THE PROBLEM OF THE ORIGIN OF SPECIES. 



31 



Moreover, the transformation has already begun in the first feather of the next 

 and last row, so that the same prediction could be extended to this bar, which is 

 the homologue of the posterior bar in the rock-pigeon. 



Glancing again at Ocyphaps, and looking at the wing as a whole, the course of 

 transformation, its mode, direction, and future termination are all very clearly 

 defined. The wing-pattern, as shown especially in the light edges of the juvenal 

 plumage (pi. 8, fig. B), takes us clear back to the turtle-dove type. Next came the 

 chequered pattern (text-fig. 10) , similar to that of the primitive rock-pigeon. Reduc- 

 tion of pigment, proceeding from before backward, fashioned the bilateral chequers 

 from the unicentral spots. The reduction kept on in the same direction, shorten- 





Text-figure 9. — Adult white-breasted crested pigeon, Lophophaps leucogaxter. Natural size. Hayashi del., Oct. 1902. 



There are only four marks on tertials. The long tips of feathers are dotted for cinnamon color. The black bars 

 are preceded by pale gray bars, not shaded. This bird stands in advance of the common crested pigeon, as shown by 

 absence of elongated marks on the long coverts. 



ing the chequers and transforming the rows successively into narrow bands, eventu- 

 ally reaching the eleventh row, where we find only one or two complete steps, 

 followed by a graded series of four to six steps, less and less decided, until we lose 

 every trace of them. So finely graded are these steps in some females that it is 

 difficult to locate the vanishing-point. 



Unless the process of transformation is arrested by the extinction of the species, 

 or through the intervention of some more potent modifying influences than have 

 thus far appeared, the fate of both posterior bars is irrevocably scaled. Granting 

 that natural selection may be credited with strengthening the iridescent splendor 

 of these bars, I believe that the orthogenetic influences are bound to prevail here 

 as in the white-breasted species. 



