2 THE TANGANYIKA PROBLEM. 



brought back from these lakes at all resembling the peculiar 

 Tanganyika forms. On the other hand, the missionaries 

 acquired further samples of shells from Tanganyika itself, 

 and anions' these collections there were forms at once so 

 strikingly different from those of any other known fresh- 

 water lake, and so curiously marine in aspect, that when 

 describing them Mr. Smith* drew attention to the 

 possibility that they might eventually turn out to be 

 relics of some former sea. But whatever interest and 

 curiosity may thus have been raised respecting the nature 

 of these Tanganyika molluscs was suddenly and com- 

 pletely eclipsed by the announcement of the further 

 discovery of jelly-fishes in the lake by the German 

 traveller, Dr. Bohm. Their existence in Tanganyika 

 was subsequently confirmed by Von Wissmann, and it 

 can, in fact, be said that it was only after these 

 announcements that what I have termed the Tanganyika 

 problem, as such, fairly took wing. The intensification 

 of the general interest in the fauna of the African lakes 

 which this discovery of jelly-fishes naturally produced, is not 

 however far to seek, for if we except the star-fishes and sea- 

 urchins there is hardly any invertebrate type more typically 

 marine, more characteristic of the ocean, than a jelly-fish. 

 Like herrings, the presence of jelly-fishes in fresh-water is 

 indicative of the past or present connection of such water 

 with the sea. Bohm's discovery thus in fact seemed to 

 show, that either in present or past times, organisms like 

 jelly-fishes could get from the sea into the lake. Eventually, 

 through the co-operation of Mr. Frederick Moir and Mr. 

 Swann, some of these medusae were sent to England, 

 and on examination were found to be quite unlike any 



* E. A. Smith. — "On a collection of Shells from Lakes Tanganyika and Nyassa. " 

 Proceedings of the Zoological Society of London, 1SS1 , page 276. 



