"2 1 6 Birtwell, An Example of Aptosochromatism. \oa 



suming — as will later be considered — that the unnatural diet 

 was the cause of the change which ensued, we may attribute the 

 gain of additional color in the feathers of the gray bird, to the 

 activity caused by 2 pounds and 14 ounces of the food during a 

 period of 53 days. 



As has been before stated, the plumage of the bird was light 

 gray — a typical example of the extreme gray phase. At the 

 time of the discontinuation of the liver diet the feathers of the 

 breast were diffused with burnt sienna very • prominently, which 

 tinged the edges of the downy parts and colored the lower portions 

 of the contour parts, while a narrow margin of the same color was 

 present about the edges of the median stripe of black and its 

 lateral branches. I noticed indications of the change as early 

 as April 18, and friends commented upon the altered color of 

 the bird, which was very noticeable from a short distance, April 

 26. The edges of the flight feathers were also affected and very 

 pronouncedly the ear tufts. The back feathers will be considered 

 later on. 



My bird was next put upon a diet of raw beef and kept at it 

 until Dec. 24, 1898 — a period of 211 days, during which the 

 bird moulted completely once and consumed approximately 10 

 Sparrows and mice, and 190 ounces of beef. The first indica- 

 tions of the effect of the new diet were noticeable in a few weeks 

 and in a curious manner. Gradually two dull sooty areas began 

 to appear upon the breast and belly, these becoming confluent 

 and diffusing over the entire under parts — more intense upon 

 the breast. A feather from the breast while in this condition 

 showed dull dusky bands radiating from an indistinct median 

 stripe and upon a ground color of dirty white. A faint trace 

 of rufous was present at the anterior end. This phase soon 

 lightened until by the time of moult (Sept. 13, 1898) the bird 

 was back in the light gray state as when captured. The mel- 

 anistic condition might have been due to the mixing of the color 

 producing substances of the reddish and gray conditions, forming 

 an intermediate or transitional stage. However, the microscope 

 could determine this. Up to this time (Sept. 13) my bird had 

 eaten about 98 ounces of beef in a space of 109 days. 



The moult lasted until November, when the gray stage was 



