271 



GEOGRAPHICAL DISTRIBUTION AND DOMINANCE IN 

 RELATION TO EVOLUTION AND PHYLOGENY. 



By John W. Taylor, Hoksfokth. 



(Plates VI-X.) 



TííE geographical distribution of life over the world is a 

 subject of far-reaching importance, bearing not only upon the 

 origin and dominancy of the various species and groups, but, 

 when properly understood, largely assisting to explain their 

 phylogenetic relationship, their place of origin, and the probable 

 route or routes by which the world has been populated ; but 

 I should scarcely have ventured to press the subject on your 

 notice, as worthy of more attention than it has hitherto received 

 from entomologists, but for the suggestion and kindly en- 

 couragement of our distinguished President- -yet the study would 

 undoubtedly materially help to explain many of the mysterious 

 problems of insect genealogy and distribution. 



Even at the present day there are scientific men who fail 

 to see that the distribution of life is an abstruse and important 

 problem, and that its dispersal is not accomplished by chance 

 or by the scattering at random of species and indi\'iduals, but 

 is a process governed by great and universal laws, and although 

 the natural tendency is, or may be, towards uniform diffusion 

 in all directions, this is prevented or hindered by physical or 

 organic barriers, and dispersal therefore tends in a large measure 

 to follow certain definable paths. 



The physical obstacles to uniform dispersal are mountain 

 chains, deserts, marshes, rivers, arms of the sea, or any natural 

 features dissimilar to those to which the particular species or 

 genus is more especially adapted. Some of these barriers to 

 dispersion have aj^parently been permanent throughout \'ast geo- 

 logical periods, but in most cases effective barriers have been 



