VARIATION 301 



ally develops individuals of extremely dark pigmentation — 

 velvety-black relieved by very dark brown bars. At one time 

 such examples were regarded as representing a distinct species 

 known as Sabine's Snipe ; but later observers have shown that 

 in reality it is not specifically distinct from the Common Snipe 

 {Gallinago celestis). But while most of these dark forms differ 

 from normal individuals only in their darker colour, they may 

 therefore be regarded as melanisms. This term by no means 

 covers all the phenomena observable in every such dark variety, 

 inasmuch as some examples have the markings of the plumage 

 of a totally different kind ; the most conspicuous feature being 

 the absence of the longitudinal stripes in the upper parts. 

 Such varieties may be put down as mutative. They are, it 

 should be noticed, more commonly obtained in Ireland than 

 elsewhere. 



This problem of the dimorphism, or of the specific distinct- 

 ness of some other forins, is much more difficult to solve. Thus, 

 according to some authorities, the Hooded and Carrion Crows 

 are to be regarded as representing but a single dimorphic 

 species. The late Professor Newton and Mr. Howard Saunders, 

 two of the foremost of British Ornithologists of their day, both 

 inclined to this view. Both forms, remarks Professor Newton 

 in his Dictionary of Birds, inhabit Europe, but their range is 

 very different. For while the " Hooded Crow " is, speaking 

 generally, a summer visitant to the south-western part of this 

 quarter of the globe, the " Carrion Crow " occupies the north- 

 eastern portion — an irregular Jine drawn diagonally from about 

 the Firth of Clyde to the head of the Adriatic roughly marking 

 their respective distribution. Both are essentially migrants, 

 and hence it follows that when the Carrion Crow, as summer 

 comes to an end, retires southward, the Grey Crow moves 

 downward, and in many districts replaces it during the winter. 

 Further than this it has been incontestably proved that along 

 or near the boundary where these two birds march, they not 

 infrequently inter-breed, and it is believed that the hybrids, 

 which sometimes wholly resemble one or other of the parents, 

 and at other times assume an intermediate plumage, pair in- 

 discriminately among themselves or with the pure stock. Hence, 

 it has seemed to some Ornithologists who have studied the sub- 

 ject, that these two birds, so long unhesitatingly regarded as 



