CHAPTER VII. 



THE TURTLE-DOVE PATTERN IN OTHER ORDERS OF BIRDS. 

 HISTORICAL AND INTRODUCTORY. 



The question of the original type of color-pattern of birds in general has received 

 attention at the hands of various workers. A brief consideration of the conclusions 

 reached in some of this earlier work may properly precede the presentation of my 

 own excursions into this field. 



Newton savs -1 Theories of Color and Pattern. 



It is a hitherto unsettled question if the longitudinally striated or the cross-barred 

 feathers are the older style of coloration. The general impression of the coloration of a 

 bird is the sum total of the coloration of all the uncovered parts of the feathers. This 

 sounds like a truism, but means that cross-barred feathers can never give the general 

 impression of a striated plumage and vice versa. 



Kerschner 2 believes that the distribution of coloring matter in transverse lines or bars 

 is the phylogenetically older method, because natural and sexual selection can not well 

 have affected the hidden parts of the feathers. On the other hand, the striated downy 

 or first plumage of the Gallinse and Ratitse has been already, by Darwin, taken to be a 

 very old stage. This appearance, however, as in Struthio, is not due to striation of the 

 single feathers, but to juxtaposition of colorless and deeply pigmented downs. To judge 

 from the growth of a feather, the production of cross-bars seems to be the older stage, since 

 they will result from the intermittent deposition of pigment, while, on the other hand, the 

 production of shaft-streaks is not yet satisfactorily explained. 



At any rate, it must be borne in mind that possibly various groups of birds have gone 

 independently through such stages, and that what is primitive or archaic in one need 

 not be so in all. But a strong proof of the soundness of Darwin's views is that we are 

 able to trace the pattern of the most beautifully adorned feathers of the argus-pheasant 

 or of the peacock step by step backwards to longitudinal stripes, spots, cross-bars, and 

 lastly to insignificant and simple irregular little dots. 



Concerning the statements of the immediately preceding paragraph, it is well 

 to recall that when such scries are studied only or chiefly by the comparative 

 method, they can usually be read with about equal facility in either direction. We 

 have shown (Chapter IV) that Darwin was thus led to read the chequers and bars 

 of the rock-pigeon wing in the reverse of the true direction of evolution. Again, 

 in attacking the problem of the origin of ocelli, as perfected in the train of the pea- 

 fowl, and in the wing of the argus-pheasant, Darwin's theory gave him a long phy- 

 letic perspective, but it revealed no unity or continuity in variation, except such as 

 was imported adventitiously through long-continued sexual selection. The com- 

 parative method, which was the chief reliance, brought no correction to the theory, 

 and, stopping short with Polyplectron, issued in the mistaken notion that the ocelli 

 of the peacock were of double origin — each arising by the gradual fusion of two 



1 Dictionary of Birds, Adam and Charles Black, London, 1893-1896, pp. 99-100. 

 2 Zeitschr. wiss. Zool., 1886, p. 681. 



117 



