FAUNA OF THE AFRICAN LAKES. 



531 



preceMliiig t:ib]es. jNiany details of lesser iniportance \vill be 

 foiiud discussed in the v;irious pnpeis on the fresh-water iislies 

 ■of Africa, mentioned in tlie bib]iogra,p]iy oi- in tlie British Museum 

 Catalogue (38). Attention must, however, Ije 'Jrawu to tlie most 

 -signiticant features, many of whicli are now brought into special 

 prominence by means of the tabular method emp1oye(h 



The point that hr^t arrests attention is that Tanganyika, con- 

 tains no fewer than 146 different fornjs of lish, which is in 

 itself a, remarkable lunnber to come from within the bounds of a 

 single lake. The fact becomes still more striking by a, comparison 

 with Victoria N)'anza Avhich contains 86 forms, and Nyasa which 

 contains 63. Thus, Tanganyika has more than half as many 

 species again as Lake Victoiia and over twice as many as Nyasa, 

 and this despite the fact that Victoria, is a bigger 1-ake than 

 Tanganyika and Kyasa not much inferior to it in size. 



It must next be observed that of the 146 species known from 

 Tanganyika, uo less than 121 are peculiar to that lalie, Vvhile in 

 •comparison 60 out of 86 are endemic in Victoria Nyanza and 43 

 out of 63 in iSTyasa. That is to s-iy, nearly 83 per cent, of the 

 fish of Tanganyika, are found in that lake alone, while of the 

 species found in Victoria Kyanza, 69 [)er cent, are peculiar to 

 the lake and in Nyasa, 67 percent. Tanganyika, indeed, contains 

 more than double as many endemic species as Lake Victoria,, 

 which shows the next largest total. 



Although the number of endemic species in Tanganyika is 

 clearly remarkable, the number of endemic genera is still more 

 -so. Of the 55 genera known to occur there, uea,rly half (26) are 

 found in that lake alone. A comparison witli the tw^o other 

 lakes, as instituted above, serves to emphasise the exceptional 

 nature of this fact. Two genera onl}^ out of 25 are endemic in 

 Victoria ^STyanza and five out of 25 in Ny^sa. The nund)er of 

 genera, recorded from Tanganyika fornrs a remarkably large 

 proportion of the total enumerated in the table of distribution. 

 A comparison of the figures shows that whereas this Like contains 

 146 species out of a grand total of 308, i. e. 47 per cent., it con- 

 tains 55 genera, out of 72 — -no less than 76 per cent. 



It will now be well to review the list of fislies in rather more 

 detail, dealing in general terms with the vaiions families and the 

 distribution of their representatives in the lakes. T'here is little 

 to comment on as far as tlie Polypteri(he and Lepidosirenida? are 

 concerned. Species of Pob/pterios and Protopterus are fairly well 

 represented in the big lakes, but the details of their distribution 

 have no pa,rticular significance. — Of the Mormyridae no species 

 have as yet been obtained from the smaller la.,kes, a,nd the family 

 has but few^ forms in tlie tliree bigger ones. Only Victoria 

 Nyanza conta,ins endemic species. — It is interesting to note that 

 the Clupeida3 are to be found in Tanganyika alone, wheie there is 

 an endemic species of the fresh- water genus Pelloihula, as well as 

 a representative of a closely allied endemic genus. — A few^ forms 

 of Characinidfe occur in the bigger lakes, of which Tanganyika 

 and Victoria each contain two types peculiar to themselves. 



