9 8 DISCOVERY REPORTS 



Genus Alloeocarpa Michaelsen, 1900 



Alloeocarpa incrustans (Herdman) (Text-fig. 33 C; PI. V, fig. 8) 



Synstyela incrustans Herdman 1886 (in part; not Philippine specimens), p. 342, pi. 46, figs. 9-14. 

 For synonymy see van Name 1945, p. 239 



Occurrence. St. 48: Falkland Islands, 1 05-1 15 m. St. 51 : Falkland Islands, 1 05-1 15 m. St. 52: 

 Falkland Islands, 17 m. St. 55: Falkland Islands, 10-16 m. St. 56: Falkland Islands, 10-5-16 m. 

 St. 58: Falkland Islands, 1-2 m. St. 141 : S. Georgia, 17-27 m. St. 145: S. Georgia, 26-35 m. 

 St. 388: Cape Horn, 121 m. St. 474: S. Georgia, 199 m. St. 1230: Magellan Strait, 27 m. St. 1941 : 

 S. Georgia, 55-22 m. St. WS 65 : S. Georgia, shore collection. St. WS 71 : Falkland Islands, 82-80 m. 

 St. WS84: Falkland Islands, 75-74 m. St. WS86: Patagonian Shelf, I5i-i47m. St. WS216: 

 Patagonian Shelf, 219-133 m. St. WS 247: Falkland Islands, 172 m. St. WS 765: Patagonian Shelf, 

 113-1191x1. St. MS 6: S. Georgia, 24-30 m. St. MS 10: S. Georgia, 26-18 m. St. MS 33 : S. Georgia, 

 40 m. St. MS 64: S. Georgia, 7-15 m. St. MS 67: S. Georgia, 38 m. St. MS 74: S. Georgia, 22- 

 40 m. 



External appearance (PI. V, fig. 8). Colonies vary from solid fleshy masses with no free space 

 between zooids to forms in which the zooids are separate and united only by a thin basal membrane 

 of test. In the preserved state the colour is brown or grey, but according to the collector's note 

 accompanying colonies from St. WS 765 they may be 'brick red' or 'lemon yellow' in life. 



Branchial sac. A number of species, subspecies and forms have been described by various 

 authors, differing mainly in the number of longitudinal branchial bars, and the number and shape of 

 the gonads. After examining many colonies from the 'Discovery' collections I have not found any 

 consistent differences in these characters. For example, Michaelsen (1904) separated two species, 

 A. zschaui and A. incrustans, by the former having sixteen or seventeen branchial bars and the ovi- 

 ducts wider than long, and the latter having twelve to fourteen bars and the oviducts longer than 

 wide. But in the 'Discovery' collections specimens are found with sixteen bars and the oviducts 

 longer than wide (St. 1941), thus combining characters of both species, and other specimens (St. 58) 

 have an even greater number of bars (twenty-two) together with similar oviducts. There is therefore 

 no reason to separate colonies on the basis of these characters. Van Name (1945) regards A. zschaui 

 as identical with A. incrustans, but Arnback (1950) allows it the rank of & form of A. incrustans. 

 A few of the colonies approach Arnback's subspecies, A. incrustans rugosa, but in this case also I doubt 

 whether the points of distinction merit the status of a subspecies. 



Gonads. In nearly all specimens the testes are confined to the left and the ovaries to the right of 

 the body, but I have found a few in which two or three ovaries are present on the left side, immedi- 

 ately in front of the testes. 



Larva (Text-fig. 33C). In shape the larva is very similar to that of Polyzoa opuntia and P. reticulata. 

 The trunk varies a great deal in size, from 0-34 up to o-8 mm. and the tail is from 0-9 to i*a mm., 

 excluding the fin of test. The great variation in size of the trunk is surprising, but no accompanying 

 differences were found in structure of either the larva or the adult, so the character seems to have little 

 systematic importance in this species. There are the usual three papillae, single black sense organ 

 (only visible on dissection) and ring of anterior ampullae (eighteen to twenty-six in number). The 

 larva is red-brown in the preserved state. In some larvae there are distinct pigment spots on the 

 surface of the trunk, and these appear to be produced by pigment cells within the test. 



Biology. The presence or absence of larvae in the colonies of the collection is shown in Table 30. 

 The numbers are small, but it is evident that breeding is not confined to a short season, although it 

 probably occurs chiefly in the months of January to May, i.e. southern summer and autumn. 



