La familia del mulo en el párrafo quingentésimo decimotercero de El Origen de las Especies
Inconcebiblemente el autor salta de plantas a animales y expone la genealogía de los híbridos de burro y caballo de manera intempestiva…. Ahorraremos en metáforas por ahora. 513 These several remarks are apparently applicable to animals; but the subject is here much complicated, partly owing to the existence of secondary sexual characters; but more especially owing to prepotency in transmitting likeness running more strongly in one sex than in the other, both when one species is crossed with…