THE PROBLEM OF THE ORIGIN OF SPECIES. L".) 



Similar vestiges are present in the mourning-dove, and here their identification 

 as marks formerly filled out with black pigment is freed from every shadow of doubt 

 by chequers m all stages of obliteration. (The conditions presented by Zenaidura 

 and Melopeha are fully discussed and illustrated in Chapter V. ED ) 



The large wood-pigeon (Columba palumbus) of Europe has departed still more 

 widely from the turtle-dove type, having lost all its black spots except a few in 

 the neck patches, which have retreated so far from the tips of the feathers as to 

 be concealed (see text-fig. 6, Vol. II). The gray plumage and the white streak along 



TEXT-FIGURE 8. Adult white-winged pigeon, Melopelia leucoptera. x .77. The feathers :it the lower outer edge of 

 the wing are white. No chequers in the adult, but structural imprints of these in a few feathers of the win*. 



the edge of the wing mark a plane in the evolution of this bird very nearly identical 

 with that of the white-winged pigeon. A little higher plane has been reached by 

 our band-tailed pigeon (Columba fasciatd) of the Pacific coast, which is also a 

 species of turtle-dove derivation, 11 as shown in the neck-markings (see text-fig. 5, 

 Vol. II) and in the voice and behavior. 



These illustrations, which could be extended into the hundreds, may be con- 

 cluded with two cases, representing wide extremes, yet governed by the same law 

 of progressive orthogenetic variation. 



11 Minute blotches of black were found in the longer scapulars of a few individuals. These are probably ata viatic 

 reminiscences of lost spots. 



