112 ORTHOGENETIC EVOLUTION IN PIGEONS. 



Domestic Pigeons. 32 



The guinea-mark is widely represented in the various breeds of common pigeons. 

 It is here exhibited, moreover, in widely different degrees, even in different indi- 

 viduals of the same breed or race. The tint or color of this typically wedge-shaped 

 area also shows some fluctuation from individual to individual. 



I obtained from a dealer two common pigeons which were nearly black, with a 

 suffusion of reddish, in both of which I find quite small guinea-marks (pi. 51). 

 The mark is of grayish color in both of these blackish birds. Another similarly 

 colored common pigeon from the same dealer has much larger marks than the pre- 

 ceding, and larger also than those of a black homer which I have had photographed 

 for comparison (pi. 52). 



From two common pigeons — a male of reddish color having strong guinea-marks, 

 and a black female (see pi. 14, Vol. II), also with plain guinea-marks — I obtained 

 from the same nest the two birds shown in plate 53. Both young have relatively 

 strong guinea-marks in the colored feathers of the wing, and both are spotted with 

 white, though the ground-color of one bird is red and the other black. 33 



From a cross of a Columba guinea X homer hybrid male (two-barred) with a 

 female dark-chequered homer, 34 I obtained two young which show the guinea-mark 

 in two different degrees, these two grades being intermediate to, but different from, 

 the two strongly contrasting states of the character in the two parents (pi. 54, figs. 

 A to C). 



The photographs show that the largest guinea-marks — the most advanced stages 

 of the division of the dark centers into lateral chequers — are associated with a de- 

 cided reduction of the pigmentation of the feathers of the anterior part of the wing. 

 This is shown best in the male parent (fig. A, pi. 54), which is typically two-barred; 

 the guinea-mark, with its lighter apical wings or margins, has here plainly cleared 

 the feather-tips of black — leaving the black of the bar truncate — for a longer dis- 

 tance than is the case in either of the two chequered offspring. Further, the young, 

 with the greater reduction of pigment in the anterior wing (fig. B, pi. 54), has also 



32 Darwin has considered the origin of domestic pigeons, and the anatomical variations of the several races, in 

 Animals and Plants, Vol. 1, Chapter VI. 



33 Other of these young obtained later m the season of 1908 hail considerable while, and al the last of the season oj 

 1909 were three-fourths white! 



"For full pedigree of the three birds see table 69, Vol. II. 



Explanation of Plate 54. 



A. Adult male Columba guinea ( l /i) x Columba tabellaria (^4) hybrid (CI 7 CC) Nov. 1908. 



This bird — typically two-barred — is an inbred (brother-sister mating) and the father of the two birds of figures 

 A ami IV The mother of the latter was a very dark chequered homer, with small "guinea-marks." 



Note that the wing-bars are narrowed from behind as compared with the homologues of these bars in the off- 

 spring. This narrowing marks the advance of the guinea-mark from its point of beginning, which is the median tip 

 of the feather. The front of the wing is swept, free of black centers and of chequers, 



Clear traces of the C. guinea neck-mark (bifid feathers) are seen, also in both offspring (figs, IS and C). 



B. Adult male C. guinea x homer hybrid. (G 7 CCA, see above) Nov. 1908. 



Shows guinea-mark stronger than mother and brother (fig. C), and great reduction of black in anterior wing; 

 less reduction than in father (fig. A) and apical advance (guinea-mark) also less than in father. 



The scapulars are well chequered, but the forepart of the wing, in front of the third bar, is nearly bare of chequers. 



C. Adult male C. guinea x homer hybrid. (C7CCB, see above) Nov. 1908. 



Guinea- mark stronger than mother, less Strong than in father and brother (tigs. A and B). Little reduction of 

 black in anterior wing. The mark is whitish-gray. In the Juvenal stage the two wing-bars of this bird showed con- 

 siderable traces of reddish brown. 



