The following method has been developed in connection with studies in the genetics of Drosophila:[long dash]Three or 4 eggs, which have been removed from the culture by means of a needle with a spatula-like tip, are placed on a clean slide at a distance of about one-third of its width from the anterior margin and arranged, properly spaced, in a row with their micropile ends all directed away from the observer. A cover slip is then rested on the eggs and 1 or 2 drops of a physiol. salt soln. placed at the edge of the cover glass. Capillary attraction pulls the cover slip down and forces the contents of each egg out through a rupture at or near the micropile. This gives a uniformly thin smear, which is more or less circular in outline. By means of a mechanical stage, such prepns. can be very quickly searched under a high-dry objective, and if sperm are present, they are easily detected. This technique has been found useful as a means for clearing up various points in genetics. It is also a simple method for determining whether mating has been successful, without having to destroy the [female] in order to see if her sperm receptacles contain spermatozoa.