EXERCISE THE TWENTY-SIXTH.
Of the nature of the egg.
Of the theorems that refer to the egg, some teach us what it is, some show its mode of formation, and others tell of the parts which compose it.
It is certain, in the first place, that one egg produces one chick only. Although the egg be in a certain sense an external uterus, still it most rarely engenders several embryos, but by far the most frequently produces no more than a single pullet. And when an egg produces two chicks, which it does sometimes, still is this egg to be reputed not single but double, and as possessed of the nature and parts of two eggs.
For an egg is to be viewed as a conception proceeding from the male and the female, equally endued with the virtue of either, and constituting an unity from which a single animal is engendered.
Nor is it the beginning only, but the fruit and conclusion likewise. It is the beginning as regards the being to be engendered; the fruit in respect of the two parents: at once the end proposed in their engendering, and the origin of the chick that is to be. “But the seed and the fruit,” according to Aristotle,[198] “differ from one another in the relations of prior and posterior; for the fruit is that which comes of another, the seed is that from which this other comes: were it otherwise, both would be the same.”
The egg also seems to be a certain mean; not merely in so far as it is beginning and end, but as it is the common work of the two sexes and is compounded by both; containing within itself the matter and the plastic power, it has the virtue of both, by which it produces a fœtus that resembles the one as well as the other. It is farther a mean between the animate and the inanimate world; for neither is it wholly endowed with life, nor is it entirely without vitality. It is still farther the mid-passage or transition stage between parents and offspring, between those who are, or were, and those who are about to be; it is the hinge and pivot upon which the whole generation of the bird revolves. The egg is the terminus from which all fowls, male and female, have sprung, and to which all their lives tend,—it is the result which nature has proposed to herself in their being. And thus it comes that individuals in procreating their like for the sake of their species, endure for ever. The egg, I say, is a period or portion of this eternity; for it were hard to say whether an egg exists for the sake of the chick that it engenders, or the pullet exists for the sake of the egg which it is to engender. Which of these was the prior, whether with reference to time or nature,—the egg or the pullet? This question, when we come to speak of the generation of animals in general, we shall discuss at length.
The egg, moreover,—and this is especially to be noted,—corresponds in its proportions with the seeds of plants, and has all the same conditions as these, so that it is to be regarded, not without reason, as the seed or sperma of the common fowl, in the same way as the seeds of plants are justly entitled their eggs, not only as being the matter or that from which, but the efficient or that by which the pullet is engendered. In which finally no part of the future offspring exists de facto, but in which all parts inhere in potentia.
The seed, properly so called, differs however from the geniture, which by Aristotle is defined to be “that which, proceeding from the generator, is the cause, that which first obtains the principle of generation; in those, to wit, whom nature destined to copulate. But the seed is that which proceeds from these two in their connection: and such is the seed of all vegetables, and of some animals, in which the sexes are not distinct; like that which is first produced by male and female commingled, a kind of promiscuous conception, or animal; for this already possesses what is required of both.”
The egg consequently is a natural body endowed with animal virtues, viz. principles of motion and rest, of transmutation and conservation; it is, moreover, a body which, under favorable circumstances, has the capacity to pass into an animal form; heavy bodies indeed do not sink more naturally, nor light ones float, when they are unimpeded, than do seeds and eggs in virtue of their inherent capacity become changed into vegetables and animals. So that the seed and the egg are alike the fruit and final result of the things of which they are the beginning and efficient cause.