The Ultrastructure of the Accessory Olfactory Organ in the River Lamprey (Lampetra Jiuviatilis)

Abstract

The accessory olfactory organ of Lampetra fluviatilis was found to consist of clusters of interconnected vesicles in tenuous connection with the exterior medium via the cavity of the olfactory organ. The walls of the vesicles are composed of two types of cells. One type are primary sense cells that resemble the olfactory sense cells in that their nucleus is situated peripherally and their axons pass directly into the brain. They differ from the olfactory sense cells in the size and number of cilia they bear, and also in the internal structure of the cilia. The second cell type are supporting and/or secretory cells. It is concluded that this sense organ is capable of responding to a “special kind” of chemical stimulus and its possible function is discussed.