136 



THE TANGANYIKA PROBLEM. 



Cichlids are on the whole primitive as far as that group is 

 concerned. If, moreover, the above view of the origin of 

 the Tanganyika fish-fauna be correct, the fact that the 

 genera of Characinidse and Siluridae living in Tanganyika 

 are not endemic would be perfectly intelligible. The first 

 of these groups is a very old one, and might easily have 

 become a wandering fresh-water stock before Tanganyika 

 became a land-locked depression ; while the second contains 

 forms which are known to be capable of migration in a high 

 degree. The same kind of reasoning thus obviously also 

 applies to the non-endemic species of the latter group. 

 Some such view of the case would at once explain other 

 matters. If Tanganyika became stocked from an ancient 

 western sea, this would account for the presence of Cichlidse 

 in the Congo, and the presence of forms like bass only in 

 the Congo, the Nile, and Tanganyika, as well as the 

 existence of several species of the ancient ganoid Polypterus 

 in these different waters. For it is a geographical fact, 

 which should be clearly understood, that at certain times 

 and at certain seasons it is possible to push one's way in a 

 boat from the upper tributaries of the Congo into those of 

 the Nile, the watersheds in this region being extremely ill 

 defined. 



Up to the present time there are known in Tanganyika 

 the following series of forms : — 



FISHES. 



1'ol.YI'TERID.E. 



1. Polypterus congicus Blgr. 1898. 



Lepidosirenid.'e. 



2. Protopterus rethicpicus Heck. 1851. 



Characinid.*. 



3. Hydrocyon lineatus Blkr. 1863. 



4. Alestes macrophthalmus Gthr. 1867. 

 5- ,, macrolepidotus C. & V. 1849 

 6. Citharinus gibbosus Blgr. 1899. 



Cyprinid.-e. 



7. Capoeta tangdnicce Blgr. 1900. 



8. Barbus platyrhimis Blgr. 1900. 



9. ,, altianalis Blgr. 1900. 



10. ,, serrifer Blgr. 1900. 



11. ,, tropidolepis Blgr. 1900. 



12. Barilius moorii Blgr. 1900. 



13. ,, tanganicm Blgr. 1900. 



