'22 



The Bird 



The first intimation of the appearance of a feather, or 

 of down, is shown l)y a thickened group, or pimple, of 

 cells in this under layer of skin, which grows and presses 

 upward toward the outer layer — the epidermis. This is 

 exactly the way in which the scales of fishes and reptiles 

 begin to form; and if, at this stage, the tiny projection 

 should flatten out, the shining scale of a carp, the armor 



Fig. 11. — Sprouting feathers of a r2-day embryo chick. Magnified 25 diameters. 



of an alligator, or the co]:)ble-scale of an iguana lizard 

 might result. Indeed, in the feathers of a penguin we 

 find transition stages of flat, almost unsplit feather- 

 scales; while on the legs and feet of birds are reptile-like 

 scales. 



The evolution of scales, hair, and feathers is a most 

 interesting problem, most of the details of which are 

 beyond the scope of this work. Suffice it to say that 



