154 WALTER GARSTANG, M.A. 



Fig. 12. — Ascidia mentula, 0. F. Miiller. The peritubercnlar area in the 

 individual A., showing the double aperture of the dorsal tubercle. 



ep. gr. = Epibranchial groove. 



p.gr. = Pericoronal groove. 



p.z. = Prsebranchial zone, studded with minute papillae. 



Fig. 13. — A. mentula. Portion of an internal longitudinal bar (i.l.b.), seen 

 obliquely from the side, showing the form of the papillae on its surface; 

 magnified. Camera lucida. 



c.d. = Connecting duct. 



h.v. = Horizontal vessel. 



i.p. = Intermediate papillae. 



p. = Papillae. 



