Iceland, (_fig. 140._) have sometimes even eight. In hot countries the rams have only two very short horns, and often are deficient of them as well as the ewes. In some the horns are smooth and round, in others they are furrowed and flat, and the points instead of turning back, are often bent and come forward, &c. This character, therefore, is not more constant than the first, and consequently, not sufficient to constitute a different species; the largeness of the tail has also been considered, by some naturalists, as an essential distinction, and from the difference in the size of that, the wool, and the horns, they have made seven or eight different species of these animals, which we have reduced to one; and this reduction appears to be so well founded, that we are not afraid of its being contradicted by future observation. It appeared necessary in composing the History of Wild Animals, to consider them one by one, and independently of genus; but on the contrary, in domestic animals, it appears requisite even to extend the genera; because, in Nature, there only exists individuals, and succession of individuals, that is, species. Men have had no influence on independent animals, but they have greatly altered, modified, and changed domestic ones; therefore, we have made physical and real generas, greatly different from metaphysical and arbitrary ones, which have never existed but in idea. These physical genera, are in reality composed of all the species, which by our management have been modified and changed, and as all these species so differently altered by the hand of man, have but one common and simple origin in nature, the whole genus ought to form but one species. For example, in writing the history of tigers, we have admitted as many species as are found in all the different parts of the world, because, we are certain that man has never subjected, nor changed the species of those untractable animals, which subsist at present such as Nature produced them. It is the same with all other free and independent animals. But in composing the history of oxen and sheep, we have reduced all the first under the species of a single ox; and the latter under that of a single sheep, because, it is also certain, that man, and not Nature, has produced the different kinds which we have enumerated. Every thing concurs to support this idea, which, although clear in itself, may not, perhaps, be sufficiently understood. That all the different oxen produce together, we have demonstrated by the experience of M. de la Nux, and the testimonies of Messrs. Mentzelius and Kalm; that the sheep also produce with one another, with the muflon, and even with the he-goat; I know from my own experience. All the different kinds of oxen, therefore, are no more than one species, and all the sheep but another, however extended the genus of both may be.