FRILLS AND FUNDAMENTAL BARS AS PLUMAGE CHARACTERS. 143 



being narrowed in the young; her nest mate was a sister, and (wo females from a 

 clutch show weakness in parents, and weakness in parents leads us to expect it in 

 the young. She had a half-sister which was nearly white; a half-brother with wing- 

 frills, and still another half-brother with a breast-frill (see table 75, Vol. II). When 

 paired with a weak (immature) male this homer produced two young, one of which 

 was much whitened 6 (see pi. 14, Vol. II). 



(2) An adult male common pigeon (red with white primaries and with small 

 guinea-marks) was obtained from a dealer in 1906. In 1909 I notice this bird has 

 small frills on the wings; they are quite small, but visible over the whole wings. 

 The primaries are strongly fluted (pi. 71, fig. A). (A son of this frilled male, by a 

 black and guinea-marked homer, was the immature mate of the above-described 

 homer (E); the pair produced two young, one of which was much whitened. — Ed.) 



(3) Another case of frills was found in inbred pouters (table 80, Vol. II), where 

 the colors of several of the offspring were much lightened (see pi. 17, Vol. II). 



THE BREAST-CREASE AND FRILL. 



In the median line of the throat and breast a notable variation from the normal 

 plumage condition is sometimes found. This variation is seen in both old and young, 

 and concerns the inadequate growth or placement of the feathers which should fill 

 out this area. Some of the feathers in, or bordering upon, this tract are often re- 

 curved or frilled. 



The Breast-Crease in Hybrids from the Common Pigeon (%) and the Japanese Turtle (}4). 



Of two young hatched from the same nest in February 1900, one (1) shows a 

 breast-crease, while the other (2) is perhaps nearly normal. At the age of 18 days, 

 the color of (1) is black, and (2) is more nearly the color of the male parent, but its 

 dark spots are more definite, approaching the chequered pattern of Columba livid. 1 



The variant (which will be spoken of as one, in contrast with two, the normal) 

 has a remarkably wide median tract, without any visible feathers or pin-feathers 

 within the region marked by the dotted lines on text-fig. 25. The feathers of the breast 

 were well unfolded and covered over much of the unfeathered tract, closing up for 

 about an inch of the middle breast, but leaving a naked area above and still another 

 below. The line of junction of the feathers formed a deep crease or groove. This 

 bird had very scanty down at the time of hatching. Two had more down, and the 

 unfeathered tract is not more than one-fourth of the width seen in one. It seems to 

 me that two represents the condition generally seen in domestic pigeons, while one is 

 certainly a wide variation. In two the feathers come more smoothly together; though 

 they are behind one in unfolding. I find that the unfeathered tract in one agrees 

 in width with the condition seen in the young "African owl" shown in text-fig. 28. 



When nearly 4 weeks old, one was able to fly. The unfeathered tract is then 

 represented (between the dotted lines in the illustration, text-fig. 25, figs. (', D) as of 

 the same width as before; but beneath the feathers of part of this area I find pin- 

 feathers coming in, advancing from the sides toward the middle, some of the outer 

 ones just beginning to unfold. The middle and wider portion of the tract still has 

 only a few pin-feathers close to the older feathers, the central part for about an inch 

 in length being still quite bare. Above and below this naked area pin-feathers 



6 Another homer (4) and his daughter (8) both have frills on the inner long coverts. 



7 The general shade of the spots very strongly reminds of the same spots in the young of the passenger-pigeon. 



