MORPHOLOGY AND FINE-STRUCTURE OF THE GLANDS OF THE DART-SAC COMPLEX IN HELICOIDEA (GASTROPODA, STYLOMMATOPHORA)

The glands of the dart-sac complex of Elona quimperiana, Trissexodon c onstrictus, Hygromia limbata, Cernuella aginnica, Helix aspersa and Ce paea nemoralis are described by light and transmission electron micros copy. All are tubular in morphology but, whereas in E. quimperiana man y tubules are held together in large club-shaped organs, in the other five species they are digitiform glands that protrude freely into the body cavity. Each tubular gland consists of a secretory epithelium, on e cell thick, surrounded by muscle fibers embedded in a wall of connec tive tissue. Axons and glial cell processes pass through this wall. A thin and continuous layer of pore-cells surrounds the glands. The epit helial cells show marked development of the organelles concerned with secretion, as well as the structural features of transporting cells. T he lumen of glands is full of secretory materials, comprising many sph eroidal granules and a filamentous matrix. This comparative analysis, made on six species of snails, reveals that there are major difference s in the ultrastructure of secretory granules and matrix in the Helico idea, while the cellular features of this organ are very similar in al l the taxa studied.