350 W. H. HUDLESTON, ESQ., M.A._, F.E.S., ON THE ORIGIN 



but there is no proof that they are. That, I think, is all I will 

 undertake to say. Of course there is just a possibility that they 

 are not marine at all. When you bear in mind the peculiar 

 position of Lake Tanganyika, there is a possibility that these things 

 may have been generated by other means. 



Communication by Eev. Dr. Irving, F.G.S. 



"May 25th, 1904. 



" Dear Professor Hull, 



" It is with much regret that I find myself unable at the last 

 minute to come to the meeting at the Victoria Institute to-day, at 

 which you have so kindly asked me to take part in the discussion. 

 Had I been able to be present I should have pointed out two or 

 three things which seem to me to bear upon the p'ohlem as to the 

 fresence of marine forms of life in the great Lake of Tanganyika, if 

 not anticipated by the author. 



" (i) The first line of inquiry would seem to be as to their 

 affinities with the present fauna of the Indian Ocean on the one hand, 

 and with that of the Atlantic on the other. The orography of the 

 African Continent and its present drainage system would suggest 

 the probability of the latter affinity being closer than the former. 



" (ii) The lake-waters are presumably 'fresh.' But inquiry is 

 needed as to what that term means in this case ; (a) whether it is 

 to connote little more than the absence of the superabundancy of 

 sodium rJdo7'ide, to which the ocean-water owes its salinity in the 

 popular sense of the word ; or (b) whether comparative analyses of 

 the lake-water and sea-water do not reveal a general equivalency 

 (or an approximate one) between the salinity (in the chemical 

 sense of the word) of the lake and ocean- waters. No doubt 

 Mr. Hudleston (who writes F.C.S. after his name) has thought of 

 this and included it in his inquiry (cf. the salinity of the Dead 

 Sea). 



"(iii) Have we yet to hand sufficient stratigraphical data of 

 those vast regions, which lie between the Lake Tanganyika and the 

 eastern or western littoral of the continent, to give us any clue to 

 the recency or remoteness of a possil)le connexion between the lake 

 and the ocean 1 



" (iv) There is no improbability in the view that the present 

 maiine fauna of the lake consists of modified descendants of a 



