As a rule, then, as was stated, the voice of the male differs
from the voice of the female, in animals where the voice admits of a
continuous and prolonged sound, in the fact that the note in the
male voice is more deep and bass; not, however, in all animals, for
the contrary holds good in the case of some, as for instance in
kine: for here the cow has a deeper note than the bull, and the calves
a deeper note than the cattle. And we can thus understand the change
of voice in animals that undergo gelding; for male animals that
undergo this process assume the characters of the female.

There is a difference

observable also in the neighings of
horses. That is to say, the female foal has a thin small neigh, and
the male foal a small neigh, yet bigger and deeper-toned than that
of the female, and a louder one as time goes on. And when the young
male and female are two years old and take to breeding, the neighing
of the stallion becomes loud and deep, and that of the mare louder and
shriller than heretofore; and this change goes on until they reach the
age of about twenty years; and after this time the neighing in both
sexes becomes weaker and weaker.

In other animals

there is no hair-growth at the pubes (for
some animals have no hair at all, and others have none on the belly,
or less on the belly than on the back), but still, in some animals the
change of voice is quite obvious; and in some animals other organs
give indication of the commencing secretion of the sperm and the onset
of generative capacity. As a general rule the female is
sharper-toned in voice than the male, and the young animal than the
elder; for, by the way, the stag has a much deeper-toned bay than
the hind. Moreover, the male cries chiefly at rutting time, and the
female under terror and alarm; and the cry of the female is short, and
that of the male prolonged. With dogs also, as they grow old, the tone
of the bark gets deeper.

In man, then, maturity is indicated by a change of the tone of
voice, by an increase in size and an alteration in appearance of the
sexual organs, as also in an increase of size and alteration in
appearance of the breasts; and above all, in the hair-growth at the
pubes. Man begins to possess seminal fluid about the age of
fourteen, and becomes generatively capable at about the age of
twenty-one years.

Further,

animals differ from one another in regard to the time
of life that is best adapted for sexual intercourse.

To begin with, in most animals the secretion of the seminal
fluid and its generative capacity are not phenomena simultaneously
manifested, but manifested successively. Thus, in all animals, the
earliest secretion of sperm is unfruitful, or if it be fruitful the
issue is comparatively poor and small. And this phenomenon is
especially observable in man, in viviparous quadrupeds, and in
birds; for in the case of man and the quadruped the offspring is
smaller, and in the case of the bird, the egg.

For animals that copulate, of one and the same species, the
age for maturity is in most species tolerably uniform, unless it
occurs prematurely by reason of abnormality, or is postponed by
physical injury.

Of the pigeon

family there are many diversities; for the peristera
or common pigeon is not identical with the peleias or rock-pigeon.
In other words, the rock-pigeon is smaller than the common pigeon, and
is less easily domesticated; it is also black, and small, red-footed
and rough-footed; and in consequence of these peculiarities it is
neglected by the pigeon-fancier. The largest of all the pigeon species
is the phatta or ring-dove; and the next in size is the oenas or
stock-dove; and the stock-dove is a little larger than the common
pigeon. The smallest of all the species is the turtle-dove. Pigeons
breed and hatch at all seasons, if they are furnished with a sunny
place and all requisites; unless they are so furnished, they breed
only in the summer. The spring brood is the best, or the autumn brood.
At all events, without doubt, the produce of the hot
season, the
summer brood, is the poorest of the three.)

(Of birds the wild species, as has been stated, as a general
rule pair and breed only once a year. The swallow, however, and the
blackbird breed twice. With regard to the blackbird, however, its
first brood is killed by inclemency of weather (for it is the earliest
of all birds to breed), but the second brood it usually succeeds in
rearing.

Birds that are domesticated or that are capable of domestication
breed frequently, just as the common pigeon breeds all through the
summer, and as is seen in the barn-door hen; for the barn-door cock
and hen have intercourse, and the hen breeds, at all seasons alike:
excepting by the way, during the days about the winter solstice.

The purple murex

breeds about springtime, and the ceryx at the
close of the winter. And, as a general rule, the testaceans are
found to be furnished with their so-called eggs in spring-time and
in autumn, with the exception of the edible urchin; for this animal
has the so-called eggs in most abundance in these seasons, but at no
season is unfurnished with them; and it is furnished with them in
especial abundance in warm weather or when a full moon is in the
sky. Only, by the way, these remarks do not apply to the sea-urchin
found in the Pyrrhaean Straits, for this urchin is at its best for
table purposes in the winter; and these urchins are small but full
of eggs.

Snails are found by observations to become in all cases
impregnated about the same season.

The octopus

pairs in winter and breeds in spring, lying hidden
for about two months. Its spawn is shaped like a vine-tendril, and
resembles the fruit of the white poplar; the creature is
extraordinarily prolific, for the number of individuals that come from
the spawn is something incalculable. The male differs from the
female in the fact that its head is longer, and that the organ
called by the fishermen its penis, in the tentacle, is white. The
female, after laying her eggs, broods over them, and in consequence
gets out of condition, by reason of not going in quest of food
during the hatching period.

Of the grey mullets,

the chelon begins to be in roe between
the

The molluscs also breed in spring. Of the marine molluscs one of
the first to breed is the sepia. It spawns at all times of the day and
its period of gestation is fifteen days. After the female has laid her
eggs, the male comes and discharges the milt over the eggs, and the
eggs thereupon harden. And the two sexes of this animal go about in
pairs, side by side; and the male is more mottled and more black on
the back than the female.

middle of November

and the middle of December; as also the sargue,
and the smyxon or myxon, and the cephalus; and their period of
gestation is thirty days. And, by the way, some of the grey mullet
species are not produced from copulation, but grow spontaneously
from mud and sand.

As a general rule, then, fishes are in roe in the spring-time;
while some, as has been said, are so in summer, in autumn, or in
winter. But whereas the impregnation in the spring-time follows a
general law, impregnation in the other seasons does not follow the
same rule either throughout or within the limits of one genus; and,
further, conception in these variant seasons is not so prolific.
And, indeed, we must bear this in mind, that just as with plants and
quadrupeds diversity of locality has much to do not only with
general physical health but also with the comparative frequency of
sexual intercourse and generation, so also with regard to fishes
locality of itself has much to do not only in regard to the size and
vigour of the creature, but also in regard to its parturition and
its copulations, causing the same species to breed oftener in one
place and seldomer in another.

Fish for the most part breed some time or other during the three
months between the middle of March and the middle of June. Some few
breed in autumn: as, for instance, the saupe and the sargus, and
such others of this sort as breed shortly before the autumn equinox;
likewise the electric ray and the angel-fish. Other fishes breed
both in winter and in summer, as was previously observed: as, for
instance, in winter-time the basse, the grey mullet, and the belone or
pipe-fish; and in summer-time, from the middle of June to the middle
of July, the female tunny, about the time of the summer solstice;
and the tunny lays a sac-like enclosure in which are contained a
number of small eggs. The ryades or shoal-fishes breed in summer.

Some fishes breed at all seasons, as the muraena. This animal
lays a great number of eggs at a time; and the young when hatched
are very small but grow with great rapidity, like the young of the
hippurus, for these fishes from being diminutive at the outset grow
with exceptional rapidity to an exceptional size. (Be it observed that
the muraena breeds at all seasons, but the hippurus only in the
spring. The smyrus differs from the smyraena; for the muraena is
mottled and weakly, whereas the smyrus is strong and of one uniform
colour, and the colour resembles that of the pine-tree, and the animal
has teeth inside and out. They say that in this case, as in other
similar ones, the one is the male, and the other the female, of a
single species. They come out on to the land, and are frequently
caught.) Fishes, then, as a general rule, attain their full growth
with great rapidity, but this is especially the case, among small
fishes, with the coracine or crow-fish: it spawns, by the way, near
the shore, in weedy and tangled spots. The orphus also, or
sea-perch, is small at first, and rapidly attains a great size. The
pelamys and the tunny breed in the Euxine, and nowhere else. The
cestreus or mullet, the chrysophrys or gilt-head, and the labrax or
basse, breed best where rivers run into the sea. The orcys or
large-sized tunny, the scorpis, and many other species spawn in the
open sea.

Of cartilaginous fishes, the rhina or angelfish is the only one
that breeds twice; for it breeds at the beginning of autumn, and at
the setting of the Pleiads: and, of the two seasons, it is in better
condition in the autumn. It engenders at a birth seven or eight young.
Certain of the dog-fishes, for example the spotted dog, seem to
breed twice a month, and this results from the circumstance that the
eggs do not all reach maturity at the same time.

Insects copulate

and breed in winter also, that is when the
weather is fine and south winds prevail; such, I mean, as do not
hibernate, as the fly and the ant. The greater part of wild animals
bring forth once and once only in the year, except in the case of
animals like the hare, where the female can become superfoetally
impregnated.

In like manner the great majority of fishes breed only once a
year, like the shoal-fishes (or, in other words, such as are caught in
nets), the tunny, the pelamys, the grey mullet, the chalcis, the
mackerel, the sciaena, the psetta and the like, with the exception
of the labrax or basse; for this fish (alone amongst those
mentioned) breeds twice a year, and the second brood is the weaker
of the two. The trichias and the rock-fishes breed twice a year; the
red mullet breeds thrice a year, and is exceptional in this respect.
This conclusion in regard to the red mullet is inferred from the
spawn; for the spawn of the fish may be seen in certain places at
three different times of the year. The scorpaena breeds twice a
year. The sargue breeds twice, in the spring and in the autumn. The
saupe breeds once a year only, in the autumn. The female tunny
breeds only once a year, but owing to the fact that the fish in some
cases spawn early and in others late, it looks as though the fish bred
twice over. The first spawning takes place in December before the
solstice, and the latter spawning in the spring. The male tunny
differs from the female in being unprovided with the fin beneath the
belly which is called aphareus.

(The aithyia, or diver, and the larus, or gull, lay their eggs
on rocks bordering on the sea, two or three at a time; but the gull
lays in the summer, and the diver at the beginning of spring, just
after the winter solstice, and it broods over its eggs as birds do
in general. And neither of these birds resorts to a hiding-place.)

The halcyon is the most rarely seen of all birds. It is seen
only about the time of the setting of the Pleiads and the winter
solstice. When ships are lying at anchor in the roads, it will hover
about a vessel and then disappear in a moment, and Stesichorus in
one of his poems alludes to this peculiarity. The nightingale also
breeds at the beginning of summer, and lays five or six eggs; from
autumn until spring it retires to a hiding-place.

With birds the far greater part, as has been said, pair and
breed during the spring and early summer, with the exception of the
halcyon.

The halcyon breeds at the season of the winter solstice.
Accordingly, when this season is marked with calm weather, the name of
'halcyon days' is given to the seven days preceding, and to as many
following, the solstice; as Simonides the poet says:

God lulls for fourteen days the winds to sleep

In winter; and this temperate interlude

Men call the Holy Season, when the deep

Cradles the mother Halcyon and her brood.

And these days are calm, when southerly winds prevail at the
solstice, northerly ones having been the accompaniment of the Pleiads.
The halcyon is said to take seven days for building her nest, and
the other seven for laying and hatching her eggs. In our country there
are not always halcyon days about the time of the winter solstice, but
in the Sicilian seas this season of calm is almost periodical. The
bird lays about five eggs.

So much for the modes of sexual intercourse in all animals; but,
with regard to the same phenomenon, there are definite laws followed
as regards the season of the year and the age of the animal.

Animals in general seem naturally disposed to this intercourse
at about the same period of the year, and that is when winter is
changing into summer. And this is the season of spring, in which
almost all things that fly or walk or swim take to pairing. Some
animals pair and breed in autumn also and in winter, as is the case
with certain aquatic animals and certain birds. Man pairs and breeds
at all seasons, as is the case also with domesticated animals, owing
to the shelter and good feeding they enjoy: that is to say, with those
whose period of gestation is also comparatively brief, as the sow
and the bitch, and with those birds that breed frequently. Many
animals time the season of intercourse with a view to the right
nurture subsequently of their young. In the human species, the male is
more under sexual excitement in winter, and the female in summer.

Insects copulate

at the hinder end, and the smaller individuals
mount the larger; and the smaller individual is I I is the male. The
female pushes from underneath her sexual organ into the body of the
male above, this being the reverse of the operation observed in
other creatures; and this organ in the case of some insects appears to
be disproportionately large when compared to the size of the body, and
that too in very minute creatures; in some insects the disproportion
is not so striking. This phenomenon may be witnessed if any one will
pull asunder flies that are copulating; and, by the way, these
creatures are, under the circumstances, averse to separation; for
the intercourse of the sexes in their case is of long duration, as may
be observed with common everyday insects, such as the fly and the
cantharis. They all copulate in the manner above described, the fly,
the cantharis, the sphondyle, (the phalangium spider) any others of
the kind that copulate at all. The phalangia-that is to say, such of
the species as spin webs-perform the operation in the following way:
the female takes hold of the suspended web at the middle and gives a
pull, and the male gives a counter pull; this operation they repeat
until they are drawn in together and interlaced at the hinder ends;
for, by the way, this mode of copulation suits them in consequence
of the rotundity of their stomachs.