THE TANGANYIKA PROBLEM. 337 



ence of the jelly-fish, the gymnolaematous, polyzoa, the 

 prawns, the sponges and the gastropods which are peculiar 

 to Tanganyika, along any of these lines. Yet these organ- 

 isms are in Tanganyika, they are not elsewhere in the 

 great lakes of the African continent ; they must have got 

 into Tanganyika from some place or medium in which 

 these sorts of animals habitually live ; and there is no 

 place or medium in which these animals habitually live, 

 except the sea. 



Along all the lines of enquiry which we have examined, 

 the explanation of the existence of the halolimnic group 

 in Tanganyika is beset with insuperable difficulties, first 

 in one direction, then in another. But, if we leave all 

 these hypothetical explanations entirely on one side, and 

 follow the direct and simple evidence afforded as to the 

 origin of the halolimnic animals, through the characters of 

 these animals themselves, the whole difficulty vanishes at 

 once. The jelly-fish, prawns, sponges and gastropods, etc., 

 are at once perfectly intelligible, if we regard their presence, 

 as in fact it is, indicative of the past extension of the sea 

 into the African interior. 



We are, therefore, inexorably driven by the force of tacts 

 to view the halolimnic organisms of Tanganyika as having 

 emanated from the sea ; or, to put the matter another 

 way, the zoological characters of the halolimnic animals, 

 and the facts of their distribution, show that the sea 

 has been connected with Tanganyika in the past. 

 That is to say, the characteristics of the halolimnic 

 group throw light upon the past history of the African 

 land-mass ; and I wish to be quite clearly under- 

 stood in this connection. We have seen that there 

 actually is no geological evidence which militates against 

 the view that Tanganyika may have been connected with 



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