THE PROBLEM OF Till! OIMCIN o| 



23 



This ancestral mark is a dark spot filling the whole central p:irt of the feather, 

 leaving only a narrow distal edge of a lighter color. This m:irk i> .-till well preserved 

 in some of the old-world turtle-doves best in the Oriental turtle-dove of ( 'hina and 

 Japan. The chequer of Columba livia differs from the dark center of Tnrliir a 

 talis (text-fig. 3) only in form and in having a lateral position. Typically thi.- .-put 

 appears in pairs, one on each side of the feather. The two spots represent the two 

 halves of the old central spot, which becomes more or less deeply divided \>y the 

 disappearance of pigment along the shaft of the feather. This change heiiii 

 the tip of the feather and advances inward, but usually more rapidly along the 

 shaft than at the sides, thus resulting in two chequers with more or less pointed 

 tips. The direction of change again coincides with that of embryonic develop- 

 ment the tips of the feather, where it begins, being first in order of development. 

 In many chequered rock-pigeons we may find in the dorsal (inner) feathers of 

 the bars undivided central spots, which pass gradually into the typical chequers 

 as we pass towards the lower (outer) ends of the bars. Transitional stages of 



EXPLANATION OF PLATE 5 Continued. 

 B. Male homer, No. 7, hatched May 1, 1904. X 0.8. Hayashi del., Oct. 1904. 



The male bearing this wing resembles his sire in size and general form. The chequers on the scapulars ait- 

 stronger and more numerous than in the sire, but fall far below the dam. The third bar li:is about the same number 

 of spots, but those are here a little stronger. 



The second bar inclines to red (red = light shading; black or rather dark gray = black). The shaft-line anil the 

 lower edge are also reddish gray in three or four of the upper (inner) tertials and long coverts. 



Measurements. 



The eighth to fourteenth secondaries of the first bar have spots almost too indistinct to incasurp with certainty. 

 (See preceding figure.) 



C. Female homer, No. 8, hatched May 1, 1904. X 0.8. Hayashi del., Oct. 1904. 



This female is pale, though not quite so pale as homer No. 3 (fig. A, this plate). The quills are whitish, but 

 less so than in homer No. 3. 



Third bar is here scarcely noticeable. 



Second bar begins with 11 nun. width, increasing in second feather to 12 mm. and 

 on nearly evenly to the seventh feather and then becomes gradually thinner. 



First bar has its greatest width on fourth and fifth feathers 122 and 20 mm. respectively, 

 on both upper and lower webs of the sixth feather. 



(The details of the breeding history of the three birds shown on this plate arc giv.-n in 



3 



