Difficult as it may be to conceive the actual process of origin of the two types _auratus_ and _cafer_, it is I think still harder to suggest any possible circumstance which can have determined their development as distinct races, or which can maintain that distinctness when created. Some will no doubt be disposed to appeal once more to our ignorance and suggest that if we only knew more we should see that the yellow quills, the black "moustache" and the red crescent, specially qualify _auratus_ for the north and eastern region, and the red quills, red "moustache" and absence of crescent fit _cafer_ to the conditions of its homes. Each can judge for himself, but my own view is that this is a vain delusion, and that to cherish it merely blunts the receptivity of the mind, which if unoccupied with such fancies would be more ready to perceive the truth when at last it shall appear. Think of the range of conditions prevailing in the country occupied by _auratus_--a triangle with its apex in Florida and its base the whole Arctic region of North America. Is it seriously suggested that there is some element common to the "conditions" of such an area which demands a nuchal crescent in the Flickers, though the birds of the _cafer_ area, almost equally varied, can dispense with the same character? Curiously enough, the geographical variation of _Sphyropicus varius_, another though a very different Woodpecker[6] shows that conversely the nuchal crescent can be dispensed with in the Eastern form though it is assumed by the Western.[7] Allen points out the interesting additional fact that superposed upon each of the two distinct forms, _auratus_ and _cafer_, are many geographical variations which can very naturally be regarded as climatic. Each decreases in size from the North southward, as so many species do.[8] They become paler in the arid plains, and show the ordinary phases which are seen in other birds having the same distribution. Such differences we may well suppose to be determined directly or indirectly, by environment, and we may anticipate with fuller knowledge it will be possible to distinguish variations of this nature as in the broad sense environmental, from the larger differences separating the two main types of _Colaptes_, which I surmise are altogether independent of such influences.