Classzfication. 25 
This general principle of natural affinity, of which 
all naturalists have seen more or less well-marked 
evidence in organic nature, and after which they have 
all been feeling, has sometimes been regarded as 
natural, but more often as supernatural. Those who 
regarded it as supernatural took it to consist in a 
divine ideal of creation according to types so that the 
structural affinities of organisms were to them expres- 
sions of an archetypal plan, which might be revealed 
in its entirety when all organisms on the face of the 
earth should have been examined. Those, on the 
other hand, who regarded the general principle of 
affinity as depending on some natural causes, for the 
most part concluded that these must have been utili- 
tarian causes ; or, in other words, that the fundamental 
affinities of structure must have depended upon funda- 
mental requirements of function. According to this 
view, the natural classification would eventually be 
found to stand upon a basis of physiology. Therefore 
all the systems of classification up to the earlier part 
of the present century went upon the apparent axiom, 
that characters which are of most importance to the 
organisms presenting them must be characters most 
indicative of natural affinities. But the truth of the 
matter was eventually found to be otherwise. For it 
was eventually found that there is absolutely no cor- 
relation between these two things; that, therefore, it 
is a mere chance whether or not organs which are of 
importance to organisms are likewise of importance as 
guides to classification ; and, in point of fact, that the 
general tendency in this matter is towards an inverse 
instead of a direct proportion. More often than not, 
the greater the value of a structure for the purpose of 
