MODE OP ARRANGING SPECIES NATURALLY. 53 



overcome, and that all the animals forming a particular group 

 had been collected, and their internal, as well as external 

 structure carefully examined ; in what way, it may be asked, 

 should we attempt to arrange them ? Is it possible to form 

 such a classification, as that they may be placed one after 

 another in a single line or series, uninterruptedly connecting 

 the lowest and the highest forms? An excellent answer to 

 this question is contained in the following quotation from the 

 writings* of a distinguished Naturalist, who has done much 

 for the advance of Zoology ; although (in the opinion of the 

 Author) he has erred by not following Nature, but by attempt- 

 ing to apply a system of his own creation, or at least founded 

 upon a limited and imperfect generalization, to the arrangement 

 of the Animal series. "Let us suppose," he says, "that an 

 Entomological student, with a well-filled cabinet of unarranged 

 insects, having his mind well stored with those simple facts 

 regarding their structure and economy, which he is to look upon 

 as solid data, let us suppose him to commence the arrange- 

 ment of the objects before him, according to what he thinks 

 their true affinities, and with a view of verifying or discovering 

 their natural arrangement. He commences by placing, one after 

 the other, those species which bear the greatest mutual resem- 

 blances, and for a time he proceeds satisfactorily, he finds the 

 several links in the chain, as it were, fit into each other so har- 

 moniously, that he begins to think the task much easier than 

 he at first expected ; and that he will not only be able to prove, 

 by these very examples before him, the absolute connection of 

 one given genus to another, but also to demonstrate that the 

 scale of nature is simple, that is, passing in a straight line 

 from the highest to the lowest organised forms. All these ideas, 

 however (generally resulting from partial reasoning or from 

 limited information), are soon found to be fallacious. As the 

 student proceeds, he meets with some insects which disturb the 

 regularity of his series, and with others which he knows not where 



* Swaiusou's Discourse on the Study of Natural History, in Lardner's Cyclo- 

 paedia, p. 201. 



