114 BRITISH TUNICATA. 



The branchial sac (PL XLII, fig. 8) is delicate and 

 the folds are rather narrow; the primary vessels are 

 stoutish, vary in size, and have an exceedingly delicate 

 vessel between them, cutting the stomata in the centre; 

 the secondary vessels are delicate and of moderate 

 length ; the ends of the stomata are rounded ; the 

 longitudinal rods are wide, there are one or two 

 between the folds, and five or six upon them. The 

 branchial tubercle (PL XLVIII, fig. 11) is rather 

 peculiar in form ; it is rounded in front with a small 

 opening in the centre which is overhung by a pointed 

 process, probably indicating a rudimentary condition 

 of the spirals. The oral lamina is narrow, but slightly 

 deepens towards the mouth. 



The alimentary canal (PL XLII, fig. 9) forms a deep 

 sigmoidal curve towards the inferior extremity of the 

 body ; the oesophagus is well developed ; the stomach 

 (PL XLII, fig. 9) is short and rounded, with the in- 

 ternal laminae seen through the surface ; the walls of 

 the first or looped portion of the intestine are thick ; 

 but the tissue is more delicate, and the calibre 

 diminishes a little towards the anus, which is not very 

 wide, and has a narrow margin with a few minute 

 denticulations. The biliary ducts are rather long, and 

 the pyloric lobe which receives them is large and 

 conical. 



The reproductive organs (PL XLII, fig. 9) are 

 numerous, rather large, oval or rounded nodules ; the 

 oviducts and male outlets are similarly arranged to 

 those of the last species (S. pomaria) ; but the male 

 vesicles do not appear to be confined to the sides and 

 base ; the ova however were not much developed in 

 the individual examined, and the relative positions of 

 the two elements might consequently be somewhat 

 modified. Numerous pallial nodules, large and very 

 irregular in form, are interspersed amidst the repro- 

 ductive organs. 



The approximate tubular apertures, regularly 

 furrowed surface, and great contractility, distin- 



