414 
CLASSIFICATION. 
Chap. XIII. 
cation, which is partially revealed to us by our classifi¬ 
cations. 
Let us now consider the rules followed in classi¬ 
fication, and the diflSculties which are encountered on 
the view that classification either gives some unknown 
plan of creation, or is simply a scheme for enunciating 
general propositions and of placing together the forms 
most like each other. It might have been thought (and 
was in ancient times thought) that those parts of the 
structure which determined the habits of life, and the 
general place of each being in the economy of nature, 
would be of very high importance in classification. 
Nothing can be more false. No one regards the external 
similarity of a mouse to a shrew, of a dugong to a whale, 
of a whale to a fish, as of any importance. These resem¬ 
blances, though so intimately connected with the whole 
life of the being, are ranked as merely adaptive or 
analogical characters; ” but to the consideration of these 
resemblances we shall have to recur. It may even be 
given as a general rule, that the less any part of the 
organisation is concerned with special habits, the more 
important it becomes for classification. As an instance: 
Owen, in speaking of the dugong, says, The generative 
organs being those which are most remotely related to the 
habits and food of an animal, I have always regarded as 
affording very clear indications of its true affinities. We 
are least likely in the modifications of these organs to 
mistake a merely adaptive for an essential character.” 
So with plants, how remarkable it is that the organs of 
vegetation, on which their whole life depends, are of 
little signification, excepting in the first main divisions; 
whereas the organs of reproduction, with their product 
the seed, are of paramount importance ! 
We must not, therefore, in classifying, trust to resem¬ 
blances in parts of the organisation, however important 
