By the mixture of the mule with the mare, of the bardeau with the she-ass, and the horse and he-ass with she mules, we should obtain individuals which would ascend towards the original species; they would be only half mules, and, like their parents, would not only have power to engender with their primitive species, but perhaps have the faculty of propagating among themselves; for being but half debased, their production would not be more vitiated than the first mules; and if the union of these half mules were sterile, or their productions rare, it appears almost certain, that by bringing them a degree still nearer their original species, the individuals which would result from such a union, and which would be no more than a fourth part debased, would produce among themselves and form a new stem, which would be precisely neither that of the horse nor the ass. Now as every thing possible has been accomplished in time, and either does exist, or has existed in Nature, I am inclined to think that the prolific mule spoken of by the ancients, and which in the days of Aristotle existed in Syria, beyond Phoenicia, might be a race of these half or quarter mules, which have been produced by the commixtures here spoken of: for Aristotle expressly says, that these prolific mules perfectly resembled the barren mules. He also very clearly distinguishes them from the onagres, or wild asses, which he mentions in the same chapter: consequently we can only refer these animals to mules which were but little vitiated, and preserved their reproductive faculties. The _czigithai_, or prolific mule of Tartary, of which we have before spoken, may also possibly not be the onagre, or the wild ass, but only this Phoenician mule, the race of which perhaps still remains. The first traveller who is able to compare them, will confirm or destroy this conjecture. The zebra itself, which even bears a greater resemblance to the horse than the ass, might probably have the same origin; the constrained regularity of his colours, alternately disposed in black and white stripes, seems to indicate that they proceed from two different species, which in their mixture have separated as much as possible; for Nature, in none of her works, is so abrupt, or so little shaded as on the coat of the zebra, where it suddenly and alternately changes from white to black, and from black to white, without any intermediate shade throughout the whole extent of the animal's body.