THE ORIGIN AND RELATIONSHIP OF THE ROCK-PIGEONS. 63 



Columba qffinis, however, is not the most primitive form among the wild pigeons. 21 

 It was derived from a more ancient type, best preserved in the turtle-doves (Turtur 

 orientalis and T. turtur). In the turtle-dove type each feather has a dark center 

 and light edge. 



The turtle-dove pattern is at the same time a general avian pattern. 



The turtle type and the rock type coexist in some forms (e.g., Phaps chalcoptera) . 



The two-barred pattern of Columba livia was reached in the simplest way by an 

 even reduction of the dark pigment, which would result, at one stage, in leaving 

 remnant spots on the long coverts and the secondaries. 



The process of reduction has run in one direction in many, if not all, pigeons, 

 and present species have reached different stages, varying all the way from a uni- 

 formly spotted condition to four, three, two, one, or part of one bar, or no bars. 



The light apical edge of the feather represents a first step in this direction 

 (reduction). 



The spotted type (many species) originated in a marginal reduction of pigment, 

 beginning at the apex of the feather and extending along both sides. Further 

 reduction advanced in the same direction, and so evenly on both sides as to leave 

 the longitudinal axis of the spot generally coinciding with the shaft of the feather. 

 The main advance of the process as a whole was anterior-posterior in direction. 



The chequered pattern of the rock-pigeon originated from the (earlier) spotted 

 type by division of the single central spot into two lateral spots. The general 

 course of reduction is the same for both types, but a slight difference in detail is 

 superadded for the chequered type. The light edge, which is an important and per- 

 manent feature in the spotted type, is very narrow and transitory in the chequered 

 type, disappearing with the molt of the juvenal feathers. 



Within this narrow light (pale-brown) edge appears a zone of gray that usually 

 enlarges at the middle and extends inward in the form of a wedge or as a mesial 

 streak, dividing the dark spot more or less deeply into two lateral chequers, with 

 pointed tips. The gray area, which arises and enlarges at the expense of the black 

 spot, varies greatly in form and extent. It may be wholly absent in some feathers; 

 it may take the form of a narrow crescent more or less thickened at the middle; 

 it may have the form of a triangular spot as in the guinea-pigeon (C. guinea) of 

 Africa, or be more obtusely pointed as in the spotted pigeon (C. maculosa) of South 

 America. 



21 The succeeding chapters on the Turtle-Dove Pattern in the Phylogeny of Pigeons furnish much of the evidence 

 for this and the several following conclusions. — Ed. 



