Generation of Animals · Book I

Aristotle · a new plain-English translation from the original language

1| Since we have spoken of the other parts found in animals, both in common and, for each kind, separately about what is peculiar to it — in what way each part exists on account of such-and-such a cause, I mean the cause that is for the sake of something (for four causes are laid down: that for the sake of which, as an end, and the account of the substance — these two we should take as practically one — and, as a third and fourth, the matter and that from which the principle of motion comes). Now concerning the others we have spoken (for the account and that for the sake of which as end are the same, and matter, for animals, is the parts: for the whole animal, the non-uniform parts; for the non-uniform parts, the uniform parts; and for these, what are called the elements of bodies). What remains is, of the parts, those that contribute to the generation of animals, about which nothing has been determined before, and, concerning the moving cause, what this is. To examine this and to examine the generation of each animal are, in a certain way, the same inquiry. That is why our discussion has brought them together into one, setting the former as the last topic among those concerning the parts, and the latter, the origin of generation, as following directly upon it.

2| Now of animals, some come to be from the coupling of female and male, in all the kinds of animals in which female and male exist. For it does not exist in all: among the blooded animals, with few exceptions, each one, once fully developed, is either male or female; but among the bloodless animals, some have both female and male, so that they generate offspring of the same kind, while others generate, but not offspring of the same kind — such are all those that come to be not from animals coupling, but from decaying earth and residues. To speak generally of the whole class: of animals capable of moving from place to place, some swimming, some flying, some walking with their bodies, in some of these the whole kind possesses both female and male, not only among the blooded animals but also among some of the bloodless ones. And among these, in some the distinction holds for the whole kind, as with the cephalopods and the crustaceans; among the kind of insects, it holds for most of them. Of these same animals, whichever come to be from the coupling of animals of the same kind also themselves generate offspring of that same kind.

3| But whichever do not come to be from animals but from decaying matter, these generate offspring, but of a different kind, and what is generated is neither female nor male. Such are some of the insects. And this happens reasonably: for if the animals that do not come to be from animals were themselves, once produced, to generate by coupling — if the offspring were of the same kind as themselves, then the generation of their begetters, right from the start, would have had to be of that same kind. And this we reasonably require, for it evidently turns out this way with the other animals. But if the offspring were unlike their parents, yet capable of coupling, then again from these a further different nature would come to be, and again another from these, and this process would go on to infinity. But nature avoids the infinite, for the infinite is incomplete, while nature always seeks an end. As for animals that are not capable of locomotion, such as the testaceans among animals, and those that live by being attached to something — because their substance is close to that of plants — just as in plants, so in these too there is no female and male strictly speaking, but the terms are already used by way of resemblance and by analogy, for they have some small difference of this sort. Indeed, even among plants there exist fruit-bearing trees of the same kind, while others do not themselves bear fruit but contribute to the ripening of those that do, as happens with the fig and the wild fig.

4| The same holds also in the case of plants: some come to be from seed, others as though nature were acting spontaneously. For they come to be either from decaying earth or from certain parts within plants. For some do not form themselves independently on their own, but arise within other trees, as does the mistletoe. Concerning plants, then, they must be examined separately, on their own; but concerning the generation of the other animals we must speak according to the argument that applies in each case, drawing our threads together from what has been said. For as we said, one would rightly set down as the principles of generation, above all, the female and the male — the male as having the principle of motion and of generation, the female as having it in the manner of matter. And one might be most persuaded of this by observing how the seed comes to be, and from where: for it is from this that things that come to be by nature are constituted, and how this comes about from the female and the male must not go unnoticed. For it is because such a part is secreted off from the female and the male, and the secretion exists in these and comes from these, that the female and the male are principles of generation. For we call an animal male if it generates in another, and female if it generates in itself; that is also why people think of the nature of the earth, taken as a whole, as female and a mother, while they address the sky and the sun, or some other such thing, as begetters and fathers.

5| The male and the female differ, in respect of their account, in that each is capable of a different thing, but in respect of perception, by certain parts: in respect of the account, in that the male is that which is capable of generating in another, as was said before, while the female is that which generates in itself, and that from which what is generated comes to be, existing within the begetter. And since it has been distinguished by a capacity and a certain function, and every function requires organs for its performance, and the organs for the capacities are the parts of the body, it is necessary that there also be parts for begetting and for coupling, and that these differ from one another, insofar as the male differs from the female. For even though the female and the male are spoken of with reference to the animal as a whole, still, the female's are the wombs, while the male's are the parts around the testicles and the perineum, in all the blooded animals — for some of them have testicles, others such passages in their place. There are differences between female and male also among the bloodless animals, in all those of them that have this opposition. Among the blooded animals, the parts concerned with mating differ in their shapes. And one must understand that when a small principle is shifted, many of the things that come after that principle tend to change along with it.

6| This is clear in the case of castrated animals: when only the generative part is destroyed, almost the whole form changes along with it, to the point that the animal comes close to seeming female, showing that the animal's being female or male does not depend on some chance part or some chance capacity. It is clear, then, that the female and the male evidently constitute a kind of principle: at any rate, many things change together when the animals change in respect of being female and male, as though a principle were shifting.

7| The parts concerning the testicles and the uteri are not alike in all blooded animals, and first let us take the parts concerning the testicles in males. Some of these animals have no testicles at all, such as the class of fishes and that of serpents, but only two seminal passages; others have testicles, but have them inside, near the loin, in the region of the kidneys, and from each of these a passage, as in those not having testicles, the two joining into one, just as in those others too, for example all birds and the egg-laying quadrupeds among those that take in air and have lungs. For all of these too have the testicles inside, near the loin, and two passages from them, similarly to serpents, for example lizards and tortoises and all the scaly animals. But the live-bearing animals all have the testicles in front, though some of them have them inside near the end of the belly, as the dolphin, and not passages but a genital organ leading from these to the outside, as in oxen; and of those that have them outside, some have them hanging free, as man, others close to the seat, as pigs.

8| These matters have been determined more precisely in the Researches on Animals. All uteri are two-parted, just as the testicles too are two in all males; some animals have these near the joints, as women and all live-bearing animals do, not only externally but also within themselves, and those fish that lay eggs visibly; others have them near the diaphragm, as all birds do and the live-bearing fish. The crustaceans also have forked uteri, and so do the soft-bodied animals; for what are called their eggs have surrounding membranes that serve as uteri. This is most indeterminate in the case of the octopuses, so that the uterus seems to be single; the cause of this is that the mass of the body is alike in every direction. The uteri of insects too are forked in those that have some size; in the smaller ones they are unclear because of the smallness of the body.

9| So the parts mentioned belong to animals in this way. But concerning the difference in the seminal organs among males, if one intends to examine the causes on account of which they exist, one must first grasp for the sake of what the constitution of the testicles exists. If indeed nature does everything either because of necessity or for the sake of the better, this part too would exist because of one or the other of these. That it is not necessary for generation is clear; for it would then belong to all things that generate, but as it is neither serpents nor fish have testicles, since they are observed copulating and having their passages full of milt. It remains, then, that they exist for the sake of something better. Now for most animals there is scarcely any function other than, as with plants, seed and fruit. Just as, in matters concerning nutrition, those with straight intestines are more voracious in their desire for food, so too those not having testicles but only passages, or having testicles but having them inside, are all quicker toward the activity of copulation. But those that need to be more temperate, just as in the case of nutrition they are not straight-gutted, so here too have passages that are coiled, so that the desire may be neither greedy nor quick.

10| The testicles are contrived for this purpose: they make the motion of the seminal residue more settled, in the live-bearing animals, such as horses and other such animals, and in humans, by preserving the doubling-back of the passage. The manner in which this doubling-back is arranged must be studied from the Researches on Animals. For the testicles are no part of the passages, but are attached to them, just as women weaving attach the loom-weights to the warp-threads; for when the testicles are removed, the passages are drawn up inside, so that castrated animals cannot generate, since if the passages were not drawn up they would be able to; and indeed a certain bull, immediately after castration, having mounted, impregnated the cow, because the passages had not yet been drawn up. In birds and the egg-laying quadrupeds the passages receive the seminal residue, so that its exit is slower than in fish. This is clear in the case of birds; for around the mating season they have much larger testicles, and as many birds as mate at one particular season, when that time has passed, have them so small as to be nearly invisible, but around the mating season very large. Those having the testicles inside, then, mate more quickly; for even those having them outside do not release the seed before drawing the testicles up.

11| Further, the organ for copulation the quadrupeds have, for it is possible for them to have it; but for birds and for the footless animals it is not possible, because in the one case the legs are set beneath the middle of the belly, in the other case they are altogether without legs, and the nature of the genital organ depends on this and is positioned there by its situation. This is why, also, in intercourse the legs become tensed; for the organ is sinewy, and the nature of the legs is sinewy. So since it is not possible for these animals to have this organ, it is necessary that they either not have testicles, or not have them there; for in those that do have the organ, the position of both is the same. Further, in those having the testicles outside, through the motion the genital organ becomes heated and the seed that has been collected comes forward, but not as though it were ready at once upon contact, as with fish. All the live-bearing animals have the testicles in front, outside, except the hedgehog; this alone has them near the loin, for the same cause as birds do. For their copulation must necessarily be quick, since they do not mount, as the quadrupeds do, upon animals lying prone, but mate standing upright because of their spines. So it has been stated for what cause those having testicles have them, and for what cause some have them outside and others inside.

12| Those animals that do not have testicles, as has been said, lack this part both because it serves not the better but only the necessary, and because it is necessary that their mating occur quickly; and such is the nature of fish and of serpents. For fish mate by coming alongside one another and separate quickly. For just as in the case of humans and all such animals it is necessary to hold the breath and so release the seed, this does not happen to fish, since they do not shut out the sea; and they would easily perish if they failed to do this. They must not, therefore, concoct the seed during copulation, as the land-dwelling live-bearing animals do, but have the seed already concocted by the season, in a mass, so that they do not produce it in the act of touching one another, but emit it already concocted. This is why they do not have testicles, but straight and simple passages, like the small part that belongs to quadrupeds around the testicles. For of the doubling-back of the passage, one part is blooded and one bloodless, which receives the seed and through which, being now seed, it travels, so that when the semen arrives there, its release is quick for these animals too. But in fish the passage throughout is of the kind that in humans and such animals corresponds to the other part of the doubling-back.

13| Snakes mate by coiling around one another; they have neither testicles nor a penis, as has been said before — no penis because they have no legs, no testicles because of their length — but ducts instead, as fish do. For because their nature is elongated, if there were still a delay at the testicles, the semen would be chilled on account of the slowness. This is exactly what happens also in animals that have a large penis: they are less fertile than those of moderate size, because cold semen is not fertile, and what travels too great a distance is chilled. So the cause why some animals have testicles and some do not has been stated. Snakes wind around one another because they are ill-suited for close contact; being extremely long, they can fit together by only a small part, and so are not easy to join. Since, then, they have no parts by which they can grip one another, in place of these they make use of the moistness of their body, coiling around one another. This is also why they seem to separate more slowly than fish, not only because of the length of their ducts but also because of the elaborate maneuvering involved in this.

14| Concerning the females, one might raise a puzzle about how matters stand with their wombs; for many contrary conditions hold among them. For not even the live-bearing animals are all alike: humans and all the land animals have the womb below, near the joints, while the live-bearing cartilaginous fish have it above, near the diaphragm. Nor are the egg-laying animals alike either: fish have it below, like man and the live-bearing quadrupeds, while birds have it above, and so do the egg-laying quadrupeds. Nevertheless these contrary conditions too hold by reason. For first, the egg-laying animals lay eggs in different ways. Some produce incomplete eggs, for example fish; for the eggs of fish are completed and grow outside the body. The cause is that these are prolific breeders, and this is their function, just as it is of plants. If then they completed the eggs within themselves, they would necessarily be few in number; but as it is they hold so many that each of the two wombs seems, at least in the small little fish, to be a single egg. For these are the most prolific of all, just as also among the other things whose nature is analogous to these, both in plants and in animals; for in these the growth in size is diverted into seed.

15| Birds and the quadrupeds among the egg-laying animals produce complete eggs, which for their preservation must be hard-shelled; for they are soft-shelled as long as they are still growing. The shell comes about through heat drawing the moisture out of the earthy matter. The place in which this happens must therefore be hot. Such is the region around the diaphragm; for it is this that concocts the nourishment. If then, the eggs must be in the womb, and the womb must be near the diaphragm for those that lay complete eggs, but below for those that lay incomplete eggs — for in this way it will be further along on its way — then the womb is by nature disposed to be below rather than above, wherever no other function of nature stands in the way; for its end lies below as well; and where the end is, there is the function; and the womb itself belongs where its function is. The live-bearing animals also differ from one another. For some bear their young live not only outside but also inside themselves, for example humans and horses and dogs and all animals that have hair, and among the water-dwellers, dolphins and whales and such cetaceans.

16| Cartilaginous fish and vipers bear their young live outside, but inside themselves they first lay eggs. They lay a complete egg; for it is in this way that the animal is generated from the egg, and from an incomplete egg nothing is generated. They do not lay eggs outside because their nature is cold, and not, as some say, hot.

17| At any rate they produce soft-shelled eggs; for because they have little heat, their nature does not dry out the outer surface of the eggs. So because they are cold they produce soft-shelled eggs, and because the eggs are soft-shelled they do not lay them outside; for they would be destroyed. But when the animal comes to be from the egg, in most cases it happens in the same way as in birds: it moves down, and the young come to be near the joints, just as also in those that are live-bearing from the start. This is why such animals have a womb unlike that of either the live-bearers or the egg-layers, because it partakes of both forms; for all the cartilaginous fish have wombs both near the diaphragm and extending down below. One must have observed, both concerning this womb and concerning the others, how they stand, from dissections and from the natural histories. So then, because they are egg-layers of complete eggs they have it above, and because they bear their young live they have it below, and they partake of both. But those that bear their young live from the start all have it below; for no function of nature stands in the way, nor do they produce offspring twice over, and besides this it is impossible for animals to come to be near the diaphragm; for the embryos must have weight and motion, and the region, being a critical one for life, could not bear these.

18| Further, difficult labor is bound to occur because of the length of the passage, since even now in the case of women, if around the time of birth they stretch upward by yawning or doing something of that sort, they have difficult labor. And empty wombs, when they rise up and press against the upper parts, cause suffocation; for it is necessary that those wombs which are going to hold an animal be stronger, which is why all such wombs are fleshy, while those near the diaphragm are membranous. And this is evidently what happens even in the very animals that produce offspring in two ways: for they hold their eggs above and to the side, but their live young in the lower part of the womb. So the cause why some animals have contrary arrangements as regards their wombs, and in general why some have them below and others near the diaphragm, has been stated.

19| As to why all animals have their wombs internal, but their testicles in some cases external and in some internal, the cause of the womb being internal in all is that in it is what is being generated, which needs guarding and shelter and concoction, whereas the region outside the body is easily harmed and cold. The testicles are internal in some, external in others, because these too need shelter and covering both for their preservation and for the concoction of the semen; for it is impossible, when they are chilled and congealed, to draw up and emit the seed. This is why all those whose testicles are exposed have a covering of skin called the scrotum. But those whose skin's nature is opposed to this, through hardness, so that it cannot enclose them and be soft and skin-like — for example those that have fish-like skin and those that have scaly skin — these necessarily have them internal. This is why dolphins and all the cetaceans that have testicles have them internal, and so do the egg-laying and scaly quadrupeds. And the skin of birds too is hard, so that it is out of proportion in size for enclosing them, and this is a cause common to all these, in addition to those stated earlier, arising from the necessities connected with mating.

20| For the same cause both the elephant and the hedgehog have their testicles internal; for in these too the skin is not well suited to have a separable covering part. The wombs also lie in opposite positions: between those that bear young live inside themselves and those that lay eggs outside, and among these, between those that have the womb below and those that have it near the diaphragm, as fish do compared with birds and the egg-laying quadrupeds, and also in those that generate by both methods, laying eggs inside themselves but bearing young live in the open. For the live-bearing animals have their wombs both inside and outside on the belly, for example man and ox and dog and other such animals; for it is advantageous for the preservation and growth of the embryos that no weight lie upon the wombs.

21| There is also a different passage, through which the dry residue exits, and through which the liquid residue exits, in all these animals. This is why all such animals have genitals, both males and females, the part through which the liquid residue is secreted — in males the semen, in females the fetal fluid. This passage lies above and toward the front, where the passage for the dry nourishment is. Those that lay eggs but lay an incomplete egg, such as the fish that lay eggs, have their uteruses not under the belly but toward the loin. For the growth of the egg is no hindrance, since what is growing is completed and advances outside the body; and the passage is the same one even in those that have no genital organ for generation, namely the passage for the dry nourishment, in all egg-laying animals, including those of them that have a bladder, such as tortoises. For the passages are double for the sake of generation, not for the sake of expelling the liquid residue; but because the nature of semen is liquid, the residue of liquid nourishment has come to share the same passage. This is clear from the fact that all animals produce semen, but not all of them produce a liquid residue.

22| Since, then, the seminal passages of the males must also be fixed in place and not wander, and likewise the uteruses in females, and this must occur either toward the front of the body or toward the back, in the live-bearing animals the uteruses are in front, because of the embryos, while in the egg-laying animals they are toward the loin and the back; and those animals that lay eggs within themselves but bear their young alive outside have it both ways, because they partake of both and are both live-bearing and egg-laying. For the upper part of the uterus, where the eggs are formed, is under the diaphragm, toward the loin and the back, but as it proceeds downward toward the belly — for there it is already bearing its young alive. In these animals too the passage is one, for both the dry residue and for mating; for none of them has a genital organ set apart, as was said before. The passages of the males are similarly disposed, both in those that have testicles and those that do not, corresponding to the uteruses of the egg-laying females. For in all of them these passages are attached toward the back and along the region of the spine. For they must not wander but be fixed in place, and such is the region behind;

23| for this region provides continuity and stability. So in those animals that have their testicles inside, they are fixed in place right along with the passages, and likewise in those that have them outside; then they meet together into one at the region of the genital organ. The passages are disposed similarly in dolphins too, but they have their testicles hidden beneath the cavity around the belly. So it has been said how the parts that contribute to generation are positioned, and for what causes. As for the other bloodless animals, the manner of the parts contributing to generation is not the same either as in the blooded animals or among themselves. The remaining kinds are four: one, that of the crustaceans; second, that of the cephalopods; third, that of the insects; and fourth, that of the testaceans. Concerning all of these the matter is not clear in every case, but it is evident that most of them do not mate; in what manner they are formed must be said later. The crustaceans mate as the animals that urinate backward do, when one lies on its back and the other on its front and they lock their tails together; for the tails, whose fins are attached far off, prevent the ones lying on their backs from mounting the ones lying on their fronts. The males have thin seminal passages, and the females have membranous uteruses alongside the intestine, split apart on this side and that; and in these the egg is formed.

24| The cephalopods copulate mouth to mouth, pressing against each other and unfolding their tentacles; and they copulate in this manner of necessity. For nature has drawn the outlet of the residue round near the mouth, bending it back, as has been said before in the account of the parts. The female clearly has a uterine part in each of these animals; for at first it holds the egg undifferentiated, then, as it is differentiated, it becomes many, and she brings forth each of these incomplete, just as the egg-laying fish do. The passage is the same for the residue and for the uterine part, in these animals as in the crustaceans. For it is there that the male discharges the milt, through the passage. This is located on the underside of the body, where the shell falls away and the sea enters in. This is why the mating of the male with the female takes place at this point; for it is necessary, if the male discharges either semen or some part or some other capacity, that he approach along the uterine passage. As for the passing of the male's tentacle through the funnel in octopuses, by which fishermen say they mate ‘with the tentacle,’ this is for the sake of embracing, not as an organ useful for generation; for it lies outside the passage and outside the body. Sometimes the cephalopods also mate front to front; but whether this is for the sake of generation or for some other cause, nothing has yet been observed.

26| Of the insects, some mate, and their generation comes from animals that share their name, as with the blooded animals — for instance locusts, cicadas, spiders, wasps, and ants; others mate and produce offspring, but not offspring of the same kind as themselves, only grubs, and these do not come to be from animals but from putrefying liquids, or in some cases from dry matter — for instance fleas, flies, and blister-beetles. Others neither come to be from animals nor mate, such as gnats, mosquitoes, and many similar kinds. Among those that mate, in most cases the females are larger than the males. The males do not appear to have seminal passages. Speaking generally, the male discharges no part into the female; rather the female discharges into the male, from below upward. This has been observed in many cases, and likewise as to which mounts which, though the opposite occurs in a few; but a division by kind has not yet been worked out. This holds, too, of most of the egg-laying fish, and of the four-footed egg-laying animals; for the females are larger than the males because of the advantage this gives with respect to the bulk that develops in them from the eggs during gestation. In the females of these animals the part analogous to the uterus is split apart alongside the intestine, as in the others; and in this the fetations are formed. This is clear in the case of locusts, and such of them as have sufficient size, being naturally disposed to mate; for most insects are extremely small. This, then, is the manner in which the organs concerned with generation stand for the animals not spoken of before. Among the uniform parts, what remains is semen and milk, about which it is now time to speak — about semen at once, and about milk in what follows.

27| Some animals plainly emit seed — those, namely, that are blooded by nature — but with insects and the soft-bodied creatures it is unclear which way it goes. So this must be examined: whether all the males emit seed or not all, and if not all, for what cause some do and some do not; and further, whether the females too contribute some seed or not, and if not seed, whether they contribute nothing else either, or contribute something, though not seed. And besides, in the case of those that do emit seed, we must examine what it is that they contribute toward generation through the seed, and in general what the nature of the seed is, and of the so-called menstrual fluid, in the case of those animals that emit this kind of fluid. Now it is thought that all things come to be from seed, and the seed from the parents. Hence it belongs to the same inquiry whether both the female and the male emit it, or only one of the two, and whether it comes away from the whole of the body or not from the whole; for it stands to reason that, if not from the whole, then not from both parents either — which is why we must examine, since some say it comes away from the whole body, how the matter stands with this point first.

28| There are, roughly, four pieces of evidence one might use to show that the seed comes away from each of the parts. First, the intensity of the pleasure: for the same affection becoming greater is more pleasant, and it is greater when it happens to all the parts than when it happens to one or a few of them. Further, that from maimed parents maimed offspring come to be: for they say that, because of the part's deficiency, no seed travels from there, and that wherever it fails to come from, this is what turns out not to be generated. Besides these, there are the resemblances to the parents: for offspring come to resemble them, just as the whole body does, so too do part resemble part; if, then, the cause of the resemblance of the whole is that the seed came from the whole, then the cause with respect to the parts would likewise be that something came from each of the parts. Further, it would seem reasonable that, just as there is something from which the whole first comes to be, so too for each of the parts — so that if there is a seed of that whole, there would also be some seed proper to each of the parts. And testimonies of this sort too lend credibility to these opinions: for children come to resemble their parents not only in their inborn features but also in their acquired ones —

29| for some parents who had scars have had children born with the mark of the scar in the same places, and in Chalcedon a father who had a brand on his arm left the same sign on his child, though blurred and not clearly articulated as writing. So it is chiefly from considerations of this sort that some people believe the seed comes from every part. But on examination the argument appears to point rather the other way: for the points just stated are not hard to refute, and besides this, other consequences follow that are impossible to maintain. First, then, resemblance is no sign that it comes away from every part, because children come to resemble their parents also in voice, nails, and hair, and in their movement — and nothing comes away from these. And some features they do not yet have when the parents beget them, such as a head of gray hair or a beard. Further, they resemble ancestors further back, from whom nothing came away; for resemblances reappear across many generations, as in the case at Elis of the woman who had intercourse with the Ethiopian — for it was not the daughter who was born dark, but the child born from her, an Ethiopian. And the same argument applies to plants as well; for it is clear that in their case too the seed would have to come from all the parts. Yet many parts they simply do not have, others could be removed, and others grow on afterward. Further, it does not come away from the fruit-coverings either, although these too come to be with the same shape reproduced. Again, does it come away only from the uniform parts, taken from each — such as flesh, bone, and sinew — or also from the non-uniform parts, such as face and hand?

30| For if it comes only from the former, yet it is the non-uniform parts — face, hands, feet — that resemble the parents more, then if these are not made to resemble by coming from the whole, what stops the uniform parts from being alike for some other cause too, and not by coming from the whole? But if it comes only from the non-uniform parts, then it does not come from all the parts. And it would indeed make more sense for it to come from these; for the uniform parts are prior, and the non-uniform parts are composed out of them, and just as offspring come to resemble parents in face and hands, so too in their flesh and nails. But if it comes from both, what would be the manner of the generation? For the non-uniform parts are composed out of the uniform ones, so that for it to come away from the former would be for it to come away from the latter, and from their composition as well — just as if it came from a written name: if from the whole, then also from each of the syllables, and if from these, then from the letters and from their arrangement. So that if flesh and bones are composed out of fire and things of that kind, it would come rather from the elements; for how could it come from the arrangement? And yet without this the resulting parts would not be alike. And if something later fashions this arrangement, that would be the cause of the resemblance, and not the fact that something came away from the whole.

31| Further, if the parts are scattered apart within the seed, how does it live? And if they are continuous, it would be a tiny animal. And what of the genitals — how does that work? For what comes away from the male is not the same as what comes away from the female. Further, if from both parents alike it comes away from all the parts, two animals are produced; for it will have the entirety from each of the two. This is why Empedocles, if one may put it so, seems to be saying something that agrees most closely with this theory, so far as that point goes — though where he says it differently, he is not right. For he says that in the male and the female there is, as it were, a matching token, but that the whole comes away from neither: "but the nature of the limbs is split apart, part in the man's." For why do the females not generate from themselves alone, if indeed it comes away from every part and they have a receptacle for it? But, as it appears, either it does not come away from every part, or it does so in the way he says — not the same things from each parent — which is why they need intercourse with one another. But this too is impossible. For just as it is impossible, even for large creatures, for them to be preserved and be alive while scattered apart, in the way Empedocles generates them, speaking of the age of Love: "whereby many heads without necks sprang up" — and then says that they grow together in this fashion — this is plainly impossible.

32| For neither can something lacking soul nor lacking any life at all be preserved, in the way he supposes, as though several already-living things grew together so as to become one again. But this is exactly the manner of thing that those who claim it comes away from every part are committed to saying: just as then, on earth, in the age of Love, so for these people it happens within the body. For it is impossible for the parts to become continuous and to come together, converging into a single place. Then again, how are up and down, right and left, front and back kept apart? All of this is unreasonable. Further, the parts are distinguished some by a power, others by affections: the non-uniform parts by being able to do something — such as tongue and hand — the uniform parts by hardness and softness and other affections of that kind, not simply by having blood or not having flesh. It is clear, then, that what comes away cannot be synonymous with the parts — blood coming from blood, or flesh from flesh. But indeed, if blood comes to be out of something other than itself, then the coming-away from all the parts could not be the cause of the resemblance either, as those who speak this way claim; for it is enough for it to come away from one thing only, if indeed blood does not come to be from blood.

33| For why would not everything come to be from one thing? For this argument seems to be the same as Anaxagoras's, that none of the homoiomerous things comes to be, except that he applies this to everything, while these thinkers apply it to the generation of animals alone. Next, in what way will these things that have departed from every part grow? For Anaxagoras reasonably says that flesh comes to flesh from the nourishment; but for those who do not say this, but claim that the seed departs from every part, how will a thing become bigger by something else being added to it, if what has come to it stays as it is? But then, if what has come to it can change, why is it not the case straightaway from the start that the seed is of such a nature that blood and flesh can come to be out of it, rather than that it already is that thing itself and blood and flesh too? For surely it is not possible to say this either — that it grows later by a kind of blending, as wine grows when water is poured into it. For then each thing would have been most itself, unmixed, right at the beginning; but as it is, each of flesh and bone and the rest of the parts becomes more fully itself later rather than earlier. And to say that something in the seed is sinew and something is bone is a claim altogether beyond what we can verify. Besides this, if male and female differ at the time of conception, as Empedocles says: "and it was poured into what was pure —

34| — such offspring turn out women, when they meet with cold." At any rate women and men are observed to change: just as the barren become fertile, so too those who bear females come to bear males, on the grounds that the cause lies not in whether something departs from every part or not, but in whether what departs from the woman and the man is well-proportioned or not, or in some other such cause. It is clear, then, if we lay this down in this way, that the female is not what it is because something departed from a given source, so that neither is the part peculiar to the male and to the female so accounted for, if indeed the same seed can become either female or male, on the grounds that the part is not present in the seed. What difference, then, does it make to say this about this case rather than about the other parts? For if seed does not even come from the womb, the same argument would hold for the other parts too. Further, some animals come to be neither from creatures of their own kind nor from creatures differing in kind — for example flies, and the kinds of what are called grubs. From these, animals do come to be, but no longer alike in nature to their parents, but a certain kind of worm. It is clear, then, that this could not be so, if likeness is a sign of the seed's departing from every part.

35| Further, from a single mating some animals too beget many offspring, and plants do so altogether; for it is clear that from a single act of generation a plant bears its whole yearly crop of fruit. And yet how is this possible, if the seed were separated off from every part? For one secretion must necessarily come from one mating and one act of separating-off. But within the womb it is impossible for it to be further divided up; for by then the dividing-off would be as if from a young plant or animal, not from seed. Further, cuttings taken from a plant bear seed of their own; it is clear, then, that even before being cut off, that part was already bearing fruit from that same size, and that the seed did not depart from the whole plant. The greatest proof of these points we have observed sufficiently in the case of insects. For even if not in all, still in most of them, in mating the female stretches some part of herself out into the male. That is why they carry out mating, as we said before, in this way: for the lower parts are observed to be sent into the upper parts — not in all, but in most of the cases we have observed. So it would be evident that not even in those creatures where the males emit semen is the departing from every part the cause of generation, but some other way, which must be considered later.

36| For indeed, if it were true that the seed departs from every part, as they say, there would be no need to claim that it departs from all the parts, but only from the part that does the fashioning — from the carpenter, say, but not from the material. But as it is, they speak as though it came from the shoes as well; for a son who resembles his father tends to wear similar shoes! As for the fact that intense pleasure arises in sexual intercourse, this is not caused by the seed's departing from every part, but because there is a strong itching sensation; that is also why, if this intercourse happens often, the pleasure felt by those having intercourse becomes less. Further, the pleasure comes at the end; but it ought to arise in each of the parts, and not all at once, but earlier in some and later in others. As for mutilated offspring coming from mutilated parents, the cause is the same as why offspring resemble their parents at all. But unmutilated offspring also come from mutilated parents, just as offspring unlike their parents come from those who begot them; the cause of these cases must be considered later, for this problem is the same as the other one. Further, if the female does not emit seed, then by the same argument it does not follow that it departs from every part either. And even if it does not depart from every part, there is nothing absurd in its also not departing from the female, but in the female being the cause of generation in some other way.

37| It is fitting next to examine this question, since it is clear that the seed is not secreted from all the parts. The starting point both for this inquiry and for what follows is to grasp first what seed is; for in this way the facts about its functions and what happens concerning it will be more readily observed. Seed is meant by its nature to be such that from it, as the first thing, the things constituted according to nature come to be — not in the sense that what does the making is itself derived from that source, as with the human being; for the human being comes to be from this because this is the seed. Now since one thing comes to be from another in many ways — in one way, as we say night comes to be from day and a man from a child, because this comes after that; in another way, as a statue comes from bronze and a bed from wood, and all the other things we say come to be as if from matter, where the whole is made from something present within and given shape; in another way again, as an unmusical man comes from a musical one and a sick man from a healthy one, and in general as the contrary comes from the contrary; and further, besides these, as Epicharmus makes his "building-up" — from slander comes abuse, and from this a fight — all these come from something as the starting point of the motion.

38| Of such things, in some the starting point of the motion is in the things themselves, as in what has just been said, for slander is a part of the whole disturbance, while in others it is outside them, as the crafts are outside the things crafted, and the lamp is outside the burning house. It is clear that seed falls under one of these two: either it produces what comes to be as being matter for it, or as being the first mover of it; for it certainly does not produce it as this coming after that, the way the voyage comes after the Panathenaic festival, nor as from a contrary; for when a thing perishes, the contrary comes to be from the contrary, and something else must underlie it as the first thing present in it out of which the result will come. So of the two we must decide under which head to place the seed — whether as matter and as something acted upon, or as a form and something that acts, or as both at once; for perhaps it will become clear at the same time also how generation from contraries holds for all things that come from seed. For generation from contraries too is natural: some things come to be from contraries, male and female, others from one alone, as plants and some animals, in all cases where male and female are not marked off as separate.

39| Now 'seed' is the term for that which comes from the begetter as its cause — in whatever beings are naturally suited to mate — being the first thing to hold the principle of generation, while 'semen' is that which has the principles from both of the pair that mated, as with plants and with some animals in which the female and the male are not separated, being like the first mixture that arises from female and male, a sort of embryo or animal already; for these already have in them what comes from both. Semen and fruit differ as later and earlier: fruit is such by being from another thing, while semen is such by another thing coming from it, since the two are in fact the same thing. But we must say again what the primary nature of what is called semen is. Necessarily, everything we take within the body is either a part of what is according to nature — and this either of the non-uniform parts or of the uniform parts — or something contrary to nature, such as a tumor, or a residue, or a colliquescence, or nourishment. By residue I mean what is left over from nourishment, and by colliquescence what is separated off from the body's growth by a dissolution contrary to nature. That it cannot be a part, then, is clear: it is uniform, but nothing is composed out of it, as things are composed out of sinew and flesh.

40| Further, it is not even marked off as a distinct part, the way all the other parts are. But neither is it contrary to nature, nor a deformity: for it is present in all animals, and it is out of this that their nature comes to be. Nourishment is plainly something brought in from outside, so it must necessarily be either a colliquescence or a residue. Now the ancients seem to have thought it was a colliquescence: for to say that it departs from every part of the body on account of the heat produced by motion amounts to saying it is a colliquescence. But colliquescences are something contrary to nature, and nothing that is according to nature comes to be from what is contrary to nature. It must therefore be a residue. But every residue is a residue either of useless nourishment or of useful nourishment. By useless I mean that from which nothing further contributes to nature, but from the greater consumption of which the body is most harmed; by useful I mean the opposite. That semen is not this useless sort of residue is clear: for those in the worst condition because of age or disease have the most of this, but the least semen — for they either have none at all, or have semen that is not fertile, because a useless and diseased residue is mixed into it. Semen, then, is a part of the useful residue. And the most useful residue is the last, the one from which each of the parts already comes to be.

41| For nourishment is at one stage earlier, at another later. Now the residue of the first stage of nourishment is phlegm, and anything else of that kind. For phlegm too is a residue of useful nourishment; a sign of this is that, mixed with pure nourishment, it nourishes, and is used up in those who exert themselves. But the last residue is the least in amount produced from the greatest amount of nourishment. One must bear in mind that the whole daily growth of animals and plants is small: for if the same small amount were continually added, the resulting size would be excessive. The opposite, then, of what the ancients said must be maintained. For they said semen was what departs from every part, whereas we shall say it is what naturally goes toward every part; and they said it was a colliquescence, but it appears rather to be a residue. For it is more reasonable that what comes in last, and becomes the residue of such a process, should be similar to it — just as for painters there is often left over, of the flesh-coloured pigment, some that is similar to what was used up. But everything that undergoes colliquescence is destroyed and departs from its own nature. Evidence that semen is not a colliquescence but rather a residue is that the large animals produce few offspring, while the small ones are prolific. For colliquescence must necessarily be greater in the large animals, but residue less; for since the body is large, most of the nourishment is used up on it, so that little residue is produced.

42| Further, no place is assigned by nature to colliquescence; it flows wherever it finds an easy passage through the body. But to all the residues that are according to nature a place is assigned: for the dry nourishment, the lower belly; for the moist, the bladder; for the useful, the upper belly; and for the seminal, the womb, the genitals, and the breasts — for it is into these that it collects and flows together. And the things that happen bear witness that what has been described is semen; and these things happen because the nature of the residue is of this sort. For exhaustion becomes evident even when only a very small amount of this has departed, since the bodies are thereby deprived of the final product that arises from nourishment. But in a few, for a short time, at certain ages, its departure brings relief when it has become excessive — just as the first stage of nourishment does, if it exceeds in quantity; for when this too departs, bodies fare better, especially when other residues depart along with it. For it is not only semen that departs, but other powers mixed in with it depart along with it, and these are diseased; which is why, in some, what is discharged is sometimes infertile, because it has little of the seminal in it. But in most, and speaking generally, exhaustion and weakness result from sexual intercourse, rather, on account of the cause just stated.

43| Further, semen is not present either in the earliest age, or in old age, or in sicknesses: in sickness, because of weakness; in old age, because nature no longer concocts enough of it; and in the young, because of growth — for it is all used up beforehand; in about five years, at least in the case of human beings, the body seems to acquire half of the total size it acquires in all the rest of its time. In many animals and plants there is a difference in these respects between one genus and another, and within the same genus among individuals of the same species compared with one another, as between one man and another, or one vine and another. For some produce much semen, others little, and others none at all — not because of weakness, but in some cases quite the opposite; for it is used up on the body, as happens with some men, since they are in good bodily condition and become fleshy. Or rather, the fatter they are, the less semen they emit, and the less they desire sexual intercourse. Similar too is what happens with vines that 'go he-goat,' which run riot because of their nourishment, since he-goats too, when they are fat, mount the female less; which is why farmers slim them down beforehand, and why they call vines 'goating' after the condition of he-goats.

44| And fat people, both women and men, appear to be less fertile than those who are not fat, because in the well-nourished the residue, once concocted, turns into fat; for fat too is a residue, one that is healthy on account of good feeding. Some plants do not bear seed at all, such as the willow and the black poplar. There are, then, other causes as well of this condition: some fail to concoct because of weakness, others use it up because of strength, as has been said. Likewise some are copiously and abundantly seminal because of strength, others because of weakness; for much useless residue also gets mixed in, so that in some it even becomes a sickness, when their purgation does not proceed easily. Some, indeed, are cured by this, but others are even destroyed by it; for they waste away by colliquescence in this way, just as also into the urine — for this too has already happened as a sickness in some cases. Further, the passage is the same for the residue and for the semen; and in those in which a residue arises from both the moist and the dry nourishment, the discharge of seed takes place along the same passage as that of the moist residue (for it is a residue of moisture, since the nourishment of all things is rather moist); but in those which do not have this separate moist residue, it takes place along the passage of the dry residue's discharge.

45| Further, colliquescence is always a sign of disease, whereas the removal of residue is beneficial; but the discharge of semen partakes of both, because it also takes on something of the non-useful nourishment. But if it were a colliquescence, it would always be harmful; as it is, it does not do this. That semen, then, is a residue of useful nourishment, and of the last stage of it — whether or not all animals emit semen — is clear from what has been said.

46| After this we must determine what kind of residue this is, and what it is of, and also deal with the menstrual fluid; for in some of the animals that bear their young live, a menstrual fluid occurs. For through these questions it will become clear also about the female, whether she too emits semen as the male does, and what comes to be is one blend from two semens, or whether no semen at all is secreted from the female; and if none, whether nothing else either contributes to the generation but she merely provides a place, or whether she does contribute something, and how and in what manner. Now that blood is the ultimate nourishment for the blooded animals, and the analogous fluid for the bloodless ones, has been said before; and since seed too is a residue of nourishment, and of the ultimate nourishment, it would have to be either blood or the analogue of blood or something composed from these. And since each of the parts comes to be out of blood as it is concocted and in some way divided up, while seed, when concocted, is secreted as something different from blood, but when unconcocted, and when someone forces the issue by indulging too often in sexual intercourse, in some men it has already come forth blood-like, it is clear that seed would be a residue of the blood-like nourishment, of that nourishment in its final distribution to the parts. And it is for this reason that it has great power.

47| For indeed the departure of pure and healthy blood is weakening; and it is reasonable that the offspring come to resemble those who begot them, for what has arrived at the parts is like what was left behind. So the seed of the hand or of the face or of the whole animal is, indeterminately, hand or face or whole animal; and whatever each of those is in actuality, such is the seed in potentiality — either in respect of its own bulk, or it has some power within itself. For this is not yet clear to us from what has been determined: whether the body of the seed is the cause of the generation, or whether it has some state and a generative principle of motion. For neither the hand nor any other of the parts is a hand, or any part at all, apart from soul or some other power, but only homonymously so. And it is also clear that in all cases where a seminal colliquescence occurs, this too is a residue. This happens when the thing dissolves back into what was added, just as when the plaster that was smeared on falls off at once; for what departs is the same as what was first added. In the same way, the final residue is the same as the first colliquescent matter. Let this, then, be the determination on these points.

48| Since it is necessary that in the weaker one too a residue arise that is more abundant and less concocted, and since such a residue must be a quantity of blood-like fluid, and the weaker is that which by nature shares in less heat, and it has been said before that the female is of this kind, it is necessary that the blood-like secretion that occurs in the female also be a residue. And such is the discharge of what is called the menstrual fluid. That the menstrual fluid is a residue, then, and that it stands to females as, analogously, seed stands to males, is clear. And that this has been correctly stated, the things that happen concerning them are signs. For at the same age at which seed begins to arise and be secreted in males, in females the menstrual flow breaks out, and their voice changes, and there are the signs concerning the breasts. And as their prime declines, the ability to beget ceases in men, and the menstrual flow ceases in women. Further, the following too are signs that this discharge is a residue in females. For as a general rule women neither get hemorrhoids nor a flow of blood from the nostrils nor any other such thing, as long as the menstrual flow is regular; and if any of these does occur, the purgations become worse, on the ground that the secretion is being used up on these instead.

49| Further, females are less full of visible veins and are more delicate and smoother-skinned than males, because the residue that would go into these is secreted along with the menstrual fluid instead. And this same cause must be thought responsible also for the fact that the bulk of the body is smaller in females than in males among the live-bearing animals; for it is in these alone that the flow of the menstrual fluid occurs outward, and among these it is most conspicuous in women, for woman discharges the most secretion of all the animals. This is why she is always most conspicuously pale and lacking visible veins, and has a plainly evident deficiency of body compared with the males. Since this is what occurs in females as seed occurs in males, and it is not possible for two seminal secretions to occur at the same time, it is clear that the female does not contribute semen to the generation; for if it were semen, there would be no menstrual fluid, but as it is, because this comes to be, that does not exist. That the menstrual fluid, then, like the semen, is a residue, has been stated; and one might take as evidence for this some of the things that happen to animals. For fat animals are less productive of semen than lean ones, as has been said before.

50| And the cause is that fat too is a residue, just as semen is, and is concocted blood, but not in the same manner as semen. So it is reasonable that when the residue is spent on fat, matters relating to seed are deficient — as, for example, among the bloodless animals, the cephalopods and the crustaceans are at their best around the time of pregnancy. For because they are bloodless and no fat forms in them, the analogue of fat in them is secreted instead into the seminal residue. A sign that the female does not emit a semen of the same kind as the male is this: nor does generation occur when the two are mixed together, as some say, on the ground that the female often conceives without pleasure occurring for her in the intercourse; and again, when it does occur, generation is no less likely; and even when male and female reach their culmination together, no generation occurs unless the moisture of what is called the menstrual fluid is present in due measure. This is why the female neither begets when it does not occur at all, nor, when it does occur, does she conceive as a rule at the time when it is flowing out, but after the purgation. For at one time she has no nourishment or matter out of which the power present in the seed from the male will be able to construct the animal.

51| At another time it is washed away together with the flow because of its abundance. But when, after the flow has occurred, it departs, what is left behind coalesces. As for those women who conceive while the menstrual fluid is not occurring, or in the interval while it is occurring but not afterward, the cause is that for these, just such an amount of moisture arises as remains behind after the purgation in fertile women, and no greater residue arises so as to also pass outward; whereas in others, after the purgation, the mouth of the womb closes up. So whenever much has departed, but a purgation is still occurring, though not so much as to wash out the seed, then women who have intercourse at that time conceive again. And there is nothing strange in its still occurring in women who have already conceived; for even later, up to a point, the menstrual fluid keeps recurring, though little and not throughout. But this is a diseased condition, which is why it happens to few women and rarely; what happens as a general rule is what is most in accordance with nature. That the female, then, contributes the matter to generation, and that this consists in the composition of the menstrual fluid, and that the menstrual fluid is a residue, is clear.

52| As for what some suppose — that the female contributes semen in intercourse because a pleasure similar to that of the males sometimes occurs for them, along with a moist secretion at the same time — this moisture is not seminal but is peculiar to the place, in each woman's case. For it is a secretion of the womb, and it occurs in some women and not in others. It occurs, generally speaking, in fair-skinned and feminine women, but does not occur in dark-skinned and masculine-looking ones. And the amount, in those in whom it occurs, is sometimes not in proportion to an emission of semen, but greatly exceeds it. Further, different foods make a great difference, in different women, as to whether this secretion occurs less or more; for instance, some pungent foods make the discharge noticeably more abundant. And the fact that pleasure occurs in intercourse is due not only to the emission of semen but also of breath, and it is from the coalescing of this that the semen is ejected. This is clear in the case of boys who are not yet able to emit semen but are near that age, and in the case of infertile men; for pleasure occurs in all of these when they are aroused. And in men whose generative power has been destroyed, sometimes the bowels are loosened, because a residue is secreted into the belly which is unable to be concocted and become semen.

53| A woman also resembles a child in form, and the female is, as it were, an infertile male. For the female is female by virtue of a certain incapacity, namely an inability to concoct semen out of the final stage of nourishment (this is either blood or its analogue in bloodless animals) because of the coldness of her nature. So just as in the stomach, through failure of concoction, diarrhea occurs, so in the veins there occur, among other hemorrhages, that of the menstrual discharge as well; for this too is a hemorrhage, but whereas those others are due to disease, this one is natural. So it is clear that it is reasonable for generation to come about from this. For the menstrual fluid is semen, not pure, but needing working-up, just as in the generation of fruit, when it has not yet been strained, the nourishment is present in it but needs working-up for its purification. This is why, when the one is mixed with the seed and the other with pure nourishment, the one generates and the other nourishes. A sign that the female does not emit semen is also the fact that the pleasure that occurs in intercourse is felt, by touch, in the same place as in males; and yet females do not emit this moisture from there. Further, this excretion does not occur in all females, but only in the blooded ones, and not even in all of these, but only in those whose wombs are not close up under the diaphragm and which do not lay eggs; and again it does not occur in the bloodless animals, but rather their analogue does.

54| For what blood is in some animals, in these a different compound takes its place. The cause of there being no purgation either in these, or in those blooded animals mentioned—those that have their wombs low down and do not lay eggs—is the dryness of their bodies, which leaves little residue, and only so much as suffices for generation, none being emitted outside. As for those that bear their young alive without laying eggs (these are man and those of the four-footed animals that bend their hind legs inward; for all of these bear their young alive without laying eggs), in all of them this purgation does occur, except if some creature is deformed in its generation, such as the mule, though the purgations do not rise to the surface in them as they do in human beings. The precise details of how these matters stand for each of the animals have been written up in the Researches on Animals. The greatest purgation among animals occurs in women, and correspondingly the greatest emission of semen occurs in men, in proportion to their size. The cause is that the constitution of their bodies is moist and hot; for in such a constitution the greatest amount of residue must necessarily arise. Further, such creatures do not have, in their bodies, parts into which the residue is diverted, as other animals do; for they have neither a great quantity of hair over the body, nor excretions in the form of bones and horns and teeth.

55| A sign that the semen is present in the menstrual fluid is this: at the same time, as has been said before, this residue arises in males, and the menstrual discharge shows itself in females, at the same age, as though the regions receptive of each residue were being differentiated at the same time; and as the regions near each are loosened, the growth of pubic hair breaks out. When the regions are about to be differentiated they swell up under the action of breath—in males more visibly around the testicles, though it shows also around the breasts, in females rather around the breasts; for when these have risen the space of two fingers, that is when the menses begin, in most cases. Now in all those living things in which the female and the male are not separated, in these the semen is, as it were, an embryo—I call an embryo the first mixture of female and male. This is why from one semen one body arises, just as from one grain of wheat one shoot, just as from one egg one animal; for twin eggs are two eggs. But in those kinds in which the female and the male are distinguished, in these it is possible for many animals to arise from one act of semen-emission, on the ground that the semen differs in nature in plants as against animals.

56| A sign of this is that from a single mating more than one offspring is produced in those able to generate more than one at a time. From this it is also clear that the seed does not come from every part of the body; for neither would separated parts, coming from the same part, be secreted at once, nor, if they arrived together at the womb, would they be separated out there; but what happens is, as is reasonable, since the male supplies the form and the origin of the motion, while the female supplies the body and the matter—just as in the curdling of milk the body is the milk, while the fig-juice, or rennet, is that which has the principle that brings it together—so it is with what comes from the male, being divided up within the female. For what cause it is divided in some cases into more parts, in others into fewer, in others into a single part only, will be a separate account. But because it makes no difference in respect of form, but only whether the part being divided off is commensurate with the matter—neither too little, so that it cannot concoct or bring it together, nor too much, so that it dries it out—more offspring are generated in this way. But from the first thing that brings it together, from one thing already one thing alone arises. That the female, then, does not contribute semen to generation, but does contribute something, and that this is the substance of the menstrual fluid and its analogue in bloodless animals, is clear both from what has been said and, for those who examine the matter in general terms, from the argument as well.

57| For necessarily that which generates and that from which it generates, even if they are one thing, must differ in form, and their account must be different; and where the powers, and the bodies, and the nature are kept separate, the nature of that which acts must be other than that of that which is acted upon. If, then, the male stands as that which moves and acts, and the female, qua female, as that which is acted upon, the female would contribute to the male's semen not semen but matter. And this is indeed what plainly happens: for the nature of the menstrual fluid is that of matter in the primary sense.

58| Let these matters be determined in this way. At the same time it is clear from this what belongs to the next inquiry: how it is, exactly, that the male contributes to generation, and in what way the semen from the male is a cause of the thing generated—whether as being present within it and being straightaway a part of the body generated, mixed together with the matter that comes from the female, or whether the body has no share at all in the semen, but only the power and motion within it. For this is what acts, while what is constituted and takes on the form is what is left of the residue within the female. In accordance with the argument, then, this is how it appears, and so it appears also from the facts. For when one examines the matter generally, it does not appear that one thing comes to be out of the passive and the active in such a way that the agent is present as a part within the thing generated, nor in general out of the moved and the mover. But indeed the female, qua female, is passive, and the male, qua male, is active, and is that from which the origin of the motion comes. So that if the extremes of each are taken, in the sense that the one is agent and mover, the other passive and moved, the thing generated does not arise out of these as one thing composed of them, but rather in the way that a bed arises out of the carpenter and the wood, or a ball out of the wax and the shape.

59| It is clear, then, that it is not necessary for anything to depart from the male, and that, even if something does depart, what comes to be is not therefore from this as something present within it, but rather as from what set it in motion and from the form — just as the one who is healed is healed from the medical art. And what actually happens agrees with this account. This is why some males, even while copulating with females, are seen to emit no part at all into the female — on the contrary, it is the female that emits into the male, which is what happens with some insects. For what the semen produces in the female in those animals that do emit it, the moisture and power within the animal itself produces in these cases, the female bringing forward the part that receives the residue; and this is why such animals remain coupled, doing this until the embryo is formed, as with semen; but once they come apart, they quickly discharge the embryo. For what it produces is incomplete: all such animals produce larvae. The greatest sign of this is what happens with birds and with the egg-laying kind of fish — namely, that the semen does not come from all the parts, and that the male does not emit any such part as will be present within the offspring, but only gives life by the power in the semen, as we said in the case of insects, where the female emits into the male.

60| For if a hen happens to be carrying wind-eggs, and is afterward mated before the egg has changed from being wholly yellow to turning white, the eggs become fertile instead of remaining wind-eggs; but if she has been mated by one male and is then mated by another while the egg is still yellow, the whole brood of chicks turns out according to the male who mated her later. This is why some of those who take pains breeding fine birds do it this way, changing the earlier matings for later ones — on the ground that the semen does not become mixed in and present within the offspring, nor come from every part of the male. For if it came from both males, the offspring would have the same parts twice over. Instead, by its power, the male's semen fashions the matter and nourishment in the female into a certain quality. For it is possible for the semen that enters later to do this, by heating and concocting it; for the egg goes on taking in nourishment as long as it is growing. The same thing happens also in the generation of egg-laying fish. For when the female has laid the eggs, the male sprinkles milt over them; and whichever eggs it touches become fertile, while those it does not touch remain infertile — which shows that the male contributes to animals not in respect of quantity, but of quality.

61| That the semen, then, does not depart from every part in those animals that emit semen, and that the female does not contribute to the generation of the things composed in the same way as the male, but rather the male contributes the principle of motion and the female the matter, is clear from what has been said. For this is why the female does not generate by itself: it needs a principle, something to set it in motion and to define it. Yet in some animals, such as birds, nature is able to generate up to a point; for these do form something, but what they form is incomplete — the so-called wind-eggs.

62| The generation of what comes to be takes place in the female, not in the male; nor again does the male emit its semen into itself, nor the female into itself, but both contribute into the female what comes from them, because it is in the female that the matter is present out of which the thing fashioned consists. And some of this matter must be present all at once straightaway, that out of which the first embryo is formed, while more of the matter must be added afterward, so that what is developing may grow. So it is necessary that the offspring be present in the female; for indeed the carpenter works upon wood and the potter upon clay, and in general all working, and the final motion, occurs upon the matter — just as house-building occurs in the things being built. From this one could also grasp how the male contributes to generation. For not every male emits semen, and in those males that do emit it, this is no part of the developing embryo — just as nothing departs from the carpenter into the wood as matter, nor is any part of the carpenter's craft present in the thing produced, but the shape and the form come to be in the matter from him through the motion; and the soul, in which the form and the knowledge reside, moves the hands, or some other part, with a certain kind of motion — a different motion when what comes to be is different, the same motion when what comes to be is the same — while the hands and the instruments move the matter.

63| In the same way, the nature that is in the male, in those animals that emit semen, uses the semen as an instrument possessing motion in actuality, just as in things produced by craft the instruments move; for in a sense the motion of the craft is present in them. Those animals, then, that emit semen contribute to generation in this way; but in those that do not emit semen, where instead the female deposits some part of itself into the male, it seems to do something like bringing the matter to the craftsman — text corrupt at this point — nature is not able to do this by other means in the case of the males, but the motions have force only when the female itself remains in close attendance, and it resembles those who mold by hand, not those who build with tools; for it does not fashion the thing being formed by touching it through some other agent, but itself, by its own parts.

64| In all animals capable of locomotion, then, the female is separate from the male, and the female is one animal and the male another, though the same in species — for instance, both are human. But in plants these powers are mixed together, and the female is not separated from the male. This is why plants generate from themselves, and emit not semen but an embryo — what are called seeds. And Empedocles puts this well when he writes, "Thus tall trees first lay eggs — olives." For the egg is an embryo, and the animal comes to be from a part of it, while the rest is nourishment; and likewise, the growing plant comes to be from a part of the seed, while the rest becomes nourishment for the shoot and the first root. In some sense these things converge in plants (text corrupt at this point), and their nature aims at their becoming one — which is manifest to sight in animals that mix and mate, one single animal coming to be out of both. And some remain joined (text corrupt at this point) until the embryo has formed, as with mating insects; while others remain joined until the male sends off some of its added parts, which will form the embryo over a longer time, as with blooded animals.

65| For some remain joined for only part of a day, while the semen takes several days to form the embryo; and once they have emitted this, they separate. And in a quite literal sense, animals seem to be divisible, like plants — as if, when a plant put forth its seed, one were to break that seed apart and separate it into the female and male present within it. And nature fashions all this reasonably. For the substance of plants has no other function or activity except the generation of seed, so that, since this comes about through the female and the male joined together, nature mixed these and arranged them together with each other; this is why in plants the female and the male are inseparable. But plants have been examined elsewhere. In the case of the animal, generating is not its only function — for this is common to all living things — but all animals also share in some kind of knowledge, some in more, some in less, and some in only a very small amount. For they have perception, and perception is a kind of knowledge. And how valuable or valueless this is differs greatly, when one looks at it in relation to practical wisdom on the one hand and to the class of lifeless things on the other. For in relation to thinking, sharing only in touch and taste seems to amount to almost nothing, but in relation to having no perception at all, it is the best thing there is;

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