Fig. 2. Ventral organ development proceeds with placode-like cell behavior. Cells (red asterisk) that will ensheath the rostral nerve originate from a focal thickening in the rostral ectoderm at the anterior margin of the CNS in hatchling larvaceans (left lateral view). They delaminate over several hours and associate with a bundle of axons from the ventral organ and brain. Ciliated epithelial cells of the ventral organ also form from an ectodermal thickening (blue asterisk) where they infold into a slit-shaped pit and protrude cilia into the environment. br, brain; ci, sensory cilia; e, endostyle; mo, mouth; ph, pharynx. Scale bar: 20 µm.