Fig. 4

Histological details of the basal areas and appendages of Monobryozoon ambulans. A Cross-section of the proximal area showing the main body cavity, thick cuticle, and an interzooidal septum between the basal appendage and the main body cavity. B Longitudinal section of a basally enlarged appendage showing the proliferating, budding cells. C, D Two different sections of basal appendages showing the parietal muscles enclosed within the appendage, past the interzooidal septum. Asterisk shows clusters of cells in the more distal part of the appendage. E, F Two different sections showing the traverse of parietal muscles within the main body cavity of the zooid. ba—basal appendage, bc—body cavity, cut—cuticle, ibl—inner budding layer, izs—interzooidal septum, obl—outer budding layer, pop—pore plate, pm—parietal muscles