FAUNA OP THE AFRICAN LAKES. 567 



represented in Tanganyika,, it is necessary to call special n.ttention 

 on account of tlieir remarkable nature. Of the former genus, no 

 fewer than twelve difierent species have been described fiom that 

 lake, eleven of which are peculiar to it, and they all, as Sars points 

 out (152, p. 756), exhibit striking features of specialisation. 

 It is also a remarkable coincidence — if it is only that — that the 

 type species of Paracypria was obtained from the same brackish 

 lagoon on the Chatham Islands as was the type of the Copepod 

 genus Schizopera, which is likewise very characteristic of Tan- 

 ganyika among the lakes. The case of Cypridopsis is perhaps 

 more significant still, since of the ten species obtained hj the 

 Third Tanganyika Expedition two only display all the features 

 • characteristic of the genus, and these are the two forms taken 

 respectively in Lakes Nyasa and Victoria. The other eight types, 

 which are confined to Ta.uganyika, exhibit certain divergences 

 which suggest that they might more suitably be removed to a new 

 genus which would then be endemic in the lake (153, p. 757). 



It is quite clear that in the case of this group also, Tanganyika 

 contains an unusually large number of forms, an exceptional 

 j^roportion of which are peculiar to the lake, and that of these 

 peculiar forms many shoAV undoubted signs of specialisation. 



Cladocera . 



The outstanding fact concerning the Cladocera is the absence 

 of any representatives from the plankton of Tanganyika, and 

 also apparently of Kivu, which is in direct communication with 

 it. Thus the sui-vey of this group of organisms I'csolves itself 

 into a, comparison of the records from the remaining lakes, and 

 this, it is not surprising to find, lacks the interest wdiich the 

 inclusion of species from Tanganyika usually affords. 



Table of Distribution of Cladocera t. 



AT.,,.,,, «f «„„„;„„ Victoria at ^ Albert Edward Other parts of 



JNauie or opc'Cius. -vi- JNyasa. -vt at j.i i i 



^ JNj'anza. •' JNyaiiza. jNyanza. ■ the world. 



Asia. 



E. Africa. Australia. 



Cosmopolitan. 

 Cosiuopolitaii. 

 Palestine, Australia. 



E. Africa. 



Asia, Australia, S. America, 



Sumatra. 



Almost cosmopolitan. 



t For further particulars consult especially Daday (76, p. 120). Additional 

 records for Lake Victoria are given by Delachaux (77) and for the smaller lakes by 

 Brehm (54). 



§ Not actually recorded from the lake itself, but from within its drainage area. 



