592 DR. W, A. CUNNINGTON ON THE 



has been inequality of investigation, so that tlie Eufiagellata, for 

 example, are only represented in Lake Victoria by a couple of 

 forms as contrasted with a large number from Nyasa. Volvox 

 africanus is an interesting species which was established to 

 receive specimens brought by Leiper from Albert Nyanza. It 

 can no longer be regarded as endemic, since it has been observed 

 in another part of East Africa. The DinoJiagellates are recorded 

 from four lakes, and a comparison may thus be instituted. Lake 

 Victoria contains representatives of the genera Ceratiuvi and 

 Gleiiodinium * . The former genus is wanting in Tanganyika, 

 where, however, Feridiniuvi and Feridiniojisis replace it. In 

 Nyasa, Ceratium and Feridiiduin occur ; in Lake Albert, Peri- 

 dinmm and Glenodiniwin. It is particularly among the ciliated 

 forms that a number of genera occur represented only by a single 

 species. The Trichodina mentioned, which has not been specific- 

 ally identified, is parasitic upon the Tanganyika jelly-fish. Since 

 the latter, or a variety of it, is known from Victoria Nyanza, it 

 may well be that a Trichodina .accompanies the medusa there 

 also, but I have no information on the subject. 



In conclusion, it only remains to point out that the Protozoa,' 

 as at present known, give no indication of an exceptional fauna 

 peculiar to any lake. At the same time it is precisely in 

 Tanganyika, if anywhere, that such might be .expected, and that 

 lake remains virtually vmexplored in this direction. 



4. GENEEAL DISCUSSION AND CONCLUSIONS. 



Having completed the systematic review of the animals at 

 present known to occm- in the lakes, the points of intei'est 

 concerning their distribution may now be fittingly discussed. 

 Far the most noticeable feature is that which has so repeatedly 

 shown itself, namely the u^nique nature of the fauna of Tan- 

 ganyika. With a recorded total of over 400 difiTerent animal 

 t^'pes, the lake is clearly exceptional ; moreover, no details of 

 certain groups which a,re known to occur are yet available for 

 incorporation. As this treatise is concerned so largely with 

 Tanganyika, it may not be oufc of place to illustrate here in a 

 graphic manner, the growth of knowledge concerning its fauna. 



Q^he curve which follows may be regarded as approximately 

 correct. It is clear that tlie labour of ascertaining the date of 

 discovery or description of eveiy type — even if possible — would be 

 out of proportion to the value of such a record. The la,rgest 

 addition to the total (159 species in all) was made by the writer's 

 expedition, which obtained, moreover, practically all the infor- 

 mation on the flora of the lake. 



* Virieux states that in the plankton which he examined he ohservx'd a specimen 

 oi Pe.ridinium, but was nnable to identify the species (197, p. 6). 



