Printed in Great Britain The Embryology of Dacus tryoni 2. Development of lmaginal Discs in the Embryo

T H E cephalic, labial, wing, haltere, leg and genital imaginal discs of Cyclorrhapha are histologically distinct in the late embryo or early larva (Weismann, 1864; Pratt, 1900; Auerbach, 1936; Kaliss, 1939; Poulson, 1950). Experimental inves-tigation of Drosophila melanogaster further suggests that the determined rudi