§17ἀλλὰ τῶν μὲν ἄλλων βλαισοῦνται 17 τὰ κῶλα διὰ τὸ μαλακὰ εἶναι, τῶν δὲ καράβων ὄντων σκληροδέρμων οἱ πόδες εἰσὶν ἐπὶ τῷ νεῖν καὶ οὐ τοῦ βαδίζειν χάριν·
17 However, in the others, the limbs are crooked because they are soft, while in lobsters, which are hard-skinned, the feet are for the sake of swimming and not of walking.
τῶν δὲ καρκίνων ἡ κάμψις εἰς τὸ πλάγιον, καὶ οὐ βεβλαίσωται ὥσπερ τοῖς τε ᾠοτόκοις τῶν τετραπόδων καὶ τοῖς ἀναίμοις καὶ πολύποσι διὰ τὸ σκληρόδερμα εἶναι τὰ κῶλα καὶ ὀστρακώδη, ὄντι οὐ νευστικῷ καὶ τρωγλοδύτῃ· πρὸς τῇ γῇ γὰρ ὁ βίος.
In crabs, the bending is to the side, and it is not crooked as in the oviparous quadrupeds and the bloodless polypods, because their limbs are hard-skinned and shell-like, since [the crab] is not a swimming animal but a hole-dweller; for its life is on the ground.
καὶ στρογγύλος δὲ τὴν μορφήν, καὶ οὐκ ἔχων ὀρροπύγιον ὥσπερ ὁ κάραβος· πρὸς τὴν νεῦσιν γὰρ τοῖς καράβοις χρήσιμον, ὁ δʼ οὐ νευστικός.
And it is round in shape, and does not have a tail-fin like the lobster; for in lobsters it is useful for swimming, but the crab is not a swimmer.
καὶ ὅμοιον δὴ τῷ ὄπισθεν τὸ πλάγιον ἔχει μόνος, διὰ τὸ πολλοὺς ἔχειν τοὺς ἡγεμόνας πόδας.
And indeed, it alone has its side similar to its rear, because of having many leading feet.
τούτου δʼ αἴτιον ὅτι οὐ κάμπτει εἰς τὸ πρόσθεν οὐδὲ βεβλαίσωται.
And the cause of this is that it does not bend to the front, nor is it crooked.
τοῦ δὲ μὴ βεβλαισῶσθαι τὸ αἴτιον πρότερον εἴρηται, ἡ σκληρότης καὶ τὸ ὀστρακῶδες τοῦ δέρματος.
And the cause of its not being crooked has been said before: the hardness and the shell-like nature of its skin.
ἀνάγκη δὴ διὰ ταῦτα πᾶσί τε προηγεῖσθαι καὶ εἰς τὸ πλάγιον, εἰς μὲν τὸ πλάγιον ὅτι εἰς τὸ πλάγιον ἡ κάμψις, πᾶσι δʼ ὅτι ἐνεπόδιζον ἂν οἱ ἠρεμοῦντες πόδες τοῖς κινουμένοις.
It is necessary therefore for these reasons to lead with all [the feet] and to the side; to the side, because the bending is to the side, and with all, because the resting feet would otherwise hinder those that are moving.
οἱ δὲ ψηττοειδεῖς τῶν ἰχθύων, ὥσπερ οἱ ἑτερόφθαλμοι βαδίζουσιν, οὕτω νέουσι· διέστραπται γὰρ αὐτῶν ἡ φύσις.
Flatfish among fish swim in the same way as one-eyed people walk; for their nature has been distorted.
οἱ δὲ στεγανόποδες τῶν ὀρνίθων νέουσι τοῖς ποσί, καὶ διὰ μὲν τὸ τὸν ἀέρα δέχεσθαι καὶ ἀναπνεῖν δίποδές εἰσι, διὰ δὲ τὸ ἐν ὑγρῷ τὸν βίον ἔχειν στεγανόποδες· ἀντὶ πτερυγίων γὰρ χρήσιμοι οἱ πόδες αὐτοῖς τοιοῦτοι ὄντες.
Web-footed birds swim with their feet; and on the one hand, because of receiving the air and breathing, they are bipeds, but on the other hand, because of having their life in the water, they are web-footed; for their feet, being of such a kind, are useful to them instead of fins.
ἔχουσι δὲ τὰ σκέλη οὐχ ὥσπερ οἱ ἄλλοι κατὰ μέσον, ἀλλʼ ὄπισθεν μᾶλλον· βραχυσκελῶν γὰρ αὐτῶν ὄντων ὄπισθεν ὄντα πρὸς τὴν νεῦσιν χρήσιμα.
And they have their legs not like the others in the middle, but rather behind; for since they are short-legged, the legs being behind are useful for swimming.
βραχυσκελεῖς δʼ εἰσὶν οἱ τοιοῦτοι διὰ τὸ ἀπὸ τοῦ μήκους τῶν σκελῶν ἀφελοῦσαν τὴν φύσιν προσθεῖναι τοῖς ποσί, καὶ ἀντὶ τοῦ μήκους πάχος ἀποδοῦναι τοῖς σκέλεσι καὶ πλάτος τοῖς ποσί· χρήσιμοι γὰρ πλατεῖς ὄντες μᾶλλον ἢ μακροὶ πρὸς τὸ ἀποβιάζεσθαι τὸ ὑγρόν, ὅταν νέωσιν.
And such creatures are short-legged because nature, having taken away from the length of the legs, has added it to the feet, and in place of length has given thickness to the legs and width to the feet; for being wide rather than long, they are useful for pushing away the water when they swim.
§1818 Εὐλόγως δὲ καὶ τὰ μὲν πτηνὰ πόδας ἔχει, οἱ δʼ ἰχθύες ἄποδες· τοῖς μὲν γὰρ ὁ βίος ἐν τῷ ξηρῷ, μετέωρον δʼ ἀεὶ μένειν ἀδύνατον, ὥστʼ ἀνάγκη πόδας ἔχειν· τοῖς δʼ ἰχθύσιν ἐν τῷ ὑγρῷ ὁ βίος, καὶ τὸ ὕδωρ δέχονται, οὐ τὸν ἀέρα.
18 And reasonably, flying creatures have feet, while fish are footless; for to the former, life is on dry land, and it is impossible to remain always aloft, so that it is necessary to have feet; but to fish, life is in the water, and they receive water, not air.
τὰ μὲν οὖν πτερύγια χρήσιμα πρὸς τὸ νεῖν, οἱ δὲ πόδες ἄχρηστοι.
Therefore, on the one hand, fins are useful for swimming, while feet are useless.
εἰ δʼ ἄμφω εἶχον, ἄναιμοι ἂν ἦσαν.
And if they had both, they would be bloodless.
ὁμοίως δʼ ἔχουσιν οἱ ὄρνιθες τρόπον τινὰ τοῖς ἰχθύσι.
And birds are in a certain way similar to fish.
τοῖς μὲν γὰρ ὄρνισιν ἄνω αἱ πτέρυγές εἰσι, τοῖς δὲ πτερύγια δύο ἐν τῷ πρανεῖ· καὶ τσῖς μὲν ἐν τοῖς ὑπτίοις οἱ πόδες, τοῖς δὲ ἔν τε τοῖς ὑπτίοις καὶ ἐγγὺς τῶν πρανῶν πτερύγια τοῖς πλείστοις· καὶ οἱ μὲν ὀρροπύγιον ἔχουσιν, οἱ δʼ οὐραῖον.
For to birds, the wings are above, and to fish, two fins are on the dorsal side; and to the former, the feet are on the ventral parts, and to the latter, in most cases, there are fins on the ventral parts and near the dorsal ones; and the former have a tail-fin, and the latter a caudal fin.
§1919 Περὶ δὲ τῶν ὀστρακοδέρμων ἀπορήσειεν ἄν τις τίς ἡ κίνησις, καὶ εἰ μὴ ἔχουσι δεξιὸν καὶ ἀριστερόν, πόθεν κινοῦνται· φαίνονται δὲ κινούμενα.
19 Concerning testaceans, one might wonder what their movement is, and if they do not have a right and a left, from where they move; yet they appear to move.
ἢ ὥσπερ ἀνάπηρον δεῖ τιθέναι πᾶν τὸ τοιοῦτον γένος, καὶ κινεῖσθαι ὁμοίως οἷον εἴ τις ἀποκόψειε τῶν ὑποπόδων τὰ σκέλη, ὥσπερ ἡ φώκη καὶ ἡ νυκτερίς· καὶ γὰρ ταῦτα τετράποδα, κακῶς δʼ ἐστί.
Or must one class all such kind as mutilated, and moving in a similar way as if someone were to cut off the legs of footed animals, just as the seal and the bat [move]; for these too are quadrupeds, but poorly so.
τὰ δʼ ὀστρακόδερμα κινεῖται μέν, κινεῖται δὲ παρὰ φύσιν· οὐ γάρ ἐστι κινητικά, ἀλλʼ ὡς μὲν μόνιμα καὶ προσπεφυκότα κινητικά, ὡς δὲ πορευτικὰ μόνιμα.
And testaceans indeed move, but they move contrary to nature; for they are not naturally mobile, but as stationary and attached creatures they are mobile, while as walking creatures they are stationary.
ἔχουσι δὲ φαύλως καὶ οἱ καρκίνοι τὰ δεξιά, ἐπεὶ ἔχουσί γε.
And crabs also have their right side poorly developed, although they certainly have one.
δηλοῖ δʼ ἡ χηλή· μείζων γὰρ καὶ ἰσχυροτέρα ἡ δεξιά, ὡς βουλομένων διωρίσθαι τῶν ἀριστερῶν καὶ τῶν δεξιῶν.
The claw shows this; for the right is larger and stronger, as if [nature] wished to distinguish the left and the right.
Τὰ μὲν οὖν περὶ τῶν μορίων, τῶν τʼ ἄλλων αὐτῶν καὶ τῶν περὶ τὴν πορείαν τῶν ζῴων καὶ περὶ πᾶσαν τὴν κατὰ τόπον μεταβολήν, τοῦτον ἔχει τὸν τρόπον· τούτων δὲ διωρισμένων ἐχόμενόν ἐστι θεωρῆσαι περὶ ψυχῆς.
Therefore, the matters concerning the parts, both the others themselves and those concerning the locomotion of animals and concerning all change of place, are in this way; and these things being determined, the next thing is to consider the soul.