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,” abounding in subtle observation ; 
