A single secretory cell type is predominant in the neurointermediate lobes of Raia clavata, R. batis and R. radiata; a few glia cells are also present. Nerve bundles entering the lobe between the cell cords contain two secretory nerve types, and possibly a third type devoid of secretory granules. Type A axons containing granules of mean diameter 2000 A are presumed peptidergic, and type B axons with 1000 A granules, aminergic. Both axon types make numerous synaptoid contacts with the secretory cells, and also make contact with the basement membrane of the capillary walls. A few neuroglial contacts were also noted. The implications of this innervation pattern with respect to the control of MSH secretion are discussed. A colloid-filled cavity present in the lobes of two juvenile fish is interpreted as a remnant of Rathke's pouch. It is lined with a layer of interdigitating undifferentiated cells bearing microvilli, interspersed by a few ciliated cells.