No. 502] 



NOTES AND LITERATURE 



tions — is not to be ascribed to the varying conditions of nutrition 

 of the individual during the growth of a particular feather. 

 While we would accept the hypothesis that varying blood- 

 pressure during the twenty-four hours may give rise to the phe- 

 nomena of "fundamental bars" and "defective lines," that 

 defective areas may result from malnutrition, and that under- 

 feeding may retard feather development, we can hardly conceive 

 that we have here a full explanation of the differentiation of a 

 feather into pennaceous. downy, and quill portions, or that the 

 widely differing plumage structure shown by owls, pigeons and 

 hummingbirds is merely a matter of nutrition, in its ordinarily 

 accepted sense. In a moulting bird, for example, there may be 

 hundreds of feathers in process of growth at the same time, and 

 feathers in all possible stages of development. If reduced nutri- 

 tion is necessary for the formation of the downy portions of the 

 feather, and still further reduction of nutrition for the forma- 

 tion of the quill, how can all of these processes of feather growth 

 take place, through experiment or otherwise, in the same indi- 

 vidual at the same time, as we know is the case in an actively 

 moulting bird? Each feather has its definite function, and its 

 predestined form and character, in accordance with its position 

 on the bird's body; and feathers differ in character in different 

 birds in accordance with their role in nature, depending upon 

 whether they are owls, or swifts, or pigeons, or penguins, etc. 

 Evidently the nutrition of the single feather and the nutrition 

 of the individual bird are not necessarily one and the same thing; 

 while defective or insufficient nutrition of the individual would 

 leave its impress upon growing feathers, it is not likely that it 

 would, in the cast' of a moulting bird, affect one phase or stage of 

 feather growth without affecting all stages. 



Each feather has its own cycle of growth, and the supply and 

 quality of the nutrition for the perfection of its different parts 

 must vary with each stage of growth, independently of degree of 

 blood-pressure dependent upon food-supply. Hence w T e should 

 not like to say that ' ' The formation of the quill is probably the 

 direct result of a progressive diniinnt inn of an already lessened 

 food-supply," but that it was due to the normally modified 

 supply and character of the nutriment furnished by the blood- 

 vessels to the feather at this particular and final stage of its 



•Jones, Lynds. The Development of Nestling Feathers. Lab. Bull. 

 No. 13, Oberlin College. Noticed in The Auk, January, 1907, p. 90. 



