592 



DR. W. A. CUNNINGTON ON THE 



has been inequality of investigation, so that the Euflageliata, for 

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

 forms as contrasted with a large number from Nyasa. Volvo.v 

 africcmus 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 Dinoflagellates are recorded 

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

 Victoria contains representatives of the genera Ceratium and 

 Glenoclinhtm* . The former genus is wanting in Tanganyika, 

 where, however, Peridbikim and Feridiniojjsis replace it. In 

 Nyasa, Ceratium and Feridiiiium occur ; in Lake Albert, Feri- 

 dinium and Glenodinium. It is particularly among the ciliated 

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

 species. The Tricliodina 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 Tricliodina 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 unexplored in this direction. 



4. GENERAL DISCUSSION AND CONCLUSIONS. 



Having completed the systematic review of the animals at 

 present known to occur in the lakes, the points of interest 

 concerning their distribution may i\ow be fittingly discussed. 

 Far the most noticeable feature is that which has so repeatedly 

 shown itself, namely the unique nature of the fauna of Tan- 

 ganyika. With a I'ecorded total of over 400 dififerent animal 

 types, the lake is clearly exceptional ; moreover, no details of 

 certain groups which are known to occur are yet available for 

 incorporation. As this treatise is concerned so largely with 

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

 graphic manner, the growth of knowledge concerning its fauna. 



I'he curve which follows may be regarded as approximately 

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

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

 out of proportion to the value of such a record. The largest 

 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 fiora of the lake. 



* Virieux states that in the plankton wliich he examined he observed a specimen 

 of Peridininm, but was uniible to identify the species (197, p. 6). 



