Fig. 1. Some aspects of embryonic expression of btd in relation to that of Dll, esg and hdc. Double immunofluorescent staining of in situ hybridisation for btd and anti-ß-gal antibodies for Dll, esg and hdc. (A) Stage 10 embryo showing btd expression (green) in two cephalic segments (maxillary and labial) and in three thoracic discs primordia (T1-T3). Note that at this stage Dll (red) is not active in the thoracic primordia. (B) Stage 13 embryos equally stained for btd and Dll to show that at this stage Dll is co-expressed with btd in the thorax. (C) Higher magnification of the thoracic disc primordia of a stage 13 embryo. Note that the btd domain is bigger than that of Dll. (D) Double staining for btd and esg in a stage 14 embryo. Higher magnification is shown in F. (E) Stage 14 embryo stained for btd and hdc. Higher magnification is shown in G.