Having detected that movement is taking place, a little adjustment of focus and a further search will reveal the bacilli to us, as little rod-like, colourless individuals. We shall see their cell contents if they are sufficiently highly magnified and also their cell walls. We may even observe them splitting, each one into two individuals. We must keep our sample of water for later examination. In fact, we may examine drops from day to day, in exactly the same manner. After a short lapse of time we shall notice that the bacteria have increased to an alarming extent and also that they no longer swim about. At this period they tend to arrange themselves in chains lengthwise, their cell walls also lose their clear cut appearance and become jelly like, yet withal they may still continue to split up. If we now examine the water from which we have taken our drop we shall probably find a scum floating on the surface; it consists of millions upon millions of hay bacilli, huddled together so to speak. It is the beginning of the end for them, nourishment is becoming scarce and important changes are about to take place. Let us continue our examination day by day, that we may discover what is happening. Before long, we shall find that within each cell wall, which is no longer jelly like, there is a darker cell contents than we saw before. The bacilli have, in fact, formed spores. Now we may plug our bottle containing the remainder of the water, with cotton wool and set it aside for some months if we wish. At the end of that time, by pouring a fresh supply of water upon the spores, we may start them all into a new vitality and the whole process will be repeated. We have mentioned that bacteria should be stained, in order to make their presence more easily detected. This is hardly the place to enter into a lengthy discussion concerning the methods of staining but, for the benefit of our readers, who wish to pursue the subject further, we will state as concisely as possible how simple staining may be accomplished. Our requirements are, a pair of Cornet’s forceps, two small bottles of stain, say Carbol-Fuchsin and Methylene Blue and a larger bottle of 1/2 per cent. Acetic acid; these may be obtained from the firm who supplied our microscope and, for the beginner at anyrate, it is cheaper to buy the solutions ready made, than to attempt to make them up at home. Slides and cover slips, we require, of course, and they must be absolutely grease proof; it may be necessary to boil them in a strong solution of caustic soda to effect this result. A small bottle of Canada Balsam completes our requirements.