♦ 
THE BIRD ITSELF 
and provides a never ending source of enquiry. Some of the 
diflferetices between young birds are very hard to explain but 
one reasonable hypothesis that has been put forward supposes 
the original birds to have been arboreal in habits* It is then 
likely that their active young (as they would be if derived from 
reptilian ancestors) would be open to many dangers if bom 
in a more or less precarious position in a tree. By reduction 
in the amount of the yolk and therefore in the size of the egg 
the young were caused to be hatched helpless and blind, pre- 
maturely in fact! It will in truth be noticed that generally 
speaking the naked helpless type of nestling is hatched from a 
comparatively small egg placed in a nest in a tree as in the case 
of the crows, etc., whereas the active, down-clad type emerge 
from large eggs placed on the ground as in the case of the 
plovers. The question of the origin of these two main types is 
but one of the mysteries that surround nestling birds. In 
concluding this very elementary sketch of birds we cannot do 
better that quote from Elliot Coues concerning the manner 
of their death, "Birds alone, of all animate beings, may be 
truly said to 'fall asleep' in death. When the silver 'cord' of 
a bird's life is loosed, the 'windows of the soul' arc gently 
closed by unseen hands, that the mysterious rites of divorce of 
spirit from matter may not be profaned. When man or any 
mammal expires, the eyes remain wide open and their stony 
stare is the sign of dissolution. Only birds close their eyes 
in dying. The closure is chiefly affected by the uprising of the 
lower lid. These are the principal external differences between 
the eyes of birds and mammals. The movements of the upper 
lid in most birds arc much more restricted than those of the 
lower." 
