144 TEST CASES [ch. xiii 



more hybrids, so that the only result of an incipient species 

 trying to gain territory at the expense of its parent would be the 

 continual formation of hybrids. Only when the sterility line had 

 been crossed would the new species really be able to conquer the 

 old, and to supplant it. But it is very hard indeed to see how this 

 line can be crossed in any case without a large mutation that will 

 create a new species at one step; one cannot easily imagine a 

 species gradually crossing the line of sterility, nor even a series of 

 small mutations doing it. 



There is evidence to show that on the whole the parent will 

 continue to gain in dispersal upon the offspring (66, p. 34), and 

 if this be so, it could not be altogether killed out, unless the 

 assumption that the offspring, by becoming better adapted to 

 place A, became thereby better adapted to B, the home of the 

 parent, were correct. There is little or no evidence that a species, 

 and still less a variety, fights as a whole, and an organisation that 

 is based upon such a contention, as so much political organisation 

 is at present based (the operation of the dead hand, so well 

 described in Woolf's Aftei' the Deluge, chap, i), has no strong 

 scientific backing. 



To carry out evolution by natural selection involves a vast 

 amount of destruction, for which we have no evidence in fossil 

 botany or elsewhere, whilst such destruction is not involved in 

 the theory of differentiation. To try to explain the phenomena of 

 geographical distribution upon the supposition that one species 

 has conquered and destroyed another is to build upon a somewhat 

 insecure foundation. It has hitherto been assumed that a widelv 

 dispersed species owes its dispersal to the fact of its superior 

 adaptation. But to ivhat is it adapted, and how in country A did 

 it become adapted to the conditions of country B ? If its range be 

 large, it must come into greater variety of conditions than if its 

 range be small, and that must mean that as it moved about it 

 became functionally adapted to all these conditions in turn, but 

 that is no proof that in becoming adapted to B it retained the 

 adaptation to A. But in any case much time must be allowed, 

 i.e. that wide-ranging species are usually old, a supposition that 

 agrees with age and area. The more local species, which do not 

 occur in such variety of conditions, are the younger. It would, 

 therefore, form a much more probable explanation to say that 

 the widely dispersed species were the old ones, dispersed before 

 the land was broken up into its present divisions, and before the 

 climates showed so much differentiation as they do at the present 



