408 



ZOOLOGY 



SECT. 



unbranched in the Carinatse and in Apteryx, branched in the other 

 Ratitse. 



The eggs may be laid on the bare ground or on the rocks by the 

 sea-shore, as in Penguins and Auks, or on the ledges on inaccessible 

 cliffs, as in the Sooty Albatross (Diomedea fuliginosa) ; but as a rule 

 a nest is constructed for their reception by the parent Birds. This 

 may be simply a hole in the sand, as in the Ostrich ; a mere 

 clearing on the hill-side surrounded by a low wall of earth, as in 

 the Wandering Albatross (Diomedea exulans) ; or a cylinder with 

 excavated top, built of grass, earth, and manure, as in the Molly- 

 ma wks (Diomedea melanophrys, etc.). It may take the form of a 

 burrow, as in many Petrels, Kingfishers, and Sand-martins, or it 



sh. 



alb 



FIG. 1012. Gallus bankiva (domestic Fowl). Semi-diagrammatic view of the egg at the time 

 of hatching, a. air-space ; alb. dense layer of albumen ; alb', more fluid albumen ; bl. blasto- 

 derm ; ch. chalaza ; sh. shell ; sh. m. shell-membrane ; sh. 1, sh. 2, its two layers separated to 

 enclose air-cavity. (From Marshall's Embryology, slightly altered.) 



may be more or less elaborately built or woven of sticks, moss, 

 leaves, hair, or feathers, showing every stage of constructive skill, 

 from the rude contrivance of sticks of the Pigeon and Eagle, to the 

 accurately constructed cup- or dome-shaped nests of many familiar 

 Passeres. In the Tailor-Bird (Orthotomus) it is formed of leaves 

 sewn together, the beak acting as needle: in a Malayan Swift 

 (Oollocalia) it is largely built of the secretion of the Bird's buccal 

 glands. 



The number of eggs laid varies from 15 18 in the Partridge, to 

 a single one in many Sea-birds and in the Kiwi. As a rule the size 

 of the eggs bears some proportion to that of the Bird, the smallest 

 being those of Humming-birds, the largest those of the Moas and 

 of ^Epyornis : but in Apteryx the egg is of disproportionate size 



