VI FORM AND FUNCTION 145 
rhinoceros. But even with feathers, if we begin with 
the simplest instead of the most elaborate, the diffi- 
culty will appear much less, though it may not entirely 
vanish. A still better plan will be to begin with the 
scale of a reptile, and show how it corresponds to a 
bird’s feather. The scale proper is formed from the 
U 
d 
a 
Fic, 37. 
as Feather of Duck, carrying nestling down feather ; (4) Nestling down of Thrush; 
c) of Pigeon ; (¢) Thread feather of Goose ; (4), (c), and (¢) after Gadow; F, Feather 
proper ; nN, Nestling down, 
skin, its horny coating from the epidermis. Where a 
feather is to grow, there is a little skin papilla or 
pimple, which corresponds to the scale proper; the 
actual feather is formed from the epidermis that 
covers the papilla, and corresponds to the horny 
covering of the scale. On the wings of the Penguin, 
or on the legs of birds of the Ostrich kind—e,g., the 
L 
