THE TANGANYIKA PROBLEM. n 9 



may not be due, as we have hitherto been in the habit of 

 supposing, to the struggle for existence between contending 

 species, but entirely to the sorting influence of a progressive 

 physical change to which the biological phenomena are 

 related in a manner of a perpetually responding reflection. 

 The struggle for existence between contending species has 

 had nothing to do with the chief features of the flora ol 

 vast areas in the African interior which are now covered 

 with natural parks. 



