sion in the water, and filtering it in a pure state, by the mechanism of their syphons, and ciliated gills. It is very interesting to watch them thus engaged, and to note the force of the stream which they project from time to time.
The only creature of the insect kind that I can recommend for general adoption is the caddis worm, a comical and interesting creature, that can never mar the beauty of the tank. Half-a-dozen may be thrown in, and searched for occasionally—the search will always be well rewarded. When the cad closes his hybernacle, it will be desirable to remove it to a jar, to obtain a better opportunity of witnessing the transformation of the dormant worm into a four-winged fly of Stephens’s family of Phryganea.
CHAPTER VII.
SELECTION OF STOCK.
The first thing to guard against is over-stocking, the common error of all beginners; taking large fish with small, I think about two or three to every gallon of water is the utmost that should be attempted. For a vessel of twelve gallons, I should recommend the following, as giving great variety, with considerable safety:—Six Prussian carp, of various sizes, one at least of five inches in length; two small Crucian carp; two small perch; two small loach; two tench, of five or six inches; six or eight minnows; one small eel; a dozen Planorbis corneus; half-a-dozen Paludina vivipara; three or four fresh-water mussels; and a dozen of different sorts of newts.
