Anaximander's opinion is, that the first animals were generated in moisture, and were enclosed in bark on which thorns grew; but in process of time they came upon dry land, and this thorny bark with which they were covered being broken, they lived only for a short space of time. Empedocles says, that the first generation of animals and plants was by no means completed, for the parts were disjoined and would not admit of a union; the second preparation and for their being generated was when their parts were united and appeared in the form of images; the third preparation for generation was when their parts mutually amongst themselves gave a being to one another; the fourth, when there was no longer a mixture of like elements (as earth and water), but a union of animals among themselves,--in some the nourishment being made dense, in others female beauty provoking a desire of spermatic motion. All sorts of animals are discriminated by their proper temperament and constitution; some are carried by a proper appetite and inclination to water, some, which partake of a more fiery quality, to live in the air those that are heavier incline to the earth; but those animals whose parts are of a just temperament are fitted equally for all places. CHAPTER XX. HOW MANY SPECIES OF ANIMALS THERE ARE, AND WHETHER ALL ANIMALS HAVE THE ENDOWMENTS OF SENSE AND REASON. There is a certain treatise of Aristotle, in which animals are distributed into four kinds, terrestrial, aqueous, fowl, and heavenly; and he calls the stars and the world too animals, yea, and God himself he posits to be an animal gifted with reason and immortal. Democritus and Epicurus consider all animals rational which have their residence in the heavens. Anaxagoras says that animals have only that reason which is operative, but not that which is passive, which is justly styled the interpreter of the mind, and is like the mind itself. Pythagoras and Plato, that the souls of all those who are styled brutes are rational; but by the evil constitution of their bodies, and because they have a want of a discoursive faculty, they do not conduct themselves rationally. This is manifested in apes and dogs, which have inarticulate voice but not speech. Diogenes, that this sort of animals are partakers of intelligence and air, but by reason of the density in some parts of them, and by the superfluity of moisture in others, they neither enjoy understanding nor sense; but they are affected as madmen are, the commanding rational part being defectuous and injured. CHAPTER XXI. WHAT TIME IS REQUIRED TO SHAPE THE PARTS OF ANIMALS IN THE WOMB.