THYROID FEEDING AND SEX CHARACTERS. 



369 



before. This had been increased from time to time, the chicks 

 being fed as much thyroid as they could stand without displaying 

 obvious signs of weakness or distress. 



TABLE II. 



It will be seen on inspection of Table II, that there is consider- 

 able variation in the length of the rectrices and the condition of 

 the contour feathers in thyroid-fed birds of both sexes. There are 

 differences, not here recorded, in size and weight also, that are 

 not, however, strictly correlated with differences in the feathering. 



FIG. 4. Normal R. I. R. female (No. 4, Table I.) twelve weeks old. 



