Stained preparations are best made with _thin_ smears on the glass slides. This is conveniently done by placing a drop of the semen on a slide and smearing it over the surface with the edge of another slide. A fairly thin and even field is thus obtained. A still better method is to first dilute the semen with physiological saline solution, so as to obtain fewer sperms in the field. After drying the preparation in air, fixation may be produced by drawing the slide through a gas flame several times, by immersion in equal parts of alcohol and ether, or even by the use of tissue fixers such as Helly’s or Zenker’s fluids. For ordinary staining, heat fixation is the quickest, and at the same time is quite satisfactory. After the slide is cooled, or washed, to remove the fixing solutions, it should be placed for a few minutes in a _freshly_ prepared solution (1 per cent) of chlorazene, as recommended by Williams, to remove the mucus and proteid material which otherwise blur the field. Other authors (38) have recommended diluting the semen with about twenty volumes of a 0.12 per cent sodium carbonate solution in 0.8 per cent sodium chloride. From this liquid the cells should be centrifuged for several minutes, removed with a pipette, and smeared on the slide. Following this, the slide should be thoroughly washed, preferably for ten minutes in running water, after which it is ready for staining. Numerous methods have been used for this procedure, but the sperms are more or less erratic in their reactions to the dyes, and one must be very careful to use the same method in all samples, in order to obtain uniform results. For quick staining, to bring out gross abnormalities of structure, and number of sperms present, one may use Gram’s stain, or a light stain with any of the aniline dyes, such as fuchsin. To bring out the finer structure, particularly of the head, more careful technic must be employed.