of twofold nature to the egg, and a twofold egg in this kind, so does he assert a twofold action and a twofold animal engen- dered. For," he proceeds, "from the first eggs, which are the primordia of generation, a worm is constantly produced ; viz. : from the eggs of flies, ants, bees, silkworms, &c., in which some fluid is contained, and from the whole of which fluid the worm is engendered ; but from the second eggs, formed by the worms themselves, butterflies are engendered and disclosed, viz. : flying animals contained in a shell, or follicle, or egg, which shell giving way the winged creature escapes; precisely as Aristotle 1 has it where he speaks of the egg of the locust." Finally, whilst the higher animals produced from eggs are per- fected by a succession of parts, the lower creatures that arise in this way, or that are formed by metamorphosis, are produced at one effort, as it were, and entire. And in the same way are engendered both those creatures that are said to arise spon- taneously, by chance or accident, and derive their first matter or take their origin from putrefaction, filth, excrement, dew, or the parts of plants and animals, as well as those that arise con- generately from the semen of animals. Because this is com- mon to all living creatures, viz. : that they derive their origin either from semen or eggs, whether this semen have proceeded from others of the same kind, or have come by chance or some- thing else. For what sometimes happens in art occasionally occurs in nature also; those things, namely, take place by chance or accident which otherwise are brought about by art. Of this Aristotle 2 quotes health as an illustration. And the thing is not different as respects the generation, in so far as it is from seed, of certain animals : their semiua are either present by accident, or they proceed from an univocal agent of the same kind. For even in fortuitous semina there is an inherent motive principle of generation, which procreates from itself and of itself; and this is the same as that which is found in the semina of congenerative animals, a power, to wit, of forming a living creature. But of this matter we shall have more to say shortly. From what has just been said, however, several paradoxes present themselves for consideration. For when we see the cicatricula enlarging in the egg, the colliquament concocted
1 Hist. Anim. lib. v, cap. 28. 4 Metaph. lib. vii, cap. 9.
