The columellar muscle system consists anteriorly of a high number of longitudinal branches surrounding a hydrocoel, which forms higher up two lateral, one ventral and four smaller dorsal bundles. These bundles enter the muscular envelope of head and nuchal region, which is formed out of the wing-wall muscles. The two lateral bundles proceed farest apically to insert on the buccal appendages; the four dorsal fibres fuse with the walls of buccal organs and oesophagus, while the ventral muscles run into the posterior and lateral footlobes. The wings are attached to the body by an extra right and left muscle neither derived from the columellar nor from the wing-wall muscle system. So the posterior and lateral footparts are mesopodal, the wings epipodal and the buccal appendages propodal, or velar, in origin.