Fine Structure of the Notochord of Amphioxus

The protochordate amphioxus has been a favorite object of study for over a century. Early workers gave particular attention to the notochord of this remarkable animal because of its unique position and structure and its evolutionary significance (1). Modern advances in microscopy have opened the way for new research on the chorda dorsalis. Tenbaum (2) recently examined it under the polarizing microscope, and we present here observations made with the electron microscope.