64 THE HISTOEY OF ANIMALS. [B. Ill, 



to become bald ; and if they have this disease after they are 

 bald, the hair sometimes grows again. The hair, when 

 cut off, does not grow again from the extremity, but in- 

 creases by growth from the root. The scales of fishes 

 become harder and thicker, and in those that are growing' 

 thin and old they become still harder. The hair and wool 

 of old animals becomes thicker, though the quantity de- 

 creases ; and the hoofs and claws enlarge as they grow old, 

 and the beaks of birds. And the claws grow in the same 

 way as the nails. 



11. Feathered animals, like birds, do not change their 

 colour by age, excepting the crane, for this bird is ash- 

 coloured, and becomes black by age. But from the change 

 of season, when it becomes cold, some of those having but 

 one colour, black or grey, become white, as the crow, 

 sparrow, and swallow ; but none of those which are white 

 become black. At different seasons of the yellr many birds 

 change the colour of their plumage, so as to render it difficult 

 for those who are not acquainted with them to recognise 

 them. 



12 And many animals change their colour with a change 

 of water ; for in one place they are black, and in another 

 white ; and the same thing takes place at the season of co- 

 ition. There are many waters of such a nature that if 

 sheep drink of them before sexual intercourse, they produce 

 black lambs ; as at that which is called the cold river in the 

 Thracian Chalcis (in Astyritis). And in Antandria there 

 are two rivers, one of which turns the sheep white, the 

 other black ; and the Scamander appears to make the sheep 

 yellow, wherefore some people think that Homer called 

 the Scamander the Xanthus. 



13. Other animals have no hair internally, nor upon the 

 bottom of their feet, though it is on the upper part. The 

 hare alone has hair on the inside of its cheeks, and upon 

 its feet, and the mysticetus 1 has no teeth in its mouth, 

 but hairs, like hog's bristles. The hair, if it is cut off, 

 increases below, but not above. Feathers do not grow 

 either above or below, but fall out. The wing of the bee, 

 if it is plucked off, does not grow again, nor that of any 

 other creature which has an undivided wing ; nor does the 

 1 Balsena Mysticetus. 



