168 CALIFORNIA ACADEMY OF SCIENCES. 



transition occurs in the secondary coverts, the last five 

 of which are figured (figs. 40-44). It is difficult to 

 say whether the spot which first appears near the tip of 

 the fifth secondary (fig. 30) spreads toward the shaft 

 forming the spot in fig. 36 and afterwards becomes re- 

 duced to a spot on the shaft as in figs. 38-39 or whether 

 the marking in fig. 36 is of distinct origin. The former 

 view, however, is the more probable one. 



This same sequence of stages seems to hold for all the 

 forms which I have examined, and the uniformity of 

 successional taxology will doubtless be found to be the 

 normal condition of wing markings. The wing of the 

 California!! woodpecker affords an excellent illustration of 

 this. Some of the changes from feather to feather are 

 rather sudden, but an examination of any particular 

 feather would enable one to predict in general what the 

 pattern of the next one was to be, so inevitably is each 

 new character foreshadowed in the antecedent feather. 

 The general color of the wing feathers in this species is 

 dark brown, with a conspicuous band of pure white 

 crossing it. The first primary is uniformly dark, with 

 the exception of a small gouge of white close to the base 

 of the inner web. In the second primary the white has 

 spread into a patch about thirty mm. long, and extend- 

 ing from the inner edge almost to the shaft. In the 

 third it has become still more elongated, and spread not 

 only to the shaft, but across it on the outer edge. In 

 the fourth and fifth primaries the white continues to 

 spread until it occupies almost the entire basal half of 

 the feather. A little dark pigment at the extreme base 

 of the fifth feather asserts itself in the sixth, forming a 

 well marked patch of brown. This spreads down the 

 shaft in the seventh feather, and in the eighth has iso- 

 lated the white in two patches, a long one along the 

 inner edge of the feather and a shorter one midway 



