FAUNA OF THE AFRICAN LAKES. 573 



The distribution in tlie lakes of the forms at present recorded 

 is made cleni- by the adjoining list of species, and it Avill at once 

 be observed that the exceptional position held by Tanganyika in 

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

 the possibility is not exclnded that fnither investigation may 

 bring to light an nnusnal nnmber of remarkal)le species in the 

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

 very probable. Njmsa with 14 different forms is closely followed 

 b}' Lake Victoria with 12. Only 6 species are recorded fi'om 

 Tanganyika and one from Lake Edward. The number of species 

 which axe endemic aftbiTls no striking contrasts, 5 out of 14 

 being peculiar to Nyasa,, and half the total nunibei' in each 

 case being peculiar to Victoria and Tanganyika. The only species 

 known from Edward ISTyanza is endemic. Thei'e are no endemic 

 genei'a on record. 



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

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

 one lake, viz. Unionicida figuralis in Tanganyika a.nd Victoria 

 a,nd E ncet^.tridoplwrus spinifer in Victoria and Nyasa. In every 

 other case the sj)ecies 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 ai'e re- 

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

 come only from Nyasa. Other genera well represented are 

 Uoiionicula and Neimrania, 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 wdiole 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 forms in 

 the Azores, there is, I believe, only the account given by Daday 

 (76, p. 236) of specimens which FiUleborn collected in and a.round 

 Lake Nyasa. The 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 Macrobiotus 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 Oligochfete 

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



