184 ORTHOGENETIC EVOLUTION IN PIGEONS. 



Eventually, after a comparative study of the various neck-patterns in different 

 species and finding that they all pointed to the turtle-dove as a progenitor, and after 

 learning to read phyletic relationships in the voices, in the courtship behavior, and 

 in the general color-patterns, I came to see in the "dark center" and the "light 

 apical edge" of the turtle-dove feather a simple unit of coloration reduced to pale- 

 ness at the distal edge, and thus converted into the simplest element possible for an 

 archetypal plumage-pattern. From this source have arisen, as I have elsewhere 

 pointed out, all the varied color-patterns of the pigeon world. 4 



This conclusion naturally turned my attention to the color-patterns of birds in 

 general. Paying special heed to the patterns of immature birds, and to the sequence 

 of patterns presented in the young and the adults of both sexes, I soon found con- 

 vincing evidence in great abundance that the pigeon unit of pattern was at the 

 same time the avian unit. If any one doubts this let him glance at almost any avail- 

 able material, such as the jungle-fowl, the pheasants, ducks, gulls, terns, etc. 



Later, a discovery of cross-bars in the feathers of a pigeon led me to another 

 series of problems, the stucty of which has opened new vistas in the feathered world, 

 confirming the conclusion just stated, and at the same time revealing a secondary 

 relation of the apical mark. The juvenal patterns of the geopelias and of several 

 American species (inca, Zenaida, etc.) were most instructive, enabling me to see in 

 this mark a forerunner, so to speak, of cross-bars appearing first near the distal end 

 of the dark center of the feather and increasing in number gradually in a basipetal 

 direction. 



If any one doubts that we have here continuous transitions, and demands demon- 

 stration by experimental breeding and establishment of new species, my reply is 

 that this has all been done over and over again in the case of domestic pigeons, and 

 the results are open to inspection in not less than 150 species, all obtained by breed- 

 ing and selecting from the parent stock — the rock-pigeons. The breeder has 

 neglected to keep written records, but his methods for thousands and thousands 

 of years have undoubtedly been essentially the same as to-day. Nowhere in the 

 plant or animal kingdom can we find achievements more remarkable or more simple 

 and instructive for study. 



Fancy has dominated the breeder's operations, but in the main he has only 

 augmented and intensified natural productions. The apical mark had probably 

 vanished from the mature plumage when man first began to cultivate the pigeon, 

 and it was therefore past his control and too inconspicuous and transient even to 

 appeal to his interest. The trend of evolution in this character has certainly con- 

 tinued the same as in the majority of the wild species, and the fancier has at most 

 only hastened its evanescence. 



Moreover, nature has performed similar experiments in hundreds of wild species, 

 and has left the results of her work in stages that keep on repeating in invariable 

 sequence. No single experimenter could ever approach the perfection of nature's 

 experiments, or ever hope to pile up such confirmations as ages of domestication 

 have turned out. 



But the field of experiments remains ever open, and out of nature's hand we may 

 take one that is direct, unequivocal, and at the same time simple in execution. 

 The natural experiment occurs regularly and automatically in the first plumage of 



« See Chapters II, III, V, and VI— Ed. 



