3 2 4 THE TANGANYIKA PROBLEM. 



I have encountered this scum repeatedly on the lake, the 

 clear green for miles appearing as if tinged with a fine 

 golden dust, the minute particles of which this is composed 

 reflecting the bright sunlight, like the crystals of some 

 yellow precipitate. 



Upon examination these yellow clouds were found to 

 consist of a large infusorian which at first sight looked 

 exactly like a peridinium, having the characteristic equatorial 

 groove, but on closer scrutiny the whole organism was found 

 to be covered with long cilia which projected in lines from 

 the pore-like apertures in the plates of the skeleton. But 

 for the groove the animal would thus compare with a large 

 col podium. 



Whatever it really is, this organism is a most conspicuous 

 object. I have never seen it in any of the other lakes, and 

 it appears to be as characteristic of Tanganyika as the rest 

 of the members of the Halolimnic group. 



Associated with the above form, and also present in the 

 surface scum, there is a large condylostoma, the affinities of 

 which are not doubtful ; and besides these two conspicuous 

 and characteristic protozoa, there were found about twenty 

 recognisable, types belonging to those groups which have 

 habitually been encountered in the fresh-waters of the 

 tropics. 



