180 J. E. S. MOOKE. 



paragraphs I have virtually fulfilled the object which I had 

 before me in collecting and examining the facts concerning 

 the distribution of the African lake faunas, before entering 

 upon any detailed examination of the evidence which can be 

 gathered from the study of the morphology of the Halolimnic 

 animals themselves. We have seen that the collateral evidence 

 afforded by the facts of distribution and the like at once clear 

 away the likelihood of the Halolimnic group having originated 

 at any time or in any manner^ de novo, in Tanganyika, and 

 that there is finally brought on a more or less direct issue 

 between the supposition of an ancient marine contamina- 

 tion of Lake Tanganyika and the ancient fresh-water 

 origin of the Halolimnic group. All the facts of dis- 

 tribution which we have examined appear to me to strongly 

 favour the former of these hypotheses ; and although we are 

 at present ignorant of the precise manner in which the marine 

 contamination of Lake Tanganyika may have been effected, 

 there is no positive geological objection to the view that it has 

 occurred, while there is the certainty of a sufficiently great 

 geological instability throughout the very districts in which 

 Tanganyika lies to have easily accounted for it. 



