586 DR. AV. A. CUNNINGTON ON THE 



on the matter. Fiesli-water jelly-tislies of other types have been 

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

 Caspian. Moreover, the distribution of the genus Limnocnida 

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

 a medusa was discovered in the great Kavirondo Gulf of Victoria 

 Nyanza and another in a fresh-wa.ter lagoon in the Niger delta,. 

 The specimens fi'om Lake Victoria were submitted to Giintlier, 

 who pronounced them indistinguishable from the Ta,nganyil<a 

 species, though he subsequently modified his view, and desci'ibed 

 them as L. tanganicoi var. victoria; (98, p. 651). The Niger 

 meduste were reported on by E. T. Browne, who considered them 

 undoubted specimens of L. tanganicce {5S : 57). In 1908, medusfe 

 were found in a, tributaiy of the Zaml)ezi. These were rega,rded 

 by C. L. Boulenger as specifically different from the Tanganyika, 

 form, and were named by him Limnocnida rhodesice (18, p. 429). 

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

 from another part of Rhodesia., where it occurred in a tributary 

 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, differs 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 medusa) 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 meduspe weie looked upon 

 as sti'ong 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 recoi'ds 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 

 afibrds another example of those Afro-Indian afiinities to which 

 reference has more than once been made. 



It will be more satisfactory to postpone a consideration of the 

 sources from which the medusa may ha.ve been derived, until the 

 general discussion — which will follow this systematic account — of 

 the zoological and of other evidence. 



PORIFBKA. 



Representatives of this group are known at present only from 

 the three largest of the six la.kes under considei'ation. Since 

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

 is very probable that sooner or later specimens will be found 



