164 CALIFORNIA ACADEMY OF SCIENCES. 



the flank feathers are less developed than the feathers 

 of the lower breast, and these in turn less advanced than 

 a stage higher up on the breast. Through all this a reg- 

 ular sequence of successional relation is maintained, 

 and we, consequently, feel justified in assuming that 

 the different parts of the body of the bird represent 

 different stages in the evolution of the feathers. Being 

 unfamiliar with any word expressive of this relation so 

 closely akin to ontogeny and taxonomy, I would suggest 

 the term SUCCESSIONAL TAXOLOGY. 



As before stated, the assumption of a uniform pig- 

 mentation by a feather is by no means universally along 

 the ideal development of Melanerpes. Thus, in the 

 yellow-breasted sapsucker (Sphyrapicus varius) the 

 transition is from the original streaked form through a 

 barred type to a uniform black. The successional tax- 

 ology in this species as indicated by the feathers along 

 the border line of the black throat-patch is represented 

 in a tolerably typical series in Plate II. The streaked 

 type generally occurs farthest from the black patch, 

 but these feathers are inconspicuous and largely con- 

 cealed, so that no streaked pattern appears in a general 

 survey of the bird. In the next phase the streak becomes 

 slightly tilted to one side (fig. 8), or it may divide 

 and extend out on both sides enclosing a white spot 

 (fig. 9). Continuing to descend, it approaches a posi- 

 tion in which it is at right angles to the shaft, forming 

 a bar (fig. 10) and presently a second bar makes its 

 appearance along the edge of the downy basal portion 

 (fig. 11). The two bars next fuse, frequently passing 

 through the stage indicated in figure 12 and end by 

 becoming perfectly black. 



I cannot see that this series can be explained by the 

 general laws of growth previously used, but would sug- 

 gest that it may not improbably be a case of correlation. 



