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species usually appear to be somewhat more definite (possibly 
from having been more studied) than genera, even when their abstract 
position is considered, the error has been less glaring. 
Let us look at this for a moment. It was at one time thought that 
a species was a specially created entity, a thing complete in itself, and 
capable of absolute definition as such. Our studies have swept 
away the notion, for, however true it may be that the study of our 
insular fauna with all its missing links enables us to congratulate 
ourselves on the ease with which we can, as a rule, discriminate the 
individuals which we are pleased to constitute as species, yet our 
own fauna gives us some difficulty even in this direction. | Who can 
separate absolutely some specimens of Agrotis tritici and A. cursoria ; 
of Cidaria russata and C. tmmanata? yet, because they can, in the 
mass, be separated with less difficulty than the parallel Zeshrosia 
bistortata (crepuscularia) and 7: crepuscularia (biundularia), some 
entomologists will maintain the distinctness of the former, and 
burke the difficulties presented by the differentiation of the latter by 
uniting them as one species, a method to be deplored as a sign of 
ideal weakness. The truth, indeed, is patent. ‘There is no sharp 
line of demarcation between any of the pairs of species just referred 
to. Species are not always the entities that we are apt to consider 
them ; they are not always capable of absolute separation nor of 
exact definition. Yet species vary in degree. In the above ex- 
amples they are doubtless in process of development, and since they 
exist largely under the influence of a similar environment, are unable 
to detach themselves absolutely. Of the specific value of the 
Larentia olivata of our hedgerows and woodsides we have no 
doubt, nor have we in Piedmont of the Alpine Zavenéia apfata. In 
Britain, Z. ofvaza is a species ; in the Swiss Alps Z. aféaza is also a 
species ; but in the Tyrol, where Z. o/vafa and L. aptata occupy the 
same ground, they produce every possible intermediate form ; and we 
learn that these two specialised forms have even recently (as such 
times go) had a common origin—nay, that what are to us normally 
two distinct species are in other parts of the world but one. It is 
true, then, that between the most closely allied species there is really 
no sharp line of distinction, and that the greater the number of 
intermediate links that have become extinct, the more isolated and 
distinct the species become. 
Who can separate all the Alpine Meliteeas, the Skippers, the 
Erebias? Only those who have the most complete knowledge of 
them, who have seen them in hundreds in their native haunts, know 
that the forms, distinct enough as species in one valley, may exist as 
varieties, or even aberrations, in the next; yet our museum men, who 
have seen a few dried bodies, will separate them absolutely and give 
ex cathedra views upon them. It is the old, old saying again of 
which one is reminded when one reads these absolute views—‘“ Fools 
rush in where angels fear to tread.” Of an earnest worker one can 
safely say that at five-and-twenty he will know everything ; at five-and- 
