SYSTEM OF NATURE. 
5 
hence no system possesses capacity sufficient to account 
for those diversified similarities which all reflecting natu¬ 
ralists must have observed, and I cannot but consider it 
the test of a natural system that structural similarity should 
be indicated by a corresponding propinquity in situation. 
Those authors who have been most anxious to claim for 
themselves the invention of a natural system have always 
placed stumbling-blocks in their own way, by assigning 
peculiar virtues to favorite numbers or cabalistic figures ; 
and when similarities of structure have occurred, too ob¬ 
vious to pass unnoticed, yet interfering with such numbers 
or figures, these have been dismissed under the title of re¬ 
lations of analogy. When this determination is once made 
the offending group is despatched to a distant part of the 
system. This clever idea saves an infinity of trouble, but it 
is subject to this little objection :—supposing an animal to 
possess three characters by which it is readily distinguished, 
a speculator may at all times refuse to notice either two of 
them, and insist on the validity of the third. As an in¬ 
stance, an insect may be arranged by its mouth, its wings, 
or its metamorphosis. Three of our modern systematists 
write about the relations of this insect. A, carefully exa¬ 
mines its mouth, gives accurate figures of every part, com¬ 
pares these with similar parts in the mouth of other insects, 
and lays down the law as to its true relations. B, reads 
A’s remarks almost with disgust; he sits down to reply, 
and he clearly proves in a paper of 20 pages, in some hot- 
pressed quarto, that A has mistaken a relation of analogy 
for one of affinity, and expresses his surprise and regret 
that a writer of the present day, and one too of acknow¬ 
ledged celebrity, should consult the mouth of an insect 
for relations of affinity, when the wings are so well known 
