by Aristotle
To return to testacea, some of them are formed spontaneously, some
emit a sort of generative substance from themselves, but these also
often come into being from a spontaneous formation. To understand this
we must grasp the different methods of generation in plants; some of
these are produced from seed, some from slips, planted out, some by
budding off alongside, as the class of onions. In the last way
produced mussels, for smaller ones are always growing off alongside
the original, but the whelks, the purple-fish, and those which are
said to 'spawn' emit masses of a liquid slime as if originated by
something of a seminal nature. We must not, however, consider that
anything of the sort is real semen, but that these creatures
participate in the resemblance to plants in the manner stated above.
Hence when once one such creature has been produced, then is
produced a number of them. For all these creatures are liable to be
even spontaneously generated, and so to be formed still more
plentifully in proportion if some are already existing. For it is
natural that each should have some superfluous residue attached to
it from the original, and from this buds off each of the creatures
growing alongside of it. Again, since the nutriment and its residue
possess a like power, it is likely that the product of those
testacea which 'spawn' should resemble the original formation, and
so it is natural that a new animal of the same kind should come into
being from this also.
All those which do not bud off or 'spawn' are spontaneously
generated. Now all things formed in this way, whether in earth or
water, manifestly come into being in connexion with putrefaction and
an admixture of rain-water. For as the sweet is separated off into the
matter which is forming, the residue of the mixture takes such a form.
Nothing comes into being by putrefying, but by concocting;
putrefaction and the thing putrefied is only a residue of that which
is concocted. For nothing comes into being out of the whole of
anything, any more than in the products of art; if it did art would
have nothing to do, but as it is in the one case art removes the
useless material, in the other Nature does so. Animals and plants come
into being in earth and in liquid because there is water in earth, and
air in water, and in all air is vital heat so that in a sense all
things are full of soul. Therefore living things form quickly whenever
this air and vital heat are enclosed in anything. When they are so
enclosed, the corporeal liquids being heated, there arises as it
were a frothy bubble. Whether what is forming is to be more or less
honourable in kind depends on the embracing of the psychical
principle; this again depends on the medium in which the generation
takes place and the material which is included. Now in the sea the
earthy matter is present in large quantities, and consequently the
testaceous animals are formed from a concretion of this kind, the
earthy matter hardening round them and solidifying in the same
manner as bones and horns (for these cannot be melted by fire),
and the matter (or body) which contains the life being included
within it.
The class of snails is the only class of such creatures that has
been seen uniting, but it has never yet been sufficiently observed
whether their generation is the result of the union or not.
It may be asked, if we wish to follow the right line of
investigation, what it is in such animals the formation of which
corresponds to the material principle. For in the females this is a
residual secretion of the animal, potentially such as that from
which it came, by imparting motion to which the principle derived from
the male perfects the animal. But here what must be said to correspond
to this, and whence comes or what is the moving principle which
corresponds to the male? We must understand that even in animals which
generate it is from the incoming nourishment that the heat in the
animal makes the residue, the beginning of the conception, by
secretion and concoction. The like is the case also in plants,
except that in these (and also in some animals) there is no
further need of the male principle, because they have it mingled
with the female principle within themselves, whereas the residual
secretion in most animals does need it. The nourishment again of
some is earth and water, of others the more complicated combinations
of these, so that what the heat in animals produces from their
nutriment, this does the heat of the warm season in the environment
put together and combine by concoction out of the sea-water on the
earth. And the portion of the psychical principle which is either
included along with it or separated off in the air makes an embryo and
puts motion into it. Now in plants which are spontaneously generated
the method of formation is uniform; they arise from a part of
something, and while some of it is the starting-point of the plant,
some is the first nourishment of the young shoots.... Other animals
are produced in the form of a scolex, not only those bloodless animals
which are not generated from parents but even some sanguinea, as a
kind of mullet and some other river fishes and also the eel kind.
For all of these, though they have but little blood by nature, are
nevertheless sanguinea, and have a heart with blood in it as the
origin of the parts; and the so-called 'entrails of earth', in which
comes into being the body of the eel, have the nature of a scolex.
Hence one might suppose, in connexion with the origin of men and
quadrupeds, that, if ever they were really 'earth-born' as some say,
they came into being in one of two ways; that either it was by the
formation of a scolex at first or else it was out of eggs. For
either they must have had in themselves the nutriment for growth (and
such a conception is a scolex) or they must have got it from
elsewhere, and that either from the mother or from part of the
conception. If then the former is impossible (I mean that nourishment
should flow to them from the earth as it does in animals from the
mother), then they must have got it from some part of the conception,
and such generation we say is from an egg.
It is plain then that, if there really was any such beginning of the
generation of all animals, it is reasonable to suppose to have been
one of these two, scolex or egg. But it is less reasonable to
suppose that it was from eggs, for we do not see such generation
occurring with any animal, but we do see the other both in the
sanguinea above mentioned and in the bloodless animals. Such are
some of the insects and such are the testacea which we are discussing;
for they do not develop out of a part of something (as do animals
from eggs), and they grow like a scolex. For the scolex grows towards
the upper part and the first principle, since in the lower part is the
nourishment for the upper. And this resembles the development of
animals from eggs, except that these latter consume the whole egg,
&
nbsp; whereas in the scolex, when the upper part has grown by taking up into
itself part of the substance in the lower part, the lower part is then
differentiated out of the rest. The reason is that in later life
also the nourishment is absorbed by all animals in the part below
the hypozoma.
That the scolex grows in this way is plain in the case of bees and
the like, for at first the lower part is large in them and the upper
is smaller. The details of growth in the testacea are similar. This is
plain in the whorls of the turbinata, for always as the animal grows
the whorls become larger towards the front and what is called the head
of the creature.
We have now pretty well described the manner of the development of
these and the other spontaneously generated animals. That all the
testacea are formed spontaneously is clear from such facts as these.
They come into being on the side of boats when the frothy mud
putrefies. In many places where previously nothing of the kind
existed, the so-called limnostrea, a kind of oyster, have come into
being when the spot turned muddy through want of water; thus when a
naval armament cast anchor at Rhodes a number of clay vessels were
thrown out into the sea, and after some time, when mud had collected
round them, oysters used to be found in them. Here is another proof
that such animals do not emit any generative substance from
themselves; when certain Chians carried some live oysters over from
Pyrrha in Lesbos and placed them in narrow straits of the sea where
tides clash, they became no more numerous as time passed, but
increased greatly in size. The so-called eggs contribute to generation
but are only a condition, like fat in the sanguinea, and therefore the
oysters are savoury at these periods. A proof that this substance is
not really eggs is the fact that such 'eggs' are always found in
some testacea, as in pinnae, whelks, and purple-fish; only they are
sometimes larger and sometimes smaller; in others as pectens, mussels,
and the so-called limnostrea, they are not always present but only
in the spring; as the season advances they dwindle and at last
disappear altogether; the reason being that the spring is favourable
to their being in good condition. In others again, as the ascidians,
nothing of the sort is visible. (The details concerning these last,
and the places in which they come into being, must be learnt from
the Enquiry.)
Book IV
1
WE have thus spoken of the generation of animals both generally
and separately in all the different classes. But, since male and
female are distinct in the most perfect of them, and since we say that
the sexes are first principles of all living things whether animals or
plants, only in some of them the sexes are separated and in others
not, therefore we must speak first of the origin of the sexes in the
latter. For while the animal is still imperfect in its kind the
distinction is already made between male and female.
It is disputed, however, whether the embryo is male or female, as
the case may be, even before the distinction is plain to our senses,
and further whether it is thus differentiated within the mother or
even earlier. It is said by some, as by Anaxagoras and other of the
physicists, that this antithesis exists from the beginning in the
germs or seeds; for the germ, they say, comes from the male while
the female only provides the place in which it is to be developed, and
the male is from the right, the female from the left testis, and so
also that the male embryo is in the right of the uterus, the female in
the left. Others, as Empedocles, say that the differentiation takes
place in the uterus; for he says that if the uterus is hot or cold
what enters it becomes male or female, the cause of the heat or cold
being the flow of the catamenia, according as it is colder or
hotter, more 'antique' or more 'recent'. Democritus of Abdera also
says that the differentiation of sex takes place within the mother;
that however it is not because of heat and cold that one embryo
becomes female and another male, but that it depends on the question
which parent it is whose semen prevails,- not the whole of the
semen, but that which has come from the part by which male and
female differ from one another. This is a better theory, for certainly
Empedocles has made a rather light-hearted assumption in thinking that
the difference between them is due only to cold and heat, when he
saw that there was a great difference in the whole of the sexual
parts, the difference in fact between the male pudenda and the uterus.
For suppose two animals already moulded in embryo, the one having
all the parts of the female, the other those of the male; suppose them
then to be put into the uterus as into an oven, the former when the
oven is hot, the latter when it is cold; then on the view of
Empedocles that which has no uterus will be female and that which
has will be male. But this is impossible. Thus the theory of
Democritus would be the better of the two, at least as far as this
goes, for he seeks for the origin of this difference and tries to
set it forth; whether he does so well or not is another question.
Again, if heat and cold were the cause of the difference of the
parts, this ought to have been stated by those who maintain the view
of Empedocles; for to explain the origin of male and female is
practically the same thing as to explain this, which is the manifest
difference between them. And it is no small matter, starting from
temperature as a principle, to collect the cause of the origin of
these parts, as if it were a necessary consequence for this part which
they call the uterus to be formed in the embryo under the influence of
cold but not under that of heat. The same applies also to the parts
which serve for intercourse, since these also differ in the way stated
previously.
Moreover male and female twins are often found together in the
same part of the uterus; this we have observed sufficiently by
dissection in all the vivipara, both land animals and fish. Now if
Empedocles had not seen this it was only natural for him to fall
into error in assigning this cause of his; but if he had seen it it is
strange that he should still think the heat or cold of the uterus to
be the cause, since on his theory both these twins would have become
either male or female, but as it is we do not see this to be the fact.
Again he says that the parts of the embryo are 'sundered', some
being in the male and some in the female parent, which is why they
desire intercourse with one another. If so it is necessary that the
sexual parts like the rest should be separated from one another,
already existing as masses of a certain size, and that they should
come into being in the embryo on account of uniting with one
another, not on account of cooling or heating of the semen. But
perhaps it would take too long to discuss thoroughly such a cause as
this which is stated by Empedocles, for
its whole character seems to
be fanciful. If, however, the facts about semen are such as we have
actually stated, if it does not come from the whole of the body of the
male parent and if the secretion of the male does not give any
material at all to the embryo, then we must make a stand against
both Empedocles and Democritus and any one else who argues on the same
lines. For then it is not possible that the body of the embryo
should exist 'sundered', part in the female parent and part in the
male, as Empedocles says in the words: 'But the nature of the limbs
hath been sundered, part in the man's...'; nor yet that a whole embryo
is drawn off from each parent and the combination of the two becomes
male or female according as one part prevails over another.
And, to take a more general view, though it is better to say that
the one part makes the embryo female by prevailing through some
superiority than to assign nothing but heat as the cause without any
reflection, yet, as the form of the pudendum also varies along with
the uterus from that of the father, we need an explanation of the fact
that both these parts go along with each other. If it is because
they are near each other, then each of the other parts also ought to
go with them, for one of the prevailing parts is always near another
part where the struggle is not yet decided; thus the offspring would
be not only female or male but also like its mother or father
respectively in all other details.
Besides, it is absurd to suppose that these parts should come into
being as something isolated, without the body as a whole having
changed along with them. Take first and foremost the blood-vessels,
round which the whole mass of the flesh lies as round a framework.
It is not reasonable that these should become of a certain quality
because of the uterus, but rather that the uterus should do so on
account of them. For though it is true that each is a receptacle of
blood of some kind, still the system of the vessels is prior to the
other; the moving principle must needs always be prior to that which
it moves, and it is because it is itself of a certain quality that