^^p 

 ^""^m 



m^m. 



a 



.■■■^. 



•-'Tnu 



% 



J 



Fig. 6. Development of down feathers: diagrammatic. 

 a, skin fragment, Ring penguin embryo, stage 37; b, longitudinal section of feather papillae; c, transverse 

 section of a feather papilla; d, longitudinal section of a feather filament at this stage; e, transverse section 



of the same. 



/, skin fragment, Ring penguin embryo, approximately half-way through the incubation period; §, longi- 

 tudinal section of a feather filament at this stage; h, transverse section of the same. 



/, skin fragment. Ring penguin embrj^o, at the close of the incubation period ;;, longitudinal section of the 

 base of a feather; k, transverse section at a higher level, to show barbules. 



ba, barb; bu, barbule; ds, dermis; co, blood corpuscle; ep, epidermis ;//>, filoplume; mu, muscle; /)f, pulp 

 cavity;M papillae; sc, "scale"; sh, sheath. (Transverse sections after Wohlauer.) 



