49 



Explanation of Plates. 

 Plate I. 



Large specimen of Ascidia mentula, from the right side, 

 natural size, from Hfe. 



Length 11"5 cm. Breadth 6 cm. Thickness 3 cm. 



A, shows the sensory edge of the branchial aperture 

 with lobes and coloured lines (the " ocelli "), enlarged. 



Plate II. 

 Reference Letters in Plates II., III., and IV. 



g.d. genital ducts. 



a. anus. 



At. atrial aperture. 



at. I. atrial lobe. 



hl.c. bladder cell. 



hl.s. blood sinus. 



Br. branchial aperture. 



hr.car. brancliio-cardiac vessel. 



hr.ao. branchial (veutral) vessel 



Br.s. branchial sac. 



br.visc. branchio- visceral vessel 



card. vise, cardie- visceral vessel 



c.c. common cloaca. 



c.d. connecting duct. 



cl. cloaca. 



C071. connective. 



c.t.c. connective tissue cell. 



d.ao. dorsal vessel. 



d.bl.s. dorsal blood sinus. 



d.l. dorsal lamina. 



d.n. dorsal nerve cord. 



d. t. dorsal tubercle. 



ec. ectoderm. 



eii. endoderm. 



end. endostyle. 



ej).c. epicardial tube. 



gl. pyloric gland. 



gl.d. duct of neural gland. 



goii. gonads. 



h. heart. 



hm. horizontal membrane. 



hijp. hypophysial (neural) gland 



liyp.d. hypophysial duct. 



i.i' . intestine. 



i.l. internal longitudinal bars. 



l.v. interstigmatic vessels. 



m. body-wall, or mantle. 



m.h. muscle bands. 



mes.c. mesoblast cell. 



VI. f. muscle fibres. 



n. nerves. 



ii.g. nerve ganglion. 



n.gl. neural gland. 



(ss. oesophagus. 



ov. ovary. 



jy.br. peribranchial cavity. 



2). br.s. prebranchial zone. 



2).c. pericardium. 



p.p'. papilliE. 



2)2).b. peripharyngeal bands. 



