PROGRESS IN THE STUDY OF VARIATION. 59 



the characters of one race with only a trace of the other to 



birds in which the two sets of characters are about equally 



blended : — 



" Thus we may have C. auratus with merely a few red feathers in the 

 black malar stripe, 1 or with the quills merely slightly flushed with orange, or 

 C. cafcr with either merely a few black feathers in the red malar stripe, or a 

 few red feathers at the sides of the nape, or an incipient, barely traceable 

 scarlet nuchal crescent. . . . The quills may be orange yellow or orange 

 red, or of any shade between yellow and red, with the other features of the 

 two birds about equally blended. But such examples are exceptional, an 

 unsymmetrical blending being the rule, the two sides of the same bird being 

 often unlike. The quills of the tail, for example, may be part red and part 

 yellow, the number of yellow or red feathers varying in different individuals, 

 and very often in the opposite sides of the tail in the same bird. The same 

 irregularity occurs also, but apparently less frequently, in the quills of the 

 wings. ... A bird may have the general coloration of true cafer com- 

 bined with a well-developed nuchal crescent, or nearly pure auratus with 

 the red malar stripes of cafer. ... Or we may have the general plumage 

 as in cafer with the throat and crown as in auratus, and the malar stripe 

 either red or black, or mixed red and black, and so on in almost endless 

 variations, it being rare to find, even in birds from the same nest, two in- 

 dividuals alike in all their features of coloration." 



Now, though from this account it appears that the 

 several characters may combine in varying ways, the great 

 irregularity and especially the asymmetry of the combina- 

 tions are strong indications that there. is not frae blending of 

 the characters, but rather that though they may co-exist in 

 the same individual they are in some degree alternative, 

 forming, in fact, a kind of patchwork. Though even in 

 this — one of the best known cases — adequate statistics are 

 still wanting, it seems to be clear that there is no great 

 population with either the mean or any other intermediate 

 form as a definite normal. 



A more complex example is provided by species of the 

 genus Quiscalus, the Boat Tail Grackle of N. America. 

 The facts are indeed so complicated that they cannot be 

 represented in a brief statement. A full account of this mat- 

 ter is given by F. M. Chapman (2) who has made as far as 



1 A Californian specimen in the Cambridge Museum shows these 

 feathers partly black and partly red. Each feather though black in its basal 

 parts has a red tip, the black pigment being apparently transmuted into red 

 pigment. 



