TO .loiKN \L OF IIIK i)i;i' \inMi:.\ T OK A(.K1( IT/riKK. 1 I I,^ . 1H22. 



Fig. 3. — Part of skin from ostrich chick, about two weeks after hatching. Four of 

 the larger feather filaments have opened out into small, tuft-like feathers, 

 composed of barbs with barbules, resembling the down which covers the young 

 chick. The feather papillae on the other scales are much smaller than those 

 on the chick bnfore hatching, and soon com|)letely atrophy: the scale-feathers 

 :dso fall away. 



'k;. 4. —Section of skin of ostrich chick, after about 20 days' incubation. As in 

 all birds and other animals, the skin consists of an outer layer or epidermis (cp.) 

 and a lower layer or dermis i^tier.). The former has a very thin layer on its 

 outer surface called the epitrichium or periderm. The feather is formed 

 entirely from the epidermis, but is nourished in its growth from the dermis, 

 which alone contains bloodvessels. At the stage represented the scales and 

 feathers show as slight thickenings of the skin, the scale-feather germs ('.s^/V/.') 

 rising a little above the general suifaco. 



Fig. ;').— Section of skin of ostrich chick, after about 25 days" incubation. The 

 scale-feather germs have now grown up into feather pa'pillae (-ifp.). but the 

 boundaries of the scales are not vet formed. 



