42 DIVERSIONS OF A NATURALIST 



willow-grouse were, at no very distant prehistoric period, 

 one species, but the race which has become isolated in 

 these islands has just the small number of marked 

 differences which I have mentioned, and it breeds true, 

 and therefore we call it a distinct " species." In Scotland, 

 the red grouse is called " muir-fowl," and a century ago 

 was almost invariably spoken of in England as moor- 

 fowl, or moor-game. It is found on moors from Mon- 

 mouthshire northward to the Orkneys, and inhabits 

 similar situations in Wales and Ireland. 



The red grouse and the willow-grouse belong to a 

 section or " order " of birds which are classified together 

 because they all have many points in common with 

 " the common fowl " or jungle-cock and the pheasants. 

 That order or pedigree-branch was named by Huxley 

 Alectoromorphae, or cock-like birds, perhaps more 

 simply termed Galliformes, Callus being the Latin 

 name for " chanticleer." When there is a question of 

 the groups recognized in the classification of animals, 

 it is well to bear in mind, once for all, that the biggest 

 branches of the animal pedigree are called " phyla " (or 

 sub-kingdoms) ; that these have branches or sub-divisions 

 which are called " classes " (birds are a class of the 

 phylum Vertebrata). Classes divide into " orders " ; 

 these often are subdivided into " sub-orders." Orders 

 comprise each several smaller branches called " families," 

 families branch into " genera," and each " genus " con- 

 tains a number of " species " which have diverged from 

 a common ancestral form, and become more or less 

 stable and unchanging (but not unchangeable) at the 

 present day. The individuals of a species are distin- 

 guishable by certain marks, shape, and colour from the 

 individuals of other species of the genus. They breed 

 true to those points when in natural conditions, and 



