Phyllidia ocellata Cuvier. Images showing a selection of the histological slides. A. Kidney gland lying on top of digestive gland; B. Cross section in heart region; note the spicule girdle around the visceral cavity in the tuberculate body wall and the lack of spicules in the median dorsal ridge between the median tubercles; C. Cross section showing one gill lamella; note the spicules in the foot (lower spi) and the dorsoventral muscle bundles (star); D. Bundles of spicules branching off from the spicule girdle of the visceral cavity into a tubercle of the body wall. Abbreviations: digl digestive gland, fo foot, gi gill leaflet, hec hemolymph channel, in intestine, kigl kidney gland, mer median notum ridge in between median tubercles, spi spicules, tu tubercle, ve ventricle, vis visceral cavity.