15 



thing appears certain, that to the presence 

 of quantities of granular black-like matter 

 is due no small share of the ultimate pro- 

 duction of blue. 



The causes of the differences in the shade 

 of the blue feathers from violet to greenish, 

 according to their position on the bird, ap- 

 peared to be very slight microscopically, and 

 I could detect no constant characters with 

 the facilities at my disposal. 



As to the causes of the activitj' necessary 

 to produce a color change, we may only 

 infer. As proved by dissection my bird was 

 not undergoing any prominent sexual 

 change, and the theory that the temperature 

 of the atmosphere might be responsible 

 would not be applicable to most cage birds 

 which are kept in warm rooms. There can 

 be no doubt, however, but that the fall 

 change of plumage is one of protective ten- 

 dency, and it is highly possible that until 

 changed in the spring, the feathers, in a 

 certain sense, are immature. In the case 

 of the double yellow-headed parrot before 

 mentioned, the color change was of a retro- 

 grade nature, but in the present example 

 the process is synthetic rather than other- 

 wise. 



l^umerous theories have been published 

 which endeavor to account for the dichro- 

 matic fall change of many birds, but it 

 would be irrelevant to discuss them here. 

 One thing appears certain, that the process 

 is deeply involved in the vital system of 

 the organism. Professor Beddard cites an 

 example noticed by Professor Weber of a 

 chaflBnch which was so colored that one-half 

 of the bird was in the male plumage and 

 the other portion in the female. Dissection 

 proved the bird to be a Hermaphrodite, i. e., 

 the side sustaining the male plumage was 



