146 



ORTHOGENETIC EVOLUTION IN PIGEONS. 



is fairly persistent, but the projection of one or two feathers is a purely transient 

 phenomenon. It is not due to feathers being ruffed by external means, but to the 

 position which they assume automatically and occasionally, showing that the con- 

 dition is such that a very slight variation — such as arises spontaneously and dis- 



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Text-figure 27. 



A. Juvenile, three-fourths hybrid, same fraternity with text-fig. 25; age SO days; black (I 1), hatched Feb. 16, 1900. 



x 0.5. Wilson del, May 7, 1900. 



This bird was beginning first molt. When the breast-feathers are held in open and loose order a median streak 

 of feathers is seen as shown in the drawing. When the feathers are held in close order these feathers are covered up, 

 but still there is usually a distinct median line formed by the meeting of the feathers from the two sides. The 

 medium streak of feathers covers the part previously naked, these feathers coming in considerably later than the 

 other breast-feathers. The median feathers are somewhat smaller and more thinly set, hence lie deeper than the ot her 

 breast-feathers. Towards the beak the median line of feathers widens somewhat, and the feathers are evidently 

 lighter in color. At times one or more of the breast -feat hers may be tilted outwards, somewhat as a result of crowd- 

 ing against the middle feathers. 



B. Juvenile homer (C2), age 66 days; in first plumage, x 0.5. May 11, 1900. 



The condition of breast is similar to that seen in figure A above, but one of the mid-tract feathers turns up and 

 out, frill-like, and a pin-feather just above it turns upward. The space just above the unfolded feather is almost 

 naked and the tract is thinly covered with small feathers. This homer has gray wings and black bars, but no chequers. 



C. Adult male homer (Bl), chequered, x 0.5. Wilson del., March 1900. 



This bird is the father of the young unchcqucred homer of figure B. He shows two or three frilled feathers. 

 Sometimes these are smoothed out so that the breast is without any frill, but it then remains creased. Usually, 

 however, a few feathers are turned outward and more or less upward. 



