THE TANGANYIKA PROBLEM. 
3 2 9 
regarded as belonging to the halolimnic group, although they 
have not the strikingly marine attributes characteristic of 
the other members of this series. At the same time, and 
in Chapter VII., it was emphasized that although the fishes 
which now inhabit Tanganyika all belong to what have 
become exclusively fresh-water forms, the fish-fauna of the 
lake differs entirely in character from the fish-fauna of any 
others of the great lakes of Central Africa, and it was 
further shown that the majority of a large section of this 
fish-fauna, the Cichlidae, is wholly restricted to the con- 
fines of Tanganyika. Actually about half the Old World 
species of this family being endemic in the lake even 
now. In this way it was rendered evident that one 
of the chief peculiarities of the more striking members 
of the halolimnic group, namely, their geographical isola- 
tion, is shared equally by a section of the fishes, and 
consequently that these fishes were in one sense as 
distinctive of the fauna of the lake as the more striking 
invertebrate halolimnic animals themselves. Or in other 
words, it was found that Lake Tanganyika possesses a 
fish-fauna which is distinctive and characteristic of that 
lake, and is wholly unlike the fish-fauna of any other 
of the great African lakes. From these considerations 
tions I was inclined, as I pointed out in Chapter VII., to 
regard at any rate the endemic Cichlidae, and probably the 
ancient Ganoids, together with some of the Caricinidae as 
the remaining and somewhat scattered piscine portion of 
the halolimnic fauna ; the wide dispersal of these animals 
being due to the obvious migratory capacities of fishes 
when compared with the invertebrate section of the 
halolimnic group. 
Turning now to the consideration of the nature of 
this group of animals, so many of which are obviously 
