ABSTRACT
The behaviour and fine structure of the Cuvierian tubules are similar in the three investigated species of Actinopyga (A. echinites, A. mauritiana, A. miliaris). They are branched and made of a basal trunk from which arises 2 to 3 primary branches which in turn give rise to 2 secondary branches. Circular and longitudinal muscle cells occur in its outermost part. These are myoepithelial cells associated with nerve processes originatiry from the hyponeural nerve plexus. The structure of the rachis remind that of the distal part of the trunk, except the mesothelium which is monostratified and only made of adluminal cells. The peduncle of the spherule consist in a connective stem that is surrounded by a flattened pseudostratified mesothelium with an upper layer of adluminal cells and a lower layer of myoepithelial cells.
