464 Evolution and Distribution of Fishes 



All of these are referable to the large typically freshwater 

 group Sponglllinae, that is now practically world-wide in 

 its included species. 



The native hydromedusan Limnocnida tanganyicae, 

 that appears according to Moore and Cunnington in count- 

 less numbers at certain seasons, is closely related to Limno- 

 codhnn sozverbyi, whose native home probably is the inner 

 river-system of the Amazon. But it is now known that the 

 former is not confined to Lake Tanganyika. For Scott Elliot 

 has found a variety of it {zgo: 643) in Victoria Nyanza; 

 while Browne has described it {2gi: 304) from the Niger, 

 Again in the Egyptian lake of Birket el Kerun (Qurun) 

 C. L. Boulenger and Cunnington met with another that 

 the former named Moerisia lyonsi. Still more recently 

 the finding in abundance of Limnocnida rhodesiae in a tribu- 

 tary of the Middle Zambesi, and also in the Limpopo river 

 system (292: 71) furnish proof that these fragile and deli- 

 cate organisms have a wide distribution over the central 

 African area. But the discovery by Gravely and Agharkar 

 and the description by Annandale of an E. Indian species 

 — Limnocnida indica — that occurs "in streams in the West- 

 ern Ghats, that finally enter tributaries of the Krishna river, 

 Satara district, Bombay Presidency" causes us to consider 

 that, from the Amazon river-basin across to and through 

 central Africa, on to the Bombay plateau, identical or close- 

 ly related freshwater medusae are often to be found in 

 profusion. 



The most recent discovery, in enormous abundance, of 

 Limnocodiiim {Craspedaciista) in freshwaters of Kentucky 

 and Indiana, in the east-central States (295: v. 26: 638; v. 

 44: 858 ; V. 50: 413) is proof, along with the above-cited 

 cases, that freshwater polyps and medusae of decidedly 

 simple structure, have had a wide distribution over the 

 earth. As the writer has already contended (/ : 385) they 

 seem even to be the ancestral and still persistent freshwater 

 forms from which the more evolved marine ones have 

 originated. The last-cited cases however are somewhat 

 open to doubt, and may be tropical importations. 



Now a feature of special interest is that most of the 

 above medusae have been found not at or near the sea- 



