenitor of the common horse of Europe) 
deserves a place amongst the ancestors of living races and breeds. 
Up to a certain period the only horses in Europe were wild 
horses ; but in course of time the horse was domesticated and 
utilised for various purposes, and, as one area after another was 
settled, the districts suitable for herds of wild horses became 
gradually circumscribed, with the result that except in the wild 
wastes of the Gobi Desert and in the vicinity of the Great Altai 
Mountains true wild horses no longer exist. 
Where, and by whom, horses were first domesticated will prob- 
ably never be known ; but this much is certain that in Europe, and 
doubtless also in Asia, tame horses from time to time ran wild, 
either to join wild herds, or to give rise to feral herds, such as 
were once common in America. 
Had all domestic breeds sprung from a single wild ancestor, the 
individuals which ran wild would have been rapidly reabsorbed 
without in any way modifying the original wild stock — as tame 
rabbits are rapidly reabsorbed by the common wild rabbit. If, 
however, the escaped individuals had sprung from several perfectly 
distinct species, the result would be that, in addition to pure wild 
herds, one might have come across herds having a distinct infusion 
of tame blood, and also herds consisting of the mixed offspring 
of several domestipated breeds. 
1 Origin and Influence of the Thoroughbred Horse, Cambridge, 1905. 
