BARB RUDIMENT 

 \ 



AREA OF 



FORMING 



RACHIS BY 



CONVERGENCE 



DORSO-MEDIAD 



COLLAR CELLS 

 DORSAL 

 VENTRAL 



MIGRATION OF COLLAR DORSALLY 

 RAPIDLY GROWING AREA OF THE COLLAR 



RUDIMENTS 



Fig. 270. Diagrams of developing feathers in chick. (A) Nestling, down-feather 

 rudiment of chick of about 12 days of incubation. (B) Feather rudiment, 12 to 14 

 days of incubation, showing beginning of definitive feather rudiment. (C) Nestling 

 down rudiment and definitive feather rudiment of chick shortly before hatching. (D) 

 Relation of nestling down feather to definitive feather shortly after hatching. (E) Later 

 stage in definitive feather development; nestling down feather is attached to distal end 

 of first definitive feather. (F-H) Cross sections of nestling down rudiment diagram- 

 matically shown in (B). (1) Cross section of definitive feather rudiment shown in 

 (D). (J) Cross section of definitive rudiment shown in (E). It is to be noted that the 

 sheath around the developing feather extends for a considerable distance beyond the 

 surface of the skin during development. This area is shortened considerably in E for 

 diagrammatic purposes. F-I based on data from Jones ('07). 



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