374 



HARRY BEAL TORREY AND BENJAMIN HORNING. 



hackle, saddle, back and shoulder feathers, that are found ordi- 

 narily only in the corresponding feathers of females. 1 



And it may further be said that when the lacing characteristic 

 of the male hackle appears also in the female that the effect of 

 thyroid is to modify it also, as in the male, by the addition of 

 barbules. 



FIG. 8. Shoulder feathers from R. I. R. birds about seven months old: a, from a 

 normal male; b, c, from a thyroid-fed male; d, from a normal female. 



* 



Thyroid feeding, then, tends to produce hen feathering in the 

 Rhode Island Red male, and, to the extent noted in the last 

 paragraph, in the female also. Toward this result there is no 

 cooperation of the gonad. That the ovary does influence the 

 action of thyroid with reference to certain characters not, 

 however, correlated with sex, will be shown in another paper. 



ZOOLOGICAL LABORATORY, 

 UNIVERSITY OF OREGON, 

 April 7, 1925. 



1 Crew and Huxley (Veler. Jour., LXXIX., No. 10) appear to have seen neither 

 of these effects in their thyroid-fed fowls. The first naturally escaped them, for 

 their birds were too old at the beginning of the experiment to develop it. That 

 the second effect also escaped them may perhaps be attributed to their material and 

 methods. Their 12 birds, of which 6 were males, were Fi hybrids from a cross 

 between a Rhode Island Red cf 1 and a Light Sussex 9 , and inherited the black 

 hackles and white ground color from the mother. An amount of thyroid equal to 

 2 grains per bird was mixed every day into the common ration of wet mash. This 

 dosage was smaller than ours, was not increased as the weight of the birds increased, 

 and was so administered as to leave in doubt just how much each male obtained 



