Fig. 2.' — Structure and Development of the Feather (diagrammatic). 



I. An ordinary pinion ; c, calamus 

 or quill ; A.S., aftershaft ; u., rhachis. 



II. An enlarged part of the vane ; 

 R.,rhachis; B.,barb; a.b.b., an anterior 

 barbule; P.B.B., a posterior barbuie. 



III. Two barbs (b) enlarged ; 

 A,B.B., an anterior barbuie; h., book- 

 lets ; P.B.B., a posterior barbuie. 



IV^. An incipient stage in the de- 

 velopment of a feather; y.f., young 

 feather; p., the internal pulp or 



dennis ; r.F., the feather folUcle; 

 D., the dermis ; s.c, stratum corneum 

 of the epidermis, which forms a 

 sheath ; s.m., stratum malpighii which 

 forms the feather. 



V. A later stage showing a layer of 

 the stratum malpighii becoming corni- 

 fied into barbs (r). the sheath (sh), 

 the other letters as before. The 

 stratum malpighii is shown as inter- 

 rupted lines. Other letters as in IV. 



