THE TANGANYIKA PROBLEM. 



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POTAMOLEPIS WELTNERI, MOORE. 



With respect to this curious form nothing more can at present be said than that 

 it is a sponge growing in the deep water of lake Tanganyika ; that in the single 

 specimen obtained it appears as a thin brown encrustation on a Paramelania shell ; 

 that it has thick, slightly curved spicules which, unlike those of Potamolepis leub- 

 nitzia, are slightly swollen at the ends, and that in general the enlarged ends of 

 these spicules are micropunctate. It should, however, be noted that the character- 

 istic spicules of this new form are closely similar to those of the old fossil genus 

 Renieria. 



Fig. 4.— Spicules of Potamolepis Weltneri. 



PROTOZOA. 



With respect to the unicellular organisms which are found 

 in Lake Tanganyika, I have encountered only two forms 

 which seem to call for any special mention. It may be 

 remembered that, in Livingstone's diary of his last journey, 

 the explorer noticed that at times the surface of Tanyganyika 

 was at times covered with what he called a "yellow scum," 

 and which, he says, he thought to be of "vegetable origin." 



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