Permanence and Evolution. 75 



neighbouring islands have different . local races 

 from which perhaps the cage varieties may be 

 descended. The yellow colour of many canaries 

 is, however, simply a case of sub-albinism arising 

 from close confinement. 



Darwin promised us a work on variation 

 under nature, a promise which has not as yet 

 been fulfilled, but many have written on this 

 subject in a more or less evolutionist sense, 

 but it does not seem to me that this very 

 obscure subject lends much more support 

 to one hypothesis than to another. We find, 

 firstly, cases of little differentiated local races, 

 but whose differentiation is permanent and 

 easily definable, as, for instance, the North 

 American and European red-fox, or the French, 

 Barbary, and Greek forms of the red-legged 

 partridge ; secondly, we find such races as I 

 have just mentioned connected by promiscuous 

 intermediate forms along a frontier, as in the 

 case of the Kalij pheasants. Evidently there is 



