THE TURTLE-DOVE PATTERN IN OTHER ORDERS OF BIRDS. 133 



Kerschner shows that the earliest stage of this eye-spot (ocellus) is found in feathers 

 "barred with black and reddish yellow." According to his description the most distal 

 black bar first shows a weak "metallic green"; this green becomes brighter, only the outer 

 border-line remaining plain black. The bar becomes wider and shows, proximally, a 

 narrow but gradually "growing zone of bronze." 35 We thus have two zones: a "distal 

 green and a proximal bronze" within the border-line of black. The bar grows wider, 

 encroaching upon and at length occupying the space of the light bar proximal to it. The 

 bar and the two zones of metallic green and bronze continue to expand in growth inward 

 (proximally). The feather becomes more pointed, the bronze zone expands more rapidly 

 in the middle — to either side of the shaft — than at the sides. The metallic color spreads 

 over the next black bar, i.e., it begins on one bar and gradually spreads inward over two 

 black bars; the intervening light bar and the last light bar following the second black bar 

 being replaced by the pigment of the growing spot. 



The original bronze-colored cross-bar (zone) contracts in its cross-length and expands 

 along the shaft, becoming pointed distally and thus triangular as a whole. This bronze 

 triangular spot has its basal angles first rounded, and then the distal angle is rounded, so 

 that we have an ovate bronze disk sharply defined against the proximal green ground. 

 By widening at its distal end, the disk becomes at first "elliptical," then obovate, and then 

 triangular, with its point directed proximally. Next, the angles on the distal base are 

 rounded, and the bronze disk expands to a nearly "circular form," with a small triangular 

 tip proximally. 



Close upon the shaft, below the center of the bronze spot, "where green persists in all 

 earlier stages," there appears a narrow green stripe, which gradually lengthens to some 

 extent, but its expansion is mainly in width, and especially in its middle portion; and so 

 by degrees it grows into a rectangle, with somewhat rounded angles, inclined at an angle 

 of about 45° to the long axis of the feather. Near the upper angle of this area there appears 

 a dull, "dark-blue point," which gradually expands to a "small circle," centered on the 

 shaft. 



The peripheral black border has meanwhile become wider. That part of the external 

 green zone that comes in contact with the black border shows a purplish gleam, while 

 next to the bronze disk the black border becomes blue-green. The rest of the black border 

 remains yellowish green. Meanwhile, the lower barbs have been lengthening and closing 

 in distally around the ocellus, which is now essentially complete. The "yellowish green" 

 portion of the black border becomes olive-green, and that part of the outer zone, described 

 as purplish, is now a coppery-brown zone, like the "bronze disk." 



The bronze disk elongates a little during these last changes; the green disk (inclosing 

 the central dark-blue spot) grows a little in width, and the central dark-blue spot, which 

 at first expanded evenly in all directions, later ceased to expand at its lower pole, and so 

 left here the "indentation" filled by the rich green zone. At the apex of feathers now 

 before me, for comparison with Kerschner's descriptions, the barbs become very slender 

 for a distance, and in this part have no barbules. Thus there is formed the "transparent 

 zone." 



"The highly elaborate tail-feather of the peacock may thus be traced back through 

 quite gradual transitions to a feather relatively simple in its color-marking. The same 

 may be said of every other ornamental feather of this bird; each and every one of them 

 leads us back, directly or indirectly, to a feather barred with black and reddish yellow. 

 This course of development repeats itself in a generalized way in the young peacock, but 

 does not advance so far, as the barring persists a long time in relatively low stages."" 1 

 (pp. 683, 684). 



35 Tliis is as in the bronze-wing (Phaps chalroptera) . 



36 Kcischner takes the side of gradual evolution against mutation. 



