The Functional Significance of the Hypocercal Tail in Pteraspis Rostrata

It is now many years since Kiaer (1924) demonstrated the existence of the hypocercaJ tail in the Anaspida, and subsequently it has been found to be universally present in the Heterostraci (Stetson, 1931; Kiaer, 1932; White, 1935). No experimental attempt seems to have been made, however, to investigate its functional significance (see Harris, 1936), although it has been realized for a considerable time that the hypocercaJ tail would tend to depress the hinder end of the body during swimming (Ahlborn, 1896; Grove & Newell, 1936). An attempt is made in this paper to determine, by experimental methods, this functional significance.