The results of unconscious selection, in an early stage, are well shown in the difference between the flocks descended from the same stock, but separately reared by careful breeders. Youatt gives an excellent instance of this fact in the sheep belonging to Messrs. Buckley and Burgess, which "have been purely bred from the original stock of Mr. Bakewell for upwards of fifty years. There is not a suspicion existing in the mind of any one at all acquainted with the subject that the owner of either flock has deviated in any one instance from the pure blood of Mr. Bakewell's flock; yet the difference between the sheep possessed by these two gentlemen is so great, that they have the appearance of being quite different varieties."[517] I have seen several analogous and {214} well-marked cases with pigeons: for instance, I had a family of barbs, descended from those long bred by Sir J. Sebright, and another family long bred by another fancier, and the two families plainly differed from each other. Nathusius--and a more competent witness could not be cited--observes that, though the Shorthorns are remarkably uniform inn appearance (except in colouring), yet that the individual character and wishes of each breeder become impressed on his cattle, so that different herds differ slightly from each other.[518] The Hereford cattle assumed their present well-marked character soon after the year 1769, through careful selection by Mr. Tomkins,[519] and the breed has lately split into two strains--one strain having a white face, and differing slightly, it is said,[520] in some other points; but there is no reason to believe that this split, the origin of which is unknown, was intentionally made; it may with much more probability be attributed to different breeders having attended to different points. So again, the Berkshire breed of swine in the year 1810 had greatly changed from what it had been in 1780; and since 1810 at least two distinct sub-breeds have borne this same name.[521] When we bear in mind how rapidly all animals increase, and that some must be annually slaughtered and some saved for breeding, then, if the same breeder during a long course of years deliberately settles which shall be saved and which shall be killed, it is almost inevitable that his individual frame of mind will influence the character of his stock, without his having had any intention to modify the breed or form a new strain.