ASCIDTA SOBDIDA. 121 



and there is generally a large oval white spot between 

 the tubes concealing the ganglia. The tubes are short 

 and conical ; the branchial one is exactly terminal, the 

 anal is placed near to it a little way down the ventral 

 margin. The muscular fibres are interwoven on the left 

 side ; on the right side a few fibres pass inwards from 

 the margins, particularly from the bases of the tubes. 



The branchial sac (PI. XII, fig. 2, and PI. XVIII, 

 fig. 4) is co-extensive with the mantle, both terminating 

 near to the posterior margin of the visceral mass. It 

 is minutely plicated ; the primary vessels are numerous, 

 regularly disposed, and a little variable in size ; the 

 stomata are somewhat elliptical, with the extremities 

 pointed. The longitudinal bars are stout, with rather 

 small obtuse papillae at the intersections ; there are no 

 small intermediate ones. The papillary membrane is 

 distinctly developed, though not conspicuously so. 

 The oral lamina (PI. XII, fig. 2) is wide and smooth, 

 and terminates at the right side of the mouth, which is 

 situated near the bottom of the branchial sac, usually 

 in the midst of a large irregular red blotch which 

 extends to the extremity of the lamina : there are no 

 tentacular points on the left of the mouth. There are 

 between fifty and sixty tentacular filaments arranged 

 in a single line. The branchial tubercle (PI. XII, figs. 

 '2 and 3, and PI. XX, fig. 7) is oval, placed lengthwise 

 with the extremities of the loop usually turned towards 

 the endostyle, though sometimes they are both in- 

 curved. 



The ovary (PL XII, fig. 3, and PI. XIII, fig. 1) is 

 situated at the left side of the visceral mass ; it is 

 branched in a radiating manner from the centre of the 

 intestinal loop, the branches extending over the whole 

 of this portion of the alimentary tube. The male ca3ca 

 (PL XII, figs. 1 and 4; and PL XIII, fig. 9) are large, 

 numerous, irregularly lobulated or branched, and fre- 

 quently bifid, with the extremities obtuse. They are 

 distributed over both sides of the looped portion of the 

 intestine, but on the right (PL XII, fig. 1) are most 



