Fig. 4. Morphogenetic movement of the interrenal gland from 20 hpf to 3 dpf. (A-E) Cartoons showing development of pronephric (black) and interrenal (red) primordia; ventral view. The notochord is represented in light blue; the second and third somites are shown as dark blue rectangles. (F-O) wt1 (black) and ff1b (red) double in situ hybridization; (F-J) lateral view, (K-O) ventral view. (A,F,K) At 20-22 hpf, the wt-expressing cells lie on both sides of the notochord and some regions are also labeled with ff1b. (B,G,L) At 24 hpf, the ff1b-expressing cells are separated from the wt1-expressing cells on both sides of the notochord. (C,H,M) At 30 hpf, the wt1-expressing cells are still separate, whereas the ff1b-expressing cells have assembled towards the right of the notochord (left when viewed ventrally). (D,I,N) At 33 hpf, the wt1-expressing cells start to fuse. (E,J,O) At 3 dpf, the wt1 cells occupy the midline, while the ff1b-expressing cells continue to proliferate and redistribute on both sides of the notochord.