228 METAMORPHOSIS AND 



stated that the feathers of birds are a modification 

 of the epidermic scales of reptiles, but investigation 

 does not fully confirm this statement. The reptilian 

 scales are retained on the tarso-metatarsal region of 

 the leg in the majority of birds, and it would be ex- 

 pected, if the view just quoted were correct, that a 

 transition from scales to feathers would be visible 

 at the ankle- joint. This, however, is not the case. 

 In fowls some breeds have scaly shanks and others 

 feathered. In those with scaly legs I have found 

 cases in which, in the chicks, there were two or three 

 very minute feathers, and I have examined these 

 microscopically by means of sections of the skin. 

 The result was to show that the minute feathers were 

 not a prolongation of the tips or edges of the scales, 

 but arose from follicles between the scales. The 

 scale is flat and is a fold of the epidermis not arising 

 from an invaginated follicle. The feather, on the 

 other hand, is a tubular structure arising from a 

 papilla at the base of a deep follicle extending 

 inwards from the surface of the skin. As the feather 

 grows the papilla grows with it. This papilla 

 consists of vascular dermal, i.e. mesodermic tissue, 

 and if the feather is pulled out during growth 

 bleeding occurs. The epidermic horny tube splits 

 posteriorly towards the apex of the feather, and is 

 divided into rachis and barbs, and thus the dermal 

 tissue within, by this time dead and dry, is exposed 

 and is shed. Every feather is in fact an open 

 wound, and is perhaps the only other case, in 

 addition to that of the antlers of stags, in which 

 vascular mesodermic tissue is normally shed in such 

 considerable quantities. When the development of 

 the feather is complete, growth gradually ceases, 



