586 



DR. W. A. CUNNINGTON ON THE 



Oil the matter. Fiesli-watei- jelly-Cislies of other types have been 

 found in the Yang-tse-Kiang, in a lake in Egypt and in the 

 Caspian. Moreover, the distribution o^ the genus Limnocnida 

 itself has proved wider to an unforeseen extent. In August 1903 

 a medusa was discovered in the great Kavirondo Gulf of Yictoria 

 Nyanza and another in a fresh -water lagoon in the Niger deU^a. 

 The specimens from Lake Victoria \\ ere submitted to Giinther, 

 who pronounced them indistinguishal)le from the Tanganyika 

 species, though he subsequently modified his view, and described 

 them as L. tanganicm var. victoria; (96, p. 651). The Niger 

 medusae were reported on by E. T. Browne, who consideied them 

 undoubted specimens of L. tanganiae (53 : 57). In 1908, medusae 

 were found in a tributary of the Zambezi. These were rega.rded 

 by C. L. Boulenger ns specifically different from the Tanganyika 

 form, and were named by him Li7nnocnida rhodesioi (18, p. 429). 

 The latter species has still more recently (1913) been obtained 

 fi-om anothei- part of Rhodesia, where it occurred in a tributaiy 

 of the Limpopo River (11). Remarkable as it was to find this 

 genus so widely distributed in Africa, the discovery of a species 

 in India in 1911 was more remarkable still (6). This type, 

 which comes from streams in the Western Ghats, diflf'ers slightly 

 from the African species, and was termed L. indica by Annan- 

 dale (9). 



The bearing which these discoveries have on the problem of the 

 origin of the Tanganyika fauna, needs little pointing out. There 

 can be no hesitation in deriving medusae from the ocean, and 

 when Tanganyika was believed to be the only locality in the 

 whole continent in which such organisms occurred, the lake was 

 naturally regarded as unique, and the medusae wei-e looked upon 

 as strong evidence in favoui- of a marine origin for its fauna. In 

 the light of present knowledge, this evidence becomes greatly 

 weakened. If Limnocnida is to be regarded as a relict form, it 

 has now attained so wide a distribution that its presence no 

 longer singles out Tanganyika as a probable " Reliktensee." 

 Moreover, it must be noted that the new records are none of 

 them from the basin of the Congo, where the medusa should 

 be forthcoming in accordance with Moore's view of the origin 

 of the lake. — The finding of a species of Limnocnida in India 

 affords another example of those Afro-Indian affinities to which 

 reference has more than once been made. 



It will be more satisfactory to postpone a consideration of the 

 sources from wdiicli the medusa may have been derived, until the 

 general discussion — which will follow this systematic account— of 

 the zoological and of other evidence. 



PORIFERA. 



Representatives of this group are known at present only from 

 the three largest of the six lakes under consideration. Since 

 however, fresh-water sponges are usually inconspicuous objects, it 

 is very probable that sooner or later specimens will be found 



