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- 
