"New breeds of sheep are frequently formed in different countries in which particular qualities predominate, according to the preference of the breeders. This is done, partly by crossing or intermixing races already constituted and well known; but in great part also by selecting individuals from the stock in which the particular qualities are more strongly marked than in the generality of the same breed. In these instances, the natural or congenital variety which the individual animal displays, perhaps for the first time, becomes perpetuated by the hereditary transmission of such characters, which is a law of the animal economy. A striking instance of this fact is to be found in the origination of a new breed of sheep in the state of Massachusetts, which has been noticed by many writers in connexion with this subject. In the year 1791, one ewe on the farm of Seth Wright gave birth to a male lamb, which, without any known cause, had a longer body and shorter legs than the rest of the breed. The joints are said to have been longer, and the fore-legs crooked. The shape of this animal rendering it unable to leap over fences, it was determined to propagate its peculiarities, and the experiment proved successful; a new race of sheep was produced, which, from the form of the body, has been termed the otter breed. It seems to be uniformly the fact, that when both parents are of the otter breed, the lambs that are produced inherit the peculiar form." We might extract other instances of physiological and psychological changes induced by domestication, but we think enough have been given to show the character and degree of such changes. The least important change, and that which appears the soonest affected, is the colour of the skin and hair. This is universally of an uniform tint in wild animals, and generally bears a close approximation to the colour of the land in which the animal lives: thus the ptarmigan, inhabiting snowy regions, is white; the grouse has the colour of heath; the hare that of dry fern or furze--a provision which has the effect of protecting the weaker tribes from the stronger and predatory ones. In domesticated animals, from causes apparently not as yet traced, the colour is variegated and various. Closely connected with the colour and nature of the skin, are the size and shape of the horns, their presence and absence. Great as is the apparent variety of appearance effected by horns, changes in these appear to be easily induced: they are connected with the epidermic structure, generally the most easily modified; and we need not cite instances to prove that different breeds of the same tribe, and occasionally different individuals of the same breed, differ materially as to horns. According to Azara, horned horses are sometimes seen in Paraguay.