2 



simile might well be carried yet farther and! 

 to better advantage. When the later sum- 

 mer or early fall approaches, certain leaves 

 undergo a complete change in color, result- 

 ing in the beautiful colors of our Septem- 

 ber and October woods. The history of the 

 underlying phenomena of autumnal col- 

 oration in leaves is very obscure, yet no one 

 doubts the occurrence of the change for an 

 instant. So it is with Aptosochromatism — 

 the individual feathers undergo in many 

 cases complete color changes, and although 

 the underlying processes of these changes 

 may be obscure, the fact of their presence is 

 to my mind undeniable. 



At the present time Aptosochromatism 

 has not progressed far enough to encourage 

 one to take up in detail the systematic oc- 

 currence of the color change in our species 

 of native birds. It seems evident that for 

 the present, attention should rather be de- 

 voted to endeavoring to demonstrate its 

 fundamental principles, without which no 

 science is firm, plainly evident as may be 

 its happening. 



Passerina cyanea, apart from its seasonal 

 fall moult by which the plumage acquired 

 in the spring is changed for the duller garb 

 of the fall, doubtless exhibts two forms of 

 Dichromatism, a term whose proper place, 

 I hope, is now recognized as the funda- 

 mental term for the complex phenomena of 

 double coloration. As I shall direct my at- 

 tention toward proving that Aptosochroma- 

 tism is concurrent in the species, and Ptoso- 

 chromatism in the present paper will play 

 an inconspicuous part. Both are compre- 

 hensive terms, by the way, coined by Dr. 

 Coues. The latter term may be defined for 

 convenience, as the occurrence of Dichroma- 

 tism depending entirely upon the loss of old 



