FINE STRUCTURE OF THE NOTOCHORD OF AMPHIOXUS

Abstract

Electron microscopy of the notochord of amphioxus shows that the cells constituting the notochordal plates contain transversely arranged strata of long, electron-opaque fibrils separated by irregular strands of organelle-containing cytoplasm. The cell membranes on the margins of the plates are highly infolded. The cells of Muller''s tissue along the dorsal and ventral surfaces of the chordal plates lack fibrils but possess a system of canaliculi. Investing the plates and Muller''s tissue is a homogeneous membrane and a double-layered sheath of collagenous fibers.