AVES. 125 



The egg, detached from the ovary, where it consists merely of 

 yolk, imbibes that external fluid, called the white, in the upper part 

 of the oviduct, and becomes invested with its shell at the bottom of 

 the same canal. The chick contained within it is developed by in- 

 cubation, unless the heat of the climate suffices for that purpose, as 

 is the case with the egg of the Ostrich. The young Bird has a lit- 

 tle horny point at the extremity of the beak, with which it splits open 

 the shell, and which falls off a few days after it is hatched. 



The industry and skill exhibited by Birds in their variously con- 

 structed nests, and their tenderness and care in protecting their eggs 

 and young, are known to every one; it is the principal part of their 

 instinct. Their rapid transitions through different regions of the air, 

 and the vivid and continual action of that element upon them, enable 

 them to anticipate atmospheric changes, to an extent of which we 

 can form no idea; and caused the ancients, in their superstition, to 

 attribute to them the power of prescience or divination. It is un- 

 questionably on this faculty, that depends the instinct which acts 

 upon the Birds of passage, prompting them to seek the south on the 

 approach of winter, and the north on the return of spring. They 

 have memory, and even imagination for they dream. They are 

 easily tamed, may be taught to render various services, and retain the 

 air and words of songs. 



Division of the Class of Birds into Orders. 



. 

 Their distribution is founded, like that of the Mammalia, on the 



organs of manducation or the beak, and on those of prehension, that 

 is on the beak, and particularly on the feet. 



The first that arrest our attention are the palmaledfeet, or those 

 in which the toes are connected by membranes, which distinguish 

 all Swimming Birds. The position of these feet behind; the length 

 of the sternum; the neck, often longer than the legs to enable it to 

 reach below; the dense, polished plumage, impermeable to water, all 

 concur with the feet in making good navigators of the Palmipedes. 



In other Birds, which most commonly are partially web-footed, at 

 least between the external toes, we observe elevated tarsi; legs divest- 

 ed of feathers at their lower extremities; a long thin shape, and in fine, 

 all the requisites for wading along the shores of rivers to seek their 

 food. Such, in fact, is the regimen of the greater number; and al- 

 though some of them inhabit dry grounds, they are called Shore- 

 Birds, or Waders. 



