Jones — Nestling Feathers. 



PLATE II. 



Figures lO to 20 arc from an 18-day chick embryo. Figures 21 to 28 are 



from a 21 -day embryo ready to hatch. 

 Figs. 10 to 20. A series of cross sections of two barb vanes in the region 



of transition from the nestling down to the first definitive feather. At 



10 to 20, Plate I, Figure 2. x 323. 

 Figs. 21 to 28. A series of cross sections of a single first down feather 



barb which was wholly cornified, to illustrate the passage of the first 



down barb into two first definitive feather barbs, x 618. 



