In preparing a =temporary mount=, place the specimen in the centre of a clean slide and add two or more drops of the temporary mounting medium, which may be water, or a mixture of equal parts of alcohol, glycerine, and water, or some micro-chemical reagent, as weak Lugol’s solution, solution of chloral hydrate, etc. Cover this with a cover glass and press down gently. Remove the excess of the mounting medium with a piece of blotting paper. Now place the slide on the stage and proceed to examine it. Such mounts can of course be used only for short periods of study; and when the period of observation is finished, the specimen should be removed and the slide washed, or the slide washing may be deferred until a number of such slides have accumulated. At any rate, when the mounting medium dries, the specimen is no longer suitable for observation. PERMANENT MOUNTS Permanent mounts are prepared in much the same way as temporary, but of course the mounting medium is different. The kind of permanent mounting medium used depends upon the previous treatment of the specimen. If the specimen has been preserved in alcohol or glycerine and water, it is usually mounted in glycerine jelly. If the specimen in question is a powder, it is placed in the centre of the slide and a drop or two of glycerine, alcohol, and water mixture added, unless the powder was already in suspension in such a mixture. Cut a small cube of glycerine jelly and place it in the centre of the powder mixture. Lift up the slide by means of pliers, or grasp the two edges between the thumb and finger and hold over a small flame of an alcohol lamp, or place on a steam-bath until the glycerine jelly has melted. Next sterilize a dissecting needle, cool, and mix the powder with the glycerine jelly, being careful not to lift the point of the needle from the slide during the operation. If the mixing has been carefully done, few or no air-bubbles will be present; but if they are present, heat the needle, and while it is white hot touch the bubbles with its point, and they will disappear. Now take a pair of forceps and, after securing a clean cover glass near the edge, pass them three times through the flame of the alcohol lamp. While holding it in a slanting position, touch one side of the powder mixture and slowly lower the cover glass until it comes in complete contact with the mixture. Now press gently with the end of the needle-handle, and set it aside to cool. When it is cool, place a neatly trimmed label on one end of the slide, on which write the name of the specimen, the number of the series of which it is to form a part, etc. Any excess of glycerine jelly, which may have been pressed out from the edges of the cover glass, should not be removed at once, but should be allowed to remain on the slide for at least one month in order to allow for shrinkage due to evaporation. At the end of a month remove