280 S. C. AKEHURST ON A TRAP FOR FREE-SWIMMING ORGANISMS. 



I have departed from the funnel shape making the metal 

 box to hold the water almost flat, which will allow any sediment 

 to settle at the bottom. If the water is very muddy, a cork can 

 be fitted into the outlet hole and left until the debris has settled 

 first filling the tube with clean pond water. 



If the cork is carefully removed, very little, if any, dirt will 

 pass down the tube. Should some slip by, this can be trapped 

 off, the tube refilled with water, when a perfectly clear gathering 

 can be secured. 



A strainer is provided, to be used, when necessary, for removing 



Fio 3. 



larvae or any of the entomostraca. It is important, that as much 

 light as possible should be concentrated on the glass tube. 



To arrange for this a bi-convex lens 1| inch diameter, silvered on 

 one side and mounted in a metal holder with a movable support 

 allowing it to be tilted at an angle, is placed under the tube, light 

 from a bull's-eye condenser is received by the lens and a bright 

 beam passed up the tube. This method of transmitting the light 

 is very effective, and the trap in consequence acts more rapidly 

 and effectively than when the bull's-eye condenser only is em- 

 ployed. The lens placed in position is shown in the illustration. 



Journ. QueketL Microscopical Club, Ser. 2, Vol. XII. , No. 74, April iyi4. 



