Ultrastructure of the tube foot sucker of a regular echinoid,Diadema antillarum Philippi,with especial reference to secretory cells

Summary Suckers of principal tube feet of a regular echinoid,Diadema antillarum, are described in an electron microscopic study. Reference is made to secretory cells and nervous elements in the sucker and their possible significance in adhesion is considered and discussed. In particular, a granule-filled secretory cell-type is described that possesses long tracts down which the granules pass to terminate on the contact edge of the sucker in secretion packets. A second cell condition is described that may represent the secretory cells in a degranulated state. The appearance and significance of mucus-producing cells in the sucker is also considered.I am indebted to ProfessorN. Millott for his help and encouragement during the course of this work, to Mr.Raynor L. Jones for his expert technical assistance, and to Dr.H. G. Vevers and the Zoological Society of London.