558 



DR. W. A. CUNNINGTON ON THE 



table fire to be regarded as specimens wliicb, in tbe existing state 

 of our knowledge, it is impossible to identify. It is nevertlieless 

 clear tbat tbe precise distribution in tbe lakes of tbese repie- 

 sentatives of tbe subgenera, of Fotamon is of little, if any, 

 significance. 



In tbis connection it sbonld perbaps be explained tbat tbe 

 grounds of identification of tbe river crabs ai-e unsatisfactory on 

 tbe wbole, external cbaracters of a compaiatively trivial and 

 fluctuating nature forming tbe basis of distinction. Systematists 

 are tbus on less sure ground tban in tbe case, for instance, of tbe 

 prawns, wbere a matter like tbe brancbial formula affords more 

 satisfactory evidence of afltinity. 



Tanganyika, witb no less than tbree species of tbe endemic 

 genus Platythel'phusa, is evidently a case sui generis. Tbere are 

 certain features in tbe anatomy of tbis unique genus wbicb 

 suggest tbat it is of a somewbat primitive and unmodified 

 character, but at the same time nothing to indicate that it is 

 more definitely marine than the other members of tbe family to 

 which it belongs. Further, it is only to be regarded as unspecial- 

 ised in compaiison with allied forms which have adopted a semi- 

 terrestrial mode of life, so that it affords in reality no support 

 for Moore's view tliat Tanganyika is tbe altered remains of an 

 ancient sea. The genus witb its three distinct species is rather 

 to be looked upon as one more example of variation and 

 divergence, bi'ougbt about, in all probability, by prolonged 

 isolation. Finally, it may be noted tbat this lake, with five 

 species, contains a larger number of difterent crabs tlian any of 

 tbe others under consideration. 



Those groups of smaller Crustacea wbicb are often associated 

 under the heading Entomostraca, are (with the exception of tbe 

 marine Cirripedia) well represented in the African lakes. In- 

 formation concei-ning them is, however, for tbe most part, of 

 fairly recent date, since such organisms would be overlooked 

 by any but trained biologists, and the use of the tow-net in 

 Central Africa has even yet yielded results which are but 

 fragmentaiy and incomplete. All the earlier records are due 

 to the zeal and energy of Stuhlmann, and concern in particular 

 Lakes Victoria and Edward. In 1898-1900, extensive collections 

 were made in Nyasa and its neighbourhood by Fiilleborn, and 

 tbis material, together with a supply from V^ictoria, Nyanza 

 collected by Borgert, forms the basis of a comprehensive treatise 

 by Daday (76), in which the whole of the microfauna is dealt 

 with. The collections made by tbe writer during the Third 

 Tanganyika Expedition have afforded information for the first 

 time concerning the Entomostraca of Tanganyika., as well as 

 providing additional records for Nyasa and Lake Victoria. 

 Finally, the work of Schubotz during tbe German Central Africa 

 Expedition has furnished further particulars relating to Lakes 

 Kivu, Edward, and Albert. 



It may here be pointed out that these lower Crustacea, with 



