PROGRESSION OF ANIMALS, xv.-xvi. 



such as the crocodile, the common and the spotted 

 hzard, and land and water tortoises, all have their 

 legs attached obliquely and stretched out upon the 

 ground ; and they bend them obliquely, since they 

 are thus useful in enabling them to crawl easily into 

 their holes and to sit upon and protect their eggs. 

 Since their legs project, they are obliged to raise 

 their whole body by drawing in their thighs and 

 placing them underneath them ; and in this process 

 they cannot bend them otherwise than outwards. 



XVI. It has already been said that bloodless 

 animals which have legs are polypods, and none of 

 them quadrupeds. Their legs, except the two 

 extreme pairs, are necessarily attached obliquely 

 and bend upwards and are themselves bowed some- 

 what backwards ; and the reason for this is plain. 

 For in all such animals the middle legs must both 

 lead and follow. If, therefore, they were under- 

 neath them, they would have to bend both for- 

 wards and backwards — forwards because they lead, 

 and backwards because they follow. But since they 

 must do both these things, their legs are bowed 

 and make their bends obliquely, except the extreme 

 pairs, which are more in accordance with nature, 

 since the first pair leads and the last pair follows. 

 The number of legs is a further reason for their being 

 bent in this way ; for they would thus be less likely 

 to get in each other's way during movement and 

 collide with one another. The reason that these 

 animals are bow-legged is that they all, or most of 



1 TrpocrcrreWoi/ra (cum Mich.) Jaeger: 7rpocrrA\oj/ra libri. 



535 



