510 



Comparative Morphology of Chordates 



PULP-^ 



Fig. 399. Four stages in the development of a feather. (A, B, C) Stages in the 

 development of a down-feather. (D) A contour feather in the feather-sheath. 

 (a-b) and (c-d) are sections of a young contour feather at the levels indicated 

 in (D). (Redrawn from Ihle, after Butschli. Courtesy. Neal and Rand: "Chordate 

 Anatomy," Philadelphia, The Blakiston Company.) 



Fig. 400. Stereogram of a developing down-feather, (bv) Blood-vessels entering 

 pulp; (c) dermis (corium); (ep) epidermis; (/) feather follicle; (p) pulp (mesen- 

 chyme) of developing feather; (per) periderm; (r) rods of epidermis, which later 

 dry, separate, and form the down. (Courtesy, Kingsley: "Comparative Anatomy 

 of Vertebrates," Philadelphia, The Blakiston Company.) 



