378 OEIGIN OF LIFE IN AMEEICA 



among the best indicators of past continental changes, 

 and that the relations of the several southern continents as 

 to their ichthyio faunas can be best understood by the assump- 

 tion that, at some remote epoch or epochs, there was distribu- 

 tion of land and water which eventually permitted an emigra- 

 tion and immigration of types from one into another. Dr. 

 Gunther * enunciated similar views. He thought that the 

 existence of so many similar forms of fishes on both sides of 

 the southern Atlantic supjiorted the supposition that they are 

 the descendants of a common stock which had its home in a 

 region now submerged under some intervening part of the 

 ocean. Since the days when these two great authorities pro- 

 nounced upon this subject, the ichthyology of both Africa and 

 South America has become better known, and new light has 

 been thrown on the relationship between the various groups 

 of fishes. We can deal with the problem now in the light of 

 the latest researches. Dr. Boulenger has made a special study 

 of the African fish fauna, while Mr. Eegan and Professor 

 Eigenmann have paid particular attention to the ichthyology 

 of South America. In his interesting address to the British 

 Association on the distribution of African fishes Dr. Bou- 

 lenger mentions Protopterus as the most noteworthy iish of 

 Africa. In some respects it approaches the amphibia. It 

 possesses a double lung as well as gills, and is able to live for 

 a long period in dried mud. Anatomically there are many 

 characters in which it differs from almost all other fishes. 

 Its only living relation, Lepidosiren of Brazil, is very similar 

 in form and so closely allied that the two are placed into 

 the same family Lepidosirenidae. Professor Pf effer f con- 

 tends that since this family is represented in the Permian 

 and Trias of western North America, in the Trias of India 

 and South Africa, in the Cretaceous of Patagonia and the 

 Trias and Jurassic of Europe it must have had a universal dis- 

 tribution. Hence he argues that the occurrence of Pro- 

 topterus in Africa and of Lepidosiren in South America can 

 have no significance in supporting the theory of a former 

 land connection between these two continents. But recent 



* Gunther, Albert, " Study of Fishes," p. 233. 



t Pfefler, G., " Zoogeographische Beziehungen," p. 433, 



