THE " TRITON " TUNICATA. 113 



Family II. — Salpid^e. 



During the "Triton" expedition only two specimens of Salpa were obtained, 

 but curiously enough these show the two conditions — solitary and aggregated 

 — of the same species, Salpa runcinata. In August 1880, during the cruise of 

 the "Knight Errant" in the same neighbourhood, some large specimens of 

 Salpa zonaria were the only Tunicata captured. 



Salpa runcinata, Chamisso. 



1. Solitary form. One specimen, measuring 2-2 cm. in length, was obtained 

 on the surface on the 18th August 1882. 



2. Aggregated form. A single member of a chain was captured in the 

 tow-net at a depth of 12 fathoms, 4th-5th August 1882. 



This is the Salpa fusi/ormis of Cuvier, and has the body prolonged both 

 anteriorly and posteriorly beyond the branchial and atrial apertures into long 

 tapering appendages. The body proper measures 15 cm. in length and 1 cm. 

 in breadth, while the anterior appendage extends beyond the branchial aper- 

 ture for 1-4 cm., and the posterior appendage beyond the atrial aperture for 

 1*7 cm. 



Salpa runcinata is a well known Scandinavian form, and has been obtained 

 in British seas before now. Early in the present century, Dr John Macculloch 

 described ( Western Isles* vol. ii. p. 187) and figured, under the name of 

 Salpa moniliformis, a form which may have been the aggregate condition of S. 

 runcinata. He found the chains occurring in abundance in autumn in the 

 harbours of Canna and Campbellton. In the spring of 1821 Dr Fleming found 

 many chains a foot and more in length upon the Caithness coast ; and about 

 thirty years later Professor Edward Forbes identified with Salpa runcinata, 

 both solitary and aggregated, some specimens captured by Lieutenant Thomas, 

 E.N., in the Orkney Seas. In 1868 Professor M'LsrrosHt came upon vast quan- 

 tities of both the solitary and the chain form of Salpa runcinata upon the east 

 shores of North Uist, in company with both forms of Salpa spinosa, Otto, a 

 species which Forbes had predicted would probably be found in the Hebrides. 



Salpa zonaria, Chamisso. 



Ten specimens of this form were obtained in the tow-net, at a depth of 20 

 fathoms, on 10th August 1880, during the cruise of the " KnightErrant." The 

 specimens are well preserved, and are all about 4 cm. in length. 



* See Forbes and Hanley, History of the British Mollusca, vol. i. p. 50, 1853. 

 f See Jour. Linn. Soc, ZooL, vol. ix. p. 41. 



