22 



The Bird 



The first intimation of the appearance of a feather, or 

 of down, is shown by 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 12-day embryo chick. Magnified 25 diameters. 



of an alligator, or the cobble-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 



