CLIMATIC VARIETIES 183 



account for the facts in a rational way. As always in a problem 

 of Evolution, two separate questions have to be answered. 

 First how did the form under consideration come into existence, 

 and secondly, how did it succeed in maintaining itself so as to 

 become a race? The evidence from the local forms, though very 

 far from giving complete answers to either of these questions 

 definitely refutes the popular notion that a new race comes into 

 existence by transformation of an older race. If a gradual mass- 

 transformation of this kind took place we should certainly expect 

 that when two types, nearly allied and capable of interbreeding, 

 overlap each other in their geographical distribution, a normally 

 intermediate population would exist. If each type can main- 

 tain itself, and if each came into existence by gradual transfor- 

 mation, then there must have been an intermediate capable of 

 existing and maintaining itself as a population; and if this had 

 ever been, surely in the region of overlapping, that intermediate 

 population should continue. Especially should such a population 

 be found when the two extreme types are adaptational forms and 

 the region of overlap is a region of intermediate conditions. 

 But of the examples we have examined there is only one, that of 

 Pararge egeria and egerides, which can at all be so interpreted, 

 and even in that case it is not impossible that more minute ob- 

 servation would reveal discontinuity between the extremes 

 and the admittedly normal intermediate population. Granting 

 provisionally however that this example, as it stands, is con- 

 sistent with the conventional theory of evolution, I know not 

 where we should look for another case equally good. When the 

 distinctions are produced by direct influence of conditions oper- 

 ating during the lifetime of the individuals, examples of inter- 

 mediate populations occupying the areas of intermediate con- 

 ditions can no doubt be produced. Many turf -like Alpine 

 plants, for instance, if protected from exposure and properly 

 nourished can grow as large as those of the same species found in 

 the valleys, and in the case of such quantitative effects, inter- 

 mediate conditions can doubtless produce intermediate characters. 

 Even these examples however are not very abundant, and 

 often the intermediate locality has not a form intermediate 



