226 AGE AND AREA [pt. ii 



nothing to show that the e^okition of the character was due to 

 this cause. 



The conchision obviously is, that specific characters have 

 evolved without any relation to their possible significance in 

 the struggle for life. The facts are contrary to the main principle 

 of the selection theory of Darwin. Moreover, intermediate steps 

 betAveen the endemic species and their parents, in the midst of 

 which they are ordinarily still living, are wanting, and therefore 

 must be assumed never to have existed. Endemic species must 

 have appeared at once, by means of one or a few distinct steps, 

 which embrace their whole differentiation from the parent type. 

 Considered in this way, it is evident that their origin is in full 

 accord with the principles of the mutation theory, and has to 

 be considered as one of the best proofs of its applicability to 

 evolution in general. 



Starting from the endemic species, Willis has worked out his 

 statistical methods of studying the relation of age to dispersal 

 for larger and larger groups. Everywhere this relation is shown 

 to be, in the main, independent of the specific characters. It 

 obeys the same laws in widely different genera and famiUes. 

 Dispersal is not due to special adaptation, and often, as in the 

 Podostemonaceae, the most beautifully adapted forms are the 

 local ones, whereas the universally spread species of the same 

 group show the smallest degree of specialisation. 



In other words, the area occupied in a country by any gi\en 

 species depends upon the age of that species in that country, 

 and not upon special characters. Of course this law applies to 

 the common type of species, and exceptions may be expected to 

 occur. For this reason the species are not studied singly, but in 

 small groups of twenty or so, and on this basis the law has been 

 found to be everywhere the same in the animal and in the vege- 

 table kingdom. 



Leaving the appreciation of the importance of this principle 

 for pure systematic studies and for the construction of family 

 pedigrees to other judges, I might here point out its bearing on 

 the mutation theory. It affords a full proof that cA-ervAvhere in 

 nature, in geological periods as well as at present, the morpho- 

 logical characters of newly originated types have no special 

 significance in the struggle for life. They are not known to aid 

 them in their initial dispersal. The}' may afterwards prove to be 

 useful or useless, but this has no influence upon their evolution. 

 Obvious instances of usefulness occur, as a rule, only at much 



