THE "TRITON" TUNIC AT A. 115 



h.m, horizontal membrane of branchial sac. 



i, intestine. 



i.l, internal longitudinal bar of branchial sac. 



1, lobe at branchial aperture. 



l.v, fine longitudinal vessel of branchial sac. 



m 1 to ??i 8 , the muscle bands in Doliolum. 



mb, membrane. 



m.b, muscular bundle. 



mh, mesh of branchial sac. 



7i, vf, nerves. 



n.a, aperture of duct from neural gland. 



n.d, duct from neural gland. 



n.g, nerve ganglion. 



02, oesophagus. 



ce.a, oesophageal aperture. 



ov, ovary. 



p, papilla ; p', smaller intermediate papilla. 



p.p, peripharyngeal band. 



sg, stigmata. 



st, stomach. 



t, testis ; t ', anterior prolongation of testis. 



tn, tn', tn", tentacles of 1st, 2nd, and 3rd order. 



tr, transverse vessel ; tr', tr", smaller transverse vessels. 



v.d, vas deferens. 



z, p'rebranchial zone. 



Plate XVI. 



Ascidia tritonis, n. sp. 



Fig. 1. — Ascidia tritonis, seen from the right side. Natural size. 

 Fig. 2. — A small portion of the surface of the test. Slightly magnified. 



Fig. 3. — Another specimen, after the removal of the test, seen from the left side. Natural size. 

 Fig. 4. — Part of the branchial sac, from the inside. Objective, Swift, 1 inch. 

 Fig. 5. — Small portion of dorsal lamina, showing free edge. Objective, Swift, 1 iuch. 

 Fig. 6. — Dorsal part of anterior end of branchial sac, showing tentacles, dorsal tubercle, peri- 

 pharyngeal bands, &c. Objective, Swift, 1 inch. 



Plate XVII. 



Figs. 1 and 2, Ciona intestinalis, Linn. Figs. 3 and 4, Ascidia virginea, 0. F. Mliller. 

 Figs. 5 and 6, Polycarpa pomaria, Sav. 



Fig. 1. — A small portion of the branchial sac of Ciona intestinalis, Linn., seen from the inside ; 



papilla? not represented. Objective, Swift, 1 inch. 

 Fig. 2. — Another small portion of the branchial sac of Ciona intestinalis, from the inside. 



Objective, Swift, 1 inch. 

 Fig. 3. — Ascidia virginea, 0. F. Miiller, var. pedunculata, from the left side. Natural size. 



