Slide showing diagrams of the 'Chromosones of the plant bug Euchistus' and 'Male and Female of the Banana fly and their chromosones'. Slide shows black and white handwritten diagrams of the 'Chromosones of the plant bug Euchistus' and the 'Male and Female of the Banana fly and their chromosones'. First figure is labelled with numbers, title explains that numbers are 'As in Fig. 77'. Second figure has the male and female flies labelled, and the chromosones labelled 'yx', and 'xx' respectively. Title below first figure reads: 'Chromosones of the plant bug Euchistus. Numbers as in Fig. 77'. Euchistus distort fruit by sucking its sap. Title below second figure reads: 'Fig. 79 - The male (left) and female (right) of the banana fly (Drosophila melanogaster) and their chromosones.' Late 19th century to early 20th century