string: Although some furrow membrane is derived from the flattening of apical microvilli, both Golgi and recycling endosomal (RE) pathways have been shown to be required for furrow ingression, and membrane-marking experiments have indicated regions where directed membrane addition is likely to occur (Lecuit and Wieschaus, 2000; Sisson et al., 2000; Pelissier et al., 2003; Riggs et al., 2003; Fabrowski et al., 2013; Figard et al., 2013).