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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- 
cinidsc and cichlidae, 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 
