144 



CHAPTER VIII. 



ON SOME CURIOUS FEATURES OF THE DISTRIBUTION OF 



SPECIES. 



In the majority of the lakes in Equatorial Africa, in all of 

 them in fact, with the solitary exception of Lake Tangan- 

 yika, there is a fauna which is in no way peculiar, and 

 although the vertebrate section of this fauna is rendered 

 distinctive of Africa by the profusion of ganoids of chari- 

 cinida; and cichlidse, its invertebrate sections are dis- 

 tinctly poor. Thus it appears to be a fact from what we 

 have seen that in most of the greater lakes of Central 

 Africa the fresh-water fauna consists of fishes and of 

 molluscs and practically of nothing else. The majority of the 

 great African lakes do not at all support the generally pre- 

 valent idea, that the fresh waters of the tropics are in posses- 

 sion of a profuse fauna. In Mwero, in Beringo and in the 

 Albert Edward Nyanza, or even in the Albert and the 

 Victoria Nyanzas for that matter, there is hardly so much 

 variety of life as there is in an ordinary American or 

 European puddle. There is often an extraordinary profusion 

 of some particular type as in the case of the Nyassa 

 Viviparas, or of Melania tuberculata in the Albert Edward 

 Nyanza, but there is no diversity or even modification among 

 the constituents of the primary fresh-water series, which 



