270 NIDIFICA TION. 



place its nest in the same way. The Song Sparrow is gen- 

 erally a ground-builder, but in the latter part of the season 

 it frequently places its nest in a hedge or in a low bush. 

 The Crow Blackbirds, in these parts, invariably build in a 

 tree, but in the south, Audubon found them appropriating 

 the cavities of trees, while Wilson not infrequently found 

 them a sort of parasite on the nest of the Fish Hawk. 



For the most part, birds' eggs are objects of great beauty. 

 Their form is unique and fine, their surface highly finished, 

 and their colors and markings often elegant. How strongly 

 differentiated too, generally, are the eggs of the birds of 

 each family! The blue-green eggs of the Thrushes; the 

 translucent white eggs of the Woodpeckers; the delicate, 

 white gems, specked with red, deposited by Titmice, Nut- 

 hatches and Creepers; the roundish, pure- white eggs of the 

 Owls; the light bluish-green eggs of the Herons; and the 

 smooth-shelled, creamy or green-tinted eggs of the Ducks, 

 are all data for classification to the naturalist. 



Richard Owen, the great comparative anatomist of Eng- 

 land, after giving the complicated and wonderful history of 

 an egg in its various stages till it reaches perfection; and 

 after showing the nice contrivances in the yolk and albu- 

 men, by which the cicatricle or germ is always held upper- 

 most, no matter how many times the egg is turned over, in 

 order to keep it in contact with the sitting dam, and so 

 secure incubation and protect it from jars or injuries in 

 harsh movements; and after showing how " the domed form 

 of the hard shell enables it to bear the superincumbent 

 weight of the brooding mother," well says: "How these 

 modifications of the oviparous egg in anticipatory relation to 

 the needs and conditions of incubation can be brought 

 about by 'selective' or other operations of an unintelligent 

 nature is not conceivable by me." 



