140 SOME ASCIDIANS FROM THE ISLE OF WIGHT. 



Fig. 6.— a. mollis. The same with the test removed, iu the same position as iu fig. 5 a. 

 Nat. size. 



an. = Anus. 

 C.S. = Cloaca! siphon. 

 ^«. = Ganglion, 



i«f. = Intestine — the descending portion, 

 as*. = Oesophagus. 

 0.5. = Oral siphon. 

 ou. = Oviduct. 

 pc. = Pericardium. 



si. = Stomach, covered with renal vesicles. 

 v.d. = Yas deferens. 



PLATE VII. 



Fig. 7. — Ascidia depressa, Alder. The largest individual, twice the natural size. 



Fig. 8. — A. depressa. The same, with the test removed, viewed from the left side, 

 showing the course of the viscera, and the rather elongated siphons. 



Fig. 9. — A. depressa, A portion of the test, magnified, showing the papilla on its 

 surface. 



Fig. 10. — A. depressa. A portion of the dorsal lamina, magnified, showing the marginal 

 teeth (ni.t.) and the lateral papillse which project from its concave surface. Camera lucida. 



Fig. 11 a. — A. depressa. A portion of the pharyngeal wall, magnified. Camera lucida. 

 A.i». = Horizontal vessels. 

 i.Z.5. = Internal longitudinal bars or vessels. 

 p. = Papillae above the connecting ducts. 

 r.i.;>. = Extremely rudimentary intermediate papilliB, here and there present where 

 the meshes are elongated. 



Fig. 11 b. — A. depressa. An enlarged view of the junction between an internal longitu- 

 dinal bar {i.l.l.) and a horizontal vessel {Ji.v.), showing the form of the disc-shaped papilla 

 (j9.), with its anterior (a.J.) and posterior buttresses. 



Fig. 12. — Ascidia mentiila, 0. F. Miiller. The pcritubercular area in the individual A., 

 showing the double aperture of the dorsal tubercle, 

 ep.^r. = Epibranchial groove. 

 jj.^)". = Pericoronal groove. 

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



Fig. 13. — A. mentula. Portion of an internal longitudinal bar {i.l.h.), seen obliquely 

 from the side, showing the form of the papilla) on its surface ; magnified. Camera lucida. 

 c.(^. = Connecting duct. 

 A.«. = Horizontal vessel. 

 i.^. = Intermediate papillae. 

 2?. = Papilla;. 



