Slide showing diagram of 'sex-linked inheritance in Drosophila' i.e. the fruit fly. Slide shows diagram of 'sex-linked inheritance in Drosophila' i.e. the fruit fly. Diagram consists of three levels, labelled from top to bottom, P1, F1 and F2. In P1and F1 there are two flies, and in F2 there are four. Each level has symbols indicating the characteristics of the white-eyed male and red-eyed female; these symbols are linked across the levels with lines. Title below images reads: 'Fig. 70. - Sex-linked inheritance in Drosophila. The cross of red-eyed female by white-eyed male. The course of the sex-chromosomes carrying the sex-linked gene W -w is traced from parents to F2. Females at left, males at right. (From Morgan, Sturtevant, Muller and Bridges, courtesy Henry Hall & Co.' Late 19th to early 20th century