FAUNA OF THE AFRICAN LAKES. 



573 



Tlie distribution in tlie lakes of the forms at present recorded 

 is made cleai- by the adjoining list of species, and it Mill at once 

 be observed that the exceptional position held by Tanganyika in 

 the case of other animal groups is not in evidence here. While 

 the possibility is not excluded that further investigation may 

 bring to light an nnnsual number of remai-ka.ble species in the 

 lake, it is not in this group of animals that such discovery is 

 very probable. Nyasa with 14 difl'erent forms is closely followed 

 by Lake Victoria with 12. Only 6 species are recorded fiom 

 Tanganyika and one from Lake Edward. The number of species 

 which are endemic alFoi'ds no striking contrasts, 5 out of 14 

 being peculiar to Nyasa, and half the total number in each 

 case being peculiar to Victoria and Tanganyika. The only species 

 known from Edward Nyanza is endemic. There are no endemic 

 genera on record. 



A point of more interest is the fact that of 31 species men- 

 tioned in the table, only two have been observed in moi-e than 

 one lake, viz. Unionicula Jiguralis in Tanganyika and Victoria 

 and E mentridoj)liorus spinifer in Victoria, and Nyasa. In every 

 other case tlie species from the lakes differ from one another, 

 and have been recorded only from a single lake, where, in some 

 instances, they are endemic. Although this is so, there is not 

 much evidence of that association of certain groups of forms with 

 certain lakes, which is elsewhere a noticeable feature. It may, 

 however, be pointed out that both species of Limnesia are re- 

 corded only from Lake Victoria, while all the species of Arrhenurus 

 come only from Nyasa. Other genera well represented are 

 Unionicula and jSfeiimania, but they both have an extended 

 range and have representatives in each of the three bigger lakes. 



While 15 species in all are described as endemic, 10 of the 

 remainder are known from other parts of Africa (including 

 Madagascar) and 6 possess an even wider distribution. Under 

 these circumstances there seems every probability that future 

 exploration will prove many of the types to occur more generally 

 in the lakes, though on the whole it may be predicted that in 

 any case their precise distribution is little likely to afibrd evidence 

 of a striking character. 



Tardigrada. 



It is not surprising that inconspicuous organisms belonging to 

 this group have been seldom observed in the fresh -waters of 

 Africa. Apart from a record of the existence of these foims in 

 the Azores, there is, I believe, oy\\j the account given by Daday 

 (76, p. 236) of specimens which Fiilleborn collected in and around 

 Lake Nyasa. Tlie specimens in this collection all belong to the 

 species Macrohiot'ns tetronyx, which Daday established to receive 

 them. While this form must be regarded as endemic in Nyasa, 

 the genus Macrohiotus is known to have a. cosmopolitan distri- 

 bution, so that the existence of this particular species in the lake 

 is doubtless a matter of little import. 



Oligoch.eta. 



It is necessary, in compiling an account of the Oligochjiete 

 worms from the lakes, to distinguish as far as possible between 



