Fig. 2. perd mutant muscles fail to form correct attachments. In wild-type embryos expressing β-galactosidase in muscle VL1 (with the 5053 Gal4 line) (A-F), this muscle sends out blunt-ended processes anteriorly during stage 13 (arrowheads in D), which continue to extend during stage 14 (E) and form mature-appearing connections by stage 16 (F). In a perd mutant (G-I), at stage 13 myotube projections appear thinner and less well-spread but are correctly oriented (arrowheads in G), then fail to extend through stage 14 (H). By stage 16, muscles are rounded up and new projections extend in inappropriate directions (arrow, I).