THE TANGANYIKA PROBLEM. 
3 
known forms and probably of an ancient type. Nothing 
more, however, could be said until some naturalist had 
visited the spot, and this impossibility of getting any further 
with the Tanganyika problem became the reason of the 
first Tanganyika expedition. The exploration was organ- 
ised by Professor Ray Lankester, who, with the help of 
others interested in this matter, obtained from the Royal 
Society the necessary grants in aid of the exploration, and I 
finally set out in the autumn of 1896. 
As a result of the journey we found that the original pro- 
blem presented by the jelly-fish had in no wise been solved. 
It had, in fact, grown enormously bigger and more difficult, 
for it was found that in Nyassa and Shirwa there were no 
jelly-fishes nor anything except purely fresh-water forms ; 
while in Tanganyika there were not only jelly-fishes but a 
whole series of molluscs, crabs, prawns, sponges and smaller 
things, none of which appeared in any of the other lakes I 
then knew, and all of which were distinctly marine in type. 
Further than this, however, I* found that none of these 
strange marine-looking animals were to be compared directly 
with any living marine forms, yet, in their structure, some of 
them certainly seemed to antecede a number of marine types 
in the evolutionary series, and in consequence they appeared 
to hail from the marine fauna of a departed age. The most 
definite result of the first Tanganyika expedition, therefore, 
appeared to be that the sea had at some former time 
been connected with the lake, but when or how 
remained a mystery. In discussing the inferences which 
could thus be directly drawn from our observations respect- 
ing the marine nature of the Tanganyika fauna before the 
Royal Society in 1898, I found, however, that I had unwit- 
* “ On the zoological evidence for the connection of Lake Tanganyika with the sea.” 
Proceedings of the Royal Society, vol. 62. 
