THE ORIGIN AND RELATIONSHIP OF THE ROCK-PIGEONS. 53 



form; but in the closed wing these spots are entirely out of sight, and only the terminal spots 

 of these feathers and portions of the "gray spots" are in sight, and these are so closely 

 folded as to fall nearly in line with the subterniinal bar, and thus appear at first sight to 

 form a part of it. The part they appear to form, however, is very small, so closely are the 

 feathers folded up under each other. 



The whole length (from top to bottom) of the first bar in this specimen is 65 mm. and 

 the part formed by the lower four secondaries is not over 8 mm. — i.e., not over one-eighth 

 of the whole bar. 



Now, in the above-described Columba livia (pi. 2) these four secondaries have no trace 

 of the subterniinal bar, and the next two feathers have only freckled indications of the bar. 



In a wild female passenger-pigeon the "terminal spots" of some six or more secondaries 

 form the lower half of the bar, and the upper half of the bar (subterniinal spots) is not 

 longer or more conspicuous than the lower half. The second bar shows five spots belonging 

 to the middle long coverts, the middle spots being the larger and longer, the upper and lower 

 spots diminishing until only the tip of the spot is visible. The third bar consists of six or 

 seven visible spots, and this bar comes mainly in the lower half of wing. The fourth bar 

 shows two to four spots in the lower middle part of the wing. In front of the fourth bar 

 I see from one to two or three spots at different points — elements of so many imperfect 

 bars, extending up to the front end of the wing. This (female passenger) wing is a very 

 instructive type, especially in a comparison with chequered homers. 



The distribution of bars and chequers among wild species of pigeons may be 

 trusted to give unequivocal indications as to the origin of bars. There are several 

 kinds of bars, all compound, and all composed of similar elements. They are found 

 in only a few of the more highly developed pigeons, such as the crested pigeons of 

 Australia, the red-breasted pigeon of the Philippines (Phlogamas luzonica), the 

 stock-dove of Europe, and the rock-pigeon. The chequers composing the bars are 

 everywhere the same, homologues of the chequers of the rest of the wing. These 

 spots are very widely distributed, and in most cases there are no bars present to 

 which their origin could be referred. 



The conditions presented by the bars are everywhere indicative, not of a simple, 

 primitive character, but of a character derived from simpler elements by various 

 modifications in form. There is no evidence that bars are the incipient stages in 

 the evolution of chequers. They appear rather to have already reached their 

 highest stage of differentiation, and in some cases to be in decadence. This is 

 most decidedly indicated in the much-reduced bars seen in the stock-dove (see 

 pis. 9 to 13). Conditions have been noted even in the rock-pigeons looking 

 towards disappearance of the bars. 5 "Occasionally," says Darwin (Animals and 

 Plants, Vol. I, p. 225), "birds are seen in Faroe and the Hebrides with the black 

 bars replaced by two or three black spots; this form has been named by Brehm 

 C. amalia?." The bars have been completely obliterated in some races of domestic 

 pigeons and more or less reduced in width in many others. 



In comparing the juvenal with the adult plumage we get another class of 

 evidences that are scarcely less than decisive in their bearing on this question. 

 In some species chequers are present in the juvenal feathers and wholly absent 

 in the adult plumage. This is the case in the small ground-doves 6 (Geopelia) of 



6 In a few individuals of our band- tailed pigeons (text-fig. 5, Vol. II) I have seen minute blotches of black cm smiu 

 feathers in the place of the bars; the affinities of this pigeon, as well as its high general finish, compel us to regard 

 these flecks as the last vestiges or atavistic reminiscences of lost bars or chequers. 



6 The geopelias are illustrated and further described in the following chapter. — Ki>. 



