§4.13.1#3τὰ δὲ σελάχη ἀλεπίδωτα μὲν τραχέα δʼ ἐστὶ διὰ τὸ χονδράκανθα εἶναι· τὸ γὰρ γεῶδες ἐκεῖθεν ἡ φύσις εἰς τὸ δέρμα κατανήλωκεν.
And the cartilaginous fish are without scales but are rough because they are cartilaginous; for nature has consumed the earthy matter from there for their skin.
ὄρχεις δʼ οὐδεὶς ἔχει ἰχθὺς οὔτ᾿ ἐκτὸς οὔτʼ ἐντός, οὐδʼ ἄλλο τι τῶν ἀπόδων οὐδέν, διὸ οὐδʼ οἱ ὄφεις.
And no fish has testicles, either externally or internally, nor does any other of the footless animals, wherefore neither do snakes.
πόρον δὲ τοῦ περιττώματος καὶ τῶν περὶ τὴν γένεσιν τὸν αὐτόν, καθάπερ καὶ τἆλλα ᾠοτόκα πάντα καὶ τετράποδα, διὰ τὸ μὴ ἔχειν κύστιν μηδὲ γίνεσθαι περίττωμ᾿ αὐτοῖς ὑγρόν.
And they have the same passage for excrement and for reproduction, just as all other oviparous animals and quadrupeds do, because they do not have a bladder and no liquid excrement is produced for them.
τὸ μὲν οὖν τῶν ἰχθύων γένος πρὸς τἆλλα ζῷα ταύτας ἔχει τἀς διαφοράς, οἱ δὲ δελφῖνες καὶ αἱ φάλαιναι καὶ πάντα τὰ τοιαῦτα τῶν κητῶν βράγχια μὲν οὐκ ἔχουσιν, αὐλὸν δὲ διὰ τὸ πνεύμονα ἔχειν· δεχόμενα γὰρ κατὰ τὸ στόμα τὴν θάλατταν ἀφιᾶσι κατὰ τὸν αὐλόν.
So, the class of fish has these differences compared to other animals. On the other hand, dolphins, whales, and all other such cetaceans do not have gills, but they have a blowhole because they have lungs; for taking in the sea through the mouth, they discharge it through the blowhole.
ἀνάγκη μὲν γὰρ δέξασθαι τὸ ὑγρὸν διὰ τὸ λαμβάνειν τὴν τροφὴν ἐν τῷ ὑγρῷ· δεξάμενα δ᾿ ἀφιέναι ἀναγκαῖον.
For it is necessary to take in the liquid because they take their food in the liquid, and having taken it in, discharging it is necessary.
τὰ μὲν οὖν βράγχιά ἐστι χρήσιμα τοῖς μὴ ἀναπνέουσιν· διʼ ἣν δʼ αἰτίαν, εἴρηται ἐν τοῖς περὶ ἀναπνοῆς· ἀδύνατον γὰρ ἅμα τὸ αὐτὸ ἀναπνεῖν καὶ βράγχια ἔχειν· ἀλλἀ πρὸς τὴν ἄφεσιν τοῦ ὕδατος ἔχουσι τὸν αὐλόν.
Now, gills are useful for those that do not breathe (and for what cause has been stated in the treatise on respiration); for it is impossible at the same time for the same animal to breathe and to have gills; but they have the blowhole for the discharge of water.
κεῖται δʼ αὐτοῖς οὗτος πρὸ τοῦ ἐγκεφάλου· διελάμβανε γὰρ ἂν ἀπὸ τῆς ῥάχεως αὐτόν.
And this is situated for them in front of the brain; for otherwise the spine would interrupt it.
αἴτιον δὲ τοῦ πνεύμονα ταῦτʼ ἔχειν καὶ ἀναπνεῖν, ὅτι τὰ μεγάλα τῶν ζῴων πλείονος δεῖται θερμότητος, ἵνα κινῆται· διὸ ὁ πνεύμων ἔγκειται αὐτοῖς θερμότητος ὢν πλήρης αἱματικῆς.
And the cause of these animals having lungs and breathing is that large animals require more heat in order to move; wherefore the lung is situated in them, being full of blood-like heat.
ἔστι δὲ ταῦτα τρόπον τινὰ πεζὰ καὶ ἔνυδρα· τὸν μὲν γὰρ ἀέρα δέχεται ὡς πεζά, ἄποδα δʼ ἐστὶ καὶ λαμβάνει ἐκ τοῦ ὑγροῦ τὴν τροφὴν ὥσπερ τὰ ἔνυδρα.
And these are in a way terrestrial and aquatic; for they receive the air as terrestrial animals, but they are footless and take their food from the liquid like aquatic animals.
καὶ αἱ φῶκαι δὲ καὶ αἱ νυκτερίδες διὰ τὸ ἐπαμφοτερίζειν αἱ μὲν τοῖς ἐνύδροις καὶ πεζοῖς, αἱ δὲ τοῖς πτηνοῖς καὶ πεζοῖς, διὰ τοῦτο ἀμφοτέρων τε μετέχουσι καὶ οὐδετέρων.
And seals and bats, because they have intermediate characters—the former between aquatic and terrestrial, and the latter between winged and terrestrial—therefore partake of both and of neither.
αἵ τε γὰρ φῶκαι ὡς μὲν ἔνυδροι πόδας ἔχουσιν, ὡς δὲ πεζαὶ πτέρυγας (τοὺς γὰρ ὄπισθεν πόδας ἰχθυώδεις ἔχουσι πάμπαν, ἔτι δὲ τοὺς ὀδόντας πάντας καρχαρόδοντας καὶ ὀξεῖς)· καὶ αἱ νυκτερίδες ὡς μὲν πτηνὰ ἔχουσι πόδας, ὡς δὲ τετράποδα οὐκ ἔχουσι, καὶ οὔτε κέρκον ἔχουσιν οὔτʼ οὐροπύγιον, διὰ μὲν τὸ πτηνὰ εἶναι κέρκον, διὰ δὲ τὸ πεζὰ ούροπύγιον.
For seals, as being aquatic, have feet, but as being terrestrial, they have fins (for they have their hind feet entirely fish-like, and furthermore, all their teeth are sharp and serrated); and bats, as being winged, have feet, but as being quadrupeds, they do not, and they have neither a tail nor a uropygium; because they are winged, they have no tail, and because they are terrestrial, they have no uropygium.
συμβέβηκε δʼ αὐταῖς τοῦτʼ ἐξ ἀνάγκης· εἰσὶ γὰρ δερμόπτεροι, οὐδὲν δʼ ἔχει οὐροπύγιον μὴ σχιζόπτερον· ἐκ τοιούτου γὰρ πτεροῦ γίνεται τὸ οὐροπύγιον.
And this has happened to them of necessity; for they are membrane-winged, and nothing has a uropygium unless it is split-winged; for it is from such feathers that the uropygium is produced.
ἡ δὲ κέρκος καὶ ἐμπόδιος ἂν ἦν ὑπάρχουσα ἐν τοῖς πτερσῖς.
And a tail, if it existed, would be an obstacle while present in the wings.
τὸν αὐτὸν δὲ τρόπον καὶ ὁ στρουθὸς ὁ Λιβυκός· τὰ μὲν γὰρ ὄρνιθος ἔχει, τὰ δὲ ζῴου τετράποδος.
In the same way also the Libyan ostrich; for it has some characters of a bird and others of a quadruped.
ὡς μὲν γὰρ οὐκ ὢν τετράπους πτερὰ ἔχει, ὡς δʼ οὐκ ὢν ὄρνις οὔτε πέταται μετεωριζόμενος, καὶ τὰ πτερὰ οὐ χρήσιμα πρὸς πτῆσιν ἀλλὰ τριχώδη.
For as not being a quadruped, it has wings, but as not being a bird, it does not fly aloft, and its wings are not useful for flight but are hair-like.
ἔτι δὲ ὡς μὲν τετράπους ὢν βλεφαρίδας ἔχει τὰς ἄνωθεν καὶ ψιλός ἐστι τὰ περὶ τὴν κεφαλὴν καὶ τὰ ἄνω τού αὐχένος, ὥστε τριχωδεστέρας ἔχειν τὰς βλεφαρίδας, ὡς δʼ ὄρνις ὢν τὰ κάτωθεν ἐπτέρωται, καὶ δίπους μέν ἐστιν ὡς ὄρνις, διχαλὸς δʼ ὡς τετράπους· οὐ γὰρ δακτύλους ἔχει ἀλλὰ χηλάς.
Furthermore, as being a quadruped, it has upper eyelashes and is bare around the head and the upper part of the neck, so that its eyelashes are more hair-like, but as being a bird, it is feathered below, and it is two-footed as a bird, but cloven-hoofed as a quadruped; for it does not have toes but hoofs.
τούτου δ᾿ αἴτιον ὅτι τὸ μέγεθος οὐκ ὅρνιθος ἔχει ἀλλὰ τετράποδος· ἐλάχιστον γὰρ ἀναγκαῖον εἶναι τὸ μέγεθος ὡς καθόλου εἰπεῖν τὸ τῶν ὀρνίθων· οὐ γὰρ ῥᾴδιον πολύν ὄγκον κινεῖσθαι σύματος μετέωρον.
And the cause of this is that it has the size not of a bird but of a quadruped; for it is necessary that the size of birds, to speak generally, is very small; for it is not easy for a large bulk of body to move suspended in the air.
Περὶ μὲν οὖν τῶν μορίων, διὰ τίνʼ αἰτίαν ἕκαστόν ἐστιν ἐν τοῖς ζῴοις, εἴρηται περὶ πάντων τῶν ζῴων καθʼ ἕκαστον· τούτων δὲ διωρισμένων ἐφεξῆς ἐστὶ τὰ περὶ τὰς γενέσεις αὐτῶν διελθεῖν.
Concerning the parts, therefore, and for what cause each exists in animals, has been stated for all animals individually; and these having been defined, it is next in order to discuss what concerns their generation.