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nial Kingdom cannot be made to follow each other in a linear series, 

 because each of the divisions, articulates, mollusks and radiates, con- 

 tains more highly organised animals than some that must necessarily be 

 placed in both the others: moreover, the first division, vertebrates, con- 

 tains animals which seem to typify or indicate respectively the articulate, 

 mollusk and radiate plans of structure. As I am aware that many of 

 my readers are not zoologists, I will select a more strikingly obvious 

 example of this typification or indication. The superior group among 

 Vertebrata contains the four well-known classes, called Mammals, 

 Birds, Reptiles and Fishes. All but the first of these are peculiarly 

 well marked : a child, before he can speak plainly, knows a bird, a 

 reptile, and a fish from each other : the mammals form a group which 

 all naturalists agree in considering of higher rank than either of the 

 others, and as a concomitant of this superiority, there should be found 

 among them animals which respectively indicate, typify, or represent, 

 birds, reptiles and fishes ; and this is strictly the case : among mam- 

 mals we find birds indicated in the bats; reptiles in the armadilloes 

 and anteaters; and fishes in the whales and dolphins. The uninstruct- 

 ed mind at once sees the force of this representation ; it even contends 

 that a bat is a bird, that an armadillo is a reptile, and that a whale is 

 a fish. This is going too far: we may fairly consider them the repre- 

 sentatives of these classes, but not as belonging to them. Bats, whales, 

 and armadilloes agree in possessing warm blood, in being truly vivi- 

 parous, and in suckling their young : it is therefore impossible to dis- 

 join them from typical mammals, such as the ordinary quadrupeds, 

 although the bats adopt the flight of a bird, together with possession 

 of many important similarities of structure ; although armadilloes and 

 anteaters have the alimentary canal, the reptant gait, the dermal arma- 

 ture of reptiles ; and although the dolphins and whales have the figure, 

 the fins, and the habits of fishes. Now, supposing the mammals 

 grouped on a level surface, the most perfect or typical occupying the 

 centre of the group, then we shall find a variety of forms, which indi- 

 cate, more or less obviously, an approach to one or other of the three 

 aberrant forms, namely bats, anteaters and whales, and we shall find 

 that these three forms differ from each other as widely as it is pos- 

 sible for animals to do, which must necessarily be regarded as part 

 of the same superior group : so that abandoning all idea of a linear 

 series, which, indeed, it is impossible to construct, and supposing the 

 Mammalia standing on the superficies of any figure, a triangle for in- 

 stance, and all arranged strictly in accordance with their degrees of re- 

 semblance to the most perfect or typical, which occupies the centre. 



