1900] MICROSCOPICAL JOURNAL. 303 



mit, from the central clear portion of the water in the bot- 

 tle remove with a pippette, enough water to fill a small 

 circular white china saucer. When the little saucer is fill- 

 ed, the large diatoms in the clear water will settle to the 

 bottom. Then oscilliating the sides rectangularly, will 

 mass the diatoms to the center, and gently twirling will 

 tangle them or gather the diatoms to the center, and their 

 presence will be easily recognized by the unaided eye as 

 a dark spot. There will be in the mass nothing but liv- 

 ing shells with their greenish endochrome, oflFset by the 

 white of the saucer. No dead shells will have been re- 

 moved from the bottle. Only such forms as were floating 

 in the clear water, on removal with pippette, will appear. 



When the little clot of diatoms is gathered together, the 

 water in the holder is carefully poured off until a couple 

 of drops only are left. The diatoms are then whirled to- 

 gether again, and can be readily dipped up and deposited 

 on a suitable slide. Shortly before doing this, take a small 

 piece of the so-called rotten pine or cypress wood, and 

 scrape it very gently transversely across the grain so that 

 no coarse particles will fall with the fine dust. Place the 

 dust on a clean dry slip, and by tapping drive the powder 

 so as to cover a space of | inch wide. Tap the slide so as 

 to dislodge any excess of wood dust, as the layer should 

 be uniformly and evenly spread. If the dust layer is too 

 dense, the diatoms will plough through it and be obscured. 

 Next apply the drop from pippette containing the living 

 diatoms over the center of the dust layer, when all the 

 diatoms will be easily found and easily followed in their 

 movements with a -J inch objective. The slip ray be sup- 

 ported on any rigid metal stage, but for inspection under 

 a i inch objective it will be necessary, in the absence of 

 a regular movable glass stage plate, to support the glass 

 slip on a separate piece of glass of about 3J inches square 

 and i inch thick for weight. The supporting stage glass 

 must be constantly moved by the hand to insure a con- 



