DISTRIBUTION OI' INSECTS. 



277 



premise that they have nothing specially to do w ith the distri- 

 bution of Beetles (a subject which Mr. Murray handles with his 

 wonted care and skill), but refer only to some matters of more 

 general import incidentally touched upon in the paper. 



The drift of Mr. Murray's main argument (as summarized 

 at p. 7) is to account for the greater part of the difficulties pre- 

 sented by the known existing distribution of animals and plants 

 over the globe, by the simple explanation of " continuity of soil 

 at some former period." While all will admit that very great 

 changes have taken place in the relative extent and position of 

 land and sea during various periods of the past, I think that I con- 

 cur with many naturalists, when I venture to express the opinion 

 that too frequent recourse has been had of late to that broad and 

 general admission as a mode of solving the difficulties in ques- 

 tion, and that a rather wholesale creation of ancient continents 

 has been the result. The process of disposing of such problems 

 by "calling up" connecting lands "from the vasty deep," in 

 which it is assumed they have been submerged, has doubtless 

 something attractive about it, and it possesses the manifest ad- 

 vantage of affording the fanciful geographer an inexhaustible 

 field wherein to disport himself, — 



"The world is all before him, where to choose." 



In saying this, I have no wish to undervalue the importance 

 of the influence on distribution necessarily exercised by changes 

 in the level of the land, there being so many facts only explica- 

 ble on the admission of those changes ; but I think that great 

 caution should be exercised in assuming the former existence of 

 great connecting stretches of land in order to account for cases 

 of generic or specific affinity at distant points of the earth's 

 surface. 



Mr. Murray's avowed inclination in favour of the "con- 

 tinuity" theory appears to me to make him attach too little im- 

 portance to other means of dispersal, particularly in the case of 

 oceanic islands*. I do not propose here to recapitulate Mr. 



* The oceanic islands (at least those of the Atlantic) are regarded by Mr. 

 Murray as the remains of submerged tracts of land ; but those who have visited 

 such islands will generally, I think, recognize the force of the following signi- 

 ficant observation of Mr. Darwin (Orig. of Spec. 4th edit. p. 427), viz. : — "Nor 

 does the almost universally volcanic composition of such islands favour the ad- 

 mission that they are the wrecks of sunken continents ; if they had originally 

 existed as mountain-ranges on the land, some at least of the islands would have 



