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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.