8 THE TANGANYIKA PROBLEM. 



wants with respect to our knowledge of the African interior, 

 eventually became the definitive motive for the formation of 

 the second Tanganyika expedition. 



In the organisation of this new venture, Professor Ray 

 Lankester took the initiative once more, and the expedition 

 was finally despatched under the auspices of a committee of 

 scientific men in England, which was formed by Professor 

 Ray Lankester, and consisted of himself, Sir John Kirk, Sir 

 William Thiselton-Dyer, Dr. Sclater, and Mr. Boulenger, 

 and I had the honour to be invited to take command of 

 the exploration in the spring of 1899. 



We have in this way briefly sketched the manner in 

 which our knowledge that there was a Tanganyika problem 

 first arose, and we have also indicated the aspect which 

 this problem presented after the first Tanganyika expedi- 

 tion had returned ; but, beyond this point, it would be 

 inconvenient to treat the matter from a similar historical 

 point of view. It will suffice to say, that on the second 

 Tanganyika expedition an immense amount of notes and 

 material were acquired, filling up the obvious lacunae which 

 had presented themselves in any attempt to study the problem 

 up to 1899. In what follows, I have dealt with the problem 

 afresh, and with all the evidence that is now available. In 

 the first place, I have found it necessary to consider the 

 nature of fresh-water faunas in general, and to discuss the 

 probabilities with respect to the origin of certain constant 

 peculiarities which these faunas are found to present. 

 In the next I have dealt at some length with the physical 

 geography and geology of Central Africa, especially in 

 relation to the fact that all the observations which have been 

 accumulated point persistently to the conclusion that the 

 structure and history of this portion of the continent are 

 not what have hitherto been supposed. All the physical 



