72 ORTHOGENETIC EVOLUTION IN PIGEONS. 



(Sp. tigrina) the dark center is reduced to a narrow mid-streak. In still another, 

 the Chinese turtle (Sp. chinensis), it is absent (pi. 23, fig. A). 



The evolution of the dark center in these forms, then, was as follows: We have 

 to start with a form most nearly represented in Turtur orientalis of China and Japan. 

 The centers of the wing-feathers have the black rounded out full behind, leaving 

 only the apical reddish bar or tip. 



In Turtur turtur of Europe the dark center becomes reduced, ending in an angu- 

 lar point behind. 



In Spilopelia suratensis the black is still further reduced to a dark mesial stripe 

 (and has also bifurcated neck-feathers). 



In Spilopelia chinensis even the mesial stripe has departed, and the neck-feathers, 

 tipped with white, are bifurcated. In these two last-named species we have the 

 neck-feathers not only bifurcated, but a large number of rows are differentiated. 



EXPLANATION OF PLATE 22. 



1. Left wing of an adult European turtle-dove, Turtur turtur. Natural size. Hayashi del., Sept. 



1898. For comparison with wing of the Japanese turtle (text-fig. 3). (Figs. 2 to 5 x 2/1, 

 Hayashi del., 1903-08). 



Dark centers smaller in size and more pointed or angular at tip ; the pale edges correspondingly increased in 

 width. These modifications effect their most striking change in the appearance of the wing in its anterior part. 



2. Third (inner) longer covert of Juvenal (4 weeks) T. orienlalis. 



The pale tip is 2 mm. wide, and the dark center leaves only slender lateral edges. 



3. Third (inner) longer covert of Juvenal (2 weeks) T. turtur. 



The pale tip is 1.3 mm. wide; the black rufous lateral margin is 5.5 mm. wide at its widest part. Practically 

 only the shaft is black at the most narrowed posterior extremity of the black center; the black of the shaft reaches 

 to but does not invade the pale tip. 



A description and comparison of the posterior scapular in orientalis and turtur follows: 



T. orientalis. Posterior scapular. The black is more extended and the brown less extended than in T. turtur. 

 The basal part shades into gray. 



T. turtur. Posterior scapular. Cinnamon-brown margin, black center arrow-pointed. Basal half gray, grading 

 into black center, which fades into a trace of gray at its border. 



The third tertials compare as follows: 



T. orientalis. Third tertial, i.e., next above longest. The brown in these feathers is darker and richer than in 

 T turtur. 



T. turtur. Third tertial. The black spot is arrow-pointed. Posteriorly the brown or dark center fades into 

 gray at the basal half. 



In both species the pointed black centers mark all of the feathers of the upper surface and wing, being larger 

 and generally less pointed in T. orientalis than in the other species. There is not an indication anywhere that the 

 black center represents a fusion of two spots. 



4. Third (inner) longer covert of Juvenal St. damarensis. 



5. Third (inner) longer covert of Juvenal Stig. senegalensis. 



These four figures show that the dark center and pale edge of the T. orientalis pattern is present in all these 

 species, and is most modified in the less closely related Slreptopelia and Sligmatopelia. 



EXPLANATION OF PLATE 23. 



A. Adult Chinese turtle-dove, Spilopelia chinensis. x 0.7. Hayashi del., Dec. 1903. 



No dark centers in the general plumage, present only in the neck-mark. 



B. Fifth feather (natural size) third row (right side) of the neck-mark of Chinese turtle (same as 



fig. A). Shows strong bifurcation, white tip, and dark center. 



C. Wing of juvenal mourning-dove and ring-dove (female parent alba-risoria x nsoria-alba hybrid) 



hybrid; hatched May 9, 1899. Natural size. Hayashi del., June 6. 1899. 4 weeks old. 



There are three small pale gray spots visible on the upper long coverts, and a fourth spot on the next tertial 

 below; the latter spot is entirely concealed. 



On the next row of coverts, at the same level, are three smaller spots, similarly placed at the lower edge of feathers. 

 On one or two of the upper tertials just a trace of a streak may be seen. 



This picture should be compared with the juvenal Melopelia leucoptera (text-fig. 14). The influence of the 

 ring-dove (chequers wholly lost from the wing) mother does not lead to a suppression of the chequers of Zenaidura, 

 but to a reduction to a stage nearly that of Melopelia. 



