CLASS 111. REPTILES. 61 



worms. All birds with this structure of the legs are ranked 

 among the Grallae, although some of them are not, properly 

 speaking, waders in their habits. To this order belong the 

 ostrich, cassowary, flamingo, heron, spoonbill, plover, rail, 

 woodcock, ox-eye, yellowleg, &c. The greater part of them 

 are possessed of strong wings, and fly well/but the ostrich and 

 cassowary, as is well known, are striking exceptions. They 

 are almost incapable of flight, but run with immense rapidity. 

 The ostrich inhabits the sandy deserts of Africa, attains to a 

 height varying from six to eight feet, and is at once the most 

 lofty of birds, and the swiftest of all animals. When chased, 

 it annoys its pursuers by throwing up gravel and stones behind 

 it with its feet. 



VI. Anseres, the Web-footed birds. Their toes are con- 

 nected together by a web or membrane, which fits them for 

 being used as oars. Indeed, the whole structure of these birds 

 is such as to adapt them for swimming. Their legs are situ- 

 ated far back upon their bodies; their feathers are thick, 

 smooth, and oily, and their skin beneath covered by a layer of 

 close down, which effectually protects them from the contact 

 of the water. Their necks are of considerable length a pro- 

 vision which enables them, while swimming upon the surface 

 of the water, to plunge their heads down to the bottom in 

 search of food. Most of them are capable of a lofty and long- 

 continued flight, as the pelican, petrel, cormorant, albatross, 

 gull, wild goose, and duck ; whilst others, from the shortness 

 of their wings, can scarcely raise themselves into the air, but 

 are principally confined to the surface of the water, as the sea- 

 diver, guillemot, penguin, awk, domestic goose and duck, &c. 



SECTION IV. 



Class III. Reptiles. 



THE class of reptiles, including the tortoises, lizards, ser- 

 pents, toads, and frogs, have cold blood, and a circulation and 

 respiration less perfect than those of the preceding classes, 

 which have warm blood. In reptiles, only a part of the blood 

 received from the body by the heart, is sent to the lungs, to 

 be subjected to the influence of the air; whilst the remainder, 

 having been mixed with a portion which has undergone the 

 change that takes place in respiration, is returned again into 

 the circulation. The greater part of the animals of this class 

 6 



