Diagrammatic section of an Ascidia, representing the three sacs and the branchial sac as the pharynx or throat: (a) branchial orifice; (b) atrial orifice; (c) tunic or test (d) mantle; (e) branchial sac; (f) gullet; (g) stomach; (h) anal orifice; (i) dorsal lamina; the dotted line indicates the endostyle.
