BUFFALO SOCIETY OF NATURAL SCIENCES 203 



conditions which obtained in the past. If there were oceans during 

 Palaeozoic time in which large accumulations of clastic material were 

 forming, we are drawn to the reasonable conclusion that there were 

 land masses from which this clastic material was derived. We must 

 also conclude, if we view the matter rationally, that there must have 

 been rivers on those ancient continents and that then, as now, they 

 constituted the principal agents of transportation of material into the 

 sea. And finally, we must believe that if there was any life in those 

 rivers, it must have been subject to the same laws of dispersal as is 

 the life in the rivers today. My statement does not say that because 

 we have life in the rivers now there must have been life in the Palaeo- 

 zoic rivers; that is obviously untrue. But if there was life in those 

 rivers, then it was subject to the same laws which are operative now. 

 It is advisable, therefore, to consider these laws and to formulate 

 them that we may have certain definite principles for future reference. 



MIGRATION AND DISPERSAL OF RECENT FLUVTATILE ORGANISMS 



Of existing taxonomic groups, the fish have received more study 

 than any other group of fluviatile organisms, and interesting as well 

 as exceedingly pertinent data are at hand in regard to migration and 

 dispersal of this group. Giinther in his Study of Fishes, makes the 

 general statement that: "The Freshwater fishes .... have 

 been spread in circumpolar zones, and in but a limited degree from 

 north to south. No family, much less a genus, ranges from the north 

 to the south, whilst a number of families and genera make the entire 

 circuit round the globe within the zone to which they belong. Not 

 even the Cyprinoids and Siluroids, which are most characteristic of 

 the freshwater fauna of our period," are an exception to this. Temper- 

 ature and climate, indeed, are the principal factors by which the 

 character of the freshwater fauna is determined; they form the 

 barriers which interfere with the unlimited dispersal of the ichthyic 

 type, much more than mountain ranges, deserts, or oceans" (97, 215). 



A few illustrations of this widespread dispersal of fishes in circum- 

 polar zones will show that the above statement is not merely theo- 

 retical. These illustrations are selected, but taken verbatim from 

 Giinther's work (97, 209-211). 



A. Species Identical in Distant Continents, i. A number of 

 species inhabiting Europe and the temperate parts of eastern North 

 America, as Perca fluviatilis, Gastrosieus pungitius, Lota vulgaris, 



