118 ORTHOGENETIC EVOLUTION IN PIGEONS. 



distinct ocelli such as are seen in pairs in the tail-feathers of Poly pled ran. We shall 

 later reconsider the case of the pheasant and Polyplcctron. 



An unusual study of the color-marking of feathers was made by Dr. Valentin 

 Hacker. 3 This author sought to start his investigation from the most original 

 forms, and hence turned to "young" birds in "juvenal plumage," and undertook 

 to find some direct connection between the pigmentation of the down and that of 

 the perfected ornamental feathers. 



His first figure (fig. 1, pi. viii) presents a feather with a "dark crescentic 

 edge" and a "light center." 4 This is regarded as a foundation type for various 

 patterns. 5 



Hacker's first object was to find the "most generally distributed color-mark" 

 in the first plumage, and to see whether like or related markings occur on "corre- 

 sponding body regions"; and further, to learn whether the marking advances 

 from behind forward according to Eimer's "wave law" (Undulationsgesetz). It 

 is claimed that the results hold for several genera of German birds of the sixth, 

 seventh, and eighth orders (Homeyer, 1885), and (?) for some other species. 6 



In his summary the author states that: 



The characteristic thrush pattern takes departure from the stage of edge-pigmenta- 

 tion, which is widely distributed in allied groups. The crescentic, reniform, or cordate 

 thrush-spot is formed from the dark edge, through the forward extension of the unpigmented 

 area, while, at the same tune, the secondary pigment begins to advance from the middle 

 of the feather. Gradually the thrush-spot is reduced ; and finally, only secondary pigment 

 is left in the feather, with a light edge remaining, as in the ring-ouzel (Turdus torquatus), 

 or ending in complete unicolor (as in the adult male ouzel, and the upper surface of most 

 thrush species). . . . The remaining genera of song-birds mentioned in the introduction 

 of this study, soon pass, usually directly, from the stage of edge-pigmentation to that of 

 uni-coloration. Some genera (shrike, wren) have already entered, in the nest plumage, 

 the stage of a secondary cross-barring which is multiplied in the single feathers, and which 

 may be supposed to arise by a symmetrical pushing-forward of rings or bars of secondary 

 or tertiary pigment. 



In pigeons we have found that the dark crescentic edge or tip is subterminal in 

 the juvenal plumage, the edge being pale whitish or yellowish or reddish-brown. 

 And further, that the cross-bars are not pushed outward, for they appear first on 

 the exposed distal end of the feather; and, when multiplied, the increase advances 

 toward the proximal end of feather, and may extend to the whole covered part of 

 the feather. 



3 Untersuchungen uber die Zeichnung der Yogelfedern. Spengel's Jahrbiicher, Abth. f., Syst. Geog. u. Biol, der 

 Thiere, III, 2, page 309, Jan. 15, 1SS8. 



* I note in this figure by Hacker a pointed darker area — just posterior to the light area (called central), to which 

 the author seems to give little attention. 



6 Reference is made to Kerschner (Zur Zeichnung der Vogelfedern. Arbeiten aus dem Zoolog. Institut zu Graz, 

 1, No. 4, Leipzig, 1SS6), who, basing his conclusions on a stud)* of the peacock's tail-feathers, takes spots or dots as 

 the point of departure for the development of the various kinds of color-marks. He derived the ornamental feathers 

 from the reddish-yellow feathers of the female (barred with black), and held, contrary to Eimer, that "transverse 

 bars" represent a more primitive form of marking than longitudinal stripes. Hacker says Kerschner's reasoning was 

 unsafe, as he started with "highly differentiated" forms. 



6 A much more extended consideration of Hacker's results was written out; but owing to the absence of suitable 

 reproductions of Hacker's figures, to which the discussion repeatedly refers, it does not seem advisable to attempt 

 to add to what is given here. — Ed. 



