LEADING GROUPS OF EXISTING SYSTEMS 187 



tions, covering indeed a much wider ground than would appear from 

 these remarks; for, upon these principles, I have already remodelled, 

 for my own convenience, nearly the whole animal kingdom and in- 

 troduced in almost every class very unexpected changes in the classi- 

 fication. 



I have already expressed above my conviction that the only true 

 system is that which exists in nature, and as therefore no one should 

 have the ambition of erecting a system of his own, I will not even at- 

 tempt now to present these results in the shape of a diagram, but 

 remain satisfied to express my belief that all we can really do is, at 

 best, to offer imperfect translations in human language of the pro- 

 found thoughts, the innumerable relations, the unfathomable mean- 

 ing of the plan actually manifested in the natural objects themselves; 

 and I should consider it as my highest reward should I find, after a 

 number of years, that I had helped others on in the right path. 



SECTION IX '^■^ 

 THE CATEGORIES OF ANALOGY 



Thus far we have considered those relations only among animals 

 which are founded upon strictly homological features of their struc- 

 ture. We now proceed to examine the more remote and less definite 

 relations, which are called analogies. 



It has already been stated in what way homologies differ from 

 analogies. Homology is that kind of relationship which is founded 

 upon identity of structure in different animals belonging to natural 

 divisions of the same kind; while analogy is a resemblance arising 

 from the combination of features characteristic of one natural group 

 with those of another group.^^ We have indeed seen that all the ani- 

 mals belonging to the same branch are homologous, as far as the plan 

 of their structure is concerned; that all the members of the same 

 class are homologous, as far as the mode of execution of that structure 



^^ [This entire section was added in the 1859 edition.] 



^ Homology has also been defined as the relationship arising from identity of struc- 

 ture without reference to function, while analogy is based upon similarity of function, 

 without reference to structure. The definition given above is more precise, as it em- 

 braces all the different categories of analogy and homology 



