But variation gives us only half the elements of the ultimate problem, even in the case of domestic kinds. For the other half, we must have recourse to human selection, which, by picking out for seed or breeding purposes certain specially favoured varieties, has produced at last all the purposive or intentional diversity between the different existing stocks or breeds. In these artificially produced domestic races we see everywhere special adaptations to man's particular use or fancy. The dray-horse has been fashioned for purposes of strength and sure-footedness in draught, the race-horse for purposes of fleetness in running. In the fox-hound, man has encouraged the special properties that tend to produce a good day's hunting; in the sheepdog, those that make for the better maintenance and safety of a herd. The cauliflower is a cabbage, with specialised and somewhat abortive flower-heads; the fuller's teasel is a sport of the wild form, with curved hooks specially adapted by a freak of nature for the teasing of wool. So in every case man, by deliberately picking out for breeding or seeding purposes the accidental variations which happened best to suit his own needs, has succeeded at last in producing races admirably fitted in the minutest particulars for the special functions to which they are applied. There appears indeed to be hardly any limit to the almost infinite plasticity and modifiability of domestic animals. 'It would seem,' said a great sheep-breeder, speaking of sheep, 'as if farmers had chalked out upon a wall a form perfect in itself, and then proceeded to give it existence.'