226 THE DOCTRINE OF DESCENT. 



leaving any progeny we do not know the cause, 

 though we may yet be able to fathom it ; but in this 

 and all similar cases the adherents of the doctrine ot 

 Creation must confess the inadequacy of their theory 

 of belief. 



Our exposition has shown that the species now extant 

 are the progeny of organisms previously existing ; the 

 present apportionment on the earth is therefore a 

 consequence of the distribution of the progenitors of 

 the present organisms, and of the manifold displace- 

 ments of land and water by which they were indirectly 

 or directly affected. We cannot hope ever to picture 

 to ourselves a faithful representation of the perpetual 

 transformations of the surface of the earth. Only, if 

 this could be accomplished, and if we, moreover, had an 

 accurate register of the animals at each period inhabiting 

 the former islands, continents, and oceans only then 

 could the distribution of the present organisms be 

 thoroughly fathomed and established. But in thus ac- 

 knowledging the incompleteness of our statistical means, 

 we are at least able to lay down with certainty the course 

 of inquiry. We must, in the first place, proceed in the 

 method of the older vegetal and animal geography 

 to ascertain the natural limits and regions of distribu- 

 tion ; and, secondly, to collate these facts with the facts 

 of the distribution of the former progenitors of the 

 present animate world as it was determined by the 

 geological conditions of those times. It is needless to 

 say that Darwin has furnished the outlines for this work 

 also. But among his followers two are specially worthy 

 of distinction : Wallace, with his researches on the 

 Malay Archipelago, 70 abounding in subtle observation ; 



