172 NATURAL HISTORY. 



history upon which he wrote so copiously. He is at the 

 present day best known, perhaps, in consequence of his 

 close connection with the ' Circular System' of classification, 

 with which he had entirely identified himself. This theory 

 we may therefore now proceed to discuss very briefly ; 

 and in so doing, it will be best to consider Swainson's 

 enlarged and amended scheme, rather than the compara- 

 tively rough outline of the circular classification given by 

 Macleay, the actual author of the system, and the originator 

 of the notion of circular affinities. 



In expounding his classification of the animal kingdom, 

 Swainson, to begin with, discusses fully what he conceives 

 should be the principles upon which a natural arrange- 

 ment of animals may be founded. He points out that the 

 likenesses which subsist between different animals are not 

 only different in degree, but also different in kind; and he 

 divides such likenesses into what he terms likenesses of 

 'analogy' and likenesses of 'affinity.' What he under- 

 stands as likenesses of ' analogy ' are all such likenesses or 

 resemblances between different animals as are either what 

 we may call accidental, or which depend merely upon 

 similarity of the mode of life. Thus, he instances the like- 

 ness between the striped skin of the tiger and that of the 

 zebra as an example of analogy. Similarly, the likeness 

 between the whales and the fishes, dependent upon the 

 purely aquatic life of both, he instances as a likeness of 

 analogy. On the other hand, Swainson recognised that 

 there exist other likenesses, affecting the whole organisa- 

 tion of the animals compared, of more real and funda- 

 mental character, and these he termed likenesses of 

 'affinity.' As an example of these, he instances the 



