266 STUDY OF NATURAL HISTORY. 



to purely aquatic animals, like the otter, the seal, 

 and the ornithorhynchus ; to these the power of 

 walking is almost denied, their feet being remark- 

 ably short, the toes connected, and the whole 

 structure adapted almost exclusively for swimming : 

 the second and last structure is restricted to the beasts 

 of prey forming the order Ferce ; the only material 

 difference between these and the ordinary feet of 

 five-toed quadrupeds, consists in the power they 

 possess of retracting and protruding their claws at 

 pleasure. The importance of this property to the 

 animal is sufficiently obvious, when we consider the 

 especial use which is made of them. Strong, and 

 peculiarly sharp, they are employed as formidable 

 weapons of offence and of defence ; with these they 

 seize their prey, tear it into pieces, and defend 

 themselves from their enemies. We cannot have a 

 better or a more familiar example of these habits, 

 than in the domestic cat. 



(183.) The feet of birds are no less varied, and 

 afford us the means of discriminating the primary 

 divisions of the feathered creation, without having 

 recourse to any other help. Nor do their differences 

 terminate here : under each of the five great modi- 

 cations, or types of formation, which may be seen 

 in birds, are contained others, still preserving the 

 essential character common to all, but deviating 

 into minor types, which again point out little as- 

 semblages of groups, or of species, more especially 

 united among themselves. The most perfect birds 

 in creation are of course such as have the greatest 

 complexity of structure, and the greatest variety of 

 powers. These are unquestionably the perchers ; 



