THYROID AND GONAD IN PLUMAGE. 23! 



Riddle and Brodie, '25) for the view that thyroxin depresses the 

 division rate when acting directly on Paramecium. 



SUMMARY. 



The results of thyroid feeding on five breeds of domestic 

 fowl are recorded. They vary with dosage and with sex. When 

 the daily ration is compatible with good health, the males of 

 pigmented breeds, both normal and castrated, tend to darken 

 conspicuously owing chiefly to an increased production of plumage 

 melanins. Normal females are affected, if at all, to a much 

 slighter degree. Castrated females, however, resemble males in 

 this respect as in others. An antagonism thus appears between 

 ovary and thyroid as indicated by their relation to the formation 

 of plumage melanins. The blanching of plumage observed after 

 excessive doses of thyroid is attributed to a toxic effect, non- 

 specific in character. A correlation between the effect of thyroid 

 feeding on melanin production and feather structure is pointed 

 out. White Leghorns show the latter but not the former, 

 being dominant whites. 



BIBLIOGRAPHY. 

 Cole, L. J., and Reid, D. H. 



'24 The Effect of Feeding Thyroid on the Plumage of the Fowl. J our. Agr 



Res., XXIX., 295. 

 Crew, F. A. E., and Huxley, J. S. 



'23 The Relation of Internal Secretion to Reproduction and Growth in the 

 Domestic Fowl. I. Effect of Thyroid Feeding on Growth Rate, Feather- 

 ing and Egg Production. Veter. Jour., LXXIX., 343. 

 Horning, B., and Torrey, H. B. 



'23, i Effect of Thyroid Feeding on the Color and Form of the Feathers of 



Fowls. Abs. in An. Rec., XXIV., 395. 

 '23, 2 Effect of Thyroid Feeding on the Moulting of Fowls. Abs. in An. 



Rec., XXIV., 399. 

 Jones, LI. 



'15 Studies on Inheritance in Pigeons. II. A Microscopical and Chemical 



Study of the Feather Pigments. J. Exp. Zool., XVIII., 453. 

 Strong, R. H. 



'02 The Development of Color in the Definitive Feather. Bull. M. C. Z. 



Harv., XL., 145. 

 Torrey, H. B., and Horning, B. 



'22 Hen Feathering Induced in the Male Fowl by Feeding Thyroid. Proc. 



S. Exp. Biol. Med., XIX., 275. 



'25, i The Effect of Thyroid Feeding on the Moulting Pn cess and Feather 

 Structure of the Domestic Fowl. BIOL. BULL., XLIX., 275. 



