QUEKETT MICROSCOPICAL CLUB. 345 



a hole in it of such a size as to permit of the screw-end of an 

 objective passing through it up to its flange. In use the plate is 

 placed over the end of the nose-piece, and the objective screwed 

 home through it. To a projecting portion of the metal plate is 

 fitted a short length of brass tube or rod say | in. diameter, 

 which has been tapped internally, the direction of the tube being 

 parallel to the optic axis, and just clear of the objective. A fine 

 screw (25 threads to an inch) is fitted to the tube, and at the 

 lower end is provided with a milled head. The microscope is 

 focused in the usual way, and the screw then screwed down until 

 it is in contact with the stage clear of the cover-glass, and so 

 prevents any movement of the body, and possible damage. If 

 required, a small amount of slack may be left for possible focusing 

 by visitors who can use a microscope. 



The President described " A Red- Water Phenomenon due to 

 Euglena." He had noticed a curious appearance in a pond near 

 Manchester : the water was of a brilliant red colour. This, on 

 examination, proved to be due to Euglena, which formed quite a 

 thick scum of the red colour. The colour was confined to the 

 surface, and had a dry, powdery appearance that was very notice- 

 able. Microscopic examination showed the Euglena to be of a 

 large species, and the red coloration to be due to the replace- 

 ment of the chlorophyll by haematochrome. The main mass of 

 the body was coloured. Those floating on the surface were in a 

 resting condition ; but, at the bottom, all were actively swimming 

 about. There was apparently no intermediate stage, and at once 

 the question arose : How did the organisms get from the bottom 

 to the top of the pond % It was found that the Euglenae at the 

 bottom of the pond secreted large quantities of mucilage. The 

 organism, in the presence of sunlight, gave off bubbles of oxygen, 

 which became entangled in the mass of mucilage, and presently 

 carried the mass to the surface, trailing Euglenae after it, so that 

 they were collected at, and formed a scum on, the surface. The 

 colour of the scum changed during the day, from red in the 

 morning to green in the afternoon, the actual change from one to 

 the other being accomplished in about half an hour. Cunning- 

 ham had observed similar changes in Euglena viridis, near 

 Calcutta, lie records the scum as bright red in the morning 

 dull red at midday, and green in the evening, and by sunset an 

 intensely vivid green. The reverse took place just about dawn, 



