THE TANGANYIKA PROBLEM. 
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Polypteridse, Lepidosirenidse, Characinidse, Cyprinidse, 
Siluridae, Cyprinodontidae, Serranidae, Cichlidae and Masta- 
cembelidae. Of these, the species occurring in Tanganyika 
which represent the Polypteridae, Lepidosirenidae, Characi- 
nidae and the Siluridae, are widely spread throughout the 
fresh-waters of the African continent. But all the seven 
species of the Cyprinidae, and the six species of Masca- 
cembelidae, which occur in Tanganyika, are endemic forms. 
The single species representing the Cyprinodontidae and 
the Serranidae are the same, while among the 2 1 genera 
and the 58 species of the Cichlidae, only one species, 
Tilapia Burtoni, is found outside the confines of Tangan- 
yika, this single species having made its way up the 
Russisi river into Lake Kivu. It is, however, only among 
the Cichilidae that endemic genera occur. 
The Cichlidae are found in the fresh-waters of the Old 
and the New World, especially in the rivers of South 
America, and we are further confronted by the extraordinary 
fact that nearly half of the Old W orld species are confined 
to the limits of Tanganyika itself, a circumstance which, 
on the face of it, would almost at once suggest that in 
Tanganyika we have the remains of the ancient point of 
origin from the sea of this particular group of fishes. 
Such a conception of the mode of origin of the Tanganyika 
fish-fauna would fit in admirably with a number of other 
facts relating to it. Thus, it was shown by Dr. Gunther 
that the fish of the African fresh waters are related to each 
other in such a manner as to suggest that they have spread 
out from a centre to which Tanganyika would correspond ; 
while more recently Mr. Boulenger, as the result of an 
examination of the fishes which I obtained during the 
Tanganyika expeditions, has confirmed this view, and 
shown that the morphological attributes of the Tanganyika 
