It is not proposed to attempt here to give rules for the exercise of the breeder’s art. The principles of breeding are very much the same in every case. It is, above all, imperative—and especially in the selection of sires—to insist on soundness and vigour of constitution; and this becomes the more imperative the more we shelter the progeny of our stock from the rigour of natural selection, and from such severe tests of endurance as are imposed on race-horses. We have seen how closely inbred the leading families of Shetland ponies are; and, while it is wholly a mistake to suppose that this necessarily causes enfeeblement or unsoundness, yet it is an additional reason for exercising the greatest care in excluding these fatal taints. In Shetland ponies also, as in other races of animals, the actual excellence of an individual is not a sufficient reason for expecting corresponding excellence in its progeny. Heredity is an element at least as important as good individual quality in the selection of sires and dams; and heredity itself—so complex are the elements that compose it—is a test of merit far less valuable and complete than the previous progeny of the animals to be bred from. Mating the best with the best, and breeding from long lines of fine pedigree, are both venerated rules; but the breeder who is fortunate enough to obtain animals already proved to be successful in their offspring has a surer ground than such rules give for expecting good results. It remains only that he should discover, by careful study and close consideration, with what type and heredity the animal he is about to breed from has been most usefully mated; and he may then hope to produce some proportion of stock approximating to the type he desires to embody. But he must, above all things, have a clear idea of what it is that he aims at creating or reproducing, not necessarily an idea to remain unaltered by experience and criticism, but yet a view and an aim independent of changes of fashion and of the varying fortunes of the showyard. Nothing but failure in breeding can result when a dominating purpose of this kind is absent. The present-day breeder of Shetland ponies is neglecting to use the chief instrument ready to his hand if he fails to take great advantage of the admirable material created in and descended from the Londonderry Stud; and he ought specially to remember the value of the combination of Odin and Prince of Thule blood, which has already been referred to. But he ought not to make this his only source. The Islands still contain animals and strains well fitted to be a strength to the breed; and one of the most interesting parts of a breeder’s work consists in the careful and gradual introduction of these outside strains of blood.