450 PROCEEDINGS OF SECTION D. 



increase of what, in the absence of the destroyed influence, assumes 

 -unnatural prominence. It is well known that, in many places, in- 

 troduced plants have destroyed — or, at any rate, seemed likely to 

 destroy — certain indi.sjenous plants, and that introduced birds have 

 vastly increased the difficnlties of the fruit producers: ^vhile it is 

 not at all improbable that if the required mammalia were introduced 

 into g-iven regions they might absohitely exterminate numerous 

 species of animals. Why so, if they do it not in their own home ? 

 I reply simply because in their own home they are a factor in 

 nature's balance of power and no more. Nature has provided 

 (I use the term "nature" not, of course, as indicating any 

 particular view of first causes, but simply to avoid involving my 

 argument in any reference to first causes with which it is not 

 eoncerned) — nature has provided the necessary check upon the 

 destructive tendencies of these things in the places where she 

 has herself placed them. They exist naturally only \vhere their 

 environment requires them. If their environment is changed by 

 natural means, ordinarily it will be by gradual means, and the 

 whole environment will change together in such fashion as to 

 preserve the balance ; but if man changes the environment, he will 

 do it -suddenly, and the balance is lost. Thus, if we take the 

 instance of that family of small Coleoptera, the Cucujidoi, which is 

 destroying vast quantities of valuable merchandise all over the 

 world, or the family of scale insects so highly injurious to orange 

 and other plantations of fruit trees, there can be little doubt that 

 each species w^as comparatively harmless in the environment where 

 it was autochthonous because it was preyed upon by other autoch- 

 thonous species, which kept it in check. But if it is accidentally- 

 established in a new region it is extremely improbable that the 

 accident which brought it there will also bring its antidote, and, if 

 not, it becomes a scourge. Surely, then, the scientijic method of 

 reducing the ravages of what, unchecked, is injurious to any of 

 man's interests is to modify its unnatural and unduly favorable 

 new environments by introducing into those environments the 

 particirlar influence that in its natural environments was hostile to 

 its holding an excess of power beyond what nature intended it to 

 wield ; and I venture the opinion that in the future this method 

 will find increasing favor in the eyes of all sensible practical men, 

 and will become increasingly available and efficient. In order to 

 apply this method it is, of course, necessary to study the natural 

 environment of any introduced species, the undue multiplication of 

 whose members it seems desirable to check. And in order to study 

 the natural environment of any species it is necessary to know 

 where it is autochthonous; and to know where it is autochthonous 

 requires that there should be a record, in some place and form 

 available to the student, of its occurrence. And in saying this I 

 ask you to notice that, if it be so, I establish my second ])roposi- 

 tion, viz., that ior practical reasons the investigation of the 



