Fig. 5

Fate of the third-quartet micromeres (3q) in the pilidium. The four middle panels show labeled domains (yellow) overlaying transmitted-light images (gray), for orientation. Peripheral panels show corresponding labeled domains alone, for clarity. Apical organ is up on all panels. Top row (A, D) shows left-side view (anterior lobe to the left); bottom row (B, C) shows right-side view (anterior lobe to the right). A Contribution of the 3a cell: nerves and muscles of left side, apical muscle (arrowhead), tile cells of esophageal wall of left side, esophageal sphincter (arrowhead), a nerve in the right lappet. B Contribution of the 3b cell: nerves and muscles of right side, tile cells of esophageal wall of right side, esophageal sphincter (arrowhead), a nerve in the left lappet, muscles of posterior lobe. C Contribution of the 3c cell: tile cells of inner right lappet, right and left ciliary ridge, inner ciliary band of the right lappet, cell near right outer posterior and inner anterior axils, esophageal sphincter. D Contribution of the 3d cell is nearly symmetrical to that of 3c, except that it does not contribute to right ciliary ridge. Scale bar 50 μm