FRESH-WATER MEDUSAE 



203 



suggested the view that Limnocodium is not properly placed in any 

 of the other orders. Goto, 1 however, in a recent paper, confirms 

 the view of the affinities of Limnocodium with the Olindiidae. 



The life-history of Limnocodium is not known, but a curious 

 Hydroid form attached to Pontederia roots was found in the 

 same tank as the Medusae, and this in all probability represents 

 the hydrosome stage of its development. The Medusae are 

 formed apparently by a process of transverse fission of the 

 Hydroid stock 2 similar in some respects to that observed in the 

 production of certain Acraspedote Medusae. This is quite unlike 

 the asexual mode of formation of Medusae in any other Craspedote 

 form. The structure of this hydrosome is, moreover, very 

 different to that of any other Hydroid, and consequently the 

 relations of the genus with the Trachomedusae cannot be re- 

 garded as very close. 



Limnocodium has only been found in the somewhat artificial 

 conditions of the tanks in botanical gardens, and its native locality 

 is not known, but its association with the Victoria regia water-lily 

 seems to indicate that its home is in tropical South America. 



Limnocnida tanganyicac is another remarkable fresh -water 

 Medusa, about seven-eights of an inch in diameter, found in the 



lakes Tanganyika and Victoria 

 Nyanza of Central Africa. 3 It 

 differs from Limnocodium in 

 having a short collar-like manu- 

 brium with a large round mouth 

 two-thirds the diameter of the 

 umbrella, and in several other 

 not unimportant particulars. It 

 produces in May and June a 

 large number of Medusa-buds by 

 gemmation on the manubrium, 

 and in August and September the sexual organs are formed in 

 the same situation. 



The fixed hydrosome stage, if such a stage occurs in the life- 

 history, has not been discovered ; but Mr. Moore 4 believes that 



1 S. Goto, I.e. 2 G. H. Fowler, Quart. Journ. Micr. Sci. xxx. 1890, p. 507. 



3 Limnocnida has recently been discovered by Budgett in the river Niger. See 

 Browne, Ann. Nat. Hist. xvii. 1906, p. 304. * 



4 " The Tanganyika "Problem," 1903, p. 298. 



|; 



Fin. 140. Limnocnida tanganyicac 

 x 2. (After Gtinther. ) 



