230 Experimental Zoology 



dary place, for adaptive mutations, like all others, are given ; 

 not made by selection. 



If it were possible to change each character of a species, so that 

 first in one respect, then in another, the organism would become 

 better suited to new conditions, — molded to them, as it were, — 

 we could imagine that the evolution of organisms has taken 

 place in this way. The process of adapting would be the same 

 as the process of evolving. This view assumes not only that 

 each character may, in turn, be changed without the rest of the 

 organism becoming seriously affected, but also that new species 

 may be created in this w^ay. It is this process that the Darwinian 

 school has assumed to take place, and hence, for them, evolution 

 and adaptation are closely similar processes. 



On the other hand, the mutation theory assumes that new 

 species appear without regard to whether the change will be an 

 adaptive one or not. If the new form should be one suited 

 to the old, or to some new locahty, it has a chance of surviving, 

 i.e. it is sufficiently adapted to exist. From this point of view the 

 problem of evolution is a different one from that of adaptation. 

 Moreover, it will be seen that while the process of evolution is one 

 that can be studied by scientific methods, the adaptation of an 

 organism is not a causal problem at all. If a new form is adapted, 

 that is the end of the matter; if it is not, it perishes. The scien- 

 tific problem deals with the origin of mutations and their causes. 

 Their adaptation is an independent question, and depends on 

 whether the proper external conditions exist at the time when 

 the mutation appears. Inasmuch as only those mutations sur- 

 vive that can survive, we find that organisms are always adapted 

 to the environment in which they exist, and this condition of 

 living things gives the appearance of a fundamental problem 

 where in reahty no such problem exists. The causal prob- 

 lem is the problem of the origin of new forms; the question 

 of their survival is only an historical question for all Hving 

 species. 



Under certain conditions, and in certain cases, the two prob- 

 lems appear, at first sight, to merge into each other. For if, 



