24 



ORTHOGENETIC EVOLUTION IN PIGEONS. 



various degrees thus connect the derived with the ancestral type in one and the 

 same individual, and so demonstrate that the two specific marks are not separated 

 by impassable mutation-gaps. While it is not necessary to go beyond the wild 

 rock-pigeons and the multitude of domestic races descended from them to learn 

 that nature has here pursued one chief direction of color variation, always leaving 

 an open door, however, to minor modifications and improvements through natural 

 and artificial selection, it is nevertheless highly instructive to make a comparative 

 study of the whole group of wild pigeons, in both adult and ju venal stages. It is 

 in this field that we find the same lessons amplified and repeated in multitudinous 



TEXT-FIGURE 4. Adult female Florida ground-dove, Chamcepelia passerina. Natural size. 

 Hayashi del., Apr. 1903. The feathers of head and neck are edged with pale dark edges, 

 crescents not so strong as in Scardafella inca. Note the dark centers in feathers of breast and 

 foreneck and the reduced spots of the wing. For fuller description of these feathers see pi. 28. 

 In the anterior part of the wing in the region of the oblique bar of some related forms (see 

 under PeristerinEe, Chapter V. -ED.) there is a noticeable persistence of spots. 



ways, confirmation confirmed, convergence of testimony complete. It will be suf- 

 ficient here to cite a few examples. 



In the little ground-doves (Chamaepelia passerina) of Florida, Arizona, Cali- 

 fornia, Central and South America, and the West Indies, we find the turtle-dove 

 pattern preserved in the whole breast region (text-fig. 4) and in the anterior, smaller 

 coverts of the wings, while in the posterior portion of the wings we meet with 

 lateral spots or chequers, of higher finish than in the rock-pigeons. In many coverts 

 of the wing we find the dark centers more or less reduced, with the distal ends of 

 their remnants in various stages of conversion into lateral spots. Here again we 

 find striking proof of gradual change from one specific type to another. 



