Red the Lake of Morat in 1925. 309 



proceeds from the brownish matter which swims above. When 

 the vessel is agitated, all the zones are mixed together, and the 

 fluid appears of a dirty lilac, more or less brownish or reddish. 

 Hence it is certain that the colour of the water depends essen- 

 tially on the reddish-brown matter which forms the upper and 

 floating zone. This matter requires to be examined with more 

 attention. 



When we examine it through a lens, there is seen only a 

 mass of very minute cylindrical filaments, which seem to be 

 what Haller has described as a purple coivferva swimming in 

 water. By using a powerful microscope, however, the filaments 

 are seen marked with transverse stripes, which are often entire, 

 and in rings sometimes interrupted. These rings are often very 

 near each other, and tolerably regular. This state of the rings 

 rendered it probable that the filaments were not conferva?, but 

 belonged to the genus oscillatoria of M. Vaucher. This suppo- 

 sition was confirmed by their own proper motions, as they were 

 seen to bend and twist themselves, sometimes in one direction, 

 and sometimes in another, and with such rapidity as to leave 

 no doubt of their being animals. 



The matter which dyed the lake of Morat red, is a new spe- 

 cies of oscillatoria, having its rings less near each other, and 

 less thick than in the oscillatoria subfusca found in the Rhone, 

 and described by M. Vaucher. 



The rings appear to be situated in the interior of a mem- 

 branous tube, at least we often see tubular portions of the fila- 

 ment deprived of rings, and fragments of rings more or less 

 complete floating on the liquid. The colouring matter appears 

 to be contained either in the rings or between the rings. It is 

 probable that, by the fermentation or "putrefaction of these sub- 

 stances, which takes place either at their death, or perhaps 

 when they are in a diseased state, this colouring matter is dis- 

 solved in the water, and forms that fine lilac rose-colour which 

 terminates by developing itself in the water upon which *the 

 oscillatoria swim. 



The shreds of dirty yellow, which were often mixed with 

 this reddish matter, were considered to resemble fragments of 

 the thallus of some foliaceous lichen. They are fetid, and a 

 little soft, having nearly the specific gravity of water, and are 



