BY C. A. ROGERS 81 



in layers as in the egg, but one large dose served to color all previous 

 deposits of fat presumably because of the circulation within the fat tissues. 



The same condition was true with Rhodamine Red. It colored all of 

 muscle tissues a bright pink whether deposited before or during the time of 

 feeding. 



THE FEATHER 



After noting the appearance of the pink tint in the chick down, the dye 

 was fed daily to young chicks just growing their first feathers. The result 

 was a decided flesh pink color in the plumage. The red did not stain those 

 parts of the feather already grown but only that portion grown while Rho- 

 damine Red was being given. When the chickens were about four weeks 

 old the dye was withheld for seven days. After this the new feather growth 

 showed no color until the dye was again fed. The result was a reappear- 

 ance of color at the base of the growing feather. A broad white band, 

 indicating the growth for the days during which the dye was withheld, 

 separated the two areas of color. It also shows by the unevenness of the 

 white band, that different feathers have different rates of growth. (Plate 

 I,F.) 



When fed to mature fowls while molting, the new feathers were tinted 

 with pink, varying in density with the amount and regularity of the color 

 feeding. 



The work here described is but the beginning of this study. It is hoped, 

 however, that it may serve to illustrate the numerous and varied fields in 

 which color dyes can be employed in the study of physiological develop- 

 ment. 



