368 



HARRY BEAL TORREY AND BENJAMIN HORNING. 



will emphasize these facts. Fig. 4 is from a photograph of No. 4 

 Table I, a typical control female twelve weeks old. Fig. 5 is from 

 a photograph of No. 13, Table I, a typical thyroid-fed female of 

 the same age. 



\ 



FIG. 3. R. I. R. male (No. 15 of Table I.) twelve weeks old, thyroid fed for eight 



weeks. Rectrices well developed. 



There was no essential difference between the last two birds at 

 the time the photographs were taken. The conclusion, however, 

 that thyroid feeding does not affect the female plumage at this 

 age must not be hastily drawn. When thyroid-fed chicks are 

 compared with controls at an earlier age, evidence is obtained to 

 show that thyroid feeding accelerates the development of both 

 rectrices and contour feathers in females as well as males. 



In Table II. such evidence is summarized. The chicks were 51 

 days old. Eight days after hatching, thyroid feeding had been 

 begun with 15 mgms. as the initial daily ration, in capsule as 



