402 Evolution and Distribution of Fishes 



CHAPTER XIV. 



Past Geographic and Geologic Conditions in 

 Relation to the Distribution of Fishes. 



In the Immediately preceding chapters an effort has been 

 made so to trace the relation of fishes in time and space, 

 as to discover some principle of evolutionary continuity 

 running through the whole. Such the writer hopes, and 

 even believes, has been established. 



But during the process certain positions have been as- 

 sumed, that are still open to wide discussion, according to 

 not a few distinguished naturalists. The heading of the 

 present chapter raises two of these disputed positions. For 

 the geographer of today, who studies the distribution of 

 plants and animals over the world, can choose any one 

 of three or four decisive views that his biological brethren 

 may present. And again one school of geologists may still 

 assert that the land and sea masses are largely at present 

 in outline and connection as they were during previous 

 epochs, while another school may proclaim that funda- 

 mental alterations in the relation of land and sea have 

 repeatedly occurred, while still a third party may advocate 

 a middle course. 



In the five chapters preceding this, the writer has 

 stated the known facts that bear on the first known ap- 

 pearance and distribution of fishes in time and space. But 

 In doing this he did not refrain from stating his views as 

 to how some of these facts might naturally and scientifical- 

 ly be linked together, so as to reach larger facts and con- 

 clusions. Now he proposes to analyze groups of these 

 facts from the geographic and the geologic standpoints. 



Ample proof we believe has been adduced, for accept- 

 ance of the view that the Dipnoi developed in, have lived 

 in, and now inhabit sluggish rivers, swamps, and related 

 freshwater areas. But if such be true it means that we must 

 also accept the view that they inhabited land which was 

 continuous in time for some part of its mass. So when we 

 successively encounter freshwater dipnoan remains in West 

 Russia, in Britain, in N. America, in Africa, In India and in 



