348 OSCAR RIDDLE. 



of growth we may consider one or two other related points. In 

 the rectrices of doves the distance separating the point where the 

 barbule cells arise, and a point at which they are practically com- 

 pletely cornified, is less than a centimeter. In his paper on the 

 Development of Color, Strong's drawings show practically the 

 same for Sterna, though he does not call attention to the fact. 

 The measurements of the rate of growth (6 mm. per day) in the 

 rectrices of the dove, when considered in relation to the distances 

 separating the origin and cornification of a barbule cell, show that 

 the entire formation and differentiation of these cells occur in the 

 short space of 24 to j6 hours. 



Since, moreover, 6 mm. of linear growth is accomplished in the 

 24 hours, 1 mm. would be grown in 4 hours. This would mean, 

 then, that where a defective area (absent barbules) is 1 mm. in 

 width that this area was produced in approximately 4 hours. 

 This cannot be otherwise since the barbs — on which the bar- 

 bules are borne — have been shown to grow steadily on during 

 fault-bar producing conditions; certainly until the third or fourth 

 day of starvation. A defective area 1 mm. wide in the rectrices of 

 doves indicates, quite certainly, very low nutritive conditions during 

 a period of about four hours. 



The Nutrition of the Feather. 



General on Feather Nutrition. — Hypotheses innumerable, con- 

 cerning the nutrition of the feather, bridge the gap between the 

 very queer conceptions of Dutrochet, Cuvier and Chadbourne. 

 Dutrochet 1 asserted that the "blood-vessels are strangers to the 

 phenomena of feather nutrition " ; that a little liquid merely filters 

 upward through the papilla. Cuvier 2 taught that the feather is 

 laid down in a mould or matrix, the freshly added particle 

 accomodatingly taking its place on the outside of parts already 

 formed. Chadbourne 3 has informed us, however, that not only 

 does the body establish blood and "vital" relations with the 



1 Dutrochet, R. J. H., " De la structure et la regeneration des Plumes," Journ. de 

 Physique, LXXXVIIL, 1819. 



2 Cuvier, F., "Observations sur la structure et le development des Plumes," Mem. 

 de Museum, XIII., 1825. 



3 Chadbourne, A. P., "The Spring Plumage of the Bobolink with Remarks on 

 •Color Change' and 'Moulting,' " The Auk, Vol. XIV., No. 2, 1897. 



