DESCRIPTION OF THE SPECIES 13 



Muscle fibres. Mean number 1777 ±3-4 for the total of M. I-VI, based on 126 specimens. 



Alimentary canal. Compact, oval nucleus. 



Embryo. Single, in the same position as S. fusiformis. 



Distribution of S. thompsoni. Restricted to the Southern Ocean. Does not occur north of the 

 subtropical convergence. Circumpolar in moderate latitudes. In high latitudes restricted to Atlantic, 

 Indian and Australian sectors. 



Salpa gerlachei sp.nov. (Text-fig. 2) 

 Salpa runcinata-fusiformis var. echinata Herdman, 1910 (part?). 

 Salpa fusiformis var. gerlachei van Beneden and de Selys Longchamps, 191 3. 



HoLOTYPE. A specimen of the solitary form 56 mm. long taken in a i m. net towed horizontally 

 (N 100 H) 5 m. belowthesurfaceat Discovery station 1654, 7S°43-6' S., 176° 59-4' E. on 25 January 1936. 



Text-fig. 2. S. gerlachei sp.nov. («) Solitary form, lateral view. Length 27 mm. (i) Aggregate form, dorsal view. Length 

 17 mm. (From Van Beneden, 1913.) Note. The aggregate form shown here is atypical in lacking an anterior protuberance 

 of the test ; probably an artefact due to wear. 



Registration NUMBER. British Museum (Nat. Hist.), i960. 10.18. i. 



Body proportions. Total length 63 mm., body length 56 mm., nucleus length 11 mm. 



Muscle-fibre number. 48 fibres in M. IV. 



Stolon. Stolon with one fully differentiated block of buds consisting of 174 blastozooids, each 

 I mm. long. Evidence that one block, at least, has already been released (see p. 25). Stolon extends for- 

 ward to level of M. II-III. 



Allotype. A specimen of the aggregate form 23 mm. long taken in a i m. net towed obliquely 

 (N looB) from 109 m. to the surface at Discovery station 1296, 69° o6-6' S., 131° 42-6' W. on i March 



1934- 

 Registration NUMBER. British Museum (Nat. Hist.), i960. 10. 18.2. 



Body proportions. Total length 34 mm., body length 23 mm., nucleus length 6 mm. 



