Entobdella diadema produces spermatophores from a pair of follicular glands lying one on each side of the body alongside the main nerve cord, and the secretion of these glands is stored in a two-chambered reservoir within the cirrus-sac.
The vagina is made up of two regions, a wide distal part to receive, accommodate and digest the spermatophores, and a proximal narrow part connected through the vitelline reservoir with the oviduct.
E. diadema Monticelli, 1901, is shown to be distinct from E. bumpusii Linton, 1900, and has been recorded from two new hosts, Dasyatis pastinaca at Plymouth, and Myliobatis aquila at Naples.
We wish to thank the directors and staffs at the Plymouth Marine Laboratory and at the Stazione Zoologica, Naples, for providing excellent facilities for the above studies to be carried out. The work was assisted by a grant to one of us (J. L.) from the Trustees of the Browne Fund, to whom grateful acknowledgement is made.