THE CUTANEOUS INNERVATION OF AMPHIOXUS - A REVIEW INCORPORATING NEW OBSERVATIONS WITH DII TRACING AND SCANNING ELECTRON-MICROSCOPY

Anatomical information on four systems of presumed non-chemosensory in nervation are discussed in the context of possible functions in the la ncelet (amphioxus) as well as evolutionary relationships to somatosens ory pathways in vertebrates. New observations provided by DiI tracing of nerves and by scanning electron microscopic observation of nerve-li ke structures are consistent with the results of earlier studies. The systems are categorized as: (1) free nerve endings similar to the Roho n-Beard system of anamniotic vertebrates; (2) ciliated primary recepto r cells; (3) corpuscles of de Quatrefages associated with the nerves t o the rostrum; and (4) specialized encapsulated nerve fibers in the me tapleural folds.