64 THE BOOK OF NATURE STUDY 



marked which live in temperate climates, the spots disappear in 

 the autumn, when the longer winter coat is assumed. And this 

 apparently because amid leafless trees a spotted animal would 

 be conspicuous. At any rate in tropical countries spotted deer 

 remain so the year round. 



Sometimes quite unexpected relations are met with in regard 

 to the coloration of animals. Thus white cats occasionally have 

 blue eyes, and when this combination occurs a further peculiarity 

 is met with such cats are always deaf ! ' Tortoise-shell " cats, 

 so-called from the curious mixture of yellow, black and white 

 which they exhibit, are always females. In certain parts of 

 Virginia only black pigs can be kept ; and this because they alone 

 are unaffected by feeding on the roots of a certain plant which 

 grows there (Lachnanthes tinctoria) which colours the bones pink ; 

 and further, in all but black pigs causes the hoofs to drop off ! 

 Similarly, in the Tarentino only black sheep can be kept, all white 

 sheep being speedily killed by eating another poisonous plant 

 (Hypericum crispum) which does not affect black sheep. 



Finally, the markings, or patterns, on the hides of mammals 

 in a wild state are always more or less symmetrical ; never forming 

 irregular blotches as in domesticated cattle, for instance. There 

 are, of course, a few exceptions to every rule. Thus the hyaena-dog 

 has irregular markings, but species which do not conform to the 

 rule just given can be reckoned on the fingers of one hand. 



