27 
the one had become, through the operation of natural selection, 
identical with those which favoured the other. 
But I will descend from the region of abstruse speculations, which 
may not interest those of you whose mental activities run in other 
directions, and will venture to give you one or two of the thoughts 
which have been the outcome of the creed which 1 have enunciated 
when I said that “ a particular species will be abundant just when and 
where therein room for it.” Not many years ago I was an uncompro¬ 
mising opponent of the experiments which seem so entertaining to a 
good many lepidopterists—of the naturalisation of species in new 
localities. I even characterised such a proceeding, without the 
fullest publicity, as “ an acted lie against scientific knowledge.” 
(Knt. Rev. viii., p. 278). I may as well say frankly that I have almost 
entirely abandoned that position, and though I have no taste myself 
for transplantation experiments, I think they are generally quite harm¬ 
less, although I would still urge entomologists to abstain from plant¬ 
ing marked local varieties or aberrations in new localities ; for in¬ 
stance, if one of you put down some thousands of pup® of Manchester 
doubledayaria in our London suburbs without publicly announcing the 
fact, you may seriously vitiate the statistics which the “Evolution 
Committee ” of the Royal Society is endeavouring to collect. But in 
other cases— i.e., the attempt to establish a new species in a particular 
locality—the reasons which convince me that it is generally harmless 
from the scientific point of view rest almost entirely upon the view 
which I have just put forth ; if there is not room for the new comer 
(and this usually proves the case) the experiment will fail—witness 
the hundreds of unsuccessful attempts to establish Porthetria dispar 
in various parts of this country ; and if there is room for it, its occu¬ 
pation of the spot will not upset any important scientific fact of 
distribution, for it is always probable that the same result might 
have been or might be brought about by natural migration, chance 
introduction, or other agencies apart entirely from the volition of 
man. For instance, it matters very little how Plusia moneta has 
become established in England, whether through accidental or 
intentional introduction ; the fact that it is capable of breeding and 
multiplying here is unimpaired whichever be the cause. Perhaps, 
however, I ought not to pass away from this subject without remind¬ 
ing you that whilst such proceedings may be free from scientific 
danger, they require the exercise of some judgment and discretion if 
we want to avoid a serious economic menace ; none of you would 
desire, for the sake of the gratified vanity which might come of a 
successfully carried-out experiment, to risk a repetition of the sad 
story of the Gypsy Moth in America. 
The reverse aspect of this question of the occupation by a 
particular species of any locality where there is room for it, is the one 
to which I referred in the early part of my address as “ dangerous 
ground ”-—the over-collecting question and our attitude towards it. 
We all know that there is such a thing, and that species have 
occasionally been almost wiped out of a particular area through the 
ignorant greed or misguied energy of a few collectors ; let us all agree, 
then, if we must err at all, to err on the safe side of over-abstemious¬ 
ness. But I have been so often amused—and occasionally even 
disgusted—at the absurdly superficial views which frequently obtain 
