VARIETIES OF PLUMAGE. 57 



correspondence of colour shows a correspondence of cause, 

 whether we shall ever be able to find out that cause or not ; 

 and when, by domestication and change of circumstances, we 

 break the connexion, the colour falls into varieties, so that 

 we have various colours in the same brood. The regions 

 which ptarmigan inhabit vary the least in locality, and those 

 of the partridge vary the most. We find the same in the 

 colour of the birds. The ptarmigan has always some stage 

 of its own changing colour j the partridge varies much, being 

 found with the upper part brown without mottling, and also 

 with nearly the whole body white. But the individual ptar- 

 migan is subjected to far greater changes of temperature than 

 the partridge, and therefore the one has seasonal varieties of 

 colour, and the other few or none. 



In many of the gallinse, the plumage of the male is much 

 finer than that of the female ; but the gaudy livery appears 

 brightest on that plumage which the male is to wear in 

 pairing time ; and the more sober plumage of the female, 

 which is of considerable service to her while she sits, remains 

 only so long as she retains the capacity of being a mother. 

 Common pullets, when they become barren, acquire part of 

 the plumage, and also the crowing note of the male bird ; 

 and in the plate opposite there is a figure, copied from nature, 

 of what is very inaccurately termed a " mule " pheasant. A 

 mule is a hybrid between two distinct species of the same 

 genus, incapable of continuing the mixed race, but readily 

 breeding back to the pure blood ; whereas the bird figured, 

 and many more of the same description, are females, in which 

 the peculiar functions have prematurely ceased; and cases 

 are mentioned in which some of these have changed so far as 

 to have one spur on the tarsus. 



It was once supposed that these changes of plumage were 

 the consequences of old age, and that they would take place 

 in all females of the species in which they occasionally appear, 



