6 



VJiliTEBRATA. 





THE GOLDEN ORIOLE : ILLUSTKATIOX OF PAIRING AND NEST-BLILDING. 



birds' nests, can generally tell at a glance the species to which a particular nest belongs. The 

 number of eggs laid is also very uniform in each species. 



In the structure and development of the egg, we find a great uniformity throughout this class, 

 the development of the embryo taking place here in precisely the same manner as in the reptiles. 

 But notwithstanding this general uniformity in the processes of reproduction, there is a remark- 

 able difference in the condition of the young birds at the moment of hatching, and this has given 

 rise to the division of the class into two great sections. In some, which usually reside upon the 

 ground, where they form their nests and hatch their young, the latter are able to run about from 

 the moment of their breaking the egg-shell, and the only care of the parents is devoted to pro- 

 tecting their offspring from danger, and leading them into those places where they are likely to 

 meet with food. The others, which in fact constitute the majority of the class, pass more of 

 theu- time in the air, and generally repose upon the trees, or in other elevated situations, where 

 they also build their nests, and the young birds for some time after they are hatched, remain in 

 the nest in a comparatively helpless state, their parents bringing them food, and attending upon 

 them most assiduously until their feathers are sufficiently grown to enable them to support them- 

 selves upon the wing. A chicken or a partridge, a day after it is hatched, will run about and 

 pick up seeds, separating them from the gravel among which they lie, while the young of the 

 tree-birds remain often a month in the nest, receiving without discrimination what is given by 

 their parents. This difference between the young of the two classes will be more apparent by a 

 glance at the engravings pages 7 and 8 . The first represents a young curlew, a day or two old, 

 going forth with all his faculties awake, and almost ready to make his way in the world ; the other 



