52 THE STORY OF THE BIRDS 



us of this special type, from which, by many 

 modifications, especially in the fore limbs and 

 the caudal region, birds as they exist to-day 

 have sprung. 



In conclusion we ought to say that, accord- 

 ing to the state in which they are hatched, the 

 young of birds are divisible into two distinct 

 groups, one of which is further separable into 

 two sections. When birds are hatched with 

 their eyes open, and clothed in down, able to 

 run almost directly they break from the shell, 

 and with sufficient food-yolk still in the stomach 

 to provide for immediate wants, they are classed 

 as Praecoces or Nidifugae. This group includes 

 the Ratitae, the Tinamous, Game Birds, Sand 

 Grouse, Cranes, Rails, Gulls, Waders, Ducks, 

 Geese and Swans, and the Grebes, Divers, and 

 Auks. When birds are hatched (it may be with 

 their eyes open or closed, or covered with down 

 or naked), unable to leave the nest, and fed 

 by their parents, and with a very small store 

 of food-yolk in the stomach, they are classed 

 as Altrices, or Lower Nidicolae. This group 

 includes the Penguins, Pelicans, Cormorants, 

 Gannets, Darters, Frigate Birds, Petrels, Herons, 

 Storks, Ibises, and Spoonbills. When, however, 

 the species in the group of Altrices are hatched 



