124 ORTHOGENETIC EVOLUTION IN PIGEONS. 



They show that we must read, not from bars to whole color, but from a dark center 



to bars."" 



The first (subterminal) bar grows gradually wider as we follow down the series 

 of long coverts, until, on the ninth feather, it fuses plainly with the dark center, 



n 1 find a narrow apical edge on all of the long coverts, and also on the upper tertials. 



EXPLANATION OF PLATE 58. 



Analogies of the robin pattern in common pigeons. 



No. lo. An upper (inner) long wing-covert (right side, May 1903) from my white-red barred dove. When gray is 



replaced by white and black by red, a black crescent is formed at the tip, or at distal end of the 



colored area. When the central (middle) area is lightened up, the black crescent boundary tends to 



appear. It may be at or near the edge, according to position of the normal black area. 

 No. 16. A mid-scapular from the above bird. Shows the black concentrated in a median subterminal spot, The 



flecking outside this spot indicates that the black chequers are here obsolescent, and that only 



scattered remnants are present. 

 No. II c. An upper long wing- covert (right side, May 1903) from a black chequered male homer, to show the area 



occupied by black, for comparison with area of red in No. I a. 

 No. II 6. A mid-scapular to correspond with No. I b from same chequered homer. Here we have a median streak 



of gray dividing the black into two spots; the streak enlarges distally into a triangular area that 



may expand into a light-gray margin, such as Hacker finds and as I find in the robin. 

 No. II 6. A mid-scapular from young of the same (chequered) homers, at age of 3 weeks. Notice median streak. 



This will close up, leaving only a small apical spot in second feathers, much as in II b. 

 The five figures, III 1 to III s are from a chequered Juvenal common pigeon about 6 weeks old (May 1903). 

 No. Ill 6 1 . A mid-scapular (right side) showing the light edge or margin; the median streak shows just a trace only. 

 No. Ill c 1 . An upper long wing-covert (right side). The apical gray spot is destined to be more or less filled up with 



black in adult. The black is more intense next to the gray spot. Notice a few prolonged barbs at 



tip; these are remnants of the pale edge. 

 No. Ill c 2 . Upper covert from the second row (next in front of III c 1 ). The median streak wider, there being less 



pigment on the inner web (upper web). Notice in all these young feathers the narrow pale-brown or 



yellowish-brown edge, and that some barbs are prolonged beyond the rest into a fine hair-like part. 

 No. Ill c'. Upper covert from the third row. The median streak reaches into the light margin, which is very plain 



and about 1.5 mm. at center to 1 mrn. at lateral parts-of tip. 



No. Ill c 4 . Covert from the fourth row. The median streak does not reach the light edge. 



No. Ill c'. Covert from the fifth row. The median streak still a little farther from tip and also a little narrower. 

 In these five coverts (III c 1 to III c 6 ) : 



(1) The black becomes more and more intense as we go backward, and more intense in the outer web than the 

 inner. The young of the cowbird, Molothrus aler, have "feathers bordered with pale buffy" (see Bendire, p. 590). 



(2) The light margin is plain in c 3 to c s ; less so in c 2 , and still less in c 1 , where we see some hair-like prolongations 

 of the barbs, remnants of the light edge, or rather perhaps imperfect reminiscences of a once wider light margin. 



(3) The light median or shaft-streak is something quite distinct from the light apical margin. 



(4) The triangular gray area at the tip may be reduced by increasing the size of the two chequers until no apica 

 gray is left, or it may be increased by reducing the two black chequers from their distal ends, as is done in all pigeons 

 with gray wings and two bars, the distal ends of the chequers being cut off more and more. 



(5) The median light streak is not a primitive mark. It is wholly secondary, if we remember that the turtle- 

 dove pattern is the starting-point. 



(6) These shaft-streaks in the young robin, and in the birds described by Hacker, are secondary, as is probably 

 the clear middle area of Hacker's feathers. 



Analogies of the robin pattern in a hybrid pigeon, C. guinea X domestic pigeon (black chequered) , Juvenal, age 13 days. 



May, 1903. Nos. IV b to IV*. 



The coverts and scapulars are developed enough to show the color of the first plumage. The coverts and scapu- 

 lars are all edged with a rich red only a little paler than the red of adult Guinea pigeon. The edging contrasts with 

 the dark brown of the rest of feather. All wing-coverts, except a very few at the anterior inner limit of the wing, 

 have the pale-gray median streak, beginning as a narrow and obscure line in the lesser coverts, just a little widened 

 at the tip, and growing stronger and wider at the tip towards the long coverts. The median light streak runs up to 

 the red edge, but does not cut through this edge. Thus we see here, more plainly than in the robin, that the streak 

 is not one and the same with the light margin. Only the posterior third of the scapulars has this median gray streak, 

 the rest boing of the turtle-dove type. 

 No. IV b. A mid-scapular (of above hybrid). 

 No. IV c 1 . A long wing-covert at about middle height. 

 No. IV c'. A covert from the second row, at about the same height. 

 No. IV c'. A covert from the third row, at about the same height. 

 No. IV r 4 . A covert from the fourth row, at about the same height, 

 No. V c 1 . From the wing of Juvenal St. humilis (10 days). 



