360 OSCAR RIDDLE. 



plex patterns will be found to have been built directly out of the 

 fundamental bars. 



On the other hand, the following definite things have been 

 accomplished in the reduction of the "inherited" color-phenomena 

 of birds, to an intelligible, physiological basis. 



1. All the feathers of all birds possess — usually in addition 

 to other coloration — regular segmental color- characters which 

 represent (roughly speaking) days and nights of growth. 



2. The darker portions are produced by day and the first part 

 of the night, the lighter portions chiefly at night between 1:00 

 and 5:00 A. M. 



3. A low blood pressure at this latter period produces a re- 

 duced nutrition. 



4. This reduced nutrition causes a slower rate of growth of 

 most — but not all — of the feather elements. The pigment is 

 one of the elements which suffers a reduction. 



5. The pigment (and certain other parts) is reduced in its rate 

 of production relative to growth in certain other parts, because 

 of the less favorable relations which the pigment producing cells 

 bear to the nutriment carried by the blood. 



The writer believes that these findings give a clearer and more 

 penetrating view of the genesis of a color character than has 

 heretofore been obtained. In no previous case has the attempted 

 analysis included reasons for quantitative variations in pigment 

 production. In fact, the whole matter of the origin of pigment 



— as distinct from the problems of its distribution or placement 



— has in all these cases been either left untouched, or only waste 

 products acting as pigments have been considered ; or again, 

 gratuitous assumptions have been made of its origin from 

 haemoglobin. 



Probably, however, the chief value of what is here presented 

 lies not in the moiety it has taken from the province of heredity 

 and added to that of physiology, but in the absolute starting 

 point which it supplies for evolutionary studies of the color-charac- 

 ters of birds. Whitman 1 has already pointed out that the funda- 

 mental bars, whose significance is here made known, are to be re- 



1 Whitman, C. O., "The Origin of Species," Bull, of Wis. Nat. Hist. Soc, 

 January, 1907. 



