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 among 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, 1881, page 276. 
