198 



ANIMAL LOCOMOTION. 



2d, Such as have light bodies and large wings with a 

 leisurely movement (fig. 60, p. 126; fig. 103, p. 186). 



3(i. Such as have heavy bodies and long narrow wings 

 with a decidedly slow movement (fig. 105, p. 200). 



4:th. Such as are intermediate with regard to the size of 

 body, the dimensions of the wing, and the energy with which 

 it is driven (fig. 102, p. 183; fig. 106, p. 203; fig. 107, 

 p. 204). 



They may be subdivided into those which float, skim, or 

 glide, and those which fly in a straight line and irregularly. 



The pheasant, partridge (fig. 59, p. 126), grouse, and quail, 

 furnish good examples of the heavy-bodied, short-winged 

 birds. In these the wing is rounded and deeply concave. 

 It is, moreover, wielded with immense velocity and power. 



The heron (fig. 60, p. 126), sea-mew (fig. 103, p. 186), lap- 

 wing (fig. 63, p. 138), and owl (fig. 104), supply examples of 

 the second class, where the wing, as compared with the body, 

 is very ample, and where consequently it is moved more 

 leisurely and less energetically. 



Fig. 104.— The Cape Barn-Owl {Strix capensis, Smith), as seen in full flight, 

 hunting. The under surface of the wings and body are inclined slightly 

 upwards, and act upon the air after the manner of a kite. (Compare with 

 fig. 59, p. 126, and fig. 102, p. ISS.)— Original. 



The albatross (fig. 105, p. 200) and pelican afi'ord in- 

 stances of the third class, embracing the heavy-bodied, long- 

 winged birds. 



The duck (fig. 107, p. 204), pigeon (fig. 1C6, p. 203), crow 

 and thrush, are intermediate, both as regards the size of the 

 wing and the rapidity with which it is made to oscillate. 

 These constitute the fourth class. 



The albatross (fig. 105, p. 200), swallow, eagle, and hawk, 

 provide instances of sailing or gliding birds, where the wing 

 is ample, elongated, and more or less pointed, and where ad- 



