CASH ON THE ROTIFER A. 197 



be periodically cleaned ; the plants must be removed when they get 

 unsightly, and others substituted ; but to think of making it valuable as 

 an adjunct to the microscope, and be perpetually dabbling in it, is hopeless. 

 As a rule the two things, a nice parlour ornament and a useful reservoir 

 of minute life, are incompatible. The principle on which I construct my 

 aquarium is this : I cover the bottom with about two inches of well-washed 

 sand, (silver sand is best,) fill up with water, and then plant Myriophyllum, 

 the water Ranunculus, the common water Moss, (Fontinalis antipyretica,) 

 which is an excellent aquarium plant, Nitella flexilis, and a sprig or two, 

 (not more, on account of its rapid growth,) ofAnacharis Alsinastrum, thvov^in^ 

 in a small quantity of Lemna, and perhaps a few detached leaves of the 

 water Violet, {HoUonia palustris.) Other plants may be used, but as a rule 

 they ought to be the finer leaved species. After allowing it to stand a 

 few days I turn in three or four minnows, and such other small fry as 

 fancy may dictate, always, of course, avoiding those pugnacious brutes 

 the sticklebacks, which ought to have an aquarium to themselves. I then 

 let it take its course, and, assuming that the water is in a state of purity, 

 do not disturb it for twelve months or so. Elegance is no object so long 

 as I make my aquarium subserve the purposes of the microscope. When 

 two or three months have elapsed I have no difficulty in finding any 

 number of Rotifers that I may want. There is Rotifer vulgaris in myriads ; 

 there are also R. macroceros — which at one time was quite as abundant as 

 R. vulgaris — and many other species, including Scaridiimi, Monocerca, Salpiiia, 

 Metopidia, Pterodina, and many others ; but, what are perhaps most to be 

 desired, the attached genera, Stephamccros, Floscidaria, (Ecistes, Melicerta, 

 and so on. This is a list which is sufficient to whet the appetite of any 

 amateur microscopist. A few days ago I made a random dip into my 

 aquarium — which has been left undisturbed for about five months— and, 

 on placing a few leaflets of Myriophyllum under the microscope, found that 

 I had netted about half-a-dozen specimens of Floscidaria campamdata, 

 two beautiful Stephanoceri, and several free rotifers, both loricated and 

 illoricated, besides other animalcules and one or two desmids. The 

 Floscules are at present very numerous, although not many weeks since 

 there was not one to be found. It is interesting to note how, at certain 

 seasons, different species of infusoria predominate. All through the 

 summer months my water plants have been covered with Stentors — not a 

 leaf could be detected which was not swarming with them— now they have 

 almost entirely disappeared, and the Floscules have i)resented themselves; 



