"Small aquaria can be made of jelly-tumblers, glass finger-bowls, and glass fruit-cans, and larger aquaria can be obtained of dealers. A good substitute for these is what is known as a battery-jar (fig. 168). There are several sizes of these, which can be obtained of most dealers in scientific apparatus. "To prepare an aquarium, place in the jar a layer of sand; plant some water-plants in this sand, cover the sand with a layer of gravel or small stones, and then add the required amount of water carefully, so as not to disturb the plants or to roil the water unduly. The growing plants will keep the water in good condition for aquatic animal life, and render changing of the water unnecessary, if the animals in it live naturally in quiet water. Among the more available plants for use in aquaria are the following: "Waterweed, _Elodea canadensis_. "Bladderwort, _Utricularia_ (several species). "Water-starwort, _Callitriche_ (several species). "Watercress, _Nasturtium officinale_. "Stoneworts, _Chara and Nitella_ (several species of each). "Frog-spittle or water-silk, _Spirogyra_. "A small quantity of duckweed, _Lemna_, placed on the surface of the water adds to the beauty of an aquarium. [Illustration: FIG. 168.--Battery-jar aquarium. (From Jenkins and Kellogg.)] "When it is necessary to add water to an aquarium on account of loss by evaporation, rain water should be used to prevent an undue accumulation of the mineral-water held in solution in other water." =Making collections.=--Much is to be learned about animals by "collecting" them. But the collecting should be done chiefly with the idea of learning about the animals rather than with the notion of getting as many specimens as possible. To collect, it is necessary to find the animals alive; one learns thus their haunts, their local distribution, and something of their habits, while by continued work one comes to know how many and what different kinds or species of each group being collected occur in the region collected over. Collecting requires the sacrifice of life, however, and this will always be kept well in mind by the humane teacher and pupil. Where one set of specimens will do, no more should be collected. The author believes that high-school work in this line should be almost exclusively limited to the building up of a common school collection. Let a single set of specimens be brought together by the combined efforts of all the members of the class, and let it be well housed and cared for permanently. Each succeeding class will add to it; it may come in time to be a really representative exhibition of the local fauna.