If some one phase in the life of any aquatic animal is to be studied during a short period, it is well to have special temporary aquaria. Also, when a talk on some of the occupants of the larger aquarium is to be given, specimens may be placed in small vessels for the time being and returned later. For such purposes glass tumblers can be used, or small fruit jars, finger bowls, broken goblets set in blocks of wood, ordinary white bowls or dishes, tubs, pails or tanks for large fishes,--in fact any wide-mouthed vessel which is easy to get. Special suggestions will be made in connection with the study of some of the water insects and others. A permanent aquarium need not be an expensive affair. The rectangular ones are best if large fishes are to be kept, yet they are not essential. Here, again, it is easier to write directions for the construction of a perfect aquarium than it is for the most patient teacher, with the help of the boys who are handy with tools, to put together a box of wood and glass that will not spring a leak some day and spoil everything. But failures do not discourage us; they make us only more determined. If a rectangular water-tight box is out of the question, what is the next best thing? One of the busiest laboratories in New York State has plants and animals living in jars of all shapes and sizes,--fruit jars, glass butter jars, candy jars, battery jars, museum jars, and others of like nature. There are rectangular and round aquaria of various sizes kept by all firms who deal in laboratory supplies, and if some money is to be spent, one of these is a good investment. Fig. 56 shows one of these rectangular ones, and Fig. 57 shows a round one of small size which is useful and does not cost much. A GOOD SCHOOL AQUARIUM. A cheap, substantial aquarium for general use may be made of glass and "angle" or "valley" tin. Pieces of glass are always handy and the tin can be had at any tin-shop. The tinsmith will know just how to cut, "angle" and solder it. The following directions for making an aquarium of this kind are supplied us by Professor C. F. Hodge of Clark University. He has made and used them for years with great satisfaction in the university laboratory and in graded schools. The illustration (Fig. 58, 59) shows various sizes. A good all-round size has these dimensions: 12 inches high, 15 inches long and 8 inches wide. One may use spoiled photographic plates for small desk aquaria, in which to watch the development of "wigglers," dragon-fly nymphs or other water insects. Lids of wire screen are shown on some of the aquaria in the picture (1, 2 and 3).