460 T. H. MORGAN. 



XIII. General Conclusions. 



The solution of the problem of metamerism has often been 

 attempted by morpliologists with varying success. It has 

 become more and more evident that the problem is a difficult 

 one, and I think the results have shown that the final solution 

 can only come with a better knowledge of the fundamental 

 relations of the parts of the body to one another, with an 

 acknowledgment of the imperfection of the phylogenetic 

 method, and with a better insight into ontogenetic laws. 



Darwin said over thirty years ago, in the ' Origin of Species,' 

 " We need not here consider how the bodies of some animals 

 first became divided into a series of segments, or how they 

 became divided into right and left sides with corresponding 

 organs, for such questions are almost beyond investigation." 

 The attempt of morphologists to solve even the simpler of 

 these phenomena, viz. metameric repetition, shows how true 

 Darwin's words remain even to-day. 



It may, therefore, seem doubtful whether anything will be 

 gained by a new analysis of the problem of metamerism, or by 

 a critical consideration of the numerous theories already 

 advanced. It would certainly be unwise to add any new 

 speculation to that already afloat. In the following pages no 

 new theory is offered, and I have attempted no more than a 

 consideration of those methods which have proved sterile or 

 erroneous as contrasted with the methods that have been 

 fruitful and suggestive. 



During the last fifteen years the methods of the phylo- 

 genists have been applied to the solution of metameric repe- 

 tition. Comparative anatomy has been the point of departure ; 

 but speculation has leaped far beyond its legitimate boundaries. 

 The results have shown that the method of phylogenetic inter- 

 pretation is subjective rather than objective, and the conclu- 

 sions have given, therefore, at most a probable course of 

 evolution, and often only a conceivable process of transition. 



It is only fair to say that in many cases the speculation has 

 been advanced tentatively, as suggestion rather than conclu- 



