THE TANGANYIKA PROBLEM. 9 



features of Equatorial Africa being, as a matter of fact, 

 clearly discernible as subordinate expressions of a still 

 continuing effort on the part of the earth to produce a 

 great mountain chain. So far, indeed, from these regions 

 being remarkable for their stability, it is a fact that the 

 interior of Africa is at the present time only rivalled in 

 instability by certain districts of South America, and in the 

 past by those records of terrestrial disturbances which we 

 have in relation to the Alps and other mountain chains. 

 These matters having been discussed, a review has been 

 made of the nature of the fresh-water fauna which is 

 found in all the great African lakes about which anything 

 is, as yet, definitely known ; and in this way it has been 

 shown that throughout Equatorial Africa, as in other great 

 continents, there is a normal fresh-water fauna which has 

 nothing peculiar about it, and is certainly not more dis- 

 tinctive of Africa than is that of North America distinctive 

 of the New World. Subsequently the fauna of Lake 

 Tanganyika has been examined in detail, and it has been 

 shown that this lake, like all the other great lakes of Central 

 Africa, contains the ordinary fresh-water fauna of the 

 continent, but that in Tanganyika, and in Tanganyika 

 alone, there are a number of organisms possessing definitely 

 marine and somewhat archaic characters. Along with these 

 the " halolimnic " members of the Tanganyika fauna, as 

 I have called them, there are others, such as the 

 prawns, sponges and protozoa, which, although, not 

 like the previous types, unique in being found in 

 Tanganyika for the first time as fresh-water forms, are, 

 notwithstanding, probably portions of the same group, for 

 they are peculiar to Tanganyika, and are not characteristic 

 of the general fresh-water fauna of the African continent. 

 Subsequently, in dealing specially with the fishes of Tan- 



