For the examination of practically all our microscopic objects we require a number of slides, little glass slips of good, thin, clear glass. They may be used over and over again unless we make permanent preparations, but we are hardly likely to do so in our early days. The slides are held in place on the microscope stage, either by a pair of clips attached thereto or by resting against a bar running across the stage. We may here remark that it is essential always to keep one’s microscope slides absolutely clean. Dirty slides denote the careless worker; moreover, dirt when magnified is misleading. Objects which are being examined in water or any other liquid should be covered with a cover-slip, an exceedingly thin circle or square of glass. The cover-slip is as much a protection for the objective as for the object and its cleanliness also, is all important. We have not mentioned any refinements such as the mechanical stage, by means of which slides on the stage may be rotated, moved to the front and to the back of the stage or from side to side. We have omitted these because they are not essential even for the very best work; they lend additional comfort to the use of the microscope but, again, they are not essential. The microscopist who requires such luxuries may learn about them in the larger text-books on the microscope. CHAPTER V ANIMAL LIFE IN THE PONDS AND STREAMS The enthusiastic microscopist will probably never lack material for his instrument, whatever branch of microscopical work he may decide to make his own. To the student of Pond Life, either animal or vegetable, there is granted a never-ending store of beautiful and interesting objects. Because one pond has been thoroughly searched and all that it can offer has been carefully examined, we must not conclude that no other pond will be worth our attention. Though indeed many little animals occur over and over again in practically every pond, there are other equally interesting animals which only occur in certain localities and for these we must keep a sharp look-out. The apparatus needed for the collection of the denizens of ponds and streams, need consist of no more than a net with a very fine mesh and a jar in which to bring our captures home; for, of course, animals which dwell in water need not be dried on the journey home. Various useful accessories for the student of pond life are sold at very reasonable rates by most scientific instrument makers.