FAUNA OF THE AFRICAN LAKES. 



591 



The most obvious comment on the table of distribution is the 

 great inequality in the totals recorded from the biggest lakes — an 

 inequality which is obviously due in this instance to unequal 

 investigation. Of the 87 species enumerated, 60 occur in Nyasa, 

 87 in Victoria Nyanza, and ouly 7 in Tanganyika. While it is 

 impossible to predict what figures will be forthcoming when the 

 Protozoa of tlie lakes are better known, the figures at present 

 available are merely an index of this disproportionate investiga- 

 tion. The records from Nyasa are the result of the extensive col- 

 lections made by Fiilleborn, which were reported on by Daday (76). 

 It will be noticed that more than half the species identified were 

 not obtained in the lake itself, but came from river mouths, 

 pools, and swamps in the vicinity. Victoria N3^anza has been less 

 adequately explored in this direction, smaller collections being 

 made by Stuhlmann and more recently by Borgert and others. 



In his book on the Tanganyika Problem, Moore devotes a few- 

 paragraphs to the Protozoa of tlie lake (137, p. 323). The two 

 forms which he mentions by name — a Condylostoma and a, large 

 Infusorian which he refers with some hesitation to the genus 

 OolpidiuTii — liave been inserted in the table of distribution. He 

 describes the latter organism as the cause of the yellow clouds 

 which occur on the surface at times and make the water appear 

 " as if tinged with a fine golden dust." This effect was also 

 observed l)y Livingstone, who thought the yellow scum to be of 

 vegetable origin. I have repeatedly observed the phenomenon 

 myself, not only on Tanganyika,* but on Nyasa, a,nd without 

 denying other possibilities, I can confidently assert that it is 

 usually due to limnetic Alga3. In conclusion, Moore remarks that 

 he found some twenty types of Protozoa belonging to groups 

 common in tropical fresh- waters, 



A consideration of the list of species shows that in the 

 gi-eat majority of cases the forms are widely distributed if not 

 cosmopolitan in range. There are very feAV endemic species 

 enumerated — four in Lake Victoria, two in Nyasa,, a,nd one in 

 I\inganyika, — and most of these are of little interest. Peridini- 

 opsis cunniv.gtonil from Tanganyika, and Uronychia pmqiera from 

 Nyasa., are perhaps of more interest, since in each case they are 

 only the second described species of the genus. Forty-eight 

 genera a,re mentioned in the table of distribution, of which the 

 greatest number occur in Nyasa. This is a large proportion of 

 genera to species, but is accounted for by the number of genera 

 represented b}^ only a single species. None of the genera are 

 endemic. 



No good purpose would be served by commenting in detail on 

 tlie genera ami species in the list, but one or two further remarks 

 on their distribution may be offered. As far as the Rhizopoda 

 are concerned, the lists from Victoria Nyanza and Nyasa may be 

 reasona.bl}^ compared, and they exliiV)it a close degree of similarity. 

 The well-known genera Arcella and TJlfjhigia are each represented 

 by a number of species. It is in the remaining groups that there 



