"Empedocles held that the first generations of animals and plants were not complete but consisted of separate limbs not joined together; the second, arising from the joining of these limbs, were like creatures in dreams; the third was the generation of whole-natured forms; and the fourth arose no longer from the homogeneous substances such as earth or water, but by intermingling, in some cases as the result of the condensation of their nurishment, in others because feminine beauty excited the sexual urge; and the various species of animals were distinguished by the quality of the mixture in them..."