ON THE LAW WHICH HAS REGULATED THE INTRODUCTION 

 OF NEW SPECIES 1 



Geographical Distribution dependent on Geologic Changes 

 EVERY naturalist who has directed his attention to the subject 

 of the geographical distribution of animals and plants must 

 have been interested in the singular facts which it presents. 

 Many of these facts are quite different from what would have 

 been anticipated, and have hitherto been considered as highly 

 curious, but quite inexplicable. None of the explanations 

 attempted from the time of Linnaeus are now considered at 

 all satisfactory ; none of them have given a cause sufficient 

 to account for the facts known at the time, or comprehensive 

 enough to include all the new facts which have since been, 

 and are daily being, added. Of late years, however, a great 

 light has been thrown upon the subject by geological investi- 

 gations, which have shown that the present state of the earth 

 and of the organisms now inhabiting it is but the last stage 

 of a long and uninterrupted series of changes which it has 

 undergone, and consequently, that to endeavour to explain 

 and account for its present condition without any reference 

 to those changes (as has frequently been done) must lead to 

 very imperfect and erroneous conclusions. 



The facts proved by geology are briefly these : That 



1 This article, written at Sarawak in February 1855 and published in the 

 Annals and Magazine of Natural History, September 1855, was intended to 

 show that some form of evolution of one species from another was needed in 

 order to explain the various classes of facts here indicated ; but at that time 

 no means had been suggested by which the actual change of species could 

 have been brought about. 



