354 THE TANGANYIKA PROBLEM. 



without interest in this connection ; for the spicules of this 

 genus are highly peculiar (see Chap. XV.), and are quite 

 indistinguishable from the old marine genus Renieria, 

 common in the Silurian epoch. There is thus obviously 

 nothing in the character of the halolimnic animals which 

 is opposed to the idea that they, together with the gas- 

 tropods, belong to some such ancient sea-stock as the fore- 

 going comparisons suggest ; while the positive ancestral 

 anatomical characters possessed by the majority of the 

 gastropods, by the jelly-fish and the crabs, is in exact 

 accordance with this view. 



From a consideration of the matters dealt with in the 

 preceding chapters, it will have been seen that along all the 

 lines of investigation that have been pursued, the result 

 reached is practically in every case the same. Thus an 

 investigation of the geological characters of Central Africa 

 showed that there was no foundation in fact for the 

 Murchison hypothesis, and that there was evidence of vast 

 disturbance in the region of the great lakes. It con- 

 sequently showed also further, that there is no positive 

 evidence of any sort or kind against the view that the 

 sea at some fairly remote period may have extended as 

 far as the present site of Tanganyika. The study of 

 the fauna of the Great African lakes showed that there 

 is a typical African fresh-water fauna common to them 

 all, and that to this the peculiar halolimnic fauna of Tan- 

 ganyika bears no sort of relationship, and is so to say 

 superadded. So also the examination of the halolimnic 

 animals themselves shows almost in every case that they 

 possess the positive attributes of primitive forms, often 

 directly anteceding in their structure certain modern marine 

 types. In this way we arrive at the conclusion that the lake 

 must have been stocked with a sea fauna very long ago ; so 



