Oscillation within posterior area of Delta and eve. Posterior area, proctodeum included (asterisk), of flat mounted germ bands double stained for eve1 and Delta, anterior to the top. Embryos A and B, very close in developmental age (around 24 LBS), show different phases of oscillation of eve1 and Delta internal to the 38th LBS ring of eve1 expression (arrow). Delta is broadly expressed close to the proctodeum in A, largely overlapping with eve, but is down-regulated in this region in B, and resolving to a 39th stripe. Once fully resolved, primary stripes of eve (magenta arrow) and Delta (blue arrow) are out of phase, while the following intercalated stripes are directly superposed (A1, high magnification of A). C: An abnormal asymmetric embryo showing different phases of oscillation on the two sides of the embryo. Asterisk marks the proctodeum. Scale bar: 100 μm in A, B, C; 50 μm in A1.