8 Mr. W. Low Sarjeant on 



Keston Common is the best hunting-ground. Arcella and 

 Difflugia are very abundant there, and the Amceba are of large 

 size. This is also a good spot for Desmids. 



The various ponds in the gravel-pits about Selhurst and 

 Thornton Heath are well worth visiting, especially those in 

 which the Anacharis is growing ; Melicerta, Stephanoceros, Stentor, 

 Carchesium, Epistylis, AlcyoneUa, and occasionally Plumatella, 

 occur, besides a host of commoner forms. 



In the direction of Beddington and Mitcham all the forms 

 previously mentioned may be taken, with the exception perhaps 

 of Hydra fusca. Magnificent specimens of Carchesium jwlypinum 

 may generally be found attached to the weeds in the slow- 

 running streams, and in the ditches near Beddington Park. 



A nearly circular pond on Mitcham Common, on the right- 

 hand side of the road before you reach the windmill in going 

 from Croydon to Mitcham, frequently contains Volvox, and is, I 

 think, the best pond on the common, although it is small. Just 

 after passing the windmill there is a large duck-pond, which, in 

 the autumn especially, swarms with a giant race of Daphnia, 

 many of them exceeding an eighth of an inch in length, and I 

 have taken them three-sixteenths of an inch in length, which is 

 an enormous size for a Daphnia. 



Now a few words on collecting ; to obtain a good gathering of 

 free-swimming forms it is necessary to use some kmd of straining 

 apparatus. Wright's collecting-bottle is perhaps the one most 

 generally used ; but for its size it is very heavy. I always use 

 an apparatus of my own construction and design, and, as it 

 answers its purpose well, is easily made, and is very light and 

 portable, I will fully describe it : — I fit a wide-mouthed bottle of 

 from 2 to 4 oz. capacity with an india-rubber stopper having two 

 holes through it (an ordinary cork will do, but an india-rubber 

 stopper is preferable, as it always fits water-tight and lasts 

 longer. I then coil up a piece of wire into a spiral rather 

 smaller in diameter than the neck of the bottle, but of sufficient 

 length to reach about two-thirds down the bottle when in its 

 place. I solder one end of it to the extremity of a short piece 

 of brass tube, which fits tightly into one of the holes in the 

 stopper, into which it is pressed. I now cover the spiral of wire 

 with a piece of muslin (coarse for the capture of large, fine for 

 small, organisms), and place the cork in the bottle with the 

 muslin strainer inside. If we now place a small funnel into the 

 other hole in the stopper and pour water into it, the water must 

 pass through the strainer before leaving the bottle, and every- 

 thing larger than the mesh of the muslin will be left in the 

 bottle. That the apparatus may be as complete as possible, I 

 make a zinc case, into wliich the bottle just fits, the lid of which 

 is a funnel; the case forms a very convenient dipper when 



