308 RESEARCH SEMINAR. 



Two black wing-bars on a gray ground have always been held 

 to be the more primitive pattern, and birds of this pattern are 

 supposed to represent the typical Columba Uina. 



The form with black chequers evenly distributed over the 

 wing and back, although once named C. affinis, as a distinct 

 species, was regarded by Darwin as a variety derived from the 

 two-barred rock, and his opinion has stood undisputed. 



It appears from a comparative study of many species of wild 

 pigeons, and from a study of the variations in domestic species, 

 that the relationship is just the reverse : C. affinis is the original 

 rock dove, and C. livia is the derived type. Domestic pigeons 

 have come from both sources. 



Columba affinis, however, is not the most primitive form 

 among the wild pigeons. It was derived from a more ancient 

 type, best preserved in the turtle doves (Turtur orientalis and 

 Turtur tiirtnr}. 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., 

 Pliaps chalcoptera). 



The two-barred pattern of Colnmba 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 uniformly spotted condition to four, 

 three, two, one or part of one bar, or no bars. 



It appears to be impossible to reverse the direction of evolu- 

 tion, and to advance from one or two bars to a complete or even 

 a partial chequered state. 



The white-winged pigeon (Melopelia leucopterd] has no black 

 spots or bars on the wing in the adult plumage, but unmistakable 

 evidence of their former existence is seen in structural imprints 

 still left on many of the coverts, and in vestigial traces of spots in 

 a few of the Juvenal feathers. 



