The structure and function of the cephalic organ of a nemertine Lineus ruber.

The structure of the organ has been studied by light- and electron-microscopy. The organ is composed of both glandular and neural cells. The glandular cells pour their secretions into a ciliated tube which connects the organ with the external medium. Within the organ lobule, the tube forms three right-angled bends and is divided longitudinally into in going and outgoing channels by the adhesion of two groups of dilated cilia arising from opposite sides of the canal epithelium. Neural elements, backing the ciliated cells, constitute a possible neural chain to the central nervous system. The function of the organ is discussed.