HASEMAX, GEOGRAPHICAL DISTRIB UTIOX IX SOUTH AMERICA 13 



and extinct forms have been carefully compared and a sharp distinction 

 is made between paleotelic (old or phylogenetic) and cenotelic (recent, 

 adaptive or physiological) characters. It is necessary to draw this dis- 

 tinction, because only paleotelic characters havt been widely distributed. 



3. That a fresh-water connection or its absence will not alone explain 

 the present distribution of the fishes. Hence, the most important factor 

 of living fish distribution is not land and water connections, i. e., bar- 

 riers, isolation, intermingling, etc., but it is the organic complex of the 

 ancestral stock and the effects of different environments on this stock. 2 



4. That much of the similarity and some of the identity of certain 

 species of the fishes of Bio Paraguay and Eio Amazonas are due to simi- 

 lar and identical evolution of the highland ancestral stock after arriving 

 in similar environments, e. g., as produced by the erosion of the high- 

 lands. 



5. That the existing highland genera, small in size, are the more gen- 

 eralized types from which the bulk of South American fishes has evolved. 



6. That the South American fishes have evolved from primitive forms 

 which originally lived in ]^orth America. 



The above statements do not in the main agree with the views ex- 

 pressed by previous zoogeographers. This difference of opinion is largely 

 due to the fact that these investigators work from the static viewpoint of 

 animal geography and have therefore only considered in some cases the 

 "disconnected graveyard material," i. e., a few isolated spots where the 

 fauna died out; and in other cases the "hot-bed material," i. e., the end 

 result of the greatest cenogenic evolution. For this reason, their static 

 faunal lists do not correctly determine the point of origin of families 

 and orders. As a result of their conception of animal geography, some 

 of these writers have maintained invasions of the sea and land-bridges 

 for which there is no evidence. They have also brought to the support 

 of their views some unnatural environments and unwarranted views of 

 the geology and the topography of South America. 



Another source of error in former interpretations is, I believe, the 

 ignoring of the possibility of similar evolution of the identical ancestral 

 stock in remote but similar environments. The necessity for the recog- 

 nition of such evolution is due to the fact that in the same river basin 

 there often exist (two or three) distinct fanual regions, one of which 

 may show close affinity with another distinctly separated basin, while 

 another river system, although connected (with the latter), may yet re- 

 tain quite distinct faunas. 



2 The idea that isolation alone produces new species implies the principle of selection, 

 which is still of doubtful value. If it is not selection, then it must be in some way the 

 direct or indirect (also debatable) influence of the environment on the germplasm or 

 else it is orthogenesis. 



