SUMMARY OF ' PHILOSOPHIE ZOOLOGIQUE? 307 



from above than from below, and find it necessary to 

 pay attention to whatever happens to be above them ; 

 this need has involved the displacement of their eyes, 

 which now take the remarkable position which we 

 observe in the case of soles, turbots, plaice, &c. The 

 transfer of position is not even yet complete in the case 

 of these fishes, and the eyes are not, therefore, symme- 

 trically placed ; but they are so with the skate, whose 

 head and whole body are equally disposed on either 

 side a longitudinal section. Hence the eyes of this fish 

 are placed symmetrically upon the uppermost side.* 



" The eyes of serpents are placed on the sides and 

 upper portions of the head, so that they can easily see 

 what is on one side of them or above them ; but they 

 can only see very little in front of them, and supplement 

 this deficiency of power with their tongue, which is very 

 long and supple, and is in many kinds so divided that 

 it can touch more than one object at a time ; the habit 

 of reconnoitring objects in front of them with their 

 tongues has even led to their being able to pass it 

 through the end of their nostrils without being obliged 

 to open their jaws. | 



" Herbivorous mammals, such as the elephant, rhino- 

 ceros, ox, buffalo, horse, &c., owe their great size to their 

 habit of daily distending themselves with food and 

 taking comparatively little exercise. They employ 

 their feet for standing, walking, or running, but not for 

 climbing trees. Hence the thick horn which covers 

 their toes. These toes have become useless to them, 

 and are now in many cases rudimentary only. Some 



* Phil. Zool.,' torn. i. p. 251. f Page 252. 



x 2 



