Of oviparous quadrupeds all those that live in holes, like

crocodiles, lizards, spotted lizards, freshwater tortoises, and

turtles, have their legs attached obliquely as their whole body

sprawls over the ground, and bend them obliquely. The reason is that

this is useful for ease in creeping into holes, and for sitting upon

their eggs and guarding them. And as they are splayed outwards they

must of necessity tuck in their thighs and put them under them in

order to achieve the lifting of the whole body. In view of this they

cannot bend them otherwise than outwards.

16



We have already stated the fact that non-sanguineous animals with

limbs are polypods and none of them quadrupeds. And the reason why

their legs, except the extreme pairs, were necessarily attached

obliquely and had their flexions upwards, and the legs themselves were

somewhat turned under (bandy-shape) and backwards is plain. In all

such creatures the intermediate legs both lead and follow. If then

they lay under them, they must have had their flexion both forwards

and backwards; on account of leading, forwards; and on account of

following, backwards. Now since they have to do both, for this

reason their limbs are turned under and bent obliquely, except the two

extreme pairs. (These two are more natural in their movement, the

front leading and the back following.) Another reason for this kind of

flexion is the number of their legs; arranged in this way they would

interfere less with one another in progression and not knock together.

But the reason that they are bandy is that all of them or most of them

live in holes, for creatures living so cannot possibly be high above

the ground.

But crabs are in nature the oddest of all polypods; they do not

progress forwards except in the sense explained above, they are the

only animals which have more than one pair of leading limbs. The

explanation of this is the hardness of their limbs, and the fact