342 LAWS OF VAEIATION. Chap. XXVI 



third chapter, white cattle with dark ears, dark feet and tip of tail, 

 formerly existed, and now exist in feral or semi-feral condition in 

 several quarters of the world. 



Under our second main division, namely, of analogous variations 

 due to reversion, the best cases are afibrded by pigeons. In all the 

 most distinct breeds, sub-varieties occasionally appear coloured 

 exactly like the parent rock-pigeon, with black wing-bars, white 

 loins, banded tail, &c. ; and no one can doubt that these characters 

 are due to reversion. So with minor details ; tui'bits properly have 

 white tails, but occasionally a bird is born with a dark- coloured and 

 banded tail ; pouters properly have their primary wing-feathers 

 white, but not rarely a " sword-flighted " bird appears, that is, one 

 with the few first primaries dark-coloured ; and in these cases we 

 have characters proper to the rock-pigeon, but new to the breed, 

 evidently ajDpearing from reversion. In some domestic varieties 

 the wing-bars, instead of being simply black, as in the rock-pigeon, 

 are beautifally edged with different zones of colour, and they then 

 present a striking analogy with the wing-bars in certain natural 

 species of the same family, such as Fhaps chalcojptera ; and this 

 may probably be accounted for by all the species of the family 

 being descended from the same remote progenitor and having a ten- 

 dency to vary in the same manner. Thus, also, we can perhaps 

 understand the fact of some Laugher-pigeons cooing almost like 

 turtle-doves, and for several races having peculiarities in their 

 flight, since certain natural species (viz., C. torquutrix undpalumbun), 

 display singular vagaries in this respect. In other cases a race, 

 instead of imitating a distinct species, resembles some other race ; 

 thus, certain runts tremble and slightly elevate their tails, like fan- 

 tails ; and turbits inflate the upper part of their oesophagus, like 

 pouter-pigeons. 



It is a common circumstance to find certain coloured marks per- 

 sistently characterising all the species of a genus, but differing much 

 in tint ; and the same thing occurs with the varieties of the pigeon : 

 thus, instead of the general plumage being blue, with the wing-bars 

 black, there are snow-white varieties with red bars, and black varie- 

 ties with white bars ; in other varieties the wing-bars, as we have 

 seen, are elegantly zoned with different tints. The Spot pigeon is 

 characterised by the whole plumage being white, excepting a spot 

 on the forehead and the tail ; but these parts may be red, yellow, or 

 black. In the rock-pigeon and in -many varieties the tail is blue, 

 with the outer edges of the outer feathers white ; but in the sub- 

 variety of the monk-pigeon we have a reversed style of coloration, 

 for the tail is white, except the outer edges of the outer feathers, 

 which are black.^^ 



With some species of birds, for instance with gulls, certain 

 coloured parts appear as if almost washed out, and I have observed 

 exactly the same appearance in the terminal dark tail-bar in certain 



^^ Beohbtein, ' Xaturgoschichte Deiitschlands,' Band iv., 1795, s. 31. 



