OF ORGANIC NATURE. 25 



absent. Now, let us make another jump. Let us go 

 to the Codfish : here you see is the forearm, in this 

 large pectoral fin — carrying your mind's eye onward 

 from the flapper of the Porpoise. And here you have 

 the hinder limbs restored in the shape of these ventral 

 fins. If I were to make a transverse section of this, I 

 should find just the same organs that we have before 

 noticed. So that, you see, there comes out this strange 

 conclusion as the result of our investigations, that the 

 Horse, when examined and compared with other ani- 

 mals, is found by no means to stand alone in nature ; 

 but that there are an enormous number of other crea- 

 tures which have backbones, ribs, and legs, and other 

 parts arranged in the same general manner, and in all 

 their formation exhibiting the same broad peculiarities. 



I am sure that you cannot have followed me even 

 in this extremely elementary exposition of the struc- 

 tural relations of animals, without seeing what I have 

 been driving at all through, which is to show you that, 

 step by step, naturalists have come to the idea of a 

 unity of plan, or conformity of construction, among 

 animals which appeared at first sight to be extremely 

 dissimilar. 



And here you have evidence of such a unity of plan 

 among all the animals which have backbones, and 

 which we technically call Vertebrata. But there are 

 multitudes of other animals, such as crabs, lobsters, 

 spiders, and so on, which we term Annulosa. In these 

 I could not point out to you the parts that correspond 

 with those of the Horse — the backbone, for instance — 

 as they are constructed upon a very different principle, 

 which is also common to all of them ; that is to say, 

 the Lobster, the Spider, and the Centipede, have a 

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