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groups—in which the genus is obvious, but the species are all but 
_indeterminable, we might be almost tempted to agree with De Can- 
_dolle, that genera are more natural than species. Another fallacy 
seems to me to lie in the notion that genera, if weakly characterized, 
are necessarily of doubtful value. As we find species extremely 
closely allied, although certainly conventionally distinct, so may we 
expect to find genera; indeed, to those who adopt the derivative 
hypothesis of the origin of species, no other conclusion would be pos- 
sible. It is partly owing to this view of the arbitrary nature of genera 
that some naturalists, not Entomologists only, seem inclined to treat 
the generic idea as comparatively unimportant, or who look on their 
multiplication as unnecessary. Now, when we recollect that at least 
500 genera are annually added to our lists, it is worth considering 
more closely on what principles they should be based. Is a genus to 
be limited to a homogeneous group of species? or is it to depend on 
a rigorous set of technical characters? For, although there may be a 
kind of via media, it is really one or the other that must be adopted. 
To a certain extent it may be held that the two are correlative, but 
this is perhaps rather the exception than the rule ; and the characters 
will be secondary, of varying degrees of amount, a little more or a 
little less, and very difficult, if not impossible, to convey clearly in 
description ; or, if we rely on decisive technical peculiarities, it will 
in many cases lead to the assembling together of species into genera 
that would go far to destroy our notions of genera altogether. Prac- 
tically nothing could be worse than to thrust guwasi-aberrant species 
into otherwise well-marked genera, where no one would think of 
seeking them. It is decidedly an advantage that one species should 
give us a good idea of those associated with it, but that cannot be 
done if the number of genera is to depend on the principle of 
adaptation to the capacities or the memories of those who, in trying 
to grasp everything, tell us that the difficulty and labour “threaten to 
overwhelm them.” So will the ever-increasing number of new spe- 
cies, if the inquirer will not satisfy himself with going thoroughly into 
one or two groups only. One thing, however, is quite certain, that if 
the genera of extra-European insects are to keep pace with the genera 
of European, then we have not at present half the number that will 
be requisite. I am far from thinking that every genus proposed is 
necessary ; on the contrary, I regret the tendency of those who, con- 
fining their attention solely to local faunas, too frequently exaggerate 
the importance of scarcely appreciable minutiz. Such genera are, 
