S 6 DISCOVERY REPORTS 



Gut (Text-fig. 10F). The oesophagus is wide, and shorter than the stomach. The stomach is 

 longer than wide, slightly laterally compressed, and has eight to ten uninterrupted longitudinal folds. 

 There are two divisions of the post-stomach (p.st.) which together are shorter than the stomach. The 

 mid-intestine (m.i.) is a short chamber lying horizontally at the lowest part of the gut loop. At its 

 junction with the mid-intestine the rectum (r) bears a pair of caeca. The rectum passes directly up 

 to the base of the thorax where it ends in a simple anus situated opposite the 22nd row of stigmata in 

 zooids with twenty-eight rows. 



Gonads. No zooid examined had an ovary. A testis was present in a few zooids and constituted 

 a series of rounded follicles (t) occupying much of the length of the post-abdomen. The sperm duct 

 (s.d.) leads straight forward towards the base of the thorax, but its terminal part could not be seen. 



Remarks. Four species of Ritterella have been described from the waters surrounding New Zealand 

 and as Table 14 shows, these are all clearly different from the present species. 



R. novae-zealandiae (Brewin) 

 R. opaca (Brewin) 

 R. aurea (Brewin) 

 R. arenosa (Brewin) 

 R. vestita sp.n. 



Table 14 



No. rows stigmata 



3, each of 21-25 

 3, each of 9 or 10 

 3, each of 15-17 

 9 or 10, each of 20-24 

 27-34, eac h °f 40-50 



Oesophagus Stomach 



Much longer than stomach Smoooth 



Much longer than stomach 4 folds 



Much longer than stomach 3 or 4 folds 



Short Smooth 



Shorter than stomach 8-10 folds 



Other species of Ritterella are known from Kamchatka and Sakhalin (R. clavata (Oka)), from 

 Japan (R. pedunculata Tokioka, R. yamazi Tokioka) and from the west coast of North America 

 (R. pulchra (Ritter), R. aequali-siphonalis (Ritter & Forsyth)). All of these species, however, are quite 

 distinct from R. vestita. 



The genus, as known at present, is confined to the Pacific Ocean. 



Distribution. North Island, New Zealand. 



Family DIDEMNIDAE Giard, 1872 

 Genus Didemnum Savigny, 1816 

 Didemnum studeri Hartmeyer 

 Didemnum studeri Hartmeyer, 191 1, p. 538. 



Occurrence. St. 56: Falkland Islands, 10-5-16 m. St. 399: Gough Island, 142-102 m. St. WS 

 246: Falkland Islands, 267-208 m. St. MS 71 : S. Georgia, 110-60 m. 



Colony. The preserved specimens are dirty white or pale buff grey. They are thin encrusting 

 sheets, some of them investing the tubes of worms, and may reach 7 cm. in greatest diameter. There are 

 a few inconspicuous common cloacal openings. The spicules range from 10 to 40 // in diameter and 

 most are under 20 ft. The rays are irregular and short, and some spicules are almost spherical in 

 outline. 



Zooid. The zooid has a rather larger atrial opening than has been described in previous accounts ; 

 there is no atrial languet or at most a small upper lip over the opening. A long slender retractor 

 process extends downwards from the lower end of the thorax. 



Gonads. No ovaries are developed in these specimens. The structure of the testis in the ' Discovery ' 

 material is, in Table 15, compared with previous accounts. 



Distribution. Subantarctic (Kerguelen, Magellanic region, Chatham Islands, Aukland, Stewart 

 Island, Macquarie Island, Tasmania, Gough Island, Falkland Islands), Antarctic (South Georgia). 



Remarks. In spite of certain differences in detail, particularly in the testis and sperm duct, the 





