1 66 



OSCAR RIDDLE. 



after its formation further growth may be absolutely inhibited or 

 stopped. If, therefore, faulty nutrition can and does completely 

 halt the growth at the proximal part of the quill, there is every 

 reason to believe that the same cause may have acted as the 

 check upon the growth at the distal and all intermediate parts of 

 the quill ; and since it has been shown that the structures pro- 





Fig. i. A feather from the humeral tract of an underfed chick, four months old. 

 d, downy portion ; m, the highly modified basal region of the down, i. e., the "quill." 

 s, the barbule bearing shaft of the modified pennaceous feather f which grew under 

 "starving" conditions and thus became downy or plumulaceous in character. 

 Drawn with a camera lucida. Actual length of feather 3 cm. 



