i m i-n ! cO ! □ ; m '. LO i o :D 5 O : rn DISCOVERY REPORTS Vol. XXX, pp. 1-160 Issued by the National Institute of Oceanography ASCIDIACEA by R. H. Millar CAMBRIDGE AT THE UNIVERSITY PRESS 1960 Price seventy shillings net DISCOVERY REPORTS VOLUME XXX DISCOVERY REPORTS Issued by the National Institute of Oceanography VOLUME XXX CAMBRIDGE AT THE UNIVERSITY PRESS 1962 PUBLISHED BY THE SYNDICS OF THE CAMBRIDGE UNIVERSITY PRESS Bentley House, 200 Euston Road, London, N.W. 1 American Branch: 32 East 57th Street, New York 22, N.Y. West African Office: P.O. Box 33, Ibadan, Nigeria Printed in Great Britain at the University Press, Cambridge (Brooke Crutchley, University Printer) CONTENTS ASCIDIACEA (published 12th February i960) By R. H. Millar Introduction pa„e ~ List of New Genera, Species and Forms ... -3 Classification _ Systematic List of Species in the Collection 4 List of Stations, and Species Collected at Each 7 Abbreviations used in Text-Figures 2a Description of Species 2. Geographical Distribution I4- Local Distribution ,„ Geographical Speciation te2 The Size of South Polar Ascidians j„ References It., Index to Genera and Species Icn Plates I- VI ............. following page 160 THE DISTRIBUTION OF PELAGIC POLYCHAETES IN THE SOUTH ATLANTIC OCEAN (published 27th May i960) By Norman Tebble Introduction paae ifa Acknowledgements ^4 Material and Methods t^A Systematic Account ^o Tomopteridae 170 Alciopidae ig* Typhloscolecidae !04 Phyllodocidae 200 Aphroditidae 205 Zoogeography 206 1. Hydrological environment 206 2. Distribution of species . . . 218 Zoogeographical Review 261 List of References 264 Appendix I 269 Appendix II 284 80441 vi CONTENTS STUDIES ON PHY S ALIA PH Y SA LIS (L) (published 4th November i960) By A. K. Totton and G. O. Mackie Part 1. Natural History and Morphology By A. K. Totton Introduction page 303 Acknowledgements 303 Material and Methods 303 Non-Technical Description of the Portuguese Man-of-War 306 Appearance and Habits 307 Morphology 326 Origin of Physalia and the Siphonophora: the Paedophore Hypothesis . . . 358 Distribution 363 Summary 365 References 366 Plates VII-XXV following page 408 Part 2. Behaviour and Histology By G. O. Mackie Introduction page 371 Behaviour 372 Histology 378 Discussion 403 Summary 403 References 405 Plates XXVI-XXVIII following page 408 PUBLISHED BY THE SYNDICS OF THE CAMBRIDGE UNIVERSITY PRESS Bentley House, 200 Euston Road, London, N.W. 1 American Branch : 32 East 57th Street, New York 22, N.Y. Printed in Great Britain at the University Press, Cambridge (Brooke Crutchley, University Printer) [Discovery Reports. Vol. XXX, pp. 1-160, Plates I-VI, text-figures 1-72, February, i960.] ASCIDIACEA By R.H.MILLAR Marine Station, Millport <* w.a WOODS HOLE, MASS. CONTENTS Introduction page 3 List of new Genera, Species and Forms 3 Classification 3 Systematic List of Species in the Collection 4 List of Stations and Species Collected at Each 7 Abbreviations used in Text-Figures 24 Description of Species 24 Geographical Distribution 147 Local Distribution 15 1 Geographical Speciation 152 The Size of South Polar Ascidians 153 References 154 Index to Genera and Species 157 Plates I-VI following page 160 ASCIDIACEA By R. H. Millar Marine Station, Millport (Plates I-VI, text-figs. 1-72) INTRODUCTION The ascidians which this report describes were collected during the years 1925-37 by R.R.S. 'Discovery', R.R.S. 'Discovery II', R.R.S. 'William Scoresby', and the staff of the Marine Biological Station at South Georgia. A large part of the material is from the Falkland Islands and Patagonian shelf in the Subantarctic, and much was also collected from the vicinity of Graham Land, South Georgia and the South Shetland, South Orkney, and South Sandwich Islands in the Weddell Sea sector of the Antarctic. Of the many other localities represented, one of the most interesting is the Three Kings district at the northern end of New Zealand. There are altogether about 2500 specimens, representing seventy-eight identifiable species. Of these, thirteen are described as new and there are three new forms of known species. The type specimens are deposited in the British Museum (Nat. Hist.). LIST OF NEW GENERA, SPECIES AND FORMS Aplidium falklandicum sp.n. Podoclavella kottae sp.n. A. stanleyi sp.n. Sycozoa anomala sp.n. A. quadrisulcatum sp.n. Cnemidocarpa tricostata sp.n. A. seeligeri sp.n. Styela schmitti f. simplex n. Aplidiopsis discoveryi sp.n. Molgula setigera f. georgiana n. Protopolyclinum gen.n. ,, >> *■ ^nanoni n. P. pedunculatum sp.n. Eugyra brezvinae sp.n. Ritterella vestita sp.n. E. drnbdckae sp.n. Didemnum trivolutum sp.n. The task of working through the material was greatly eased by the fact that Dr A. Arnback-Christie- Linde had completed the process of sorting the collection before her death. She also made prelimi- nary identifications of a number of the specimens and left notes on some of them. Her notes, which were made available to me, have been very valuable. Nevertheless, I have had to re-examine all the material, and this report represents my own views, which differ in many points from those which Dr Arnback-Christie-Linde would have expressed had she lived to write the account of the Ascidiacea from the ' Discovery ' collections. CLASSIFICATION I have adopted the classification used by Huus (1937-40) in Kiikenthal and Krumbach's Handbuch der Zoologie, with the following modifications : In the order Enterogona, suborder Phlebobranchiata I have recognized the family Diazonidae Garstang, 1891, as distinct from the family Cionidae Lahille, 1887, using these groups as defined by Berrill (1950). Ciona occupies a somewhat isolated and probably primitive position, indicated especially by the failure of the two epicardia to fuse and by the position of the gut (Berrill, 1936), and therefore merits a family to distinguish it from the diazonids (Diazona, Tylobranchion, Rhopalea). 4 DISCOVERY REPORTS In the order Pleurogona, suborder Stolidobranchiata, I have again followed Berrill (1950), who gave convincing reasons for dividing the family Styelidae Sluiter, 1895, into two subfamilies only, Botryllinae Adams, 1858, and Styelinae Herdman, 1881, although Huus and others have recognized a third subfamily Polyzoinae Hartmeyer 1903. Two minor points in which the present classification differs from that of Huus concern the genera Herdmania Lahille, 1887, and Bathypera Michaelsen, 1904. I have used the generic name Herdmania for the species H. momns (Savigny), although Huus used it for a polyclinid species generally referred to as Euherdmania claviformis (Ritter). The generic name Herdmania was preoccupied when Ritter (1903) proposed it, as he himself later recognized (Ritter, 1904). The position of Bathypera is still doubtful, and although Huus placed this genus in the family Molgulidae, I believe that a number of characters show it to be better placed in the family Pyuridae. SYSTEMATIC LIST OF SPECIES IN THE COLLECTION Order ENTEROGONA Perrier, 1898 Suborder APLOUSOBRANCHIATA Lahille, 1886 Family POLYCLINIDAE Verrill, 1871 Subfamily Polyclininae Adams, 1858 Genus Aplidium Savigny, 1816 A. circumvolutwn (Sluiter) A. caeruleum (Sluiter) A. fuegiense Cunningham A. stanleyi sp.n. A. variabile (Herdman) A. qnadrisidcatum sp.n. A. falklandicum sp.n. A. seeligeri sp.n. A. radiatum (Sluiter) Genus Synoicum Phipps, 1774 S. adareanum (Herdman) S. giardi (Herdman) S. georgianum Sluiter S. kuranui Brewin Genus Aplidiopsis Lahille, 1890 A. discoveryi sp.n. Genus Protopolyclinum gen.n. P. pednnculatum sp.n. Subfamily Euherdmaniinae Seeliger, 1906 Genus Ritterella Harant, 1931 R. vestita sp.n. Family DIDEMNIDAE Giard, 1872 Genus Didemnum Savigny, 181 6 D. studeri Hartmeyer D. trivolutum sp.n. D. biglans (Sluiter) Genus Leptoclinides Bjerkan, 1905 L. diemenensis Michaelsen Genus Trididemnum Delia Valle, 1881 T. auriculatum Michaelsen SYSTEMATIC LIST OF SPECIES IN THE COLLECTION Family CLAVELINIDAE Forbes & Hanley, 1848 Subfamily Clavelininae Seeliger, 1906 Genus Podoclavella Herdman, 1890 P. cylindrica (Quoy & Gaimard) P. kottae sp.n. Genus Clavelina Savigny, 181 6 C. claviformis (Herdman) Subfamily Polycitorinae Michaelsen, 1904 Genus Sycozoa Lesson, 1830 S. sigillinoides Lesson S. anomala sp.n. S. georgiana (Michaelsen) Genus Distaplia Delia Valle, 1881 D. colligans Sluiter D. cylindrica (Lesson) Genus Hypsistozoa Brewin, 1953 H. jasmeriana (Michaelsen) Genus Cystodytes van Drasche, 1883 C. dellechiajei (Delia Valle) C. dellechiajei f. antarctica (Sluiter) Genus Atapozoa Brewin, 1956 A. marshi Brewin Suborder PHLEBOBRANCHIATA Lahille, 1886 Family DIAZONIDAE Garstang, 1891 Genus Tylobranchion Herdman, 1886 T. speciosum Herdman Family ASCIDIIDAE Adams, 1858 Genus Ascidia Linnaeus, 1767 A. translucida Herdman A. interrupta Heller A. challengeri Herdman A. sydneiensis Stimpson Family AGNESIIDAE Huntsman, 191 2 Genus Agnesia Michaelsen, 1898 A. glaciata Michaelsen Genus Caenagnesia Arnback, 1938 C. bocki Arnback Family CORELLIDAE Lahille, 1887 Subfamily Corellinae Herdman, 1882 Genus Corella Alder & Hancock, 1870 C. eumyota Traustedt DISCOVERY REPORTS Order PLEUROGONA Perrier, 1898 Suborder STOLIDOBRANCHIATA Lahille, 1886 Family STYELIDAE Sluiter, 1895 Subfamily Botryllinae Adams, 1858 Genus Botryllus Gaertner, 1774 }B. separatus Sluiter Genus Polyzoa Lesson, 1830 P. opuntia Lesson P- reticulata (Herdman) Genus Alloeocarpa Michaelsen, 1900 A. incrustans (Herdman) Genus Amphicarpa Michaelsen, 1922 A. diptycha (Hartmeyer) Subfamily Styelinae Herdman, 1881 Genus Cnemidocarpa Huntsman, 191 2 C. pfefferi (Michaelsen) C. verrucosa (Lesson) C. nordenskjoldi (Michaelsen) C. tricostata sp.n. C. drygalskii (Hartmeyer) Genus Styela Fleming, 1822 S. schmitti van Name f. simplex n. S. paessleri Michaelsen S. insinuosa (Sluiter) S. partita (Stimpson) S. magalhaensis Michaelsen Family PYURIDAE Hartmeyer, 1908 Genus Pyura Molina, 1782 P. stolonifera (Heller) P. georgiana (Michaelsen) P. setosa (Sluiter) P. bouvetensis (Michaelsen) P. discoveryi (Herdman) P- jacatrensis (Sluiter) P. squamata Hartmeyer P- vittata (Stimpson) P. legumen (Lesson) Genus Herdmania Lahille, 1887 H. momus (Savigny) Genus Bathypera Michaelsen, 1904 B. splendens Michaelsen Family MOLGULIDAE Lacaze-Duthiers, 1877 Genus Molgula Forbes & Hanley, 1848 M. pedunculata Herdman M. bacca Herdman M. falsensis Millar M. setigera Arnback f. georgiana n. M. platei Hartmeyer M. setigera Arnback f. marioni n. M. malvinensis Arnback M. sabulosa (Quoy & Gaimard) LIST OF STATIONS AND SPECIES COLLECTED AT EACH 7 Genus Ascopera Herdman, 1881 A. gigantea Herdman Genus Paramolgula Traustedt, 1885 P. gregaria (Lesson) Genus Eugyra Alder & Hancock, 1870 E. kerguelenensis Herdman E. drnbdckae sp.n. E. brewinae sp.n. LIST OF STATIONS AND SPECIES COLLECTED AT EACH R.R.S. 'Discovery' Station 1. 16. xi. 25. Clarence Bay, Ascension Island, 70 55' 15" S., 140 25' W. Medium rect- angular net, coralline, sand and shells, 16-27 m- Pyura vittata (Stimpson). 1 specimen. Station 2. 17. xi. 25. Clarence Bay, Ascension Island, St Catherine's Pt. and Collyer Pt. Shore collection. Styela partita (Stimpson). 2 specimens. Station 27. 15. iii. 26. West Cumberland Bay, South Georgia; 3-3 miles S. 440 E. of Jason Lt. Large dredge, mud and rock, no m. lAplidium fuegiense Cunningham. 1 specimen. Pyura discoveryi (Herdman). 29 specimens. A. radiatum (Sluiter). 2 specimens. Molgula pedunculata Herdman. 23 specimens. Cnemidocarpa tricostata sp.n. 1 specimen. Station 39. 25. iii. 26. East Cumberland Bay, South Georgia. From 8 cables S. 81 ° W. of Merton Rock to 1-3 miles N. 70 E. of Macmahon Rock. Large otter trawl, grey mud, 179-235 m. Aplidium circumvolutum (Sluiter). 1 specimen. Cnemidocarpa verrucosa (Lesson). 4 specimens. Sycozoa georgiana (Michaelsen). 5 specimens. Pyura georgiana Michaelsen. 2 specimens. Distaplia cylindrica (Lesson). 2 specimens. Molgula pedunadata Herdman. 7 specimens. Ascidia translucida Herdman. 1 specimen. Ascopera gigantea Herdman. 2 specimens. Station 42. i.iv. 26. Off mouth of Cumberland Bay, South Georgia. From 6-3 miles N. 890 E. to 4 miles N. 390 E. of Jason Lt. Large otter trawl, mud, 120-204 m. Caenagnesia bocki Arnback. 1 specimen. Pyura discoveryi (Herdman). 44 specimens. Polyzoa reticulata (Herdman). 1 specimen. P. georgiana Michaelsen. 4 specimens. Cnemidocarpa pfefferi (Michaelsen). 1 specimen. Molgula pedunculata Herdman. 2 specimens. C. verrucosa (Lesson). 1 specimen. Ascopera gigantea Herdman. 8 specimens. Station 45. 6. iv. 26. 27 miles S. 850 E. of Jason Lt., South Georgia. Large otter trawl, grey mud, 238-270 m. Sycozoa sigillinoides Lesson. 3 specimens. Molgula pedunculata Herdman. 10 specimens. Distaplia cylindrica (Lesson). 1 specimen. Ascopera gigantea Herdman. 24 specimens. Cnemidocarpa verrucosa (Lesson). 7 specimens. Station 48. 3. v. 26. 8-3 miles N. 530 E. of William Pt. Beacon, Port William, Falkland Islands. Large otter trawl, sand and shell, 105-115 m. Alloeocarpa incrustans (Herdman). 1 specimen. 8 DISCOVERY REPORTS Station 51. 4. v. 26. Off Eddystone Rock, East Falkland Island. From 7 miles N. 500 E. to 7-6 miles N. 630 E. of Eddystone Rock. Large otter trawl, fine sand, 105-115 and 115 m. Aplidium fuegiense Cunningham. 1 specimen. Polyzoa reticulata (Herdman). 1 specimen. A. falklandicum sp.n. 2 specimens. Alloeocarpa incnistans (Herdman). 2 specimens. Sycozoa sigillinoides Lesson. 7 specimens. Paramolgula gregaria (Lesson). 1 specimen. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station 52. 5. v. 26. Port William, East Falkland Island, 7-4 cables N. 170 E. of Navy Pt. Hand lines, 17 m. Alloeocarpa incrustans (Herdman). 1 specimen. Paramolgula gregaria (Lesson). 1 specimen. Pyura legumen (Lesson). 4 specimens. Station 53. 12. v. 26. Port Stanley, East Falkland Island. Hulk of ' Great Britain '. Mussel rake, 0-2 m. Aplidium falklandicum sp.n. 1 specimen. Styela paessleri Michaelsen. 4 specimens. Sycozoa sigillinoides Lesson. 28 specimens. Pyura legumen (Lesson). 1 specimen. Cnemidocarpa nordenskjoldi (Michaelsen). 4 specimens. Paramolgula gregaria (Lesson). 9 specimens. C. verrucosa (Lesson). 7 specimens. Station 55. 16. v. 26. Entrance to Port Stanley, East Falkland Island, 2 cables S. 24° E. of Navy Pt. Small beam trawl, 10-16 m. Corella eumyota Traustedt. 4 specimens. Pyura legumen (Lesson). 1 specimen. Cnemidocarpa verrucosa (Lesson). 4 specimens. Paramolgula gregaria (Lesson). 2 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Station 56. 16. v. 26. Sparrow Cove, Port William, East Falkland Island, 1-5 cables N. 500 E. of Sparrow Pt. Small beam trawl, 10-5-16 m. Didemnum studeri Hartmeyer. 2 specimens. Pyura legumen (Lesson). 7 specimens. Alloeocarpa incrustans (Herdman). 3 specimens. Paramolgula gregaria (Lesson). 1 specimen. Station 57. 16. v. 26. Port William, East Falkland Island, 5-5 cables S. 200 W. of Sparrow Pt. Small beam trawl, 15 m. Pyura legumen (Lesson). 2 specimens. Paramolgula gregaria (Lesson). Station 58. 19. v. 26. Port Stanley, East Falkland Island. Mussel rake, 1-2 m. Polyzoa reticulata (Herdman). 13 specimens. Cnemidocarpa verrucosa (Lesson). 32 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Paramolgula gregaria (Lesson). 3 specimens. Station 90. 10. vii. 26. Simon's Town, False Bay, South Africa. Basin of H.M. Dockyard. Hand net, 0-2 m. Ascidia sydneiensis Stimpson. 1 specimen. Pyura stolonifera (Heller). 2 specimens. Station 91. 8. ix. 26. 0-5 mile off Roman Rock, False Bay, South Africa. Small rectangular net, sand, 35 m. Agnesia glaciata Michaelsen. 1 specimen. Molgula falsensis Millar. 6 specimens. Station 123. 15. xii. 26. Off mouth of Cumberland Bay, South Georgia. From 4-1 miles N. 540 E. of Larsen Pt. to 1-2 miles S. 620 W. of Merton Rock. Large otter trawl, grey mud, 230-250 m. Distaplia cylindrica (Lesson). 4 specimens. ?Styela magalhaensis Michaelsen. 2 specimens. Tylobranchion speciosum Herdman. 1 specimen. Pyura georgiana Michaelsen. 8 specimens. Cnemidocarpa pfefferi (Michaelsen). 1 specimen. Molgula pedunculata Herdman. 20 specimens. C. verrucosa (Lesson). 1 specimen. Ascopera gigantea Herdman. 5 specimens. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 9 Station 140. 23. xii. 26. Stromness Harbour to Larsen Pt., South Georgia. From 540 02' S., 360 38' W. to 540 11' 30" S., 360 29' W. Large otter trawl, green mud and stones, 122-136 m. Synoicum georgiamim Sluiter. 1 specimen. Pyura discoveryi (Herdman). 42 specimens. Sycozoa georgiana (Michaelsen). 1 specimen. P. georgiana Michaelsen. 5 specimens. Distaplia cylindrica (Lesson). 1 specimen. Molgula pedunculata Herdman. 5 specimens. Polyzoa reticulata (Herdman). 1 specimen. Ascopera gigantea Herdman. 2 specimens. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station 141. 29. xii. 26. East Cumberland Bay, South Georgia, 200 yards from shore, under Mt. Druse. Small beam trawl, mud, 17-27 m. Polyzoa reticulata (Herdman). 2 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Station 142. 30. xii. 26. East Cumberland Bay, South Georgia. From 540 11' 30" S., 360 35' W. to 540 12' S., 360 29' 30" W. Large otter trawl, mud, 88-273 m- Distaplia cylindrica (Lesson). 1 specimen. Station 143. East Cumberland Bay, South Georgia. 540 12' S., 360 29' 30" W. Large otter trawl, mud, 273 m. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station 144. $.i. 27. Off mouth of Stromness Harbour, South Georgia. From 540 04' S., 36°27' W. to 530 58' S., 360 26' W. Large otter trawl, green mud and sand, 155-178 m. Synoicum georgianum Sluiter. 3 specimens. P. georgiana Michaelsen. 5 specimens. Tylobranchion speciosum Herdman. 5 specimens. Molgula pedunculata Herdman. 7 specimens. Pyura discoveryi (Herdman). 25 specimens. Station 145. 7. i. 27. Stromness Harbour, South Georgia. Between Grass Island and Tonsberg Pt. Small beam trawl, 26-35 m- Sycozoa sigillinoides Lesson. 8 specimens. Alloeocarpa incrustans (Herdman). 2 specimens. Ascidia challengeri Herdman. 1 specimen. Pyura georgiana Michaelsen. 1 specimen. Polyzoa opuntia Lesson. 1 specimen. Station 148. 9. i. 27. Off Cape Saunders, South Georgia. From 540 03' S., 360 39' W. to 540 05' S., 360 36' 30" W. Large otter trawl, grey mud and stones, 132-148 m. Distaplia cylindrica (Lesson). 4 specimens. Pyura discoveryi (Herdman). 10 specimens. Polyzoa reticulata (Herdman). 1 specimen. P. georgiana Michaelsen. 1 specimen. Cnemidocarpa verrucosa (Lesson). 2 specimens. Station 149. 10. i. 27. Mouth of East Cumberland Bay, South Georgia. From 1-15 miles N. 76^° W. to 2-62 miles S. n° W. of Merton Rock. Large otter trawl, mud, 200-234 m. Synoicum georgianum Sluiter. 1 specimen. Distaplia cylindrica (Lesson). 1 specimen. Sycozoa georgiana (Michaelsen). 3 specimens. Station 152. 17. i. 27. 530 51' 30" S., 360 18' 30" W. Large dredge, rock, 245 m. Pyura discoveryi (Herdman). 3 specimens. Ascopera gigantea Herdman. 1 specimen. P. georgiana Michaelsen. 1 specimen. Station 156. 20. i. 27. 530 51' S., 360 21' 30" W. Large dredge, rock, 200-236 m. Ascidia challengeri Herdman. 3 specimens. Pyura georgiana Michaelsen. 1 specimen. Styela insinuosa (Sluiter). 1 specimen. Ascopera gigantea Herdman. 1 specimen. IO DISCOVERY REPORTS Station 159. 21. i. 27. 530 52' 30" S., 360 08' W. Large dredge, rock, 160 m. Cnemidocarpa pfefferi (Michaelsen). 1 specimen. Molgula malvinensis Arnback. 3 specimens. C. verrucosa (Lesson). 4 specimens. M. setigera Arnback f. georgiana n. 4 specimens. Pyura discoveryi (Herdman). 10 specimens. Ascopera gigantea Herdman. 1 specimen. Station 160. 7. ii. 27. Near Shag Rocks, 530 43' 40" S., 400 57' W. Large dredge, stones and rock, 177 m. Aplidium variabile (Herdman). 21 specimens. Cnemidocarpa verrucosa (Lesson). 1 specimen. Tylobranchion speciosum Herdman. 2 specimens. Pyura discoveryi (Herdman). 2 specimens. Ascidia challengeri Herdman. 2 specimens. Molgula pedunculata Herdman. 1 specimen. Station 164. 18. ii. 27. East end of Normanna Strait, South Orkneys, near C. Hansen, Corona- tion Island. Small beam trawl, 24-36 m. Aplidium radiatum (Sluiter). 1 specimen. Distaplia colligans Sluiter. 1 specimen. A. falklandicum sp.n. 7 specimens. Ascidia challengeri Herdman. 2 specimens. Station 170. 23. ii. 27. Off Cape Bowles, Clarence Island, 6i° 25' 30" S., 530 46' W. Large dredge, rock, 342 m. Aplidium circumvolutum (Sluiter). 4 specimens. P. bouvetensis (Michaelsen). 8 specimens. Pyura discoveryi (Herdman). 1 specimen. Station 175. 2. iii. 27. Bransfield Strait, South Shetlands, 630 17' 20" S., 590 48' 15" W. Large dredge, mud, stones and gravel, 200 m. Aplidium circumvolutum (Sluiter). 1 specimen. Pyura setosa (Sluiter). 1 specimen. Synoicum adareanum (Herdman). 2 specimens. Molgula bacca Herdman. 1 specimen. Station 177. 5. iii. 27. 27 miles south-west of Deception I., South Shetlands. 630 17' 30" S., 6i° 17' W. Large dredge, mud, coarse sand and stones, 1080 m. Pyura discoveryi (Herdman). 1 specimen. Station 181. 12. iii. 27. Schollaert Channel, Palmer Archipelago, 640 20' S., 63°oi'W. Large otter trawl, mud, 160-335 m- Aplidium radiatum (Sluiter). 6 specimens. Pyura bouvetensis (Michaelsen). 2 specimens. Cystodytes dellechiajei f. antarctica (Sluiter). 1 specimen. Bathypera splendens Michaelsen. 1 specimen. Caenagnesia bocki Arnback. 1 specimen. Station 182. 14. iii. 27. Schollaert Channel, Palmer Archipelago, 64°2i'S., 620 58' W. Large otter trawl, mud, 278-500 m. Didemtium biglans (Sluiter). 1 specimen. Caenagnesia bocki Arnback. 4 specimens. Station 186. 16. iii. 27. Fournier Bay, Anvers Island, Palmer Archipelago, 640 25' 30" S., 630 02' W. Large dredge, mud, 295 m. Aplidium radiatum (Sluiter). 1 specimen. Station 187. 18. iii. 27. Neumayr Channel, Palmer Archipelago, 640 48' 30" S., 630 31' 30" W. Large otter trawl, mud, 259-354 m- Didemnum biglans (Sluiter). 1 specimen. P. squamata Hartmeyer. 1 specimen. Cnemidocarpa drygalskii (Hartmeyer). 3 specimens. P. bouvetensis (Michaelsen). 49 specimens. Pyura discoveryi (Herdman). 1 specimen. Station 189. 23. iii. 27. Port Lockroy, Wienke Island, Palmer Archipelago. Hand net, o m. Distaplia cylindrica (Lesson). 1 specimen. LIST OF STATIONS AND SPECIES COLLECTED AT EACH n Station 190. 24. iii. 27. Bismarck Strait, Palmer Archipelago, 640 56' S., 650 35' W. Large dredge, stones, mud and rock, 93-126, and 315 m. Aplidium circumvolutum (Sluiter). 3 specimens. Cnemidocarpa verrucosa (Lesson). 1 specimen. A. radiatum (Sluiter). 3 specimens. Pyura discoveryi (Herdman). 1 specimen. A. caendeum (Sluiter). 1 specimen. P. bouvetensis (Michaelsen). 8 specimens. Cystodytes dellechiajeii. antarctica (Sluiter). 1 specimen. Molgula pedunculata Herdman. 1 specimen. Station 195. 30. iii. 27. Admiralty Bay, King George Island, South Shetlands, 620 07' S., 580 28' 30" W. Medium otter trawl, mud and stones, 391 m. Ascidia challenged Herdman. 6 specimens. Ascopera gigantea Herdman. 1 specimen. Pyura bouvetensis (Michaelsen). 3 specimens. Station 279. 10. vii. 27. Off Cape Lopez, French Congo. From 8-5 miles N. 710 E. to 15 miles N. 240 E. of Cape Lopez Lt. Large otter trawl, mud and fine sand, 58-67 m. Ascidia interrupta Heller. 3 specimens. Station 363. 26. ii. 30. 2-5 miles S. 8o° E. of S.E. point of Zavodovski Island, South Sandwich Islands. Large dredge, 329-278 m. }Sycozoa georgiana (Michaelsen). 7 specimens. Station 366. 6. iii. 30. 4 cables south of Cook Island, South Sandwich Islands. Large dredge, black sand, 155-322 m. Distaplia cylindrica (Lesson). 7 specimens. Ascopera gigantea Herdman. 27 specimens. Cnemidocarpa verrucosa (Lesson). 10 specimens. Eugyra drnbdckae sp.n. 46 specimens. Station 370. 10. iii. 30. 2 miles north-east of Bristol Island, South Sandwich Islands. Large otter trawl, 18-80 m. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station 371. 14. iii. 30. 1 mile east of Montagu Island, South Sandwich Islands. Large otter trawl, 99-161 m. Tylobranchion speciosum Herdman. 2 specimens. Ascopera gigantea Herdman. 5 specimens. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station 388. 16. iv. 30. 560 19' 30" S., 670 09' 45" W. Large dredge, 121 m. Styela schmitti van Name f. simplex n. 6 specimens. Alloeocarpa incrustans (Herdman). 35 specimens. Station 399. 18. v. 30. 1 mile S.E. of S.W. point of Gough Island. Large dredge, 141-102 m. Didemnum studeri Hartmeyer. 1 specimen. Station 474. 12. xi. 30. 1 mile west of Shag Rocks, South Georgia. Large dredge, 199 m. Synoicum georgianum Sluiter. 1 specimen. Styela insinuosa (Sluiter). 2 specimens. Polyzoa reticulata (Herdman). 1 specimen. Pyura discoveryi (Herdman). 11 specimens. Alloeocarpa incrustans (Herdman). 2 specimens. Molgula malvinensis Arnback. 2 specimens. Cnemidocarpa verrucosa (Lesson). 1 specimen. M. setigera Arnback f. georgiana n. 1 specimen. Station 476. 12. xi. 30. 1 mile north of Shag Rocks, South Georgia. 1 m. tow-net, 165-0 m. (net touched bottom). Distaplia colligans Sluiter. 1 specimen. Station 599. 17. i. 31. 670 08' S., 690 06' 30" W. Large dredge, 203 m. Cnemidocarpa verrucosa (Lesson). 1 specimen. Molgula pedunculata Herdman. 1 specimen. Pyura bouvetensis (Michaelsen). 1 specimen. 12 DISCOVERY REPORTS Station 600. 17. i. 31. 670 09' S., 690 27' W. Large otter trawl, 501-527 m. Pyura bouvetensis (Michaelsen). 3 specimens. Station 652. 14. iii. 31. Burdwood Bank, 540 04' S., 6i°4o'W. Large otter trawl, 171-169111. Large dredge, 164 m. Aplidium fuegiense Cunningham. 1 specimen. Sycozoa sigillinoides Lesson. 1 specimen. A. falklandicum sp.n. 3 specimens. Station 929. 16. viii. 32. 340 21' S., 1720 48' E. to 34° 22' S., 1720 49' 48" E. Large otter trawl, 58-55 m. Sycozoa anomala sp.n. 4 specimens. Clavelina claviformis (Herdman). 2 specimens. Station 934. 17. vii. 32. 340 11' 36" S., 1720 10' 54" E. to 340 11' 24" S., 1720 10' 18" E. Large otter trawl, 98-92 m. Protopolyclinum pedunculatum gen.n., sp.n. 4 specimens. Cystodytes dellechiajei (Delia Valle). 4 specimens. Ritterella vestita sp.n. 1 specimen. IBotryllus separatus Sluiter. 1 specimen. Podoclavella kottae sp.n. 1 specimen. Station 935. 17. viii. 32. 340 11' 30" S., 1720 08' 30" E. to 340 11' 54" S., 1720 08' 30" E. Large dredge, 84 m. ^Aplidium quadrisulcatum sp.n. 4 specimens. Hypsistozoa fasmeriana (Michaelsen). 1 specimen. A. seeligeri sp.n. 1 specimen. Atapozoa marshi Brewin. 2 specimens. Synoiciun kuratmi Brewin. 6 specimens. Cystodytes dellechiajei (Delia Valle). 3 specimens. Leptoclinides diemenensis Michaelsen. 1 specimen. Station 936. 18. viii. 32. 350 03' 30" S., 1720 58' 12" E. to 350 05' 24" S., 1720 58' 42" E. Large otter trawl, 50-57 m. Eugyra brewinae sp.n. 17 specimens. Station 939. 18. viii. 32. 350 49' 36" S., 1730 27' E. to 350 51' 36" S., 1730 28' 54" E. Large otter trawl, 87 m. Aplidium quadrisulcatum sp.n. 5 specimens. Agnesia glaciata Michaelsen. 4 specimens. Station 941. 20. viii. 32. 400 51' 24" S., 1740 48' 12" E. to 400 55' 48" S., 1740 46' 42" E. Large dredge, 128 m. Aplidium seeligeri sp.n. 1 specimen. Aplidiopsis discoveryi sp.n. 1 specimen. Station 1 1 13. 5.11.33. 630 04' 30" S., 620 15' W. Tow-net, 275-130 m. Distaplia colligans Sluiter. 1 specimen. Station 1 159. 17. iii. 33. 550 48' 42" S., 140 45' 12" E. Tow-net, 230-0 m. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station 1230. 23. xii. 33. 6-7 miles N. 620 W. from Dungeness Lt., Magellan Strait. Russell's bottom tow-net, 27 m. Sycozoa sigillinoides Lesson. 5 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Polyzoa opuntia Lesson. 13 specimens. Paramolgu/a gregaria (Lesson). 4 specimens. P. reticulata (Herdman). 1 specimen. Station 1563. 7. iv. 35. 460 48' 24" S., 370 49' 12" E. Large dredge, 113-99 m- and 101-106 m. ? Aplidium caeruleum (Sluiter). 1 specimen. Molgula setigera Arnback f. marioni n. 1 specimen. Pyura jacatrensis (Sluiter). 1 specimen. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 13 Station 1652. 23. i. 36. 750 56' 12" S., 1780 35' 30" W. Harvey's phytoplankton net, 567 m. Ascidia challengeri Herdman. 3 specimens. Corella eumyota Traustedt. 2 specimens. Station 1660. 27. i. 36. 740 46' 24" S., 1780 23' 24" E. Large otter trawl, 351 m. Synoiaim adareanum (Herdman). 5 specimens. Ascidia challengeri Herdman. 1 specimen. Station 1686. 4. iii. 36. 380 16' 6" S., 1440 40' 12" E. Queenscliffe Jetty, Port Philip, Victoria, Australia. Mussel rake, o m. Podoclavella cylindrica (Quoy & Gaimard). 1 specimen. Herdmania momus (Savigny). 1 specimen. Ascidia sydneiensis Stimpson. 1 specimen. Molgula sabulosa (Quoy & Gaimard). 1 specimen. Amphicarpa diptycha (Hartmeyer). 1 specimen. Station 1873. 13. xi. 36. 6i° 20' 48" S., 54° 04' 12" W. Russell rectangular dredge, 210-180 m. Ascopera gigantea Herdman. 1 specimen. Station 1900. 27-28. xi. 36. 490 49' 30" S., 66° 14' 24" W. to 490 49' 24" S., 66° 14' 48" W. 1 m. tow-net, 0-5 m. Distaplia cylindrica (Lesson). 1 specimen. Station 1902. 28. xi. 36. 490 48' S., 670 39' 30" W. 4 miles S. 320 E. of Cape San Fransisco de Paula Lt. Large otter trawl, 50-80 m. Aplidium j alklandicum sp.n. 4 specimens. Par amolgula gregaria (Lesson). 4 specimens. Polyzoa opuntia Lesson. 13 specimens. Station 1906. 29-30. xi. 36. 530 54' 36" S., 630 58' 6" W. 1 m. tow-net, 0-5 m. Distaplia cylindrica (Lesson). 2 specimens. Station 1 941. 29. xii. 36. Leith Harbour, South Georgia. Small dredge, 38 and 55-22 m. Synoicum georgianum Sluiter. 1 specimen. Eugyra kerguelenensis Herdman. 77 specimens. Alloeocarpa incrustans (Herdman). 2 specimens. Station 1948. 4. i. 37. 6o° 49' 24" S., 52° 40' W. Russell rectangular dredge, 490-610 m. Pyura discoveryi (Herdman). 1 specimen. Station 1952. 11. i. 37. Between Penguin Island and Lion's Rump, King George Island, South Shetlands. Russell rectangular dredge, 367-383 m. Aplidium caendeum Sluiter. 2 specimens. C. verrucosa (Lesson). 1 specimen. Cnemidocarpa pfefferi (Michaelsen). 1 specimen. Pyura bouvetensis (Michaelsen). 3 specimens. Station 1955. 29. i. 37. 6i° 35' 6" S., 570 23' 18" W. Russell rectangular dredge, 440-410 m. Pyura bouvetensis (Michaelsen). 1 specimen. R.R.S. 'William Scoresby' Station WS 25. 17. xii. 26. Undine Harbour (North), South Georgia. Small beam trawl, mud and sand, 18-27 m- Aplidium f alklandicum sp.n. 1 specimen. Cnemidocarpa verrucosa (Lesson). 1 specimen. Ascidia translucida Herdman. 2 specimens. Polyzoa reticulata (Herdman). 1 specimen. Station WS 27. 19. xii. 26. 530 55' S., 380 01' W. 1 m. tow-net, gravel, 104 and 107 m. Aplidium j 'alklandicum sp.n. 1 specimen. Ascidia challengeri Herdman. 1 specimen. Synoicum giardi (Herdman). 1 specimen. Polyzoa reticulata (Herdman). 1 specimen. Tylobranchion speciosum Herdman. 18 specimens. Molgula pedunculata Herdman. 1 specimen. i4 DISCOVERY REPORTS Station WS 33. 21. xii. 26. 540 59' S., 350 24' W. 1 m. horizontal tow-net 0-5 m., 1 m. horizontal tow-net, grey mud and stones, 1 30 m. Synoicum adareanum (Herdman). 1 specimen. Distaplia cylindrica (Lesson). 1 specimen. tSycozoa georgiana (Michaelsen). 1 specimen. Station WS 62. 19. i. 27. Wilson Harbour, South Georgia. Small beam trawl, 26-83 m. Pvura georgiana Michaelsen. 3 specimens. Station WS 65. 21. i. 27. Undine Harbour (North), South Georgia. Shore collection. Alloeocarpa incrustans (Herdman). 1 specimen. Station WS 71. 23. ii. 27. 6 miles N. 6o° E. of Cape Pembroke Lt., East Falkland Island. Com- mercial otter trawl, 82-80 m. Aplidium fuegiense Cunningham. 4 specimens. Cnemidocarpa nordenskjoldi (Michaelsen). 5 specimens. Polyzoa opuntia Lesson. 6 specimens. C. verrucosa (Lesson). 10 specimens. P. reticidata (Herdman). 1 specimen. Pyura legumen (Lesson). 3 specimens. Alloeocarpa incrustans (Herdman). 7 specimens. Paramolgula gregaria (Lesson). 6 specimens. Station WS 72. 5. iii. 27. 510 07' S., 570 34' W. Commercial otter trawl, 95 m. Aplidium variabile (Herdman). 3 specimens. Paramolgula gregaria (Lesson). 6 specimens. A. falklandicum sp.n. 3 specimens. Station WS 73. 6. iii. 27. From 510 02' S., 580 55' W. to 51° S., 580 53' W. Commercial otter trawl, 121-130 m. Aplidium fuegiense Cunningham. 26 specimens. Paramolgula gregaria (Lesson). 9 specimens. A. falklandicum sp.n. 1 specimen. Station WS 75. 10. iii. 27. From 510 S., 6o° 30' W. to 51° 02' 42" S., 6o° 31' 42" W. Commercial otter trawl, 64-104 m. Polyzoa opuntia Lesson. 1 specimen. Station WS 76. n. iii. 27. From 510 S., 620 W. to 510 S., 620 04' 36" W. Commercial otter trawl, fine dark sand, 205-207 m. Aplidium fuegiense Cunningham. 4 specimens. Station WS 79. 13. iii. 27. From 510 S., 650 W. to 510 03' S., 640 59' W. Commercial otter trawl, fine dark sand, 1 32-1 31 m. Aplidium fuegiense Cunningham. 2 specimens. Paramolgula gregaria (Lesson). 5 specimens. A. falklandicum sp.n. 4 specimens. Station WS 80. 14. iii. 27. From 500 58' S., 630 39' W. to 500 55' 30" S., 630 36' W. Commercial otter trawl, fine dark sand, 152-156 m. Aplidium fuegiense Cunningham. 1 specimen. Station WS 81. 19. iii. 27. 8 miles N. ii° W. of North Island, Falkland Islands. From 510 03 'S., 6i° 15' W. to 510 30' 30" S., 6i° 10' W. Commercial otter trawl, sand, 81-82 m. Aplidium falklandicum sp.n. 4 specimens. Cnemidocarpa verrucosa (Lesson). 11 specimens. Station WS 82. 21. iii. 27. From 540 05' S., 570 45' W. to 540 07' S., 570 47' 30" W. Commercial otter trawl, 140-144 m. Polyzoa reticulata (Herdman). 1 specimen. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 15 Station WS 83. 24. iii. 27. 14 miles S. 640 W. of George Island, East Falkland Island. From 520 28' S., 6o° 06' W. to 520 30' S., 6o° 09' 30" W. Commercial otter trawl, fine green sand and shells, 137-129 m. Aplidium fuegiense Cunningham. 4 specimens. Station WS 84. 24. iii. 27. 7! miles S. 90 W. of Sea Lion Island, East Falkland Island. From 520 33' S., 590 08' W. to 520 34' 30" S., 590 11' W. Commercial otter trawl, coarse sand, shells and stones, 75-74 m. Aplidium fuegiense Cunningham. 3 specimens. Sycozoa sigillinoides Lesson. 1 specimen. A. falklandicum sp.n. 3 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Trididemnum auriculatum Michaelsen. 1 specimen. Pyura legumen (Lesson). 1 specimen. Station WS 85. 25. iii. 27. 8 miles S. 66° E. of Lively Island, East Falkland Island. From 520 09' S., 580 14' W. to 520 08' S., 580 09' W. Commercial otter trawl, sand and shells, 79 m. Aplidium fuegiense Cunningham. 2 specimens. Polyzoa reticulata (Herdman). 13 specimens. Sycozoa sigillinoides Lesson. 1 specimen. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station WS 86. 3. iv. 27. From 530 53' S., 6o° 37' W. to 530 54' S., 6o° 30' W. Commercial otter trawl, sand, shells and stones, 1 51-147 m. Aplidium fuegiense Cunningham. 3 specimens. Polyzoa opuntia Lesson. 1 specimen. A. falklandicum sp.n. 1 specimen. Alloeocarpa incrustans (Herdman). 1 specimen. Station WS 88. 6. iv. 27. From 540 00' S., 650 00' W. to 540 00' S., 640 55' W. Commercial otter trawl, 118 m. Paramolgula gregaria (Lesson). 1 specimen. Station WS 89. 7. iv. 27. 9 miles N. 21 ° E. of Arenas Pt. Lt., Tierra del Fuego. From 530 01' S., 68° 07' W. to 520 59' 30" S., 68° 06' W. Commercial otter trawl, mud, gravel and stones, 23-21 m. Pyura legumen (Lesson). 1 specimen. Paramolgula gregaria (Lesson). 5 specimens. Station WS 90. 7. iv. 27. 13 miles N. 830 E. of Cape Virgins Lt., Argentine Republic. From 520 18' S., 68° W. to 520 19' 30" S., 670 57' W. Commercial otter trawl, fine dark sand, 82-81 m. Aplidium fuegiense Cunningham. 4 specimens. Distaplia cylindrica (Lesson). 1 specimen. A. falklandicum sp.n. 3 specimens. Pyura legumen (Lesson). 1 specimen. Sycozoa sigillinoides Lesson. 1 specimen. Station WS 91. 8. iv. 27. From 520 54' 30" S., 640 39' W. to 520 53' S., 640 36' W. Commercial otter trawl, fine dark sand and shells, 191-205 m. Aplidium fuegiense Cunningham. 2 specimens. A. falklandicum sp.n. 4 specimens. A. variabile (Herdman). 15 specimens. Station WS 92. 8. iv. 27. From 520 S., 650 W. to 510 57' S., 650 02' W. Commercial otter trawl, fine dark sand and stones, 145-143 m. Aplidium fuegiense Cunningham. 1 specimen. Sycozoa sigillinoides Lesson. 11 specimens. Station WS 93. 9. iv. 27. 7 miles S. 8o° W. of Beaver Island, West Falkland Island. From 510 51' S., 6i° 30' W. to 510 54' S., 6i° 30' W. Commercial otter trawl, grey sand, 133-130 m. Aplidium circumvolution (Sluiter). 1 specimen. A. variabile (Herdman). 1 specimen. A. fuegiense Cunningham. 3 specimens. A. falklandicum sp.n. 1 specimen. Station WS 94. 16. iv. 27. From 500 S., 650 W. to 500 S., 640 55' 30" W. Commercial otter trawl, fine dark sand, 1 10-126 m. Aplidium fuegiense Cunningham. 2 specimens. Cnemidocarpa nordenskjoldi (Michaelsen). 2 specimens. 16 DISCOVERY REPORTS Station WS 95. 17. iv. 27. From 480 57' S., 640 45' W. to 480 59' 30" S., 640 45' W. Commercial otter trawl, fine dark sand, stones and shells, 109-108 m. Aplidium fuegiense Cunningham. 2 specimens. Polyzoa opuntia Lesson. 1 specimen. Sycozoa sigillinoides Lesson. 1 specimen. Station WS 99. 19. iv. 27. From 490 41' S., 590 14' W. to 490 43' S., 590 15' W. Commercial otter trawl, fine dark sand, 251-225 m. Didemnum trivolutum sp.n. 3 specimens. Station WS 108. 25. iv. 27. From 480 30' S., 630 36' W. to 480 31' 30" S., 630 31' 30" W. Com- mercial otter trawl, fine dark sand, 1 18-120 m. Aplidium fuegiense Cunningham. 7 specimens. A. falklandicum sp.n. 5 specimens. Station WS 154. 26. ii. 28. 540 S., 360 52' W. Tow-net, 115-0 m. Aplidium falklandicum sp.n. 1 specimen. Station WS 182. 8. iii. 28. 550 30' S., 340 50' W. Tow-net, 750-520 m. Aplidium falklandicum sp.n. 1 specimen. Station WS 210. 29. v. 28. 500 17' S., 6o° 06' W. Commercial otter trawl, green sand, 161 m. Paramolgula gregaria (Lesson). 2 specimens. Station WS 214. 31. v. 28. 480 25' S., 6o° 40' W. Commercial otter trawl, fine dark sand, 208-219 m. Sycozoa sigillinoides Lesson. 2 specimens. Station WS 215. 31. v. 28. 470 37' S., 6o° 50' W. Commercial otter trawl, fine green sand, 219-146 m. Sycozoa sigillinoides Lesson. 2 specimens. Station WS 216. 1. vi. 28. 470 37' S., 6o° 50' W. Commercial otter trawl, fine sand, 219-133 m. Alloeocarpa incrustans (Herdman). 1 specimen. Station WS 219. 3. vi. 28. 470 06' S., 620 12' W. Commercial otter trawl, dark sand, 116-114 m. Aplidium fuegiense Cunningham. 4 specimens. A. falklandicum sp.n. 1 1 specimens. A. variabile (Herdman). 5 specimens. Station WS 220. 3. vi. 28. 470 56' S., 620 38' W. Commercial otter trawl, brown sand, 108-104 m. Aplidium fuegiense Cunningham. 1 specimen. A. falklandicum sp.n. 2 specimens. A. variabile (Herdman). 1 specimen. Sycozoa sigillinoides Lesson. 2 specimens. Station WS 221. 4. vi. 28. 480 23' S., 65°i5'W. Commercial otter trawl, brown sand, mud, pebbles, large stones and shells, 76-91 m. Polyzoa opuntia Lesson. 2 specimens. Cnemidocarpa nordenskjoldi (Michaelsen). 1 specimen. Station WS 222. 8. vi. 28. 480 23' S., 650 W. Commercial otter trawl, coarse brown sand and shells, 100-106 m. Aplidium falklandicum sp.n. 6 specimens. Paramolgula gregaria (Lesson). 1 specimen. Station WS 226. 10. vi. 28. 490 20' S., 620 30' W. Commercial otter trawl, green sand, 144-152 m. Sycozoa sigillinoides Lesson. 14 specimens. Station WS 229. i.vii.28. 500 35' S., 570 20' W. Commercial otter trawl, fine green sand, 210-271 m. Aplidium stanleyi sp.n. 1 1 specimens. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 17 Station WS 233. 5. vii. 28. 49 ° 25' S., 590 45' W. Commercial otter trawl, fine green sand, 185-175 m. Aplidium fuegiense Cunningham. 1 specimen. Station WS 235. 6. vii. 28. 470 56' S., 6i° 10' W. Commercial otter trawl, dark green sand, 155 m. Aplidium variabile (Herdman). 1 specimen. Station WS 237. 7. vii. 28. 460 S., 6o° 05' W. Commercial otter trawl, coarse brown sand and shells, 150-256 m. Aplidium variabile (Herdman). 1 specimen. Sycozoa sigillinoides Lesson. 1 specimen. Station WS 239. 15. vii. 28. 510 10' S., 620 10' W. Commercial otter trawl, coarse dark sand, 196-193 m. Aplidium falklandicum sp.n. 2 specimens. Sycozoa sigillinoides Lesson. 1 specimen. Station WS 243. 17. vii. 28. 510 06' S., 640 30' W. Commercial otter trawl, coarse dark sand, 144-141 m. Aplidium falklandicum sp.n. 5 specimens. Cnemidocarpa nordenskjoldi (Michaelsen). 7 specimens. Sycozoa sigillinoides Lesson. 2 specimens. Paramolgula gregaria (Lesson). 4 specimens. Tylobranchion speciosum Herdman. 1 specimen. Station WS 244. 18. vii. 28. 520 S., 620 40' W. Commercial otter trawl, fine dark sand and mud, 253-247 m- Aplidium circumvolutum (Sluiter). 13 specimens. Sycozoa sigillinoides Lesson. 8 specimens. A. falklandicum sp.n. 6 specimens. Station WS 245. 18. vii. 28. 520 36' S., 630 40' W. Commercial otter trawl, dark green sand, 304-290 m. Sycozoa sigillinoides Lesson. 28 specimens. Station WS 246. 19. vii. 28. 520 25' S., 6i° W. Commercial otter trawl, coarse green sand and pebbles, 267-208 m. Didemnum studeri Hartmeyer. 2 specimens. Station WS 247. 19. vii. 28. 520 40' S., 6o° 05' W. Large heavy dredge, rocks, 172 m. Aplidium fuegiense Cunningham. 1 specimen. Cnemidocarpa nordenskjoldi (Michaelsen). 1 1 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Station WS 249. 20. vii. 28. 520 10' S., 570 30' W. Large heavy dredge, fine brown and green sand, shells and stones, 166 m. Aplidium fuegiense Cunningham. 1 specimen. Station WS 567. 6. iii. 31. 530 54' 15" S., 370 05' 30" W. 70 cm. tow-net, 145 m. Pyura georgiana Michaelsen. 1 specimen. Station WS 582. 30. iv. 31. 530 42' 30" S., 700 55' W. Hand lines, 12 m. Cnemidocarpa nordenskjoldi (Michaelsen). 1 specimen. Station WS 583. 2. v. 31. 530 39' S., 700 54' 30" W., Magellan Strait. Small beam trawl, 14-78 m. Aplidium fuegiense Cunningham. 2 specimens. Cnemidocarpa nordenskjoldi (Michaelsen). 2 specimens. Station WS 742. 5. ix. 31. 380 22' S., 730 41' W. Small beam trawl, 47-35 m. Molgula platei Hartmeyer. 27 specimens. 3 DM i8 DISCOVERY REPORTS Station WS 756. 10. x. 31. From 500 53' S., 6o° W. to 500 56' 18" S., 590 56' W., to 500 59' 30" S., 590 52' W. Commercial otter trawl, black gravel, green mud and sand, 104-119 m. Paramolgula gregaria (Lesson). 1 specimen. Station WS 764. 17. x. 31. From 440 40' S., 620 W. to 440 36' 30" S., 6i° 57' W., to 440 41' S., 6i° 52' W. Commercial otter trawl, fine green sand, 1 10-104 m. Aplidium fuegiense Cunningham. 6 specimens. A. falklandicum sp.n. 7 specimens. Station WS 765. 17. x. 31. From 450 06' S., 6o° 30' W., to 450 08' S., 6o° 26' 30" W. Com- mercial otter trawl, brown and green mud and sand, 113-119 m. Aplidium falklandicum sp.n. 2 specimens. Distaplia cylindrica (Lesson). 1 specimen. Sycozoa sigilliuoides Lesson. 24 specimens. Alloeocarpa incrustans (Herdman). 2 specimens. Station WS 771. 29. x. 31. From 420 40' S., 6o° 32' W. to 420 43' 30" S., 6o° 30' W. Com- mercial otter trawl, dark green sand, 90 m. Aplidium fuegiense Cunningham. 1 specimen. A. falklandicum sp.n. 1 specimen. A. variabile (Herdman). 1 specimen. Station WS 772. 30. x. 31. From 450 13' S., 6o° W. to 450 13' 48" S., 6o° 00' 30" W. Com- mercial otter trawl, grey sand, 309-163 m. Aplidium variabile (Herdman). 2 specimens. Sycozoa sigillinoides Lesson. 9 specimens. Station WS 774. 1. xi. 31. From 470 09' S., 620 W. to 470 07' S., 620 04' W. Commercial otter trawl, dark green sand and mud, 139-144 m. Aplidium falklandicum sp.n. 2 specimens. Station WS 775. 2. xi. 31. From 460 44' 30" S., 630 30' W. to 460 45' S., 630 36' W. Commercial otter trawl, gravel and fine grey sand, 115-110 m. Aplidium circumvolutum (Sluiter). 3 specimens. Sycozoa sigillinoides Lesson. 3 specimens. A. fuegiense Cunningham. 1 specimen. Agnesia glaciata Michaelsen. 3 specimens. A. falklandicum sp.n. 1 specimen. Station WS 776. 3. xi. 31. From 46° 19' S., 650 W. to 460 17' 30" S., 650 04' 30" W. Commercial otter trawl, grey mud and sand, 110-99 m- Aplidium fuegiense Cunningham. 1 specimen. Paramolgula gregaria (Lesson). 1 specimen. Styela magalhaensis Michaelsen. 1 specimen. Station WS 781. 6. xi. 31. From 500 29' S., 580 52' W. to 500 31' S., 580 48' W. Commercial otter trawl, dark green sand and mud, 148 m. Aplidium fuegiense Cunningham. 7 specimens. Paramolgula gregaria (Lesson). 2 specimens. A. variabile (Herdman). 6 specimens. Station WS 782. 4. xii. 31. From 50° 30' S., 580 19' W. to 500 28' 30" S., 580 23' 30" W. to 500 27' S., 580 31' W. Commercial otter trawl, green sand and rocks, 141-146 m. Aplidium circumvolutum (Sluiter). 1 specimen. A. falklandicum sp.n. 1 specimen. A. variabile (Herdman). 6 specimens. Paramolgula gregaria (Lesson). 3 specimens. Station WS 783. 5. xii. 31. From 5o°o3'3o"S., 6o°o8' W. to 50°02'S., 6o°i2' W. to 5o°o3'3o"SM 6o° 16' W. Commercial otter trawl, 165-0 m. Conical dredge, 157 m. Aplidium circumvolutum (Sluiter). 26 specimens. A. variabile (Herdman). 2 specimens. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 19 Station WS 784. 5. xii. 31. From 490 48' 30" S., 6i°03'W. to 490 47' S., 6i°07'W. Com- mercial otter trawl, dark green sand and rocks, 170-164 m. Aplidium circumvoluttim (Sluiter). 1 specimen. Cnemidocarpa nordenskjoldi (Michaelsen). 5 specimens. Sycozoa sigillinoides Lesson. 1 specimen. Paramolgula gregaria (Lesson). 2 specimens. Station WS 785. 6. xii. 31. From 490 27' S., 620 32' W. to 490 26' S., 620 36' W. to 490 24' 30" S., 620 39' W. to 490 23' S., 620 43' 30" W. Commercial otter trawl, dark green sand, 150-147 m. Sycozoa sigillinoides Lesson. 7 specimens. Station WS 787. 7. xii. 31. From 480 44' S., 650 24' 30" W. to 480 48' S., 650 25' W. Commercial otter trawl, coarse brown speckled sand, 106-110 m. Aplidium ftiegiense Cunningham. 15 specimens. A. falklandicum sp.n. 5 specimens. A. variabile (Herdman). 1 specimen. Distaplia cylindrica (Lesson). 3 specimens. Station WS 788. 13. xii. 31. From 450 06' 30" S., 640 56' W. to 450 07' 30" S., 640 52' W. Com- mercial otter trawl, speckled grey mud, sand and gravel, 82-88 m. Polyzoa opuntia Lesson. 1 specimen. Pyura legumen (Lesson). 1 specimen. Station WS 791. 14. xii. 31. From 450 38' S., 620 57' W. to 450 39' 30" S., 620 53' W. to 450 44' S., 620 37' W. Commercial otter trawl, green sand, 97-95 m., 95-101 m. Aplidium fuegiense Cunningham. 15 specimens. A. falklandicum sp.n. 12 specimens. A. variabile (Herdman). 3 specimens. Paramolgula gregaria (Lesson). 1 specimen. Station WS 792. 15. xii. 31. From 450 49' S., 620 23' W. to 450 50' S., 62°i8'3o"W. to 450 54' 30" S., 620 04' W. Commercial otter trawl, dark green sand and rocks, 102-106 m. Aplidium fuegiense Cunningham. 7 specimens. A. falklandicum sp.n. 8 specimens. Station WS 793. 15. xii. 31. From 450 52' 18" S., 6i° 37' W. to 450 53' 48" S., 6i° 33' W. Com- mercial otter trawl, rocks, 108-111 m. Aplidium variabile (Herdman). 8 specimens. A. falklandicum sp.n. 4 specimens. Station WS 794. 17. xii. 31. From 460 11' 48" S., 6i° 01' W. to 460 13' 30" S., 6o° 57' 30" W. Commercial otter trawl, 123-126 m. Aplidium variabile (Herdman). 1 specimen. Synoicum georgianum Sluiter. 2 specimens. Station WS 796. 21. xii. 31. From 470 51' S., 630 43' W. to 470 56' S., 630 22' W. Commercial otter trawl, 106-113 and 108-112 m. Aplidium variabile (Herdman). 2 specimens. Paramolgula gregaria (Lesson). 8 specimens. A. falklandicum sp.n. 1 specimen. Station WS 797. 20. xii. 31. From 470 44' S., 640 22' W. to 47°45'i2"S., 640 18' W. to 470 50' 18" S., 63 ° 57' W. Commercial otter trawl, 11 5-1 11 m. Aplidium fuegiense Cunningham. 9 specimens. Paramolgula gregaria (Lesson). 3 specimens. A. variabile (Herdman). 6 specimens. Station WS 798. 20. xii. 31. From 470 31' 30" S., 620 05' W. to 470 32' 30" S., 640 58' W. Com- mercial otter trawl, pebbles, shells and sand, 49-66 m. Polyzoa opuntia Lesson. 7 specimens. Paramolgula gregaria (Lesson). 3 specimens. Station WS 799. 21. xii. 31. From 480 03' 30" S., 620 50' 18" W. to 480 05' S., 620 46' W. to 480 10' S., 620 31' W. (a) Hand net, o m.; (b) commercial otter trawl, dark green sand, 141-137 m. Aplidium variabile (Herdman). 1 specimen. Sycozoa sigillinoides Lesson. 6 specimens. 3-2 20 DISCOVERY REPORTS Station WS 800. 21-22. xii. 31. From 480 15' S., 620 11' 48" W. to 480 16' 30" S., 620 08' W. to 480 21' 30" S., 6i° 48' W. Commercial otter trawl, dark sand and shells, 137-139 m. Aplidium fuegiense Cunningham. 3 specimens. Sycozoa sigillinoides Lesson. 2 specimens. Station WS 801. 22. xii. 31. From48° 25' 30" S., 6i° 30' W. 1048° 27' S., 6i° 26' W. Commercial otter trawl, dark sand, 165 m. Aplidium fuegiense Cunningham. 1 specimen. Station WS 805. 6. i. 32. From 500 11' S., 630 37' W. to 500 09' 30" S., 630 31' W. Commercial otter trawl, coarse dark speckled sand, 148-150 m. Cnemidocarpa nordenskjoldi (Michaelsen). 1 1 specimens. Station WS 807. 7. i. 32. From 490 51' S., 65°oi'W. to 490 50' S., 650 05' W. Commercial otter trawl, dark sand, 124-126 m. Aplidium fuegiense Cunningham. 2 specimens. A. falklandicum sp.n. 1 specimen. Station WS 808. 8. i. 32. From 490 41' S., 650 40' W. to 490 39' 30" S., 650 44' W. Commercial otter trawl, brown and green sand, 1 10-106 m. Aplidium fuegiense Cunningham. 6 specimens. Par amolgula gregaria (Lesson). 1 specimen. A. variabile (Herdman). 3 specimens. Station WS 809. 8. i. 32. From 490 29' S., 620 27' W. to 490 27' 30" S., 66° 31' W. to 490 32' 3o"S., 66° 51' 30" W. Commercial otter trawl, brown speckled sand, 104-101 m. Aplidium fuegiense Cunningham. 1 specimen. Station WS 811. 10. i. 32. From 510 22' S., 68° 03' W. to 510 27' 30" S., 670 43' W. Commercial otter trawl, 99 m. Aplidium fuegiense Cunningham. 1 specimen. Didemnum trivolutum sp.n. 1 specimen. A. variabile (Herdman). 2 specimens. Pyura legumen (Lesson). 2 specimens. Station WS 813. 13. i. 32. From 51° 34' 30" S., 670 18' 30" W. to 510 36' S., 670 14' W. Com- mercial otter trawl, dark speckled sand, 106-102 m. Aplidium fuegiense Cunningham. 1 specimen. A. falklandicum sp.n. 2 specimens. A. variabile (Herdman). 107 specimens. Station WS 814. 13. i. 32. From 510 44' 30" S., 66° 38' W. to 510 46' S., 66° 42' W. Commercial otter trawl, speckled sand, 112-119 m. Sycozoa sigillinoides Lesson. 2 specimens. Station WS 816. 14. i. 32. From 520 09' 30" S., 640 58' W. to 52°io' S., 640 54' W. Commercial otter trawl, shingle, 150 m. Aplidium variabile (Herdman). 3 specimens. Sycozoa sigillinoides Lesson. 2 specimens. Station WS 818. 17. i. 32. From 52° 30' 30" S., 630 27' W. to 520 32' S., 630 23' W. to 520 37' S., 630 02' W. Commercial otter trawl, dark speckled sand, 272-278 m. Sycozoa sigillinoides Lesson. 5 specimens. Station WS 819. 17.1.32. From 520 41' 18" S., 62°4i'W. to 520 42' 30" S., 620 38' W. to 52° 47' 30" S., 620 17' W. Commercial otter trawl, dark speckled sand, 313-329 m. Sycozoa sigillinoides Lesson. 1 specimen. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 21 Station WS 823. 19. i. 32. From 520 12' 30" S., 6o° 02' W. to 520 16' 30" S., 6o° W. Commercial otter trawl, green grey fine sand, 80-95 m- Polyzoa reticulata (Herdman). 1 specimen. Paramolgula gregaria (Lesson). 1 specimen. Cnemidocarpa verrucosa (Lesson). 1 specimen. Station WS 824. 19. i. 32. From 520 31' S., 580 29' W. to 520 27' 30" S., 580 28' 30" W. Com- mercial otter trawl, green speckled sand and shells, 146-137 m. Aplidium circumvolutum (Sluiter). 11 specimens. A. variabile (Herdman). 5 specimens. Station WS 833. 1. ii. 32. From 520 28' S., 68° W. to 520 32' S., 68° W. Commercial otter trawl, brown and grey mud and fine sand, 38-31 m. Sycozoa sigillinoides Lesson. 3 specimens. Station WS 834. 2. ii. 32. From 520 57' S., 68° 07' W. to 52° 58' 30" S., 68° 09' 30" W. Com- mercial otter trawl, dark brown grey shingle and stones, 27-38 m. Sycozoa sigillinoides Lesson. 50 specimens. Pyura legumen (Lesson). 1 specimen. Polyzoa opuntia Lesson. 2 specimens. Paramolgula gregaria (Lesson). 8 specimens. Station WS 837. 3. ii. 32. From 520 48' 30" S., 66° 30' W. to 520 50' S., 66° 26' W. Commercial otter trawl, coarse dark green sand and pebbles, 102 m. Aplidium fuegiense Cunningham. 10 specimens. Polyzoa opuntia Lesson. 2 specimens. Station WS 838. 5. ii. 32. From 53° 11' S., 650 02' W. to 530 12' 30" S., 640 58' W. Commercial otter trawl, 149-159 m. Aplidium variabile (Herdman). 2 specimens. Station WS 839. 5. ii. 32. From 530 29' 30" S., 630 31' W. to 530 31' S., 630 27' W. Commercial otter trawl, 503-534 m. Sycozoa sigillinoides Lesson. 1 specimen. Station WS 841. 6. ii. 32. From 540 11' S., 6o° 23' W. to 540 12' 30" S., 6o° 20' W. Commercial otter trawl, shingle and shells, 110-121 m. Aplidium fuegiense Cunningham. 1 specimen. Tylobranchion speciosum Herdman. 1 specimen. Sycozoa sigillinoides Lesson. 3 specimens. Styela paessleri Michaelsen. 1 specimen. Station WS 847. 9. ii. 32. From 500 15' S., 670 59' W. to 500 16' 30" S., 670 55' W. to 500 21' S., °7° 33' W. Commercial otter trawl, 57-84 m. and 51-57 m. Aplidium fuegiense Cunningham. 6 specimens. Sycozoa sigillinoides Lesson. 5 specimens. A. variabile (Herdman). 3 specimens. Cnemidocarpa nordenskjoldi (Michaelsen). 1 specimen. A. falklandicum sp.n. 2 specimens. Paramolgula gregaria (Lesson). 4 specimens. Station WS 849. 10. ii. 32. From 500 56' 30" S., 650 W. to 500 57' S., 66° 22' W. Commercial otter trawl, dark sand, 137 m. Paramolgula gregaria (Lesson). 1 specimen. Station WS 852. 21. iii. 32. 440 12' 30" S., 640 13' W. Small beam trawl, 86-88 m. Pyura legumen (Lesson). 1 specimen. Station WS 854. 22. iii. 32. 450 16' S., 640 25' W. Small beam trawl, 97 m. Eugyra kerguelenensis Herdman. 8 specimens. Station WS 856. 23. iii. 32. 460 35' S., 640 11' W. Small beam trawl, 104 m. Aplidium circumvolutum (Sluiter). 30 specimens. Eugyra kerguelenensis Herdman. 1 specimen. 22 DISCOVERY REPORTS Station WS 857. 23. iii. 32. From 470 11' S., 640 15' W. to 470 12' S., 640 09' W. Commercial otter trawl, 123-124 m. Aplidium variabile (Herdman). 2 specimens. Station WS 858. 24. iii. 32. From 45° 42' S., 6o° 30' W. to 450 40' 30" S., 6o° 33' W. Commercial otter trawl, 132-123 m. Aplidium falklandicum sp.n. 1 specimen. Station WS 861. 27. iii. 32. 470 40' S., 640 12' W. Small beam trawl, 1 17-124 m. Paramolgula gregaria (Lesson). 4 specimens. Station WS 863. 28. iii. 32. 490 05' S., 640 09' W. Small beam trawl, 121-117 m. Paramolgula gregaria (Lesson). 2 specimens. Station WS 864. 28. iii. 32. From 490 32' S., 640 15' W. to 490 35' S., 640 17' W. Commercial otter trawl, 128-126 m. Paramolgula gregaria (Lesson). 4 specimens. Station WS 865. 29. iii. 32. 500 03' S., 640 14' W. Small beam trawl, 126-128 m. Aplidium variabile (Herdman). 3 specimens. A. falklandicum sp.n. 2 specimens. Station WS 869. 31. iii. 32. 520 15' 30" S., 640 13' 48" W. Small beam trawl, 187-201 m. Aplidium variabile (Herdman). 10 specimens. Station WS 871. 1. iv. 32. 530 16' S., 640 12' W. Small beam trawl, 336-342 m. Aplidium fuegiense Cunningham. 2 specimens. Cystodytes dellechiajei Delia Valle. 11 specimens. Marine Biological Station Station MS 6. 12. ii. 25. East Cumberland Bay, South Georgia. \ mile south of Hope Pt. to i\ cables south by east of King Edward Pt. Lt. Small beam trawl, 24-30 m. Alloeocarpa incrustans (Herdman). 1 specimen. Station MS 10. 14. ii. 25. East Cumberland Bay, South Georgia. J mile S.E. of Hope Pt. to I mile S. of Government Flagstaff. Small beam trawl, 26-18 m. Synoicum georgianum Sluiter. 2 specimens. Polyzoa reticidata (Herdman). 1 specimen. Ascidia translucida Herdman. 2 specimens. Alloeocarpa incrustans (Herdman). 1 specimen. Station MS 14. 17. ii. 25. From 1-5 miles S.E. by S. to 1-5 miles S. \ W. of Sappho Pt., East Cumberland Bay, South Georgia. Small dredge, 190-nom. Sycozoa georgiana (Michaelsen). 4 specimens. Pyura georgiana Michaelsen. 4 specimens. Polyzoa reticidata (Herdman). 1 specimen. Station MS 33. 1. v. 25. 1 cable E. of Hobart Rock, East Cumberland Bay, South Georgia. Small beam trawl, 40 m. Polyzoa opuntia Lesson. 1 specimen. Alloeocarpa incrustans (Herdman). 1 specimen. Station MS 62. 24. ii. 26. East Cumberland Bay, South Georgia. \ cable E. to 3! cables S. of Hobart Pt. Small beam trawl, 31m. Polyzoa reticulata (Herdman). 1 specimen. Station MS 63. 24. ii. 26. East Cumberland Bay, South Georgia. 1-3 miles S. by E. to i-6 miles S.E. by S. of Hope Pt. Small beam trawl, 23 m. Distaplia colligans Sluiter. 2 specimens. LIST OF STATIONS AND SPECIES COLLECTED AT EACH 23 Station MS 64. 24. ii. 26. East Cumberland Bay, South Georgia. i-8 miles S.E. by S. of King Edward Pt. Lt. Small dredge, 7-15 m. Aplidium variabile (Herdman). 3 specimens. Polyzoa opuntia. Lesson 1 specimen. Synoictim giardi (Herdman). 1 specimen. Alloeocarpa incrustans (Herdman). 2 specimens. Station MS 65. 28. ii. 26. East Cumberland Bay, South Georgia. i-6 miles S.E. of Hobart Rock to 1 cable N. of Dartmouth Pt. Small beam trawl, 39 m. Aplidium circumvolutum (Sluiter). 1 specimen. Ascidia translucida Herdman. 1 specimen. Station MS 67. 28. ii. 26. East Cumberland Bay, South Georgia. 3 cables N.E. of Hobart Rock to \ cable W. of Hope Pt. Small beam trawl, 38 m. Alloeocarpa incrustans (Herdman). 1 specimen. Station MS 68. 2. iii. 26. East Cumberland Bay, South Georgia. 1-7 miles S. \ E. to 8 \ cables S.E. by E. of Sappho Pt. Large rectangular net, 220-247 m. Sycozoa georgiana (Michaelsen). 4 specimens. Pyura georgiana Michaelsen. 6 specimens. Distaplia cylindrica (Lesson). 7 specimens. Molgula pedunculata Herdman. 1 specimen. Ascidia translucida Herdman. 2 specimens. Ascopera gigantea Herdman. 39 specimens. Cnemidocarpa verrucosa (Lesson). 2 specimens. Station MS 71. 9. Hi. 26. East Cumberland Bay, South Georgia. q\ cables E. by S. to 1-2 miles E. by S. of Sappho Pt. Small beam trawl, 110-60 m. 1 Aplidium fuegiense Cunningham. 3 specimens. Ascidia challenged Herdman. 1 specimen. \A. variabile (Herdman). 22 specimens. Polyzoa reticulata (Herdman). 1 specimen. Synoicum adareanum (Herdman). 1 specimen. Cnemidocarpa verrucosa (Lesson). 3 specimens. 5. giardi (Herdman). 1 specimen. Paramolgula gregaria (Lesson). 3 specimens. Didemnum studeri Hartmeyer. 1 specimen. Station MS 74. 17. iii. 26. East Cumberland Bay, South Georgia. 1 cable S.E. by E. of Hope Pt. to 3-1 miles S.W. of Merton Rock. Small beam trawl, 22-40 m. Synoicum georgianum Sluiter. 1 specimen. Polyzoa reticulata (Herdman). 1 specimen. Distaplia colligans Sluiter. 2 specimens. Alloeocarpa incrustans (Herdman). 8 specimens. British Graham Land Expedition, 1934-7 Stella Creek (6. v. 35) Ascidia challenged Herdman. 3 specimens. Cnemidocarpa verrucosa (Lesson). 14 specimens. Stella Creek. (5. X. 35) Distaplia cylindrica (Lesson). 1 specimen. Port Lockroy. (23. i. 35) Distaplia cylindrica (Lesson). 1 specimen. Deception Island, South Shetlands 3.1.24. 25— 30 m. Ascopera gigantea Herdman. 6 specimens. Port Stanley, Falkland Islands 9. iii. 26. Shore collection Polyzoa opuntia Lesson. 1 specimen. 17. vi. 28. Shore collection Polyzoa opuntia Lesson. 1 specimen. 24 DISCOVERY REPORTS ABBREVIATIONS USED IN TEXT-FIGURES a. anus a.l. atrial languet amp. ampulla a.o. atrial opening a.p. ampulla of pyloric gland a.s. atrial siphon a.sw. ampullary swelling b.c. blood channels b.f. branchial fold b.p. branchial papilla br.p. brood pouch c.cl.c. common cloacal chamber d.f. dorsal fold d.l. dorsal languet d.la. dorsal lamina d.p. dorsal papilla d.t. dorsal tubercle e. endostyle emb. embryo en. endocarp ep.c. epicardiac cavity ep.s. suture of epicardium and body wall fl. flange g- gonad ga- ganglion ll. heart i. intestine inf. infundibulum La. lateral ampulla Lb. longitudinal bar lg- ligament l.m. longitudinal muscles l.t.o. lateral thoracic organ m.a median ampulla m.i. mid-intestine mus. muscle oe. oesophagus od. oviduct 0.0. oral opening o.s. oral siphon ov. ovary P- papilla p.a. post-abdomen p.b. parastigmatic bar p.bd. peripharyngeal band pc. pericardium pyx. pyloric caecum p.st. post-stomach r. rectum rb. rib of oral tentacle res. reserve material r.s. renal sac r.v. radial vessels s.d. sperm duct s.d.c. sperm duct convolutions sk. stalk sn. stolon St. stomach st.c. stomach caecum t. testis th. thorax t.m. transverse muscles tn. tentacle t.p. transverse-bar papilla tri. thoracic triangle t.t. test teeth t.s. terminal zooid v. vesicle v.c. vacuolated cell v.p. ventral papilla v.pr. vascular process v.pr.o. origin of vascular process DESCRIPTION OF SPECIES Order ENTEROGONA Perrier, 1898 Suborder APLOUSOBRANCHIATA Lahille, 1886 Family POLYCLINIDAE Verrill, 1871 Subfamily Polyclininae Adams, 1858 Genus Aplidium Savigny, 1816 The genera Aplidium Savigny, 181 6, and Amaroucium Milne Edwards, 1842, are not readily distin- guishable and recently there has been a tendency to regard them as synonymous. A varying number of diagnostic characters (Table 1) has been used by different authorities to separate the two genera. Van Name (1945), using six diagnostic characters, noted that, even on this basis, 'there are inter- mediate forms that may be assigned to either genus', (p. 28). He stated that Amaroucium 'hardly DESCRIPTION OF SPECIES 25 merits recognition as anything more than a rather indefinitely distinguished subgenus or section of Aplidium Savigny', although it is 'universally adopted in all books on ascidians' (p. 30). Berrill (1950) pointed out the difficulties involved in using van Name's list of diagnostic characters, and concluded that 'the situation is clearly absurd'. He adopted Aplidium as the comprehensive genus, with Amaroucium as a subgenus. Using van Name's list of characters, I have compared forty species variously assigned to Aplidium and Amaroucium, taking details from published accounts. An additional character included in the comparison was the position of the anus relative to the rows of stigmata (Tokioka, 1953). With regard to this last character I find that, although in some species the anus is situated opposite the 4th row of stigmata, and in others opposite the 7th to 10th, yet the ratio of rows of stigmata anterior to anus to rows of stigmata posterior to anus gives no clear separation of species into two groups. The two characters which might be used to separate Aplidium and Amaroucium are (1) the arrangement of the Hartmeyer (1923-4) Harant & Vernieres (1933) Huus (1937) van Name (1945) Table 1 Aplidium Atrial siphon with or without languet Testis follicles in a bunch Atrial languet absent Atrial opening with or without languet Stomach longitudinally folded Post-abdomen relatively short Testes in a bunch or cluster Colony sessile by a broad base Zooids rather stout, with few rows of stigmata Short post-abdomen Stomach with a few deep longitudinal folds Atrial opening well back on dorsal side Testes in a compact mass Amaroucium Atrial siphon always with languet Testis follicles more or less regularly arranged along sperm duct Atrial languet present Atrial opening with long languet Stomach longitudinally folded Post-abdomen long Testis follicles biserially arranged along sperm duct Colony massive or capitate Zooids large with many rows of stigmata Long post-abdomen Stomach with distinct longitudinal plications Atrial opening well forward Testes serially arranged along the sperm duct testes, and (2) the length of the post-abdomen. The first of these characters is undoubtedly influenced by the second, a short post-abdomen tending to produce a bunching of the testis follicles, but the length of the post-abdomen is itself an unsatisfactory character for generic distinction, as it varies greatly during the annual cycle of the zooids. Another result of the shortening of the post-abdomen has been the development in Aplidium pallidum (Verrill) of a type of budding shown by Brien (1925) to involve division of the stomach. Should this feature be found to occur in other species, it might serve as a diagnostic character of Aplidium, but as so far it has been studied only in A. pallidum, such a course is not at present practicable. The above considerations lead me to believe that there is no generic distinction to be made within the group, and I therefore agree with Berrill (1950) and Kott (1954) in adopting for all species the generic name Aplidium, which has priority over Amaroucium. Aplidium circumvolutum (Sluiter) (Text-fig. 1; PI. I, fig. 1) Psammaplidium circumvolutum Sluiter, 1900, p. 14, pi. 1, fig. 7; pi. 3, fig. 1. Amaroucium circumvolutum Michaelsen, 1924, p. 383. Amaroucium circumvolutum var. kerguelenense Peres, 1952, pp. 213-15, figs. 1, 2. 26 DISCOVERY REPORTS Occurrence. St. 39: S. Georgia, 179-235 m. St. 170: S. Shetlands, 342 m. St. 175: S. Shetlands, 200 m. St. 190: Palmer Archipelago, 93-126 m. St. WS 93: Falkland Islands, 133-130 m. St. WS 244: Patagonian Shelf, 253-247 m. St. WS 775 : Patagonian Shelf, 115-nom. St. WS782: Patagonian Shelf, 141-146 m. St. WS 783 : Patagonian Shelf, 157 m. St. WS 784: Falkland Islands, 2 cm 6 1 — 1 1111%^ ik'M ■■■&>'■> X--..0) f °\ f u wli'ill ^$ii& ■&, y. .■ ■ 0 . . ■ .<& ..,„•„..'«* / cm Text-fig. 1. Aplidium circumvolutum (Sluiter): A, colony from Patagonian Shelf (St. WS783); B, colony from S. Georgia (St. 39); C, zooid (St. WS 783); D, abdomen and post-abdomen of zooid with testis (St. WS 824); E, abdomen and post- abdomen of zooid with ovary but no testis (St. WS 256); F, larva (St. 856). DESCRIPTION OF SPECIES 27 170-164 m. St. WS824: Patagonian Shelf, 146-137 m. St. WS856: Patagonian Shelf, 104 m. St. MS 65 : S. Georgia, 39 m. Colony. Most of the colonies collected from the region of the Falkland Islands and the Patagonian Shelf were rather small, forming rounded or pillow-shaped masses with a flattened lower surface, and were generally under 2 cm. in diameter (Text-fig. 1 A). Sand was present on the surface and also within the colony. The test matrix was clear, rather sparse, and not very tough. The specimens from farther south tended to be larger, attaining a diameter of 7-9 cm., and generally contained less sand (Text-fig. 1 B). There is no obvious arrangement of the zooids in systems, a feature noted also by Peres (1952), and common cloacal openings could not be seen. Zoom (Fig. 1 C). Contracted zooids measured 2-5 mm. in length, but must have been longer than this in life. Thorax. The atrial opening has a characteristic languet (a.l.) which is wide and divided into three pointed lobes, of which the central is longest. Another feature which distinguishes the species is the very strong coat of longitudinal thoracic muscles which continue into the abdomen as a narrowing ventral band. (l.m.). Transverse muscles are also well developed. There are seven to eleven rows of stigmata, and a series of short languets on the left branchial wall. Gut. The oesophagus (oe.) is narrow and long, and the stomach (st.) short, wide, and provided with five or six folds which are usually distinct but sometimes shallow. This number of folds is charac- teristic of the species, and was noted by Michaelsen (1924), although Sluiter (1900) described a smooth stomach in the type specimen. The remainder of the gut has no distinctive features. Two rounded lobes are present on the anus (a), which is situated opposite the 5th row of stigmata in zooids with 8-10 rows. Gonads. The ovary (ov.) is small and placed close below the loop of the intestine, and the testis (t) consists of an irregular series of block-like or pear-shaped follicles below the ovary. In some zooids the follicles are condensed to form a compact group (Text-fig. 1 D, t) in others (Text-fig. 1 C, t) they are extended as usual in the genus and a few zooids show no testes (Text-fig. 1 E). The compact arrangement of the follicles has been regarded as a characteristic of the species (Michaelsen, 1924), but Peres (1952) noted that in some zooids follicles were also present farther back in the post-abdomen. There is, in fact, variation according to the stage of the reproductive cycle. Larva (Text-fig. i F). Larvae vary from 0-5 to o-8 mm. in length, measured from the end of the papillae to the base of the tail. There are three rather widely spaced papillae, and between each two, a pair of notched median ampullae (m.a.) occur. In most species of Aplidium the larva has a single ampulla between each two papillae, but in this species each has evidently divided. The most charac- teristic feature of the larva is the great development of fringing lateral ampullae (La.) round the anterior end of the trunk ; this fringe clearly distinguishes the larva of circumvolutum from all others found in the ' Discovery ' collections. Both ocellus and otolith are present. Larvae from subantarctic and antarctic colonies differ only in size (see below). Comparison of Specimens from the Falkland-Patagonian region with Antarctic Specimens. Table 2 shows the constant differences between specimens from the Falkland Islands and Patagonian Shelf and those from South Georgia and the Palmer Archipelago. Table 2 Subantarctic Antarctic Colony Small, with rather soft test Large with firm test Zooid Mean length 3 mm., 7 or 8 rows of stigmata Mean length 5 mm., 10 or 11 rows of stigmata Larvae 2 or 3 per breeding zooid. Mean length o-6 mm. Up to 1 1 per breeding zooid. Mean length o-8 mm. 4-2 2g DISCOVERY REPORTS Biology. Table 2 suggests that in its Antarctic range this species has larger colonies, larger zooids with a better developed branchial sac, and larger and more numerous larvae. The inference is that the centre of distribution is in the Antarctic rather than the Subantarctic. Examination of many specimens showed that all the zooids of a colony keep in phase in their sexual cycle, but that different colonies taken from the same station at the same time differ widely in their sexual state. Thus colonies collected from St. WS 856, on 23 March 1932 varied sexually, as follows: No. of colonies No gonads present 8 Zooids in male phase 3 Zooids in female phase 3 Zooids with embryos 1 The occasional occurrence, in other samples, of zooids with both ovary and testis shows that the sexes are not separate ; it is likely that the species is protandrous, as usual in Aplidium. The comparative rarity of such zooids, however, suggests that the regression of the testis is rapid after the zooid has functioned as a male. The relatively large number of colonies with zoiods lacking gonads and the absence of gonads in zooids carrying embryos further indicates that the ovary also regresses rapidly after functioning. Embryos or larvae were present only in colonies collected as follows : South Georgia Falkland Islands 28. ii. 1926 5. xii. 1931 25. iii. 1926 19. i. 1932 23. iii. 1932 As the species did not occur in collections made in other months, however, no more can be said than that breeding takes place in the southern summer, with an indication of an earlier start in the Sub- antarctic than in the Antarctic region. Remarks. This is a species which shows slight anatomical differences in different parts of its range. A variety described by Peres (1952) from Kerguelen (var. kerguelenense), has each of the oral lobes bifid, and a very wide atrial languet. The differences which I have noted above between the sub- antarctic and the antarctic specimens in the ' Discovery ' collections do not seem to merit systematic distinction. Distribution. New Zealand; Chatham Islands; Subantarctic (Kerguelen, Patagonian Shelf), Antarctic (Graham Land, S. Georgia). Aplidium fuegiense Cunningham (Text-fig. 2 A; PI. I, fig. 2) Aplidium fuegiense Cunningham, 1871, p. 66. For synonymy see van Name, 1945, p. 43. Occurrence. ?St. 27: S. Georgia, no m. St. 51: Falkland Islands, 105-115 m. St. 652: Burdwood Bank, 171-169 m. St. WS 71 : Falkland Islands, 82-80 m. St. WS 73 : Falkland Islands, 121-130 m. St. WS76: Patagonian Shelf, 207-205 m. St. WS79: Patagonian Shelf, 132-131 m. St. WS80: Patagonian Shelf, 152-156 m. St. WS 83, Falkland Islands, 137-129 m. St. WS84: Falkland Islands, 75-74 m. St. WS85: Falkland Islands, 79 m. St. WS 86: Patagonian Shelf, 151-1471™. St. WS90: Patagonian Shelf, 82-81 m. St. WS 91 : Patagonian Shelf, 191-205 m. St. WS92: Patagonian Shelf, 145-143 m. St. WS93: Falkland Islands, 133-130 m. St. WS 94: Patagonian Shelf, 1 10-126 m. St. WS95: Patagonian Shelf, 109-108 m. St. WS108: Falkland Islands, 118- 120 m. St. WS219: Patagonian Shelf, n6-ii4m. St. WS220: Patagonian Shelf, 108-104 m. St. WS233: Falkland Islands, 185-175 m. St. WS247: Patagonian Shelf, 172 m. St. WS249: DESCRIPTION OF SPECIES * 29 Patagonian Shelf, 166 m. St. WS583: Magellan Strait, 14-78111. St. WS 764: Patagonian Shelf, 110-104111. St. WS 771 : Patagonian Shelf, 90 m. St. WS775: Patagonian Shelf, 115-nom. St. WS776: Patagonian Shelf, 110-99 m. St. WS 781 : Patagonian Shelf, 148 m. St. WS787: Patagonian Shelf, 106-nom. St. WS 791 : Patagonian Shelf, 97-95 m. St. WS792: Patagonian Shelf, 102-106 m. St. WS797: Patagonian Shelf, 115-inm. St. WS800: Patagonian Shelf, Text-fig. 2. Aplidium fuegiense Cunningham: A, zooid; A1, larva (St. WS 84). Aplidium variabile (Herdman) : B, zooid ; B1, larva (St. WS 824). 3o DISCOVERY REPORTS 137-139111. St. WS 801: Patagonian Shelf, 165 m. St. WS 807: Patagonian Shelf, 124-126111. St.WS 808: Patagonian Shelf, 1 10-106 m. St. WS809: Patagonian Shelf, 1 04-101 m. St. WS811: Patagonian Shelf, 99 m. St. WS 813 : Patagonian Shelf, 106-102 m. St. WS 837: Patagonian Shelf, 102 m. St. WS 841 : Patagonian Shelf, 110-121 m. St. WS847: Patagonian Shelf, 57-84 m. St. WS 871 : Patagonian Shelf, 336-342 m. ?St. MS 71 : S. Georgia, 110-60 m. Colony. As van Name (1945) has said, this species is so variable that 'an attempt to describe the colonies in respect to form and size is impossible to fulfill '. Some colonies in the ' Discovery ' collec- tions are relatively short and rounded, but many have a very characteristic long form tapering gradu- ally to a fine point at the free end (PI. I, fig. 2). These long colonies were apparently attached by the lower rounded end to a bottom of sand. The colour of the preserved colonies is usually some shade of orange, yellow or brown, and the zooids sometimes show through the test, but not always. Generally there are no obvious systems of zooids, but in a few cases the zooids could be seen to be arranged in double rows, probably representing narrow oval systems. The surface is usually smooth and without encrusting sand, but the interior of the colony may have a good deal of embedded sand. Some of the Table 3 Maximum Mean no. Mean no. diameter of of rows of of folds on colony (cm.) stigmata stomach o-5 18 5 i-5 18 5 2-0 16 5 3-0 17 5 7-0 21 6 7-0 21 5 8-o 22 5 8-o 20 5 9-0 17 5 io-o 18 5 15-0 16 5 28-0 15 5 long narrow colonies appear to have lain horizontally on the sand during life, as sand is adhering to the test at several places along the length of the colony (St. WS 808). In most of the specimens, the surface-layer of the test has a characteristic appearance owing to the presence of many small round pale yellow or orange-coloured vesicles. When the colony is cut open the zooids are seen to be closely spaced. The longest colony in this collection is one of 63 cm. from the Patagonian Shelf (St. WS 808), but one specimen from the same region is recorded as forming a 'portion of a colony weighing 300 g.'. Zoom (Text-fig. 2 A). The length of the zooids in the 'Discovery' material varies a good deal, from about 6 to 18 mm., and depends largely on the development of the post-abdomen. The most characteristic features of the zooid are: (1) the moderately developed and forwardly directed atrial languet; (2) the small atrial opening placed a short distance back along the dorsal side of the thorax; (3) the large branchial sac with ten to twenty-two rows of stigmata; and (4) the stomach with five or six sharply defined undivided longitudinal folds. The number of rows of stigmata and the number of folds on the stomach do not show any clear correlation with the size of the colony, as shown in Table 3. Gut. Van Name (1945) states that the stomach has usually four to six folds, but sometimes at least eight or ten. Having examined several zooids from each of many colonies in the ' Discovery ' col- lection, I have found the number of folds on the stomach to be always five or six, which I conclude to be the normal number at least in specimens from the Patagonian Shelf. The rest of the gut shows no DESCRIPTION OF SPECIES 31 diagnostic features. The anus is placed about half way along the branchial sac, opposite the 8th or 9th row of stigmata in zooids with 16 rows. It has two lobes. Gonads. Mature zooids generally have both ovary (ov.) and testis (t.). The ovary has a few ova of various sizes and is situated immediately below the intestinal loop. The testis follicles form a long series extending down the post-abdomen. In several colonies, mature zooids had the sperm duct convoluted opposite and just below the intestinal loop (s.d.c). This is not the result of abdominal contraction and the increased length of sperm duct may serve as a reservoir for sperm. Larva (Text-fig. 2 A1). The variations in length of the larvae are shown in Table 4. Table 4 Date 3-ii- 32 6. Hi. 27 13. iii. 27 14. iii. 27 14. iii. 31 24. iii. 27 24. iii. 27 1. iv. 32 7. iv. 27 Length (mm.) o-86 0-70-0-88 0-70 0-70 o-86 o-86 0-70 0-88-0-90 0-66-0-72 All the colonies with these larvae were obtained from the Falkland Islands and the Patagonian Shelf. There is no correlation between length of the larva and the month of the year. The larva is charac- terized by the rather rounded and robust appearance of the trunk, the widely spaced papillae (p.), and the four lateral ampullae on each side, each with a rounded swelling near the base (Fig. 2 A1, a.sw.). Biology. The breeding season is indicated in Table 5 which shows the number of colonies examined in each month in which the species was taken, and also the number of these colonies containing larvae. Table 5 Month May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. No. of colonies examined 3 3 3 o o 4 7 36 12 8 14 15 No. of colonies with larvae 000000000 1103 When allowance is made for the small number of colonies collected between May and September owing to the difficulty of working during the winter months, it is still evident that the breeding season is limited to a short period in the southern summer and autumn, mainly the months of February, March and April. Between one and seven larvae were found in the atrial cavity of zooids in different colonies. The zooids with only one larva were smaller than those with several larvae. An examination of the colonies gives some picture of the annual cycle of growth and reproduction in the species. In December most colonies have well-developed zooids but few have acquired gonads. During the next three months the development of gonads takes place and few colonies were then found which lacked gonads. Breeding follows with the greatest production of larvae in March. Subse- quently, the gonads disappear and all the colonies collected in July had de-differentiated zooids representing the normal post-breeding or overwintering condition in species of Aplidium. Remarks. It is difficult to be certain that all the suggested synonyms for this species are reliable, and that all records under the name A.fuegiense refer to the same species. Of the reported occurrences in the West Antarctic, those from Mac Robertson Land and Enderby Land (Kott, 1954) may not refer to the present species. The colony and zooid described by Kott agree quite well with the specimens from the Magellan region, but the number of folds on the wall of the stomach (8) is rather high. The main difference, however, is the size of the larva, which Kott says is twice that of A. caeruleum (Sluiter). The larva of the latter species is, according to Kott's scale drawing, about 1 mm. from the end of the papillae to the base of the tail, which means that the larvae from MacRobertson Land and Enderby Land were about 2 mm. in length. This is a very large larva indeed, and is between two and 32 DISCOVERY REPORTS three times the size of the larvae of A.fuegiense in the 'Discovery' collections, placing it beyond the probable range of variation of that species. A. fuegiense is, I think, typically a subantarctic species, the 'Discovery' collections providing very many specimens from the Patagonian Shelf and the neighbourhood of the Falkland Islands, and only two doubtful records from elsewhere (South Georgia). The specimens from South Georgia were in a state of de-differentiation, the zooids being reduced to post-abdomens, and the identification is therefore uncertain. I disagree with van Name (1945) when he says that A. variable (Herdman, 1886) is 'very likely synonymous' with A. fuegiense. A comparison of the two species is given on p. 33. Distribution. Subantarctic (Falkland Islands, Patagonian Shelf, Magellan region, coast of Argentina to La Plata); ? Antarctic (South Georgia). Aplidium variabile (Herdman) (Text-fig. 2B) Amaroucium variabile Herdman, 1886, p. 216, pi. 29, figs. 7-12, text-fig. 9. For synonymy see Kott (1954), p. 174. Occurrence. St. 160: Shag Rocks, 117 m. St. WS72: Falkland Islands, 95 m. St. WS91: Patagonian Shelf, 191-205 m. St. WS93: Falkland Islands, 133-130 m. St. WS219: Patagonian Shelf, 116-114111. St. WS220: Patagonian Shelf, 108-104 m. St. WS235: Patagonian Shelf, 155 m. St. WS237: Patagonian Shelf, 150-256 m. St. WS 771 : Patagonian Shelf, 90 m. St. WS 772: Patagonian Shelf, 309-163 m. St. WS 781 : Patagonian Shelf, 148 m. St. WS 782: Patagonian Shelf, 141-1461^ St. WS783: Patagonian Shelf, 165-0 m. St. WS787: Patagonian Shelf, 106- 110 m. St. WS791: Patagonian Shelf, 95-101 m. St. WS793: Patagonian Shelf, 108-111 m. St. WS 794: Patagonian Shelf, 123-126 m. St. WS 796: Patagonian Shelf, 1 08-1 13 m. St. WS 797: Patagonian Shelf, 115-111 m. St. WS799: Patagonian Shelf, 141-137 m. St. WS808: Patagonian Shelf, 1 10-106 m. St. WS 811 : Patagonian Shelf, 99 m. St. WS 813: Patagonian Shelf, 106-102 m. St. WS816: Patagonian Shelf, 150 m. St. WS 824: Patagonian Shelf, 146-137 m. St.WS838: Patagonian Shelf, 149-159 m. St. WS847: Patagonian Shelf, 57-84 m. St. WS857: Patagonian Shelf, 123-124 m. St. WS865: Patagonian Shelf, 126-128 m. St. WS869: Patagonian Shelf, 187-201 m. St. MS 64: S. Georgia, 7-15 m. ?St. MS 71 : S. Georgia, 110-60 m. Colony. Colonies of many shapes are present in the collection, the shape depending to some extent on the object to which the colony is attached. The colonies which have been growing on the stems of hydroids tend to be long and narrow and often laterally flattened. Other colonies have apparently been on a sandy bottom and these are usually more globular with a short irregular stalk. Some specimens are slightly lobed. A few colonies have the long narrow finger-like form commonly found in A. fuegiense. The colour in preserved specimens is generally pale buff-yellow, buff, or buff-grey. In most cases the surface is smooth and the colony without sand ; although some specimens have a light coating of sand all over, sand, when present, is more often confined to the stalk or basal part of the colony. Usually the zooids show through the test quite distinctly. Definite arrangement of the zooids is seldom ap- parent, but sometimes they are grouped into small indistinct systems. Usually the zooids lie obliquely to the surface of the colony and not at right angles as in Kott's (1954) specimens. The colonies may reach a length of 12 cm. but are generally under 4 cm. in their greatest dimension. Zooid (Text-fig. 2B). The length of the zooids varies from 1-5 to 8-o mm. according to the degree of contraction and the development of the post-abdomen. In large zooids the thorax may attain 3-5 mm. and the abdomen 2-0 mm. Herdman (1886), in his original account, gave 2-5 mm. as the DESCRIPTION OF SPECIES 33 usual measurement of the thorax and abdomen together, but one of the colonies from the ' Challenger ' collection which I have examined has well-expanded zooids with thorax 3-5 mm., abdomen 2-0 mm. and post-abdomen 4-0 mm. Thorax. The oral siphon is 6-lobed and the atrial siphon has a simple or 3-cleft languet. The branchial sac has from nine to fifteen rows of stigmata. Gut. The stomach has from ten to sixteen longitudinal folds, generally from twelve to fifteen. One or two of the folds often extend only part of the length of the stomach. The anus has two distinct lips. It is situated opposite the 8th row of stigmata in zooids with fifteen or sixteen rows. Larva (Text-fig. 2B1). The larva of this species has not been described. It ranges from 0-58 to 070 mm. in length, measured from the end of the papillae to the base of the tail. The trunk is rather deep and stout. The most characteristic feature of the larva is the presence of many small apparently isolated vesicles (v.) arranged in a semicircle round the anterior end of the trunk. The three anterior papillae are rather widely spaced and have slender stalks. There are no paired or median ampullae, a feature unusual in species of Aplidium. Both ocellus and otolith are present. There are up to ten larvae in the atrial cavity of breeding zooids. Remarks. Herdman (1886) pointed out that this species somewhat resembles A. fuegiense in external appearance, and Hartmeyer (191 1, 1912) also regarded the species as similar. Van Name (1945) stated that they are 'very likely synonymous'. I have examined many specimens of both species, including thirteen colonies of Herdman's type material of A. variabile, kindly lent by the British Museum (Natural History). In my opinion the species are certainly separate, and reliable distinctions are found in both zooids and larvae, as shown in Table 6. Table 6 Stomach Larva A. fuegiense 5 or 6 undivided folds Trunk 0-66-0-90 mm. ; paired club-like anterior ampullae; no small isolated vesicles A. variabile Usually 10-15 folds, a few of them divided Trunk 0-58-70 mm. ; no club-like anterior ampullae; or incomplete many small isolated vesicles With regard to these features, the stomach of A. fuegiense is very characteristic and I find that the number of folds does not exceed six, even in the largest colonies with fully mature zooids. The 'Discovery' material, therefore, gives no confirmation of van Name's (1945) statement that the folds on the stomach sometimes number at least eight or ten. In the type specimens of A. variabile the zooids which I have examined show thirteen to fifteen folds, thus agreeing with Herdman's statement and illustration. Hartmeyer (191 1) found fourteen folds, sometimes fewer, and later (1912) stated that the number may be as low as six; he may have been confusing the two species. There is little doubt, however, that the number is generally at least twelve, and Kott (1954) always found fourteen or fifteen folds. Although there were embryos in one of the type specimens, no fully developed larvae were present, and the larval description is based on ' Discovery ' specimens from the Patagonian Shelf. The larvae of A. variabile and A. fuegiense cannot be confused. Apart from one record for the Chatham Islands (New Zealand) by Sluiter (1900), A. variabile has previously been taken only from Kerguelen, where it seems to be fairly common. Michaelsen (1924) was in some doubt whether to accept the record from New Zealand, and if we ignore it, the previous records were confined to Kerguelen. The wide geographical separation of the previous and the new localities is perhaps not surprising, when it is remembered that the latitude of Kerguelen Island and 34 DISCOVERY REPORTS the Falkland Islands is almost the same and that many Subantarctic and Antarctic species have a very wide distribution. Distribution. Subantarctic (Kerguelen; Patagonian Shelf; Falkland Islands); Antarctic (Shag Rocks; South Georgia). Aplidium falklandicum sp.n. (Text-fig. 3, A-H; PI. I, figs. 3, 4) Holotype. St. WS 73, 121-130 m. Length of colony: 19-0 cm. Diagnosis of species. Colonies low, pillow-shaped, globular, or elongate. Systems of zooids oval or elongate. Zooid with atrial languet simple and triangular, or slightly trifid; about seven moderately strong longitudinal muscles ; ten to twenty-three rows of stigmata ; stomach with five to seven shallow longitudinal folds, or a few indistinct marks or quite smooth. Larva with trunk 0-40-0-70 mm. long; papillae closely spaced, with slender stalks ; four narrow median ampullae ; about four pairs of lateral ampullae; a dorsal and a ventral lateral series of small vesicles. Occurrence. St. 51: Falkland Islands, 105-115111. St. 53: Falkland Islands, 0-2 m. St. 164: S. Orkneys, 24-36 m. St. 652: Burdwood Bank, 171-169 m. St. 1902: Patagonian Shelf, 50-80 m. St. WS 25 : S. Georgia, 18-27 m- St- WS 27: S. Georgia, 107 m. St. WS 72: Falkland Islands, 95 m. St. WS 73 : Falkland Islands 121-130 m. St. WS 79: Patagonian Shelf, 132-131 m. St. WS 81 : Falk- land Islands, 81-82 m. St. WS 84: Falkland Islands, 75-74111. St. WS 86: Falkland Islands, 151-1471T1. St. WS 90: Patagonian Shelf, 82-81 m. St. WS 91 : Patagonian Shelf, 191-205 m. St. WS 93 : Falk- land Islands, 133-130 m. St. WS 108: Falkland Islands, 1 18-120 m. St. WS 154: S. Georgia, 115-om. St. WS 182: Palmer Archipelago, 750-520 m. St. WS 219: Patagonian Shelf, n6-ii4m. St. WS220: Patagonian Shelf, 108-104 m. St. WS 222: Patagonian Shelf, 100-106 m. St. WS 239: Falkland Islands, 196-193 m. St. WS 243: Patagonian Shelf, 144-141 m. St. WS 244: Patagonian Shelf, 253-247 m. St. WS 764: Patagonian Shelf, 1 10-104 m- St. WS 765: Patagonian Shelf, 11 3-1 19 m. St. WS 771 : Patagonian Shelf, 90 m. St. WS 774: Patagonian Shelf, 139-144 m. St. WS 775: Patagonian Shelf, 115-110 m. St. WS 782: Patagonian Shelf, 141-146 m. St. WS 787: Patagonian Shelf, 106-110 m. St. WS791: Patagonian Shelf, 97-95 m. St. WS792: Patagonian Shelf, 102-106 m. St. WS793: Patagonian Shelf, 108-111 m. St. WS 796: Patagonian Shelf, 106-113 m. St. WS 807: Patagonian Shelf, 124-126 m. St. WS813: Patagonian Shelf, 106-102 m. St. WS847: Patagonian Shelf, 57- 84 m. St. WS 858: Patagonian Shelf, 132-123 m. St WS 865: Patagonian Shelf, 126-128 m. Colony. (Text-fig. 3 A; PI. I, figs. 3, 4.) Colonies vary from low dome-shaped or globular, to ovoid, long or tongue-like masses and often attain a diameter of 6-8 cm. Generally the colony is simple but is occasionally divided into a few lobes. Attachment is sometimes by a broad base, but often by a narrow area, and occasionally a short pedicel is formed. The surface is usually smooth, but sand is sometimes present, especially at the base. Preserved specimens are pale yellow-grey to buff, and a pattern may be formed by the systems of zooids showing through the semi-transparent test. The common cloacal openings are many, small and round. The largest colonies in the collection are about 20 cm. long. In a few specimens there is no apparent place of attachment, and these colonies may have rested freely on the bottom, but most specimens were attached to shells or small stones. Zoom (Text-figs. 3B, C, E). In well-developed and expanded zooids the thorax is 1-8-3-0 mm. in length. The abdomen is about the same length or slightly shorter. The post-abdomen varies greatly in length, often exceeds 6 mm. and sometimes reaches 20 mm. (Text-fig. 3 B). The thorax is the widest part of the zooid and the post-abdomen the narrowest but the differences in width are slight. Thorax. There are six pointed oral lobes, and the atrial opening, which lies opposite the first or second row of stigmata, is surmounted by a short triangular simple, or slightly trifid languet (a.l.). Six DESCRIPTION OF SPECIES 35 to eight moderately strong longitudinal muscles are present on each side of the thorax. Zooids from different colonies vary a good deal in the development of the branchial sac, which may have from ten to twenty-three rows of stigmata. Each row generally has twelve to fifteen stigmata. The dorsal languets are quite large. In about half of the specimens the zooids have a conspicuous triangular 3 mm Text-fig. 3. Aplidium falklandicum sp.n. : A, colony; B, zooid; C, anterior part of zooid with no thoracic triangles; D, larva (St. WS 793); E, zooid with thoracic triangles; F, G, stomach of zooids showing indistinct markings; H, larva (St. WS 72). 5-2 36 DISCOVERY REPORTS white area on each side of the body wall near the base of the ventral part of the thorax (Fig. 3 E, tri.). Other specimens have no trace of this (Fig. 3 C). Gut. The oesophagus is usually longer than the stomach and is widest at its branchial end. There is much variation in the stomach. The zooids of some colonies have a stomach with five to seven shallow but distinct longitudinal folds (Text-fig. 3 C), but in other specimens (Text-fig. 3 E, F, G) the folds are reduced to a variable degree, or broken up into a few indistinct swellings or completely absent. In the last case the stomach is like that of Synoicwn. The intestine and rectum are of the type usual in Aplidium. The anus has two small diverging lips ; it is situated opposite the 9th row of stigmata when twelve rows are present and opposite the 12th row in zooids with twenty-one rows. Gonads. The ovary is either close behind the intestinal loop (Text-fig. 3E, ov.) or at some distance from it (Text-fig. 3 C, ov.). A long series of small testis follicles (t) occupies much of the length of the post-abdomen. Larva (Text-figs. 3 D, H). The trunk of the larva ranges in length from 0-40 to 0-70 mm. The three papillae are closely spaced and are borne on slender stalks. There are four long narrow median ampullae and four pairs of shorter stouter lateral ampullae. On each side of the dorsal and ventral part of the trunk there is a slender strand of tissue bearing a series of small rounded vesicles (ves.). Both ocellus and otolith are present. Table 7 A. falklandicum Colony Variable ; low to elongate Stomach 5-7 shallow folds, or reduction of folds, or smooth A. fuegiense Variable ; low to elongate 5-7 deep folds Larva Slender. Trunk 0-40-0-70 mm. Papillae close. Lateral series of dorsal and ventral vesicles Stout. Trunk o-6 — 0-90 mm. Papil- lae distant. No series of vesicles Biology. Colonies were collected in all months of the year except August and September, and larvae were found in the subantarctic material in January, February, March, April, June, July, October, November and December. There were no larvae in the antarctic specimens. It appears that the species breeds throughout the year, and in this respect resembles A. caeruleum as described by Hartmeyer (191 1). The larvae in each breeding zooid number from four to nine. None of the colonies showed the accumulation of reserve material in the post-abdomen which is commonly found during the post-breeding and overwintering period in many species of polyclinid ascidians. It may be that in species which breed almost continuously throughout the year the de- differentiation of zooids and the accompanying resting phase have been reduced. Remarks. I have been surprised that this species, which is apparently common round the Falkland Islands and on the Patagonian Shelf, could not be identified with any known species, and I suspect that hitherto it has been confused with A. fuegiense, with which it is often collected. A comparison of the two species is shown in Table 7. It is evident from the table that the larva affords the best characters for distinguishing the species, as will be seen also by comparing Text-figs. 2 A1 and 3D, H. The larva also indicates that specimens possessing white thoracic triangles and those lacking them are both of A. falklandicum (see Text-figs. 3 D, H). It unites, too, a whole series of specimens showing structural differences in the stomach, which might otherwise have been thought to indicate specific differences. Distribution. Subantarctic (Falkland Islands, Patagonian Shelf); Antarctic (Graham Land, S. Orkneys, S. Georgia). DESCRIPTION OF SPECIES 37 Aplidium radiatum (Sluiter) (Text-fig. 4 A, B; PI. I, fig. 5) Psammaplidium radiatum Sluiter, 1906, p. 25, pi. 2, figs. 23, 24; pi. 4, fig. 52. Amaroucium radiatum Hartmeyer, 1 909-11, p. 1471. Aplidium radiatum. Kott, 1954, p. 173. Occurrence. St. 27: S. Georgia, 110 m. St. 164: S. Orkneys, 24-36 m. St. 181: Palmer Archi- pelago, 160-335 m- ^t' J86: Palmer Archipelago, 295 m. St. 190: Palmer Archipelago, 93-126 m. Colony (PI. I, fig. 5). Most colonies have a stalk which, in the 'Discovery' material, is always shorter than the head, although sometimes only slightly shorter. In a few colonies there is no stalk, 1.0 mm w ■53 2 cm 1.0 mm Text-fig. 4. Aplidium radiatum (Sluiter): A, zooid; B, transverse sections of stomach of two zooids (St. 186). Aplidium seeligeri sp.n. : C, D, two colonies (Sts. 935, 941); E, zooid (St. 941). 38 DISCOVERY REPORTS the lower end of the colony merely being flat. The head of the stalked colonies is almost spherical, or ovoid or cylindrical. The general colour of the preserved colony is grey, patterned by the regular double rows of zooids, converging at the apex of the colony, which constitute one of the most charact- eristic features of the species. The double rows are produced by the adjacent long narrow oval systems of zooids. Each of the systems has a long central cloacal canal, and the canals of most of the systems open into a common depression at the apex of the colony. Although this is the condition generally found in the species, some colonies have, in addition, other cloacal openings scattered over the surface, as observed by Kott (1954). Sand is almost always present within the common test, especially in the superficial layers, but the test material itself is transparent. The largest and smallest specimens in the collection are 6-4 and 1-5 cm. in total length. Zooid (Text-fig. 4 A). The zooid is large and stout, the thorax being about 3 mm. long and the abdomen about the same length; the post-abdomen is variable, and often exceeds the combined length of the thorax and abdomen. Thorax. The three narrow pointed lobes of the atrial languet (a.l.) are always present. Sluiter (1906) noted that the atrial opening is placed a short distance back on the dorsal side of the thorax. The ' Discovery ' specimens not only confirm this as a constant feature of the species, but also show that in all well-expanded zooids the opening is of a size unusually great in Aplidium, and exposes a large part of the dorsal side of the thorax (a.o.). There are thirteen to nineteen rows of stigmata, the number being independent of the size of the colony, at least in the ' Discovery ' specimens, all of which are well grown. Gut. The oesophagus varies in length. According to Sluiter (1906) and Kott (1954) the stomach has four longitudinal folds, but I find a considerable variation in the appearance of the stomach in zooids even from the same colony. In many there are six to eight folds (Text-fig. 4B), but other zooids have a stomach showing no true folds. One or other of these conditions is probably an artifact. The folds, when present, are rather shallow in the 'Discovery' specimens. The undivided anus lies between the 8th and 9th rows of stigmata in zooids with 13 rows. Gonads. In some colonies zooids were seen with an ovary and in others there was a very slightly developed testis (t) in the form of a row of small pear-shaped follicles. Biology. There is not enough material to give much information on this subject. One specimen taken in March (St. 190) had large eggs in the oviduct and one specimen in the same month (St. 27) had embryos in the atrial cavity, but larvae were not found in any colony. Kott (1954) recorded embryos in January in her specimens from the neighbourhood of Enderby Land, but unfortunately they too were not fully developed. The embryos are very large, according to Kott. Remarks. Some of the ' Discovery ' specimens were taken from near the type locality in the Palmer Archipelago, but others extend the known range of the species to the South Orkneys and South Georgia. This species has two features unusual in the genus: (1) sharp division of the colony into a head which carries the oral and cloacal openings and a stalk which lacks them; and (2) the openings of cloacal canals from several systems into a common apical depression. These are both characters found elsewhere principally in species of Sycozoa. Distribution. Western Antarctic (Graham Land, South Orkneys, South Georgia), Eastern Antarctic (Enderby Land). DESCRIPTION OF SPECIES 39 Aplidium caeruleum (Sluiter) (Text-fig. 5) Amaroncium caeruleum Sluiter, 1906, p. 16, pi. 1, figs. 13-16; pi. 4, fig. 49. Aplidium caeruleum Kott, 1954, p. 172, fig. 66. Occurrence. St. 190: Palmer Archipelago, 93-126111. ?St. 1563: Marion Island, 113-99111. St. 1952: S. Shetlands, 376-383 m. %n 8 / cm 3 mm Text-fig. 5. Aplidium caeruleum (Sluiter): A, colony; B, zooid; C, transverse section of stomach; D, stomach with low broken folds (St. 1952); E, larva (St. 190). 4o DISCOVERY REPORTS Colony (Text-fig. 5 A). Most of the colonies in the collection show the characteristic shape of a stout club or cone attached by the narrow end. They reach a height of 4 cm. The specimens do not show the blue coloration which gives the species its name; Hartmeyer (191 1) also found that much of his material was not blue, but van Name (1945) mentions the colour as being characteristic of most material. The superficial layer of the common test is firm and is impregnated with sand grains, but the test within the colony has no sand and is soft and clear, this being the usual condition in the species. Sand is also lacking immediately round the oral openings of the zooids and round the margin of the common cloacal opening. The zooids are arranged in a single peripheral layer with their oral openings forming a ring round the upper part of the colony, slight swellings marking the position of the zooids. The zooids number up to fifteen in a colony. Zoom (Text-fig. 5B). Table 8 shows the principle characters of the zooids of the 'Discovery' specimens compared with those described by Sluiter (1906), Hartmeyer (191 1) and Kott (1954). Atrial languet Oral tentacles Stigmata Stomach Larva No. of larvae per breeding zooid Table 8 ' Discovery ' 3-lobed Sluiter Toothed 20 20-30 8 rows, each crossed 10 rows by a parastigmatic transverse bar; or 16 rows without bars 10-13 low folds sometimes broken 8 entire folds and a few short ones 1-11 4or5 Hartmeyer 3-lobed ? No true folds ; in- stead pigmented lines Trunk i-omm. long Trunk 1-2 mm. long ? 4 or 5 Kott 3-lobed 16-20 rows, the anterior rows with parastigmatic trans- verse bars Smooth externally; intern- ally with papillae some- times arranged in rows Trunk i-o mm. long (measurement taken from fig. 66, Kott) ? Thorax. The branchial sac is of a kind unusual in Aplidium in that parastigmatic transverse bars (p.b.) are often present. These cross all the rows of stigmata in some of the 'Discovery' specimens, but in others are entirely absent. As specimens with parastigmatic bars have only half the number of rows possessed by specimens lacking the bars, it is evident that each row crossed by a bar is later divided into two rows. This accounts for the large range in the number of rows. It may also explain the fact that Sluiter noted ten rows of stigmata but eighteen dorsal languets, the additional languets presumably corresponding in position to parastigmatic transverse bars which may have been present in parts of the branchial sac. Gut. The true structure of the stomach is by no means certain. Deep and well-developed folds are apparently rarely or never present, and are sometimes represented by pigmented lines or rows of internal papillae. In the 'Discovery' specimens the folds are usually undivided (Text-fig. 5B, St.), but sometimes broken up (Text-fig. 5D). The anus is opposite the 5th row of stigmata. Gonads. The gonads have the position usual in Aplidium, but the testis follicles (t.) are crowded together instead of being biserially arranged. Larva (Text-fig. 5 E). The larva, with a trunk 1 mm. long, is unusually large for species of Aplidium. The papillae are not very widely spaced, and have stout stems. Four median ampullae (m.a.) are present, and on each side lies a series of lateral ampullae (l.a.) which number six according to Kott (1954), but are much more numerous in the ' Discovery ' specimens. The lateral ampullae are attached DESCRIPTION OF SPECIES 41 to a ridge which extends on each side along the dorsal and ventral parts of the trunk. This arrangement is like that described by Carlisle (1952) in Polyclinum aurantium Milne Edwards. The only colonies in the collection with larvae were two taken in March (St. 190); all the larvae from one colony have both ocellus and otolith (Text-fig. 5E), but all those from the other colony lack an ocellus. This is a very curious fact, but as the larvae and the zooids from which they come are identical in all other respects, I cannot doubt that both colonies are of A. caeruleum. According to Sluiter (1906) and Kott (1954) the larvae are contained in a brood pouch, but Hart- meyer (191 1) doubted the existence of a special pouch. In the ' Discovery ' specimens the larvae were lying in the atrial cavity, as they normally do in species of Aplidium. Biology. It is not possible to add anything regarding the general biology of the species from the scanty material available. Hartmeyer (191 1), however, from a study of his rich material, found all stages of male and female ripeness at all seasons, the larvae not being confined to any one period. They were present, for instance, both in January and in July. This is a remarkable case of independence of temperature in the breeding cycle of an antarctic ascidian. Remarks. The identification of the specimens in the collection is not in doubt, except the single colony from Marion Island (St. 1563). In this colony all the zooids are degenerate and identification rests on the shape and texture of the colony, which closely agree with typical colonies of the species. There must remain considerable doubt, however, especially in view of the more northern latitude of the station. Distribution. Western Antarctic (Graham Land, South Shetlands), Eastern Antarctic (Kaiser Wilhelm II Land, MacRobertson Land, Enderby Land). (PMarion Island.) Aplidium stanleyi sp.n. (Text-fig. 6 A, B, C) Diagnosis of species. Colony consisting of low heads arising from a sandy base. Zooids with the atrial opening a little way back along the dorsal side of the thorax. Twelve to fifteen rows of stigmata. Post-abdomen narrow, even with fully developed gonads. Stomach with twenty to twenty-four longitudinal folds. Testis a long series of small follicles. Occurrence. St. WS 229: Falkland Islands, 210-271 m. Holotype. St. WS 229: size — 12 mm. wide at base, 11 mm. high. Colony (Text-fig. 6 A). This species is represented by many colonies taken in a single haul from the continental shelf round the Falkland Islands. The largest colony is 1-4 cm. high and 1-4 cm. wide. Typically each colony consists of one head or a few heads joined basally, where there is an expansion of the common test which is here heavily impregnated with sand. At its junction with this base, the head is narrowed and the upper part is expanded with a rather flattened or slightly dome-shaped apical end. The test material is sufficiently clear to allow the zooids to show through. They are arranged in a single system in each head, no head having been found with more than one common cloacal opening. The basal sandy test is often produced into a number of finger-like processes or broad lobes, and the colonies appear to have been loosely attached to the sandy substratum. Zoom (Text-fig. 6B). The zooids are small, averaging about 5 mm. in length, of which the thorax and abdomen account for about 2 mm. Thorax. The oral siphon has six pointed lobes. The atrial opening is placed a short distance back along the dorsal side of the thorax, opposite to the 3rd row of stigmata, and is a simple round hole, bearing on its dorsal margin a languet («./.). The languet is sometimes simple and triangular, but more often is divided into a long narrow median lobe and a short pointed lobe at its base on each side. The muscles on the thorax are only moderately well developed. There are from twelve to fifteen rows of stigmata in the branchial sac, each row with about fifteen stigmata. 42 DISCOVERY REPORTS Gut. The oesophagus is short in all zooids examined, and the stomach (st.) barrel-shaped with from twenty to twenty-four narrow close longitudinal folds. The intestinal loop is usually rather short. The anus has two shallow lobes and is situated opposite the 5 th or 6th row of stigmata in zooids with twelve rows. Post-abdomen. In some zooids the post-abdomen is short but when fully grown it is very long and narrow, extending far down into the basal sand-covered test. It is typically very slender, being only half the width of the abdomen. 0.5 mm Text-fig. 6. Aplidium stanleyi sp.n. (St. WS 229): A, colony; B, zooid; C, transverse section of stomach. Aplidium quadrisulcatum sp.n. (St. 939): D, colony; E, zooid. DESCRIPTION OF SPECIES 43 Gonads. The ovary is represented in some zooids by a small group of ova in the upper part of the post-abdomen (oik). The testis consists of a long narrow series of many small pear-shaped follicles occupying much of the length of the post-abdomen (t). No larvae were found. Remarks. This species is distinguished from all species of Aplidium described from South America, the Subantarctic, and the Antarctic by the following combination of characters: (1) colony small and loosely attached to a sandy substratum; (2) stomach with twenty to twenty-four folds; (3) post- abdomen conspicuously narrower than abdomen. It most resembles three species from New Zealand: A. phortax (Michaelsen, 1924), A. benhami Brewin, 1946, and A. adamsi Brewin, 1946. From these species it is distinguished by characters (1) and (3). Distribution. Falkland Islands. Aplidium quadrisulcatum sp.n. (fig. 6D, E) Holotype. St. 939: size of colony 1 cm. in diameter. Diagnosis of species. Colony of variable shape, with sand embedded in the test. Zooids small; oral siphon with six shallow or deep lobes; atrial opening about one-third of the length of the thorax from the base of the oral siphon; atrial languet with 1 median and 2 short lateral lobes; nine to eleven strong longitudinal muscles; 10 rows of stigmata; stomach with four or five indistinct folds. Occurrence. ?St. 935 : North Island, New Zealand, 84 m. St. 939: North Island, New Zealand, 87 m. Colony (Text-fig. 6D). The colonies from St. 939 are small, the largest being 1-3 cm. in diameter. These colonies vary in shape from flat cushion-like masses to single or lobed ovate heads with a narrow stalk. Sand is present on the surface and throughout the common test, rendering the colonies very firm. Systems of zooids are not visible, but a single common cloacal opening is present in each small colony and on each lobe of the larger colonies. A few specimens from St. 935, which probably belong to this species, reach a diameter of 2-3 cm., and completely lack sand. Table 9 Rows of Stomach Colony Longitudinal muscles stigmata folds A. quadrisulcatum sp.n. With sand 9-1 1 10 4or 5 A. scabellum (Michaelsen) With sand 1 strong dorsal muscle 20 6 A. nottii (Brewin) No sand 10-12 14-16 4 or 5 A. novae-zealandae Brewin With sand H 14 or 15 4 or s A. oamaruensis (Brewin) With sand 10 16-18 4 A. thomsoni Brewin With sand Concentrated on ventral side of post-abdomen 5 5 or 6 Zoom (Text-fig. 6E). The zooid is small, not exceeding 2-0 mm. in length. In most zooids there is no post-abdomen, or a very short one, probably owing to the specimens having been collected out of the breeding season. Thorax. The short wide oral siphon is divided into six broad, pointed lobes, and the oval atrial opening (a.o.), is situated opposite the 3rd and 4th rows of stigmata, that is about one-third of the length of the thorax from its anterior end. There is a triangular pointed atrial languet (a.l.) of variable length, with two short pointed lateral lobes near its base. Nine to eleven longitudinal muscles converge on the sides of the abdomen. Ten rows of short stigmata are usually present, with twelve to fifteen in each row. Gut. The oesophagus is quite wide, and the squat stomach has four or five rather indistinct longi- tudinal folds. The divisions of the intestine are short. The wide rectum ends in the plain-edged anus opposite the 7th row of stigmata. 6-2 44 DISCOVERY REPORTS Gonads. None of the zooids examined showed any trace of gonads, and no embryos or larvae were found. Remarks. The characters of A. quadrisulcatum are given in Table 9 for comparison with those of species from New Zealand and the Chatham Islands with which it is most likely to be confused. These species all have a small number of folds on the stomach, but can be separated by other characters. Distribution. North end of North Island, New Zealand. Aplidium seeligeri sp.n. (Text-fig. 4, C, D, E) Holotype. St. 935. Size of colony 4 by 1-5 by 2-5 cm. Diagnosis of species. Colony consisting of a head of variable shape borne on a short stalk. Zooids irranged in small round systems with central common cloacal openings. Zooids with six-lobed oral iphon and a very short atrial siphon surmounted by a triangular languet with two lateral lobes ; ten .0 twelve equally spaced longitudinal muscles ; thirteen to sixteen rows of stigmata ; oesophagus quite long; stomach with nineteen to twenty-two folds. Occurrence. St. 935: North Island, New Zealand, 84m. St. 941 : North Island, New Zealand, 128 m. Colony (Text-fig. 4C, D). The larger of the two specimens (Text-fig. 4C) is a somewhat flattened mass, 4 cm. long, 2-5 cm. across, and 1-5 cm. in height; the lower part is narrowed to form a short tapering stalk apparently attached to the substratum by a small area. This specimen is buff-coloured in the preserved state, smooth and soft, with the zooids showing through as brown spots. The other colony (St. 941) (Text-fig. 4D) has an almost spherical head and a short stalk rather more than half the diameter of the head. This specimen is 1-5 cm. in total length. The surface is smooth and rather soft, and of a pale dirty buff colour through which the zooids can be faintly seen. In both colonies the zooids are arranged in small round systems of six to twelve zooids, with a small central cloacal opening. Zoom (Text-fig. 4E). In well-expanded zooids the thorax and abdomen each measures about i-8 mm., and the post-abdomen up to 5 mm. Thorax. Six shallow lobes are present on the oral siphon, and the atrial opening (a.o.) is at the end of a very short siphon opposite the 3rd and 4th row of stigmata. There is a short triangular atrial languet with two small lateral lobes near the base. Ten to twelve slender longitudinal muscles are equally spaced round the thorax and continue along the sides of the abdomen and post-abdomen without appreciably converging in the post-abdomen. There are thirteen to sixteen rows of short oval stigmata, with about twelve stigmata in each row. Table 10 Longitudinal Atrial Colony muscles opening Stigmata Oesophagus Stomach A. seeligeri Stalked 10-12 Short siphon 13-16 rows Long 19-22 folds A. phortax Sessile 13 or 14 Sessile 10-13 rows Short 23-26 folds Gut. The oesophagus is more than twice as long as the stomach and narrows at both its upper and lower ends. The stomach is barrel-shaped with nineteen to twenty-two narrow continuous folds. The rectum is wide and ends in a simple anus at the level of the 10th row of stigmata. Gonads. The post-abdomen of some zooids contains a series of small testis follicles (t), with a straight common sperm-duct. No ovary was present, but a few zooids had a single brown egg or developing embryo in the atrial cavity. In these embryos the rudiment of the trunk measured 0-52 mm. in length. Remarks. A. seeligeri bears more resemblance to A. phortax (Michaelsen), a species also found in DESCRIPTION OF SPECIES 45 New Zealand, than to any other species. The principle characters serving to distinguish these species are shown in Table 10. Distribution. North end of North Island, New Zealand. The genera Synoicum Phipps, Aplidiopsis Lahille, and Polyclinum Savigny differ from Aplidium in having the stomach without longitudinal folds. Their main distinguishing characters are shown in Table 11. Aplidiopsis is intermediate between Synoicum and Polyclinum, but is apparently closer to Synoicum from which it differs only in having a constriction at the junction of abdomen and post-abdomen. It may be doubted whether this is a character of generic value but I retain Aplidiopsis because A. discoveryi sp.n. (see p. 51) confirms the generic characters. Table n Branchial Stomach papillae wall Gut loop Synoicum Absent Areolated or smooth Not twisted Aplidiopsis Absent Smooth Not twisted Polyclinium Present Smooth Twisted Post-abdomen Not narrowed to form a pedicel joining abdomen Narrowed to form a pedicel joining abdomen Narrowed to form a pedicel joining abdomen Gonads Testis compact, sometimes partially surrounding ovary Testis compact partially surrounding ovary Testis compact partially surrounding ovary Genus Synoicum Phipps, 1774 Synoicum adareanum (Herdman) (Text-fig. 7E; PI. I, fig. 6) Polyclinum adareanum Herdman, 1902, p. 195, pi. 22, figs. 1-9. For synonymy see van Name 1945, p. 59. Occurrence. St. 175: S. Shetlands, 200 m. St. 1660: Ross Sea, 351 m. St. WS 33: S. Georgia, 130 m. St. MS 71 : S. Georgia, 110-60 m. Colony. The numerous colonies from St. 1660, in the Ross Sea, are very typical of this species. There is a stalk of variable length with diameter always less than that of the head, but sometimes only slightly less. The stalk is brown, tough, and transversely wrinkled. The head is ovate or roughly conical, smoother than the stalk, grey or pale pink-grey. Systems of zooids are circular and not very large. Kott's (1954) statement that the systems in her specimens were from 20 to 80 mm. in diameter is difficult to understand, as the diameter of the whole head rarely exceeds 100 mm. Sluiter (1906) records a specimen 180 mm. long and 120 mm. in diameter. A large specimen in the 'Discovery' material has the head 70 mm. long and the stalk 30 mm., and another specimen has a total length of 130 mm. This material is therefore among the largest yet recorded. The colonies may be single, but often two stalks arise from a common base. There is an error (possibly typographical) in van Name's statement that Sluiter's (1906) illustration was of a specimen 10 cm. high and 65 cm. in diameter; the diameter should have been 6-5 cm. Several small colonies from South Georgia, which I place in this species, also have a short stalk and rounded head with distinct circular systems of zooids. The largest of these colonies is 18 mm. high. ZooiD. The zooids may attain 12 mm. in length, of which the thorax and abdomen commonly occupy about 4 mm. Thorax. The number of oral tentacles in several zooids examined varied between sixteen and twenty-four, a number considerably greater than that given by van Name (1945) who recorded about twelve. All zooids examined had eighteen to twenty rows of stigmata, each row with thirty, or a few more, stigmata. Van Name (1945) states that there are 'a dozen or more' stigmata in a row but Kott (1954) found twenty to thirty. 46 DISCOVERY REPORTS Gut. In uncontracted zooids the stomach (Text-fig. 7E) has a narrow anterior end, is widest just behind the middle and somewhat narrowed posteriorly. The anteroventral margin is slightly concave. In the ' Discovery ' specimens the stomach is quite sharply marked off from both the oeso- phagus and the intestine, although Kott (1954) did not find this in her material. The anus is situated opposite the 13th or 14th row of stigmata and has two lips which are usually reflected. Remarks. The synonymy of this species is still obscure. According to van Name (1945), S. georgi- anum Sluiter and S. kohli Sluiter should probably both be referred to S. adareanum, but I believe that 1.0 cm Text-fig. 7. Synoicum georgianum Sluiter (St. 149): A, colony; B, zooid; C, fully developed larva; D, larva showing break-up of papillae and ampullae. Synoicum adareanum (Herdman) (St. 1660): E, gut DESCRIPTION OF SPECIES 47 this is not so (see below). If S. adareanum extends to South Georgia, and I have here accepted several specimens from that area as S. adareanum, the small size of these specimens might be explained by less favourable conditions prevailing on the boundary of the geographical range. Distribution. Antarctic (Graham Land, South Shetlands, South Georgia, Ross Sea, Kaiser Wilhelm II Land, Enderby Land, Adelie Land, MacRobertson Land), Subantarctic (Kerguelen). Synoicum georgianum Sluiter (Text-fig. 7 A, B, C, D; PI. I, fig. 7) Synoicum georgianum Sluiter, 1932, p. 11, figs. 9, 10. Occurrence. St. 140: S. Georgia, 122-136 m. St. 144: S. Georgia, 155-178 m. St. 149: S. Georgia, 200-234 m. St. 474: S. Georgia, 199 m. St. 1941: S. Georgia, 55-22 m. St. WS794: Patagonian Shelf, 123-126 m. St. MS 10: S. Georgia, 26-18 m. St. MS 74: S. Georgia, 22-40 m. Colony (Text-fig. 7A; PI. I, fig. 7). The colonies are all small, never exceeding 2-5 cm. in length. Two, three or four heads generally arise from a common base, are narrow in their lower part and gradually widen towards the distal end. Some colonies consist of many small heads attached to a mass of basal, somewhat root-like processes, a condition approaching that described by Sluiter for the type colonies, and in these colonies the individual heads constitute single systems each with an apical common cloacal opening, as described by Sluiter. In other, larger, heads there are up to five round systems of zooids. Usually the surface of the colony is bare, but sometimes there is a coating of sand or broken shell which is confined to the outer layer of the test. The test material is very clear, soft and flexible. Zoom (Text-fig. 7B). The size and proportions of the zooid are variable, but often the thorax is about 2 mm. long and the abdomen 2 or 3 mm. The post-abdomen is narrow and may be longer than the thorax and abdomen combined. In some zooids the post-abdomen contains reserve material (res.) similar to that often stored in the post-abdomen of other polyclinid species. Thorax. The oral siphon has six lobes, which are sometimes very shallow. The anterior margin of the atrial siphon is elongated into a languet (a. I.) almost always provided with three narrow teeth. On the posterior margin there are generally three short teeth. Branchial sac. Thirteen to fifteen rows of stigmata are present, each with about thirty stigmata. Gut. The gut is indistinguishable from that of S. adareanum, except that the stomach is not pear- shaped, but this is a slight difference. The anus lies opposite the 8th row of stigmata, and is provided with two lips. Gonads. In two of the specimens collected in December gonads are present. The ovary (ov.) is small and compact, with few ova, and lies a short distance below the loop of the intestine, not, as in Sluiter 's specimen, overlapping the lower part of the loop. In a few zooids there is a long series of testis follicles below the ovary. Larva (Text-fig. 7C, D). One colony (St. 144, 5. i. 1927) had fully developed larvae in the atrial cavities of the zooids. These varied from 0-54 to 0-64 mm. in length from the end of the papillae to the base of the tail. In the earlier stages of development (Text-fig. 7C) the three anterior papillae and the four median ampullae were seen together with a few large dorsal and ventral (lateral?) ampullae. In later stages the gut and siphons could be seen and the sensory vesicle containing only a spherical otolith and no trace of the ocellus. Still more advanced larvae (Text-fig. 7D) showed a breaking-up of the papillae and ampullae : this stage may represent the early metamorphosis of larvae retained beyond the normal period in the atrial cavity. Remarks. In dealing with S. adareanum I have already mentioned that S. georgianum has been regarded as a synonym (van Name, 1945). Sluiter pointed out, however, in his original description, that the formation of the colony in S. georgianum was different, and the colonies described above 48 DISCOVERY REPORTS confirm this. As these colonies contain mature zooids, they are not to be regarded as young specimens. Corresponding differences in the zooids are more difficult to find, but Table 12 lists the constant distinctions shown by the colony and zooids of the specimens in the ' Discovery ' collections. Table 12 S. adareanum S. georgianum Colony Stalk firm, opaque, wrinkled and sharply marked off Stalk and head not sharply marked off from each from head. Colony massive other; both transparent. Colony slender Zooid 18-20 rows of stigmata I3_I5 rows of stigmata Anus opposite 13th row Anus opposite 7th or 8th row Stomach pear-shaped Stomach not pear-shaped Previous accounts do not always bear out these distinctions. Thus the number of rows of stigmata in S. adareanum is variously given as ten to twelve (Sluiter, 1906), fifteen to twenty (Kott, 1954), fourteen or fewer up to twenty (van Name, 1945), and about twenty (Herdman, 1902). The relative position of the anus is not clear in previous descriptions, and the stomach has been variously described but was often stated to be contracted. The most reliable distinction appears to be the form and habit of the colony, and accounts of S. adareanum agree with most of the characters listed above. Distribution. Antarctic (South Georgia), Subantarctic (Patagonian Shelf). Synoicum giardi (Herdman) (Text-fig. 8 A; PI. I, fig. 8) Morchellium giardi Herdman, 1886, vol. 14, p. 181, pi. 25, figs. 1-3. Synoicum giardi Hartmeyer, 191 1, p. 550, pi. 47, fig. 7, pi. 56, figs. 1-3; Kott, 1954, p. 169, fig. 62. For other references see Kott, 1954, p. 169. Occurrence. St. WS27: S. Georgia, 107 m. St. MS 64: S. Georgia, 7-15 m. St. MS 71: S. Georgia, 1 10-60 m. Colony (PI. I, fig. 8). One colony measures 2-7 by i-6cm. in diameter, and about 0-5 cm. in thickness, and is thus rather flatter than the colonies of this species already described by Herdman (1886), Hartmeyer (1911) and Kott (1954). Another colony is 3 cm. long and 1-5 cm. in thickness, being of a low-dome-like shape. The surface of the colonies is smooth, and the colour grey to buff, with star-shaped markings produced by the regular arrangement of the zooids in circular systems. No sand is present on the surface or within the colonies, and the common test is semi-cartilaginous in texture. Zoom (Text-fig. 8 A). The thorax and abdomen together measure about 3 mm. and the post- abdomen is at least as long. Some reserve material (res.) was present in the lower part of the post- abdomen of a few zooids, and this part was frequently bent so as to lie almost parallel to the base of the colony. Thorax. There are six moderately developed lobes on the oral siphon, and the atrial siphon has a simple languet. Twelve to fourteen rows, each with about twelve stigmata, are present in the branchial sac, compared with fourteen to sixteen rows in Hartmeyer's and eighteen in Kott's specimens. Gut. The gut is typical of the species, with an ovoid stomach having conspicuous areolations which, however, do not project so much as in the specimens described by previous authors. The anus is level with the 8th or 9th row of stigmata. Gonads. In a few zooids a small ovary (ov.) was present at some distance below the end of the intestinal loop, and a few poorly developed testis follicles (t.) occurred in a series posterior to the ovary. Remarks. All the previous records of this species are from the region of Kerguelen, and the ' Discovery ' specimens therefore extend the range to South Georgia and suggest that the species may have a wider distribution in the Antarctic. Distribution. Antarctic (South Georgia), Subantarctic (Kerguelen). DESCRIPTION OF SPECIES 49 Synoicum kuranui Brewin (Text-fig. 8B, PI. I, fig. 9) Synoicum kuranui Brewin, 1950, p. 355, text-fig. 1. Occurrence. St. 935: North Island, New Zealand, 84 m. Colony (PL I, fig. 9). A number of stalked heads are present in the collection, but it is uncertain whether these represent the heads of a single colony or are distinct colonies. The longest of these B 1.0 mm Text-fig. 8. Synoicum giardi (Herdman) (St. MS 71): A, zooid. Synoicum kuranui Brewin (St. 935): B, zooid. Aplidiopsis discoveryi sp.n. (St. 941): C, zooid. 5o DISCOVERY REPORTS pieces is 4-5 cm., of which the head occupies about 1 cm. The average lengths are about i-o cm. for the head and 2-5 cm. for the stalk. The head is conical, ovoid, or inverted conical, and has a greatest diameter about twice that of the stalk. The stalk is of uniform diameter except where it expands on joining the head. Both head and stalk have a coating of sand and broken shell, but the coating is thicker on the stalk. The head is fairly soft and the stalk hard. The zooids are arranged roughly at right angles to the surface of the head of the colony. A longitudinal section of the colony shows that the thorax and abdomen of the zooids form a uniform peripheral layer and that the post-abdomens are contained in the core. Sand is relatively scarce in the peripheral layer and densely packed in the core where it occupies most of the space between the post-abdomens. Sand is also abundant within the stalk. Zoom (Text-fig. 8B). The thorax averages 3 mm. and the abdomen 1-5 mm. in length; the post- abdomen varies greatly and often extends for many millimetres down into the stalk. When preserved in alcohol the zooids are brown. Thorax. The oral siphon is moderately wide and its rim scarcely lobed. The short atrial siphon is far forward, with a small simple opening, and a strap-like bifid languet («./.). There may be a small tooth on the posterior margin of the atrial opening. Nine or ten thin longitudinal muscles pass down the sides of the thorax and condense into a strong band (mus.) which extends to the end of the post- abdomen. The oral tentacles are slender and few, apparently about eight in number. Fourteen rows of stigmata are usual, each with sixteen to eighteen stigmata. The dorsal languets are short and curved. Gut. The oesophagus is narrow and curved so that it enters the antero-dorsal side of the stomach. The walls of the stomach are marked by rather few and not very prominent round areolations. Sometimes these are reduced to little more than superficial marks. The anus, which lies opposite the nth row of stigmata, has two distinct lobes. Gonads. In none of the zooids was any trace of gonads found, nor were larvae found. Table 13 Colony S. kuranui (type material) Capitate heads united by basal mass S. kuranui ('Discovery' material) Capitate heads, possibly origi- nally united at the base 5. arenaceum Cylindrical heads united by basal mass Atrial languet Moderate length, with 3-5 short apical lobes Moderate length with 2 short apical teeth Long, with 2 or 3 apical teeth Longitudinal muscles Stigmata Stomach 10-13, slender 10 rows, each with 14 or 15 stigmata Low areolations 9 or 10, slender 14 rows, each with 16-18 stigmata Low areolations About 5, wide 15 rows, each with 12 stigmata Smooth or with faint irregular marks Gonads Ovary distant from intestinal loop Not developed Ovary distant from intestinal loop Remarks. Brewin (1950) pointed out the resemblance between this species and S. arenaceum (Michaelsen, 1924), but maintained that the zooids differ specifically. Table 13 gives a comparison between Brewin's type material, the ' Discovery ' specimens, and S. arenaceum. The similarities between the type specimens and those in the 'Discovery' collection indicate that they are of the same species. It is difficult, with the limited material, to decide whether S. are- naceum is a separate species, especially as the ' Discovery ' specimens are in some respects intermediate between the type specimens of S. kuranui and S. arenaceum, e.g. in the number of rows of stigmata. DESCRIPTION OF SPECIES 51 With the present evidence it seems best to recognize S. kuranui and S. arenaceum as separate species, while admitting that they may have to be united if more specimens become available. Distribution. Northern part of North Island, New Zealand. Genus Aplidiopsis Lahille, 1890 Aplidiopsis discoveryi sp.n. (Text-fig. 8C) Holotype. St. 941. Size of colony 1-5 x 1-2 x 07 cm. Diagnosis of species. Colony of irregular shape, with several common cloacal openings. Zooids with six pointed oral lobes and a wide simple or toothed atrial languet. About fourteen rows of stigmata; no papillae on transverse bars. Stomach smooth ; intestinal loop not twisted. Post-abdomen arising from abdomen by a narrow pedicel. Testis follicles in an ovoid or elongated mass but not serially arranged; ovary embedded amongst testis follicles. Occurrence. St. 941 : North Island, New Zealand, 128 m. Colony. The colony is an irregular simple mass, not divided into lobes, and broadly attached to a barnacle shell. The common test is semi-transparent, and, there being no sand on or within the test, the zooids are visible. They are arranged in several small systems each with an oval or slit-like common cloacal opening. Zoom (Text-fig. 8C). Zooids vary from 4-5 to 7-5 mm. in total length. The thorax is 2-3 mm. long, slightly wider than the abdomen which measures 1-5-2-5 mm. in length; the post-abdomen is generally at least as long as the abdomen. The size of the post-abdomen, however, varies according to the degree of development of the gonads; it is narrow and attached to the abdomen by a short and slender pedicel. Pigment, which in the preserved state is orange in colour, is present on much of the body wall, especially in the post-abdomen. Thorax. The oral siphon has six pointed lobes, and the round atrial opening, which is opposite the first or second row of stigmata, is surmounted by a fairly wide simple or distally toothed languet (a.L). Eight to ten narrow longitudinal muscles run down each side of the thorax. At the posterior end of the thorax the muscles condense to form a single band on each side, and the left band passes over to the right ventral side of the abdomen where it unites with the right band. The single muscle (mus.) thus formed continues into the post-abdomen and ends at its posterior end. Fourteen or fifteen rows of stigmata are present, each with fifteen to twenty stigmata. The trans- verse bars bear the pointed triangular dorsal languets, but no papillae. Gut. The oesophagus is quite long and narrow, and enters the stomach on its oblique antero- dorsal face. The stomach is ovoid, with the anterior end generally wider than the posterior. Two short narrow chambers constitute the post-stomach. The intestine makes a simple loop. The rectum extends to the level of the 10th row of stigmata and ends in a two-lipped anus (a). Gonads. Much of the post-abdomen is occupied by the bulky testis (t) composed of numerous pear-shaped follicles. The follicles, instead of being serially arranged as in Aplidium, are grouped into an ovoid or somewhat elongated mass as in Polyclinum. As in that genus also, the ovary (ov.) is a small body embedded amongst the testis follicles. Neither sperm duct nor oviduct could be dis- tinguished in the ' Discovery ' specimen. Remarks. No other species of Aplidiopsis is known from New Zealand. A. discoveryi is not likely to be confused with any other species hitherto described. Distribution. North end of North Island, New Zealand. 7-2 52 DISCOVERY REPORTS Genus Protopolyclinum gen.n. Diagnosis of the genus. A genus of the family Polyclinidae with the atrial siphon opening directly on the surface of the colony, not into a common cloacal cavity ; the zooids divided into thorax, abdomen and post-abdomen, the post-abdomen joined to the abdomen by a narrow neck, and containing the gonads and heart, and having muscles in its body wall; the branchial sac with papillae on the trans- verse bars, and the intestine not twisted as in Polyclinum. Protopolyclinum pedunculatum gen.n., sp.n. (Text-fig. 9, PI. I, fig. 10) Holotype. Size: stalk, 12-6 cm.; head, 1-4 cm. Occurrence. St. 934 : North Island, New Zealand, 92-98 m. Colony (PL I, fig. 10). There are four specimens, measuring, including the stalk, 10, 12, 13 and 14 cm. The heads have respectively the following measurements: Length (mm.) 6, 10, 14, 14 Greatest diameter (mm.) 5, 7, 10, 10 The head of the colony is ovoid, and usually slightly narrower towards the point where it joins the stalk. In the preserved state it is pale yellow grey, and of a soft consistency. In most of the specimens the stalk is widest at its junction with the head, but in the two smallest colonies the greatest width is a little way below the head. The lower half or quarter of the stalk becomes gradually narrower, so that near the point of attachment it has a diameter of only 1 mm. At its widest it may reach a diameter of 4 mm. Immediately below the narrowest part, the stalk expands to form a wider base by which the colony is attached to the substratum. The two smallest heads arise from a single expanded basal mass of test and, although the other two are separate, it is possible that originally all four specimens were members of a single complex colony. The stalk is firmer than the head, especially in its lower half. In its upper part it has the same colour as the head, but the lower part becomes gradually darker and more orange coloured. A series of dark rings round the stalk gives it an annulated appearance. The zooids are not arranged in systems, and have no apparent order in the head. Zoom (Text-fig. 9). The zooid is divided into thorax, abdomen and post-abdomen. In a specimen of average size these measure respectively about 27, 2-0 and 4-0 mm. ; these lengths do not include the long post-abdominal process which extends for several centimetres down inside the stalk. Thorax. The thorax is wider than the other two divisions of the zooid. The oral (o.s.) and atrial (a.s.) siphons are both short and wide, and show no lobes or only very shallow ones. The siphons are placed close together at the anterior end of the thorax. The atrial siphon opens directly on the surface of the colony and not into a common cloacal cavity as in other members of the family Polyclinidae. On each side of the thorax there are about six longitudinal muscles, divided into a few branches at their upper end, and converging as they approach the abdomen. Longitudinal muscles are present not only on the abdomen, but also down the whole length of the post-abdominal process. There are about twelve simple oral tentacles arranged in a single circle at the base of the siphon. The dorsal tubercle is a small ovoid body, with a simple longitudinal slit. The branchial sac has about thirteen rows of stigmata which are rather wide and rectangular and number about sixteen in a row. On the transverse bars of the branchial sac there are small papillae similar to those in the genus Polyclinum. The dorsal languets are short and curved. Gut. The oesophagus is of moderate length and width. The stomach is wide and roughly barrel- shaped, with the walls almost smooth, but showing large, faint areolations or ovoid markings. In some zooids these are outlined by little more than slight irregular transverse ridges. The post-stomach m id. 1.0, DESCRIPTION OF SPECIES 53 is divided into two chambers by an expanded ring, and the mid-gut also has two chambers, the first of which has a granulation on the walls. At its junction with the mid-gut the rectum has a pair of small lobes as in other members of the family. The loop of the intestine is not twisted as in Poly- clinic, and the post-stomach and mid-gut lie on the right side of the rectum as in Aplidium. The anus has two lips, and lies about halfway along the length of the branchial sac opposite the 7th row of stigmata. Post-abdomen. A narrow and very short neck joins the post-abdomen to the abdomen. Below this neck the post- abdomen swells to accommodate the gonads. The ovary (ov.) lies near the anterior end of the post-abdomen and has a few ova of various sizes. A few testis follicles lie anterior to the ovary, but most of them are posterior to it (t). They are not arranged in a single or double series as they commonly are in Aplidium, but instead form, immediately below the ovary, a wide mass which gradually decreases in thickness and passes into the narrow posterior part of the post-abdomen as a single series of follicles. The sperm-duct (s.d.) as it passes back over the ovary divides into several smaller ducts which spread out to the testis follicles. Below the level of the testis the post- abdomen continues as a slender process which passes down- wards inside the stalk of the colony for a distance of several centimetres. This lower process is divided by a central septum separating the two blood channels. The walls of the process are provided with thin longitudinal muscles. Near the lower end of the post-abdominal process there is often seen an accumulation of cells containing reserve material. At its extreme lower end is the heart, a simple U-shaped tube. Larva. Some zooids in one colony contained a few larvae which unfortunately were not, I believe, fully developed. The most advanced of these larvae measures about 0-7 mm. from the end of the papillae to the base of the tail. There are three anterior papillae, flanked on each side by a row of four rounded ampullae. No epidermal vesicles are present at the stage of development represented by these larvae. There is an ocellus and an otolith. The tail when coiled round the larva reaches to about the sensory vesicle. Remarks. With the exception of the atrial siphon which opens directly to the exterior, all the characters of this interesting genus indicate that it should be placed in the subfamily Polyclininae. The existence of branchial papillae and the form of the post-abdomen suggest a systematic position closer to Polyclinum than to Aplidium. But it is separated from Polyclinum, not only by the absence of common cloacal cavities, but also by the presence of muscles on the wall of the post-abdomen. Protopolyclinum probably branched off from the primitive Polyclinum stock after that stock had acquired its main characters, but before all of them had been fixed as we know them in recent species. Thus the loss of Text-fig. 9. Protopolyclinum pedunculatum gen.n., sp.n. (St. 934): Zooid. 54 DISCOVERY REPORTS post-abdominal muscles had not occurred and probably the arrangement of zooids in systems with common cloacal cavities had not yet been acquired. It is possible, however, that common cloacal cavities were originally present and subsequently lost, but this seems unlikely for the possession of these structures must be assumed to be useful as they are a common feature in several unrelated groups of compound ascidians. If these assumptions about the origin of Protopolyclinum are correct, the two main lines of the Polyclininae typified by Polyclinum and Aplidium respectively must have acquired common cloacal cavities independently of each other, an interesting case of convergent evolution. The presence of a stalk shows a degree of specialization which finds a parallel not in the Poly- clinidae but in the Polycitoridae, where Sycozoa has a similar form. Distribution. North end of North Island, New Zealand. Subfamily Euherdmaniinae Seeliger, 1906 Genus Ritterella Harant, 1931 Harant (1931) created the genus Ritterella for a species described and named by Ritter & Forsyth (1917) as Amaroucium aequali-siphonalis . This genus differs from Aplidium (syn. Amaroucium) only in having the two siphons equal and both opening directly on the surface of the colony. Oka (1933) created the genus Sigillinaria for a species S. clavata, the genus being distinguished from Aplidium by the same single character. Sigillinaria is therefore a synonym of Ritterella. This is not always recognized, and some authors use the name Sigillinaria (van Name, 1945; Brewin, 1950), while others use Ritterella (Huus, 1933, Tokioka, 1953). Ritterella vestita sp.n. (Text-fig. 10) Diagnosis of species. Zooids completely embedded; oral and atrial siphons each with six shallow pointed lobes and both opening directly on the surface; about twenty-four simple oral tentacles; dorsal tubercle with a simple transverse opening; twenty-seven to thirty-four rows of stigmata; stomach with eight to ten longitudinal folds; testis follicles in a long series in the post- abdomen. Occurrence. St. 934: North Island, New Zealand, 98-92 m. Colony (Text-fig. 10 A). The single specimen, the holotype, which is probably incomplete, consists of a stalk 2 cm. long and about 0-4 cm. in diameter, from the end of which a triangular, expanded head arises, about 2 cm. long and 2-4 cm. wide at the distal end, where the width is greatest. The whole specimen is rough and mottled grey, its appearance being due to the heavy layer of en- crusting broken shell which completely covers the test. The common test itself is clear and the shell is confined to the surface. Zoom (Text-fig. 10B). The zooids are entirely embedded in the common test and show no arrange- ment in systems. When exceptionally well expanded the thorax measures about 8 mm., but in most zooids it is more or less contracted and may then measure less than 4 mm. in length. The abdomen is between 2 and 4 mm. long, and the post-abdomen may exceed 10 mm. In the preserved state the zooids are dull orange in colour. The wide oral siphon (o.s.) is terminal, of moderate length, and has six shallow pointed lobes. The atrial siphon (a.s.) lies a short distance back along the dorsal side of the thorax; it also opens on the surface, is short and wide, and has six pointed lobes. The body wall is rather thick and opaque, with up to twenty-five slender longitudinal muscles and many slender circular muscles. The longitudinal muscles converge in the sides of the abdomen and continue along the whole length of the post-abdomen. DESCRIPTION OF SPECIES 55 Branchial sac. There are about twenty-four simple oral tentacles of alternating sizes (Text- fig. 10C). The dorsal tubercle is very simple and has an oval transverse slit (Text-fig. ioC, d.t.). Twenty-seven to thirty-four rows of narrow stigmata are present, each row usually containing forty to fifty stigmata. There are no parastigmatic transverse bars. The hooked dorsal languets (Text- fig. 10 D, d.l.) are wide at the base and taper rapidly to a point. The languets towards the posterior end of the branchial sac become progressively larger. B 4.0 mm I ii»»»*l 2.0 Text-fig. 10. Ritterella vestita sp.n. (St. 934): A, colony; B, zooid; C, oral tentacles and dorsal tubercle; D, part of roof of branchial sac, showing dorsal languets; E, transverse section of stomach; F, part of gut. S6 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, each °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 DESCRIPTION OF SPECIES 57 ' Discovery ' specimens belong, without much doubt, to D. studeri. The nearest existing records of the species are from Tierra del Fuego and the Strait of Magellan. It is not surprising to find it at the Falkland Islands, but the record from Gough Island is considerably farther north, where the tempera- ture at 150 m. is about 40 C. higher. Table 15 Hartmeyer Michaelsen Kott 'Discovery' 191 1 1919 1954 No. of follicles 2-4 3 2-3 3 No. of spiral turns 4-7 At least 7 7-8 7-10 Didemnum biglans (Sluiter) (Text-fig. 11) Leptoclinum biglans Sluiter, 1906, p. 29, pi. 2, figs. 27, 28. For synonymy see Kott, 1954, p. 159. Occurrence. St. 182: Palmer Archipelago, 273-500 m. St. 187: Palmer Archipelago, 259-354 m- Colony. The colony from St. 182 is attached to the sandy tube of a worm, and measures about 5 cm. in length. It is thick and fleshy, and, preserved, is of a pale buff-grey colour, the zooids forming paler spots on the surface. Four round or oval common cloacal openings are found scattered over the surface of this colony. Although the zooids are grouped there is no very obvious arrangement in systems. No spicules whatever are present in the common test, but the superficial layer has round empty spaces very like the cavities occupied by sp icules in other didemnids, and I am inclined to believe that this colony may originally have had a layer of spicules near the surface and that these have been destroyed after the specimen was collected, possibly by acid in the preserving liquid. This explanation of the superficial empty spaces is supported by Sluiter's (1906) statement that no vesicular cells are present in this species. On the other hand, it may be that the colony had no spicules in life. Within the colony there are very large cavities, especially in the upper half of the test, the thoraces of the zooids being contained in strands of test which pass from the upper layer down to the basal layer of common test, a con- dition very like that found in Diplosoma. The specimen from St. 187 is in all essentials like that from St. 182, but is smaller and was growing on the test of a specimen of Pyura discoveryi. Zooid (Text-fig. 11). The zooids are small, having an average length of 2 mm. The oral siphon is short with six indistinct lobes. Much of the dorsal surface of the branchial sac is exposed by the large atrial opening which extends, in well-expanded zooids, from the 1st to the 4th row of stigmata. The opening is surmounted by a short triangular atrial languet (a.L). There is no trace of lateral thoracic organs. 0.5 mm Text-fig. 11. Didemnum biglans (Sluiter) (St. 182): Zooid. 58 DISCOVERY REPORTS Branchial sac. Ten to twelve long stigmata are present in each of the four rows. The stigmata are generally of the width shown in Text-fig. 1 1 , but in a few exceptionally well expanded zooids they are much wider and rectangular in shape. The three dorsal languets are long, and usually forwardly directed. Gut. The oesophagus is narrow and about as long as the stomach, which is a wide barrel-shaped organ. The post-stomach is about equal in length to the intestine, and the wide rectum ends in a two- lipped anus situated at the base of the thorax, opposite the 4th row of stigmata. Gonads. In most zooids the ovary is not developed, and when present it is represented by one large ovum, and a group of smaller ova. The testis consists of two or three rounded follicles (t.) on the surface of which the sperm-duct makes four to six spiral turns. Developing embryos were present in the common test below several of the zooids, but none had reached the larval stage. Remarks. I have had some difficulty in deciding the identity of these specimens, mainly owing to the complete absence of spicules. This feature may be an artifact, as suggested above, or may repre- sent the extreme reduction of spicules which previous authors (van Name, 1945; Kott, 1954) have noted as being scarce in some colonies which they examined. It is relevant that considerable variation is known in the abundance of spicules in other species of Didemnidae (e.g. Trididetnnum tenerum (Verrill), van Name, 1945, Berrill, 1950; T. opacum (Ritter), van Name, 1945 ; Didemnum helgolandicum Michaelsen, unpublished personal observation). Table 16 Spicules ' Discovery ' Absent Sluiter Common only upper layer in Hartmeyer As Sluiter's description van Name Usually common in upper layer, sometimes very few Kott Mainly in upper layer, nowhere dense Atrial opening Lateral thoracic organs Large Absent p Present Small Present ? Present ? Present No. of stigmata per row No. of testis follicles No. of turns of sperm duct 10-12 2 or 3 4-6 p 1 3 ? 2 3-4 10-12 ? ? ? 2 4-5 A comparison of the 'Discovery' specimens with the descriptions given by Sluiter (1906), Hart- meyer (191 1), van Name (1945) and Kott (1954) is given in Table 16. The differences shown above seem less important than the similarities, especially considering the doubtful nature of the absence of spicules, and I conclude that the colonies are within the probable range of variation of D. biglans. Distribution. Antarctic (Graham Land, Enderby Land, Kaiser Wilhelm II Land). Didemnum trivolutum sp.n. (Text-fig. 12) Holotype. St. WS811. Diagnosis of species. Colony thin and encrusting, with spicules densely packed throughout the whole depth of the test. Spicules of a regular stellate shape, 20 to 40 /i in diameter with eight to twelve rays in optical section; also some spicules with very thin needle-like rays. Zooid with wide, long atrial opening, surmounted by a languet; lateral thoracic organs large; stomach rather rect- angular; testis undivided, with sperm-duct making three spiral turns. Occurrence. St. WS 99: Falkland Islands, 251-225 m. St. WS 811 : Patagonian Shelf, 99 m. Colony. The specimens consist of large sheeting masses, sometimes growing round the tubes of worms, and reaching a length of 10 cm. The average thickness of the colony is 3 mm. In colour the DESCRIPTION OF SPECIES 59 preserved colonies are generally pale grey or almost white, with a pattern of darker spots marking the positions of the zooids. A few slit-like common cloacal openings are present on the surface. All parts of the common test are crowded with spicules, which are present even in the most superficial layer, there being no bladder cells such as are often found in the uppermost layer of the test in didemnids. The spicules are mostly of a regular stellate form, reaching 40 fi in diameter and having from eight to twelve pointed conical rays in optical section (Text-fig. 12B). A few spicules were also seen consisting of bundles of very thin needle-like rays arranged in a stellate pattern, these spicules also being 30- 40 /i in diameter (Text-fig. 12 C). A system of common cloacal canals lies a little above the middle level of the colony. B 3 0^ Text-fig. 12. Didemnum trivolutum sp.n. (St. WS 811): A, zooid; B, C, spicules. Zoom (Text-fig. 12 A). The thorax is about i-6 mm. long and the abdomen about i-o mm. The prominent oral siphon has six pointed lobes. A large part of the dorsal side of the thorax is exposed by the atrial opening which extends at least half the length of the thorax and often extends almost the whole length. On the anterior border the opening bears a short triangular languet («./.). There are large oval lateral thoracic organs with associated masses of small spicules. These organs occupy most of each side of the thorax. Branchial sac. There are about eleven long narrow stigmata in each of the four rows. The three dorsal languets are long, curved, and directed anteriorly. 8-2 60 DISCOVERY REPORTS Gut. The oesophagus is narrow and the stomach (st.) large with a somewhat rectangular outline. The post-stomach is generally quite long and conical, but is sometimes short. The intestine is short and narrow. The rectum is wide at its lower end but soon narrows. The narrow part is bent into an S-shaped curve. The anus, which is situated at the base of the thorax, opposite the 4th row of stig- mata, has two shallow lips. Gonads. The testis (t) is undivided and the sperm duct makes three spiral turns round it. In some colonies only the ovary was developed. Remarks. D. trivolutum somewhat resembles two other species from South American waters, D. tenue (Herdman) and D. chilense Arnback. The characters which most readily separate D. tri- volutum are listed in Table 17. In this comparison the characters of D. chilense were taken from Arnback (1929, fig. 5), and the diameter of the spicules of D. tenue was measured in specimens of Herdman's original material kindly lent by the British Museum (Natural History). It will be seen that D. tenue and D. chilense are not distinguished from each other by the characters listed. But Arnback, having compared material of the two species, was satisfied that, in spite of similarities 'the differences are more essential, lying in the form of the zooids, which are not very elongated but larger in the species tenue, having a short atrial languet, a longer and more sharply curved intestinal loop '. Table 17 D. trivolutum D. tenue D. chilense Spicules Up to 40 /a in diameter Up to 25 /i in diameter Up to 26 in/x diameter Lateral thoracic organs Large ; placed half-way along thorax Small ; placed at posterior end Not described of thorax Sperm duct 3 spiral turns Unknown 6-7 spiral turns Genus Leptoclinides Bjerkan, 1905 This genus was characterized by Bjerkan as having four rows of stigmata and a backwardly directed funnel-like atrial siphon. Van Name (1945) suggested that it should be no more than a subgenus of Didemnum, and Carlisle & Carlisle (1954) gave reasons for dividing the species hitherto assigned to Leptoclinides among other genera of the Didemnidae, while retaining Leptoclinides as a subgenus of Didemnum. I believe, however, that the well-developed funnel-like atrial siphon clearly distinguishes Leptoclinides from Didemnum, no species of which shows any tendency towards the production of an atrial siphon. Leptoclinides diemenensis Michaelsen (Text-fig. 13) Leptoclinides diemenensis Michaelsen, 1924, p. 331, fig. 12. Occurrence. St. 935 : North Island, New Zealand, 84 m. Colony. The colony is about 3 cm. long and 07 cm. in thickness. It is pale orange brown in colour. The upper surface has a number of low rounded swellings, each with a common cloacal opening at its centre. These openings are less than 1 mm. in diameter and are spaced about 5 mm. apart. Around each opening is an irregular system of closely spaced zooids. The colony is firm and its surface smooth. Sections show that the uppermost layer of the common test is composed largely of closely pressed bladder cells, each about 70-80 ft in diameter and extending to about five cells in depth. Below these is a layer of densely packed spicules. Spicules are also present in the deeper parts of the common test, but are more scattered. The spicules are generally 20-35 fi in diameter, only a few reaching 40 fi. DESCRIPTION OF SPECIES 61 They are of a regular stellate shape, with about eight rays in optical section (Text-fig. 13 B). Small spindle-shaped and irregular cells are also present in the test, but no pigment cells. Zooid (Text-fig. 1 3 A). The thorax often reaches 2 mm. in length. The abdomen, including the long waist, is about the same length, or slightly more. These zooids are larger than Michaelsen's (1924), which had a total length of 2-5 mm. In most zooids the oral siphon (o.s.) is quite long, tubular 7.0 mm Text-fig. 13. Leptoclinides diemenensis Michaelsen (St. 935): A, zooid; B, spicule. to conical, and muscular, with six shallow pointed lobes. The base of the atrial siphon (a.s.) is at or slightly posterior to the middle of the branchial sac. The siphon varies in length in different zooids, but often is longer than the oral siphon. It is frequently, but not always, backwardly directed. Five or six slender longitudinal muscles pass along each side of the thorax. Near the posterior end of the thorax there is a conspicuous lateral thoracic organ (l.t.o.) on each side. The mass of spicules occupying the cavity of the organ is about 125 ju in diameter. Branchial sac. There are twelve to fourteen long narrow stigmata in each of the four rows. The dorsal languets are short, triangular, and blunt. 62 DISCOVERY REPORTS Gut. This agrees well with Michaelsen's account, except that in the ' Discovery ' material the anus (a) is rather farther forward, and lies opposite the 3rd row of stigmata instead of the 4th. Gonads. There is no trace of gonads in any of the specimens. Remarks. Five species of Leptoclinid.es have been described from New Zealand and Chatham Islands: L. diemenensis Michaelsen, L. sparsus Michaelsen, L. sluiteri Brewin, L. marmoreus Brewin, and L. auranticus Brewin. L. sparsus is similar to L. diemenensis from which it differs in having stellate pigment cells in the test. The characters which separate the remaining species are given in Table 18. Some of these characters are not very satisfactory for distinguishing the species, but as the variation within each species is not known at present, it is best to maintain them. Table 18 Diameter °f Length of No. of spicules zooids stigmata M (mm.) per row Abdomen Oesophagus Sperm duct L. diemenensis 20-35 Up to 4 12-14 Not wider than thorax Longer than stomach 6-7 turns L. sluiteri 12-25 Up to 1 9 or 10 Wider than thorax Equal in length to stomach 9 or 10 turns L. marmoreus 10-45 Up to i-6 10 Not wider than thorax Shorter than stomach 9 turns L. auranticus 10-60 Up to 1 11 or 12 Equals thorax in width Equal in length to stomach 7 turns Sluiter (1909) has described, under the name Polysyncraton, a number of species from the Indo- nesian region evidently belonging to Leptoclinides. It is a little doubtful if these are all different species, and I should not be surprised if a proper revision of the group, as represented in Australasian waters, showed that the same species has been described under several names. This view is also expressed by Tokioka (1949) in dealing with L. rufus (Sluiter) from Japanese waters. Distribution. North of North Island, New Zealand. Genus Trididemnum Delia Valle, 1881 Trididemnum auriculatum Michaelsen (Text-fig. 14) Trididemnum auriculatum Michaelsen, 1919, p. 38, text-fig. 3. Occurrence. St. WS 84 : Falkland Islands, 75-74 m. Colony. The specimen is a large sheeting colony, varying from 2 to 4 mm. in thickness, of a dirty white colour. Two or three common cloacal openings are visible on the surface. Regular stellate spicules are densely packed in all layers of the test, and range from 37 to 66 n in diameter. Zoom (Text-fig. 14A). The zooid agrees closely with the description given by Michaelsen (1919), except that the ' Discovery ' specimen has about seven spiral turns of the sperm duct, (s.d.), instead of only five in the type specimen. The lateral thoracic organs are large and conspicuous, as in Michaelsen's material. Larva (Text-fig. 14B). The larva is of the usual didemnid type, with three vertically arranged papillae (p.) and four pairs of anterior ampullae (amp.). Both ocellus and otolith are present. The larvae measure from 0-5 to o-6 mm. in length from the end of the papillae to the base of the tail. Remarks. Van Name (1945) suggested that perhaps this species was not distinct from T. pro- pinquum (Herdman), but Arnback (1929) stated that a comparison of the species 'shows at once that they are not identical'. The distinguishing characters particularly mentioned by Arnback are given in Table 19. DESCRIPTION OF SPECIES 63 These do not seem to be entirely satisfactory distinctions, and the difficulty arises from the in- complete description of T. propinquum given by Herdman (1886). Arnback, however, was convinced that the two species are distinct, and there is no doubt that the 'Discovery' specimen belongs to T. auriculatum. Distribution. Subantarctic (Strait of Magellan; Guaitecas Islands, Chile; Falkland Islands). Table 19 T. propinquum T. auriculatum Zooids Short Long and slender Abdomen About same length as thorax Twice as long as thorax Stigmata Short Long and narrow 1.0 mm 0.2 mm Text-fig. 14. Trididemnum auriculatum Michaelsen (St. WS 84): A, zooid; B, larva. There are also in the collections several colonies of didemnid ascidians which I am unable to place, even in their correct genus, because the zooids have no gonads. It would be very unwise to try to name these specimens using other characters, because with few exceptions the nature of the testis and sperm duct is almost essential for the determination of genera and species in this family. 64 DISCOVERY REPORTS Family CLAVELINIDAE Forbes & Hanley, 1848 Sub-family Clavelininae Seeliger, 1906 Genus Podoclavella Herdman, 1890 Podoclavella cylindrica (Quoy & Gaimard) (Text-fig. 15) Polyclinum cylindricum Quoy & Gaimard, 1834, p. 618. For synonymy see Michaelsen, 1930, p. 475. Occurrence. St. 1686: Victoria, Australia, o m. Colony. The colony consists of a bunch of zooids united only at their lower ends where a narrow stalk joins a stouter cylindrical stem. This is attached to the substratum by an expanded base. 3.0 mm Text-fig. 15. Podoclavella cylindrica (Quoy & Gaimard) (St. 1686): Zooid. Zoom (Text-fig. 15). Large zooids reach a length of 1 1 mm. but many of the zooids in the colony are much shorter. The body is widest anterior to the middle and tapers towards the base, where it abruptly narrows to join the stalk. Thorax. The oral siphon (o.s.) does not occupy the extreme anterior end of the thorax, being instead displaced slightly down the ventral border. This siphon is also curious in being sharply bent in a ventral direction. The atrial siphon (a.s.) is terminal. Both siphons have numerous circular muscles. Fifteen to twenty slender muscles pass obliquely across the thorax and abdomen. DESCRIPTION OF SPECIES 65 Branchial sac. In large zooids there are up to twenty-eight simple oral tentacles of alternating sizes. The very small dorsal tubercle lies transversely and has a simple slit-like opening. Eleven or twelve rows of narrow stigmata are present, the rows being separated by prominent raised bars. In large zooids there may be as many as forty-five stigmata in a row. The dorsal languets are long and slender. The branchial sac lies obliquely in the body and the rows of stigmata lie in a correspondingly oblique position. Abdomen. The abdomen is much shorter and narrower than the thorax. Gut. The oesophagus (oes.) is long and narrow, and passes straight back to the stomach (st.), which is ovoid and has smooth walls. Below the stomach the intestinal loop is short, but the rectum is very long and in its anterior half diverges from the dorsal side of the branchial sac. The simple anus (a) lies near the base of the atrial siphon. Remarks. This species has been described under a number of generic names, but it certainly belongs to Podoclavella where Kott (1957) placed it, and not to Clavelina to which it was assigned by Michaelsen (1930). The 'Discovery' material shows some differences from that described by Kott (1957), and is in certain respects intermediate between P. cylindrica and P. australis (Herdman). But P. australis is very probably a synonym of P. cylindrica, or at most a geographical form, as suggested by Kott. The comparison of the only marked differences that is given in Table 20 shows the intermediate position of the ' Discovery ' material, and strongly suggests that only one species is involved, P. cylindrica. Table 20 P. cylindrica P. australis ' Discovery (Kott, 1957) (Kott, 1957) specimen No. of muscles About 25 12 15-20 No. of rows of stigmata 21 10 11 or 12 Distribution. West and south coast of Australia; Bass Strait. Podoclavella kottae sp.n. (Text-figs. 16, 17; PI. II, fig. 1) Holotype. Size, largest zooid 12 cm. long. St. 934. Diagnosis of species. Zooids united only at base. Thorax short and ovoid; abdomen stalk-like and many times larger than thorax. Atrial opening terminal; oral opening in basal half of thorax; both openings with strong wide sphincter muscles. Branchial sac with up to twenty-seven rows of stigmata, the anterior and posterior rows much shorter than the middle rows. Oesophagus and intestine very long and narrow ; stomach ovoid and situated in a basal swelling of the stalk ; anus close to oesophageal mouth. Occurrence. St. 934: North Island, New Zealand, 98-92 m. Colony (Text-fig. 16A; PL II, fig. 1). The specimen has eight zooids, the largest being 12 cm. long. Fully developed zooids consist of a short thorax (th.) borne on a long slender stalk (sk.) which con- stitutes the abdomen. The stalks have a basal swelling the lower part of which is united to a short compact creeping stolon (sn.). The stalks are buff-coloured and the thoraces clear. Zoom (Text-fig. 16B, C). Thorax. The thorax of a well-developed zooid is 5-6 mm. long and 3-4 mm. wide. It is ovoid, narrowest at its junction with the stalk and widest about one-third to one-half of its length up from the stalk. The atrial siphon (a.s.) is terminal or almost so, and the oral siphon (o.s.) slightly behind the middle of the thorax. Each opening is sessile and wide, the oral being the wider of the two. A wide and conspicuous band of circular muscle surrounds each opening. About fourteen muscles radiate 66 DISCOVERY REPORTS across the thorax from the margin of the oral opening, seven on each side. Anatomically these are longitudinal muscles, although in fully developed zooids they lie transversely to the longitudinal axis of the zooid. Their origin as longitudinal muscles is, however, shown by their position in young developing zooids (Text-fig. 16C, l.m.). A few narrow and irregular transverse strands are present on the thorax. Only the young developing stages of the zooid have transverse muscles in the abdomen (t.m.) and they are confined to the upper part of it. Branchial sac. The large oral tentacles number twenty-six to twenty-eight and are arranged in a single circle. The dorsal tubercle (Text-fig. 16D) is small, with a simple transverse oval slit. B 1.0 mm 4.0 cm Text-fig. 16. Podoclavella kottae sp.n. (St. 934): A, colony; B, thorax of zooid; C, abdomen with regenerating thorax; D, dorsal tubercle. DESCRIPTION OF SPECIES 67 A row of pointed triangular languets occupies the mid-dorsal line of the branchial sac. The trans- verse rows of stigmata number thirteen to twenty-seven, according to the size of the zooid, and the rows lie in line with the long axis of the stalk. The anterior and posterior rows are shorter than the middle ones, and the shortest rows have less than twenty stigmata, whereas at least sixty are present in the longest. The endostyle (e) is conspicuous and strongly curved. Table 21 P. detorta P. kottac Number of rows of stigmata 'Apparently 6' (van Name, 19 18) Up to 27 Lower end of intestinal loop Some distance up from base of At base of stalk stalk Anus Far anterior to oesophageal Beside oesophageal mouth ; mouth; lobed (Sluiter, 1904) without lobes as Text-fig. 17. Podoclavella kottae sp.n. Suggested stages in its evolution from A, the unmodified form illustrated by Clavelina, through B, the modified form illustrated by Podoclavella cylindrica to C, P. kottae. Abdomen. The abdomen lies within the stalk, occupying the whole length. It is much narrower than the thorax, except at the lower end which is enlarged and accommodates the stomach and intestinal loop. Gut. The oesophageal mouth is at the postero-dorsal corner of the branchial sac and lies within the anterior one-third of the thorax. From there the oesophagus (oe.) passes back behind the postero- ventral border of the branchial sac and into the stalk, within which it runs down to the basal swelling. The stomach (st .) is ovoid and has smooth walls. Behind it is a short conical post-stomach and a short horizontal intestine (?) not clearly marked off from the rectum. The rectum is wide at its lower end but narrows as it passes up within the stalk. In both stalk and thorax it lies close to the oesophagus. The anus (a.) is situated to the left of the oesophageal mouth and is small and simple without lobes. Gonads. Neither ovary nor testis was present in any of the zooids. Remarks. This species most resembles P. detorta Sluiter, but is distinguished as shown in Table 21. 9-2 68 DISCOVERY REPORTS Other characters might help to distinguish the two species, but the accounts of P. detorta by Sluiter (1904) and van Name (19 18) differ with regard to these characters. Thus the very wide and strong sphincters on the oral and atrial openings of P. kottae are characteristic. According to van Name (19 1 8) the corresponding muscles of P. detorta are slender, but Sluiter (1904) describes them as strong, although his figure gives no suggestion of this. The orientation of the thorax and the great development of the abdomen in P. detorta and P. kottae are features deserving notice. The structure of P. kottae can be derived from the unspecialized type of Clavelina through a stage like that represented by Podoclavella cylindrica. In this series (Text-fig. 17) two processes have been involved: (1) the formation of a stalk, and (2) unequal growth of the dorsal and ventral sides of the thorax. The former process led finally to the enclosure of the abdomen within a very long narrow stalk with the consequent elongation of the oesophagus and rectum. The latter process has shifted the oral siphon down towards the stalk and at the same time drawn the oesophageal mouth up towards the still terminal atrial siphon. Distribution. North Island, New Zealand. Genus Clavelina Savigny, 18 16 Clavelina claviformis (Herdman) (Text-fig. 18; PI. II, fig. 2) Colella claviformis Herdman, 1899, p. 67, pi. Dist. 3, figs. 1-15. Clavelina sigillaria Michaelsen, 1924, p. 269, figs. 1-4. Clavelina claviformis Kott, 1957, p. 88, fig. 22. Occurrence. St. 929: North Island, New Zealand, 58-55 m. Colony (PL II, fig. 2). Two examples are present in the 'Discovery' collections, from the same station and probably derived from the same group of colonies. One specimen is a single stalked head, and the other consists of a group of about twelve stalked heads attached to a common base. The largest of these has a head 11 cm. long on a stalk of 8 cm., and the smallest is less than half that size. In outline the head is ovate to lanceolate, and is sometimes slightly compressed, but this may be an artifact. The stalk is narrower than the head and is of uniform diameter down to the base. Both the head and the stalk are semi-transparent or pale grey, smooth and without any encrusting matter. The common test is tough and cartilaginous, but the surface has a slimy consistency. The zooids show through the test quite clearly. Zoom (Text-fig. 18 A). The thorax is shorter and usually wider than the abdomen, especially when contracted. One typical zooid had a thorax 17 mm. and an abdomen 3-0 mm. long. The two siphons are of almost equal length, and are close together at the anterior end of the thorax. They have circular openings with lobes scarcely marked or entirely wanting. The body wall of the thorax has a series of nine to eleven prominent longitudinal muscles which, passing up from the abdomen, diverge as they approach the anterior part of the thorax, where they generally divide into a few branches. The more ventral muscles of the series diverge towards the ventral margin of the thorax, recalling the course of the muscles in Tylobranchion. Branchial sac. From twelve to twenty long slender simple oral tentacles are present in a single circle. The dorsal tubercle is small, with a narrow transverse oval slit. In some zooids the branchial sac has nine rows of stigmata, but more often there are ten to twelve complete rows and two or three short anterior rows, each consisting of a few stigmata in the dorsal part of the branchial sac and none in the ventral part. There are up to forty-five stigmata in the complete rows. The dorsal languets are pointed and moderately long, those at the posterior end being the longest. Gut. The long narrow oesophagus passes down to the stomach which lies in the posterior third DESCRIPTION OF SPECIES 69 of the abdomen. The stomach (st.) is ovoid or in some zooids nearly globular. There are four folds on the walls, best seen in a transverse section (Text-fig. 18 B). The intestine is short and the rectum (r) long and narrow. The anus (a) lies far back in the thorax, opposite the last or second last row of stigmata; it has two deep rounded lobes. Gonads. Some of the zooids have a well-developed testis (t.) consisting of a large group of many small pear-shaped follicles, lying on the right side of the zooid near the lower part of the intestinal 0.5 mm Text-fig. 18. Clavelina claviformis (Herdman) (St. 929): A, zooid; B, transverse section of stomach. 70 DISCOVERY REPORTS loop. The sperm duct passes almost straight forward beside the rectum. No ovary was found in any zooid examined, but the zooids are known to be hermaphrodite. Distribution. Eastern Australia; North Island, New Zealand. Subfamily Polycitorinae Michaelsen, 1904 Berrill (1950) proposed the subfamily Holozoinae for the three genera, Distaplia Delia Valle, 1881, Holozoa Lesson, 1830, and Sycozoa Lesson, 1830, and pointed out that these genera formed a very natural group of closely related forms. Many authors have had difficulty in deciding whether these three genera are in fact separate. Thus Hartmeyer (1909, in Bronn) regarded Distaplia as a synonym of Holozoa, but maintained Sycozoa. Van Name (1945) allowed the separation of Holozoa mainly on the grounds of the shape of the colony and the alleged pelagic phase in its adult life, but was evidently not entirely satisfied that it is distinct from Distaplia. Brewin (1953) united the two genera under the nomen conservandum Distaplia, at the same time maintaining the separation of Sycozoa, and estab- lishing a new genus Hypsistozoa. I agree with Brewin's decision to unite Holozoa and Distaplia, but the position of Sycozoa is more difficult to determine. Before Brewin's (1953) paper, the colony of Sycozoa had been described as typically having one terminal common cloacal opening, but she found in living material from New Zealand waters a ' very regular arrangement of the common cloacal apertures around the periphery of the distal part of the head, a region entirely free of zooids . . . '. As I shall show below, this is certainly not the case in the ' Discovery ' specimens, in which examination of many well-preserved colonies, both of S. sigillinoid.es and S. georgiana, showed one terminal common cloacal opening. Brewin emended the generic description to agree with her New Zealand material, and acceptance of the emended diagnosis would exclude both the type species S. sigillinoides and also S. georgiana. This seems to be unjustified, and I suggest that the arrangement of the common cloacal openings be disregarded. The question is further complicated by the structure of a new species, Sycozoa anomala, in the ' Discovery ' collections, from north of New Zealand. The main reason for separating Sycozoa from Distaplia has hitherto been the unisexual nature of the colonies of Sycozoa and their hermaphrodite nature in Distaplia. But the new species, S. anomala, from the ' Discovery ' collections, which in all other respects agrees well with other species of Sycozoa, has hermaphrodite colonies as well as uni- sexual ones. The distinction between the two genera thus seems to break down. In 5. anomala the position of the ovary also is somewhat intermediate between the genera, and the logical course might be to unite Sycozoa with Distaplia, the name Sycozoa having priority. But as there are many well- known species bearing the name Distaplia, this course would undoubtedly lead to great confusion, and I have retained both Distaplia and Sycozoa. Genus Sycozoa Lesson, 1830 There are several reasons why separation of species of Sycozoa is difficult, one of the more im- portant being ignorance of the changing forms of the colony during its normal annual cycle, and under different conditions of environment. Thus S. ramulosa (Herdman) and S. umbellata (Michaelsen) may be two forms of S. sigillinoides. The characters of S. ramulosa which Arnback (1950) used to distinguish it from S. sigillinoides are: (1) its longer body and especially the branchial sac; (2) the extension of the testis beyond the intestinal loop; (3) the small number (one to three) of eggs in each brood pouch. The shape of the body depends greatly on its state of contraction and is rather a difficult character to determine. The size of the testis varies according to the degree of sexual development of the zooid and is therefore also unreliable. It may be noted that, among the ' Discovery ' material, there are colonies combining character (2) of S. ramulosa with character (3) of S. sigillinoides (e.g. St. 1230). Moreover, DESCRIPTION OF SPECIES 71 Michaelsen (1924) found brood pouches in S. sigillinoid.es containing from one to three larvae, and I have found from two to fourteen in different specimens of the same species. I therefore agree with van Name (1945) and Kott (1954) that S. ramulosa is a synonym of S. sigillinoides. Regarding S. ambellata (Michaelsen) both Michaelsen (1924) himself and Arnback (1950) are inclined to regard this also as a synonym of S. sigillinoides. S. georgiana (Michaelsen) is another form which some authors think might be S. sigillinoides (Brewin, 1953). But I believe that the speciess hould be maintained (see p. 74), although I am not altogether sure that it is distinct from S. gaimardi (Herdman), an insufficiently known form. Herdman (1886) described S. quoyi from Kerguelen, but his description did not sufficiently dis- tinguish it from S. sigillinoides. Kott (1954) maintains their separation on the grounds of slight anatomical distinctions in the gut and the much larger size of the larva. In view of the variations in larval size which can occur within one species I am still doubtful about the validity of S. quoyi. Sycozoa sigillinoides Lesson (Text-fig. 19, PI. II, figs. 3-8) Sycozoa sigillinoides Lesson, 1830, p. 436, pi. Moll. 13, fig. 15, 15b. Non Sycozoa sigillinoides Brewin, 1952, p. 190, text-fig. 2. For synonymy see van Name, 1945. Occurrence. St. 45: S. Georgia, 238-270 m. St. 51: Falkland Islands, 105-1151^ St. 53: Falkland Islands, 0-2 m. St. 145: S. Georgia, 26-35 m. St. 652: Burdwood Bank, 164 m. St. 1230: Magellan Strait, 27 m. St. WS 84: Falkland Islands, 75-74 m. St. WS 85: Falkland Islands, 79 m. St. WS90: Patagonian Shelf, 219- 144-152 m. St. WS 243 Patagonian Shelf, 309- Text-fig. 19. Sycozoa sigillinoides Lesson. Cut-away section of the upper part of the head. Patagonian Shelf, 82-81 m. St. WS92: Patagonian Shelf, 145-143 m. St. WS95: Shelf, 109-108 m. St. WS 214: Patagonian Shelf, 208-219 m. St. WS 215: Patagonian -146 m. St. WS220: Patagonian Shelf, 108-104 m. St. WS226: Patagonian Shelf, St. WS 237: Patagonian Shelf, 150-256 m. St. WS 239: Patagonian Shelf, 196-193 m. : Patagonian Shelf, 144-141 m. St. WS 244: Patagonian Shelf, 253-247 m. St. WS 245: Shelf, 304-290 m. St. WS 765 : Patagonian Shelf, 113-119 m. St. WS 772: Patagonian 163 m. St. WS 775: Patagonian Shelf, 115-110 m. St. WS 784: Patagonian Shelf, 170- ?2 DISCOVERY REPORTS 164 m. St. WS 785 : Patagonian Shelf, 150-147 m. St. WS 799: Patagonian Shelf, 0 m. St. WS 800: Patagonian Shelf, 137-139 m. St. WS 814: Patagonian Shelf, 112-119 m. St. WS 816: Patagonian Shelf, 150 m. St. WS 818: Patagonian Shelf, 272-278 m. St. WS 819: Patagonian Shelf, 313-329 m. St. WS 833 : Patagonian Shelf, 38-31 m. St. WS 834: Patagonian Shelf, 27-38 m. St. WS839: Patagonian Shelf, 503-534 m. St. WS 841 : Patagonian Shelf, 110-121 m. St. WS 847: Patagonian Shelf, 51-57 m. Colony. The shape of the colony varies greatly but the causes of variation are only partly known. In many specimens which are fully developed and more or less intact there is a stout main stem which in life appears to have lain on the sandy bottom either free or loosely fixed. This stem fulfils the function of a creeping stolon and gives rise to one or a few bunches of upright stalks, each stalk bearing a single head (PI. II, figs. 3,4). A true rooting system does not seem to be developed, but in other respects the habit is very like that of the Australian species S. tenuicaulis (Herdman) (see Herdman, 1899, pi. Dist. 1, fig. 2; Brewin, 1953. Text-fig. iB). Many specimens, however, have a single stalk bearing one head (e.g. St. WS 90) ; these are perhaps broken pieces of complex colonies, for they have the same characters of stalk and head. A third type of colony consists of a simple or slightly branched stalk attached basally to a solid object (e.g. St. WS 95). Many unattached heads were also taken in the collections, and these will be referred to later (see p. 73). Finally there is the headless condition represented either by isolated hard orange-coloured stalks or by whole complex colonies completely lacking zooids (e.g. St. WS 800) (PI. II, fig. 5). In well-developed complex colonies the stalks reach 6 cm. in length, occasionally more, and the heads up to 2-5 cm. long and i-o cm. wide. Two groups of specimens from South Georgia (St. 45, St. 145) have a short fleshy stalk attached to an alga, and a head at least twice as long as the stalk (PI. II, fig. 8). As the structure of the head, the zooids and their arrangement, and the larvae all agree closely with the other examples of 5. sigillinoides in the collection, I am including these specimens within that species, although not entirely satisfied with this course. They are very like the specimens also from South Georgia figured by Arnback (1950, fig. 26) as S. sigillinoides, and like Herdman's (1886) type of his species 5. quoyi from Kerguelen, and also like Michaelsen's (1907) specimens from South Georgia, which he named S. quoyi var. zschaui. I regard S. quoyi as a synonym of S. sigillinoides. In the ' Discovery ' colonies, which are preserved in alcohol, the head is soft and usually yellow-grey. It is almost cylindrical, and rounded or tapered at each end. The stalk, although wide at the upper end, is sometimes constricted where it joins the head, and is narrowest at the base. It is firm, buff or dull orange in colour, and typically marked with fine annular ridges. The basal stem is similar to the stalk but is stouter and usually shorter. As I have already remarked, I disagree with Brewin (1953) in her description of the common cloacal openings in the genus. In well-preserved specimens of S. sigillinoides which I have examined, the apex of the head has a single common cloacal opening, all the more clearly marked because the test bears a series of teeth round its border (Text-fig. 19, t.t.). The opening is ring-shaped as viewed from the apex of the colony owing to the projection of the central core of common test of the head. The individual cloacal canals, each serving a double row of zooids, lead into the terminal opening, and not directly to the surface of the colony. Zoom. The atrial languet has been described as 'of varying length ' (van Name, 1945), and 'some- times fringed with a number of lobes ' (Kott, 1954). I have found that differences in the atrial languet are related to the position of the zooid in the colony. All zooids except the terminal one in each row Table 22 June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 3 6 5 1 6 4 6 9 3 i 0 — 2 0 1 1 2 4 1 DESCRIPTION OF SPECIES 73 have a pointed triangular languet. In the terminal zooids only, that is those immediately round the common cloacal opening, the end of the atrial languet is wide and straight with a row of pointed or leaf-like teeth. These teeth correspond to the teeth present on the test round the common cloacal opening, already mentioned, and doubtless are responsible for their formation. The intestine only occasionally shows the subdivisions which Kott (1954) used to distinguish S. sigillinoides from S. quoyi. Larva. The larvae from different colonies vary in size from 0-40 to 0-76 mm., measured from the end of the papillae to the base of the tail, the majority being between 0-50 and o-6o mm. Caullery (1909), Salfi (1925) and Kott (1954) have already described the larva. The sensory vesicle contains only one black pigment spot, the spherical otolith, 22-26 /i in diameter. Biology. Breeding probably does not occur in the southern winter, yet as shown by the figures in Table 22 it is not restricted to a short period of the year. Month May No. of colonies examined 3 No. of colonies with 1 embryos In different colonies the embryos in the brood pouches numbered from two to fourteen. The heads and zooids are unisexual, but all zooids in a head are not at the same stage of develop- ment. In a single head buds and young non-functional zooids may be found at the base ; then a zone of functional but sexually unripe zooids occurs; and finally the distal part of the head is devoid of zooids but contains many isolated brood pouches with embryos and larvae. The brood pouches dis- appear finally, having presumably been set free by the disintegration of the common test. Whether the larvae escape before or after this is unknown. It has long been known that heads occur free in the water, and indeed the first record of the species (Lesson, 1830) was of an isolated pelagic head. Free heads were frequent amongst the 'Discovery' material, having been taken in various years in January, February, October and December, i.e. in the southern spring and summer. Brewin (1953) suggests that the breaking off of heads is caused by rough weather, but van Name (1945) considers it as probably a normal event in the life of the species. Head- less stalks, at any rate, seem to be a part of the annual cycle (PI. II, fig. 5) ; they occur in the ' Discovery ' collections sometimes in December, but most often in May, June and July, i.e. in the southern winter. At the depths from which these headless stalks were collected (137-304 m.) storm action could not account for the loss of the heads, and I conclude that they were lost in the normal course of events. But headless stalks do not necessarily imply free pelagic heads, as heads disintegrate after breeding. Whether intact heads also break off, except by storm or other accidental damage, is still doubtful. The headless stalks do not die, and PI. II, fig. 7, illustrates the growth of new heads. The old stalk consists of a firm outer layer with a sharply defined upper margin, and a softer central core of test material containing many small rounded orange bodies and perhaps a few remaining vascular processes from the zooids which formerly occupied the head. Caullery (1909) and Salfi (1925, 1926) have shown that these rounded bodies are buds formed by multiple constriction of the vascular processes of the zooids. The reduced state of the colonies, containing the buds but no zooids, recalls the overwintering condition of colonies of the Family Polyclinidae, but I do not know if the colony of Sycozoa also has a period of quiescence. When the buds develop they produce new zooids within the central test near the upper end of the old stalk, and at the same time new central test material begins to bulge out from the end of the stalk. As the new test continues to grow it forms a new head containing the 74 DISCOVERY REPORTS developing zooids. Regenerating heads on old stalks were taken in December, March and May, but most often in June and July. We may conclude that loss of the head follows breeding and is in turn followed by regeneration of a new head, the speed of regeneration perhaps depending on water temperature, as in colonies of Aplidium in northern temperate waters. In the related genus Hypsistozoa, Brewin (1956a) has shown that, accompanying and following the production of larvae, the distal part of the head of the colony is resorbed. Meanwhile, new zooids at the junction of the stalk and the old head are forming a new head. This is a process very similar to that occurring in Sycozoa. It seems curious that one species should show two habits so different as the single stalk and the branched complex form. Perhaps some of the apparently simple forms are stalks broken off from more complex colonies, but it is also possible that the simple and the complex forms represent different phases of the life cycle. This is suggested by the growth of several young heads instead of one, from the end of the old stalks, a process seen in several specimens (PI. II, fig. 7). Perhaps the colonies which develop from settled larvae have single stalks, which, after breeding and loss of the head, may develop a group of new heads from the original stalk, thus giving rise to a complex colony, the original stalk becoming the stout basal stem of the new colony. Distribution. Owing to the confusion regarding species it is difficult to state exactly the distri- bution of S. sigillinoides, but it is certainly widely spread in both western and eastern parts of southern and Subantarctic waters (Falkland Islands, Patagonian Shelf, Tierra del Fuego, Kerguelen, Macquarie Island, Tasmania, South Australia) and the Antarctic (South Georgia, Graham Land, Kaiser Wilhelm II Land, Enderby Land, MacRobertson Land). Sycozoa georgiana (Michaelsen) (PI. Ill, fig. 5) Colella georgiana Michaelsen, 1907, p. 62, pi. 1, fig. 6; pi. 3, fig. 15. For synonymy see van Name, 1945, pp. 154-5. Occurrence. St. 39: S. Georgia, 179-235 m. St. 140: S. Georgia, 122-136 m. St. 149: S. Georgia, 200-234 m. ?St. 363 : S. Sandwich Islands, 329-278 m. ?St. WS 33 : S. Georgia, 130 m. St. MS 14: S. Georgia, 190-110 m. St. MS 68: S. Georgia, 220-247 m. Colony (PI. Ill, fig. 5). The form of the colony and the shape of the head are the main features which distinguish this species from S. sigillinoides. Colonies are attached to some solid object over which spreads a system of creeping branched stolons giving rise at intervals to single or grouped stalks. Each stalk bears a characteristic head which is pear-shaped or almost globular, and never, in the specimens examined, long as in S. sigillinoides. The heads in the ' Discovery ' material are not laterally compressed as in Michaelsen's (1907) description. Usually the head is as wide as long, and sometimes is wider. One of the largest specimens has a stalk of 4-7 cm. and a head 0-7 cm. long by 0-9 cm. wide. The stalk and the head are of the same pale grey colour and the same smooth rather soft consistency, whereas in S. sigillinoides the head and stalk differ from each other. Zooids are generally absent from the lower part of the head, and the oral openings are confined to a wide zone round the single terminal common cloacal opening. Sluiter (1932) found that the zooids were not arranged in rows, and Michaelsen (1907) did not mention any regular arrangement. At first sight this also seems to be the case in the 'Discovery' specimens, but careful examination shows that the zooids are in short rows each with a few zooids. Zoom. The zooid seems to present no characters by which it can be distinguished from S. sigil- linoides. Certainly it cannot be separated by the number of branchial stigmata in a row, as Kott (1954, p. 155) has done in her key. Sluiter (1932) stated that in young zooids the stigmata number ten to twelve in each half row, but in fully developed zooids there are up to twenty, and in the ' Discovery ' DESCRIPTION OF SPECIES 75 material I have counted eighteen stigmata in a half row. This is the same number as in many zooids of S. sigillinoides. As in S. sigillinoides the zooids immediately surrounding the common cloacal opening have a broad-ended atrial languet, but in other zooids it is pointed. The brood pouches are long, narrow and coiled at the lower end. Larva. Embryos and larvae together numbering from ten to twenty-eight in a brood pouch are present in some colonies collected in March. The larvae measure from o-6o to 0-65 mm. from the end of the papillae to base of the tail, and could not be distinguished from larvae of S. sigillinoides, unless by a somewhat longer tail, but this is a variable character. Remarks. In spite of its resemblance to S. sigillinoides, I do not doubt that S. georgiana is a valid species. Its known range is confined to South Georgia and perhaps the South Sandwich Islands (St. 363). It is not a form that has often occurred in any collections, and owing to its scarcity, little is known of its biology. One colony from South Georgia (St. WS 33) has a shape very like that described for S. gaimardi (Herdman, 1886). But as no characters other than the mushroom-shaped head and the large number of embryos in the brood pouch seem reliable in that species, and the ' Discovery ' colony is without embryos, I have included the specimen in S. georgiana. Distribution. Antarctic (South Georgia, ?South Sandwich Islands). Sycozoa anomala sp.n. (Text-fig. 20; PI. Ill, fig. 6) Holotype. Size: head i-8 cm., stalk 2-0 cm. long. St. 929. Diagnosis of species. Colonies hermaphrodite or unisexual. Zooids unisexual; female with coiled brood pouch ; branchial sac with no parastigmatic transverse bars ; stomach smooth externally ; ovary somewhat projecting below the abdomen. Larva with otolith but no ocellus. Occurrence. St. 929: North Island, New Zealand, 55-58 m. Colony (PI. Ill, fig. 6). The material consists of three single colonies and a compound colony with four stalked heads. The largest of the single heads has a length of i-8 cm. and a breadth of 1-3 cm., and is carried on a stalk of 2-0 cm. The compound colony has a basal stem of 1-3 cm. at the end of which is a group of four stalks, the longest 1-3 cm. The heads of the isolated colonies are a little flattened but the compound colony has round heads. The head is smooth and pale translucent buff- grey, the zooids being visible as double rows of paler spots. Longitudinal furrows separate the ad- jacent double rows. The stalk is rather paler than the head, widest at its attachment to the head, and tapering towards the base. The compound colony has a certain amount of sand sticking to the basal stem, but the other colonies are quite free of sand. At the apex of each head there is a single simple common cloacal opening, through the centre of which the terminal common test may project slightly. Zoom (Text-fig. 20 A). The zooid is about 2 mm. in length, seldom more, and the thorax and abdomen are of about equal length, except when the gonads are highly developed and projecting. The oral siphon (o.s.) has six short pointed lobes and the atrial opening is large with a triangular atrial languet (a. I.). The zooids surrounding the common cloacal opening have a wide languet with a few small teeth; the remaining zooids have a narrower triangular languet without teeth. Branchial sac. There are about sixteen long slender oral tentacles of varying length. The four rows of stigmata have no parastigmatic transverse bars. A short blunt languet is present on each transverse bar of the left side. The stigmata are long and narrow, and number at least fifteen in each row. The endostyle is wide. Gut. The oesophagus (oe.) is of moderate length, narrow and curved ventrally. The ovoid or pear- shaped stomach (st.) has walls which are smooth externally, but internally are provided with minute papillae. White pigment spots are scattered on the surface of the stomach. A short post-stomach (p.st.) 76 DISCOVERY REPORTS leads to the intestine (i) which forms a short loop. The rectum is straight and ends with a two-lipped anus lying level with the transverse bar separating the third and fourth rows of stigmata. Vascular process. A slender vascular process (v.pr.) arises from the left side of the abdomen and passes down below the zooid into the common test of the colony. Some of these processes, but not all, extend down into the stalk of the colony. Gonads. In the compound colony all the zooids were male, but two of the single colonies had both male and female zooids ; the third single colony was in degeneration. 0.5 mm Text-fig. 20. Sycozoa anomala sp.n. (St. 929): A, female zooid; B, abdomen of male zooid; C, brood pouch with embryos. The ovary (ov .) lies slightly behind the intestinal loop, but in contact with it, and bulges out from the abdomen to form a small sac-like projection recalling the condition in Distaplia. The ovaries examined contained a group of ova of various sizes. In male zooids the testis (t) is a rosette of six to ten wedge-shaped follicles contained in a projection from the abdomen similar to that accommodating the ovary in female zooids, but generally larger. The sperm duct (s.d.), arising from the centre of the rosette, loops back before passing forward beside the rectum (Text-fig. 20 B). Many of the female zooids had well-developed brood pouches (Text-fig. 20 C). These are rather short, strongly coiled, and usually contained from nine to eleven embryos. DESCRIPTION OF SPECIES 77 None of the zooids showed any sign of hermaphroditism, and the youngest buds in which any gonad was visible were clearly either male or female. Larva. The larva could not be distinguished from that of S. sigillinoides except by its rather smaller size, 0-44-0-48 mm. from the end of the papillae to the base of the tail. This size, however, falls within the range of the larva of S. sigillinoides. Remarks. In most respects this species is a quite typical Sycozoa, but the hermaphrodite nature of the colonies is exceptional. The species seems to come closest to S. pulchra (Herdman) from the Torres Strait between Australia and New Guinea, and S. kanzasi (Oka) from Japanese waters. S. pulchra has herm- aphrodite zooids and is therefore clearly different. S. kanzasi is more difficult to distinguish, but the species can be separated as shown in Table 23. Table 23 S. kanzasi S. anomala Oral siphon Usually with plain margin With 6 short pointed lobes Oral tentacles 12 16 Knob-like structure over stomach Present Absent Anus With plain margin With 2 lips There is little doubt that the two species are very nearly related. Unfortunately the gonads of the specimens seen by Oka (1930) and Tokioka (1953) were not well developed. The knob-like process over the stomach is perhaps an unsatisfactory character for separating the species, because it is inter- preted by Tokioka as a rudimentary bud and is therefore liable to be present or absent according to the phase of asexual development at which the zooid is examined. Distribution. North end of North Island, New Zealand. Genus Distaplia Delia Valle, 1881 Distaplia colligans Sluiter (Text-fig. 21 ; PI. Ill, fig. 3) Distaplia colligans Sluiter, 1932, p. 7, figs. 5-8. Occurrence. St. 164: S. Orkneys, 24-36 m. St. 476: S. Georgia, 165-0 m. St. 11 13: Bransfield Strait, 275-130 m. St. MS 63: S. Georgia, 23 m. St. MS 74: S. Georgia, 22-40 m. Colony. The colonies from stations 164, MS 63 and MS 74 are all very similar. The largest of these specimens is 1-2 cm. long and 0-3 cm. thick (St. MS 63). The preserved colour is a dull purple brown, marked with paler spots where the zooids show through the test. Generally the colonies are rather low and flattened or pillow shaped, not subdivided or lobed. No common cloacal openings are apparent on the surface, and usually no regular arrangement of the zooids can be made out, although in parts of one of the colonies from St. MS 63 there is an appearance of linear arrangement. In one of Sluiter's specimens there was a regular alignment of the zooids in double rows, but in the other this was apparently not conspicuous. The common test is soft and pliable, and semi-transparent but with a slightly cloudy appearance owing to the presence of many small pale cells, especially in the surface layer. Zoom (Text-fig. 21). The zooids generally measure about 3 mm. in length, but their length in life was probably rather more, as the thorax in most colonies is much contracted, except in the specimens from St. 476 and St. n 13, which will be discussed later (p. 78). The oral siphon (o.s.) is short, sometimes quite distinctly six-lobed, but more often almost without lobes. Narrow but fairly strong thoracic muscles are present. A triangular and moderately long atrial languet {ad.) is found in all zooids. I could find no trace of a vascular process from the posterior end of the zooids. 78 DISCOVERY REPORTS Gut. The oesophagus is narrow and of moderate length. In some colonies the wall of the stomach (st.) is distinctly marked with many fine ridges, but in others the wall is almost smooth externally. Sluiter does not describe any markings on the stomach of his type specimens, and his figure shows none. Gonads. The gonads in Sluiter's specimens were evidently not very well developed, only a group of small testis follicles being present, and no trace of an ovary. Sluiter concluded that the colonies were unisexual. 'Discovery' specimens collected in February and March show a variety of sexual stages. In one colony some zooids are seen with a group of about twelve testis follicles (t) and a few small ova (ov.), and other zooids have a testis and quite large ova. The colony from the South Orkney 1.0 Text-fig. 21. Distaplia colligans Sluiter (St. MS 63): Zooid. Islands has zooids with only the ovary present and no testis. It is likely that Sluiter's two specimens were in the early male phase. The gonads are situated beside the loop of the intestine and scarcely project from the body except when at the height of their development. Only in some colonies from South Georgia and the South Orkney Islands is there any sign of a brood pouch ; the zooids have a small sac-like projection from the dorsal body wall behind the atrial opening, evidently in the early stages of development. Remarks. All these colonies, with the possible exception of the ones from St. 476 and St. 11 13, are in good agreement with Sluiter's type specimens of D. colligans, although the new specimens differ slightly in having markings on the wall of the stomach, and in the larger size of the zooids. The single colonies from St. 476 and St. 1 1 13 (PI. Ill, fig. 3) are larger (2 cm. in diameter and 7 cm. long respectively) and paler than those already described. The zooids also are much larger, reaching 8 mm. in length when fully expanded. In other respects, however, they are similar and I am inclined to think that the differences may be due to the stage of the annual cycle at which the colonies have arrived. DESCRIPTION OF SPECIES 79 D. colligans must be considered rather scarce or at least hard to find, and it may prove to have a wider distribution in the Antarctic than at present appears. Distribution. Antarctic (South Georgia; South Orkney Islands; Bransfield Strait). Distaplia cylindrica (Lesson) (PI. Ill, fig. 4) Holozoa cylindrica Lesson, 1830, p. 439. For synonymy see van Name (1945), p. 143. Occurrence. St. 39: S. Georgia, 179-235 m. St. 45: S. Georgia, 238-270 m. St. 123: S. Georgia, 230-250 m. St. 140: S. Georgia, 122-136 m. St. 142: S. Georgia, 88-273 m- St. 148: S. Georgia, 132-148 m. St. 149: S. Georgia, 200-234 m. St. 189: Palmer Archipelago, o m. St. 366: S. Sand- wich Islands, 155-322 m. St. 1900: Patagonian Shelf, 0-5 m. St. 1906: Patagonian Shelf, 0-5 m. St. WS33: S. Georgia, 0-5 m. St. WS90: Patagonian Shelf, 82-81 m. St. WS765: Patagonian Shelf, 113-119 m. St. WS 787: Patagonian Shelf, 106-110 m. St. MS 68: S. Georgia, 220-247 m. B.G.L.E., Stella Creek. B.G.L.E., Port Lockroy, 0-5 m. Colony. Many of the specimens in the collection are only parts of colonies, but there are also a few intact specimens, in which the base is attached, generally to a few small stones or pebbles. This basal area is sometimes wider than the rest of the colony, and in other cases the colony widens towards the base but narrows again at the immediate area of attachment. The largest colony (St. 148), measures, in the preserved state, 460 cm., but a label with the specimen showed that an earlier measurement, probably in the fresh state, was 485 cm. Even this colony was not intact. Another specimen was part of a 'strip floating on the surface', 20-25 ft. long. This floating fragment, over 7 m. in length, repre- sents one of the longest specimens ever recorded. In alcohol the colony is usually a dull greyish green, but the collector of the large floating strip has given the following description of the fresh colony: 'general colour pale yellow white; details of colour: background pale indeterminate, zooids bright creamy white'. Zoom. Arnback (1949, 1950) has shown that, contrary to the belief of previous workers, the zooids are hermaphrodite, with the testis maturing before the ovary. The material on which she worked was part of the 'Discovery' collection (St. 149), which I have been able to re-examine. This and other specimens show that the zooid in the fully developed female condition has two large eggs. Two embryos, or occasionally three, are found in the brood pouch. Biology, (a) Breeding. The breeding condition of all colonies in the ' Discovery ' collection is shown in Table 24. The zooids are classed as ' well developed male ', in which the testis is moderate or large ; 'well developed female', with moderate or large eggs in the ovary; and 'with embryos', in which the brood pouch contains one, two, or three developing embryos. No colonies were collected in the winter months of May to September, but enough material was taken during the rest of the year to show that zooids were already well advanced as males in October and that the testis was present from then on until January when it began to regress. In October and November the ovary had not yet started to develop, in December and January it was large, and thereafter decreased. The presence of eggs or embryos in the samples of December, March and April indicates a breeding season confined to the southern summer. No fully developed larvae were seen in any of the zooids during that period, perhaps owing to a long period of incubation. If this is so larval settlement is not likely to take place before April. Zooids in different parts of a colony are in different sexual conditions. One large colony of 130 cm. illustrates this (St. 366). Zooids are absent from the basal 6 cm. of the colony. Zooids at 10 cm. from the base have no gonads, no brood pouch, and no embryos. Some zooids at 20 cm. from the base have an ovary and others have not, and some zooids have a spherical brood pouch, but without embryos. 80 DISCOVERY REPORTS At 30 cm. the gonad has disappeared but many of the zooids have two embryos in the brood pouch, and this is the usual condition throughout the rest of the colony, with some variations in the state of the ovary. This grading of sexual development in the zooids indicates that towards the base of the colony the zooids are younger than those higher up the colony, and is to be expected in forms with a linear arrangement of the zooids (e.g. Sycozoa) but not necessarily in D. cylindrica which has small oval systems. In some at least of the colonies which have embryos the zooids contain very little or no food in the gut, and it is likely that the zooids become moribund once the eggs are passed into the brood pouches. Specimens collected in April and containing embryos had non-functional zooids and some colonies lacked zooids altogether. None of the colonies in the collection showed any sign of the accumulation of reserve materials or other provision for overwintering and how the species passes through the winter is not known. Table 24 Month May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. Well-developed male — — 2331 — 00 Well-developed female — — — 0043 — 10 With embryos — — — — — o o 1 o — 3 1 (b) Feeding. The contents of the gut show one or two interesting features. In the branchial sac of zooids in several colonies there was much coarse sand as well as organic matter (PI. VI, figs. 4, 5), but the stomach and intestine showed no large sand grains, (PI. VI, fig. 3). Unless this is an artifact produced in some way during collection or handling of the specimens, there seems to be some kind of sorting mechanism at work between the branchial sac and the stomach, a feature noticed in other and unrelated species (see p. 146). Coarse matter is present in the branchial sac right up to the mouth of the oesophagus, but none enters the oesophagus. That the mechanism is not simply one which excludes large particles is indicated by the presence of some diatoms in the intestine, equal in size to the sand grains which are excluded. The oesophagus perhaps accepts mainly organic matter, or particles with a smooth surface, but I do not know which of these characters is the important one or how the selection mechanism works. There must be an accumulation of sand particles in the branchial sac which is presumably cleaned at intervals by thoracic contractions expelling the whole contents of the branchial sac. Distribution. Antarctic (Graham Land, Kaiser Wilhelm II Land, MacRobertson Land, South Georgia, South Sandwich Islands), Subantarctic (Patagonian Shelf, Strait of Magellan). Genus Hypsistozoa Brewin, 1953 Hypsistozoa fasmeriana (Michaelsen) (Text-fig. 22, PI. Ill, fig. 2) Distaplia j'asmeriana Michaelsen, 1924. Hypsistozoa fasmeriana Brewin, 1953, p. 56. Occurrence. St. 935 : North Island, New Zealand, 84 m. Colony (PI. Ill, fig. 2). The single specimen of this interesting species is a colony with head 1-3 cm. long and i-i cm. wide, borne on a stalk i-6 cm. long and 0-7 cm. wide. The head is greyish brown and the stalk dull pale orange ; both are smooth and without any encrusting matter. Rows of zooids are visible through the test; the systems are in fact long narrow elipses, but so narrow that the zooids have the appearance of being arranged in double rows. The common cloacal openings, of which there are several, are scattered on the surface of the colony, but are largely confined to the distal part. Each opening is round or oval and is bordered by a projecting rim of test. DESCRIPTION OF SPECIES 81 Zoom (Text-fig. 22). The zooids agree closely with Michaelsen's (1924) detailed description, except that the stomach (st.) of the ' Discovery ' specimens has rather more folds, there being up to twenty instead of fifteen as noted by Michaelsen. Gonads. Many of the zooids in the ' Discovery ' colony have no trace of gonads, but in a few there is a large testis (t.), consisting of many closely packed small orange-coloured follicles forming a long body situated entirely behind the loop of the intestine. The sperm duct (s.d.) is sinuous or hooked at Text-fig. 22. Hypsistozoa fasmeriana (Michaelsen) (St. 935): Zooid. its origin. No female gonads were seen, although, as Brewin (1946) has shown, the zooids are herm- aphrodite. There were also no brood pouches. Remarks. The species was very carefully described by Michaelsen (1924) who, in the absence of gonads in his specimens, put it in the genus Distaplia. But Brewin (1946) found specimens with gonads which projected into the right anterior part of the vascular process, and she later erected a new genus Hypsistozoa for the species (Brewin, 1953). The annual cycle and the complex and interesting embryonic development have been described in detail by Brewin (1956a). 82 DISCOVERY REPORTS Distribution. H. fasmeriana has been previously recorded from Stewart Island, to the south of South Island, New Zealand (Michaelsen, 1924) and from Christchurch, South Island, New Zealand, and East Cape, North Island, New Zealand (Brewin, 1946, 1950, 195 1, 1953). The 'Discovery' record considerably extends the range northwards. The species seems to be confined to the New Zealand region, but within that region it exists in the different temperature conditions which prevail at the extreme south and extreme north of these islands. Genus Cystodytes von Drasche, 1884 Cystodytes dellechiajei (Delia Valle) Distoma dellechiajei Delia Valle, 1877, p. 40. For synonymy see van Name (1945), p. 133. Occurrence. St. 934: North Island, New Zealand, 98 m. St. 935: North Island, New Zealand, 84 m. St. WS 871 : Patagonian Shelf, 336-342 m. Colony. The several colonies collected from St. 935 are ovoid rather than flat and encrusting; the largest is 3-0 cm. in length. The colony from St. 934 has its outline broken by a number of projecting lobes. Distribution. This species is very widely distributed, mainly in tropical and subtropical waters. It also extends to the more temperate waters of New Zealand and the Chatham Islands (Brewin, 1948, 1951, 1952, 19566). C. dellechiajei f. antarctica (Sluiter) (Text-fig. 23) Cystodytes antarcticus, Sluiter, 1912, p. 460; 1914, p. 27; Arnback, 1950, p. 26, pi. 5, fig. 25, text-figs. 6-8. Occurrence. St. 181: Palmer Archipelago, 160-335 m- St. 190: Palmer Archipelago, 93-126 m. Colony. Several colonies were collected from the Palmer Archipelago, and the largest of these measures 6 cm. long by 1-5 cm. wide and about 1-5 cm. thick. This colony is considerably larger than 0.3 mm Text-fig. 23. Cystodytes dellechiajei (Delia Valle): A, spicules of f. antarctica (St. 190); B, spicules of typical form (St. 934); C, spicules of typical form (St. WS 871) any collected by the second Charcot Expedition or the Swedish Antarctic Expedition of 1901-3, the only two expeditions which have hitherto taken the form. The disc-shaped spicules (Text-fig. 23 A), which reach 0-3 mm. in diameter, have a crenelated margin, as described by Arnback (1950). DESCRIPTION OF SPECIES 83 Zoom. The zooid is much as described by Arnback, but there is only a relatively short waist joining the thorax and abdomen. This condition may have resulted from contraction. Larva. No fully developed larvae were found in any of the colonies, but the large colony from St. 190 had some advanced embryos with the tail differentiated. These embryos had a length of i-i to i-2 mm. Remarks. Sluiter (191 2) described a species C. antarcticus, which Arnback (1950) retained, but thought would very probably prove to be a form of C. dellechiajei, if more material could be studied. The only way of distinguishing C. dellechiajei and C. antarcticus, other than by their distribution, is by the shape of the spicules. All antarctic specimens so far examined, including the ' Discovery ' ones, have spicules with a distinctly crenelated margin (Text-fig. 23 A). Specimens from other regions have the margin smooth or minutely notched (Text-fig. 23 B, C), but there is sufficient variation in the size and distinctness of the notches to render doubtful the value of this character for separating species. I therefore propose that the present specimens, together with those previously called C. antarcticus, should be recognized as a form antarctica nom.nov. of C. dellechiajei. Distribution. The form antarctica is recorded only from the vicinity of Graham Land. Subfamily Atapozoinae Brewin, 1956 Genus Atapozoa Brewin, 1956 Atapozoa marshi Brewin (Text-fig. 24) Atapozoa marshi Brewin, 1956c, p. 31, fig. 1. Occurrence. St. 935 : North Island, New Zealand, 84 m. Colony (Text-fig. 24 A, B). There are two specimens. The larger has a cylindrical stalk 1-3 cm. long and an ovoid head i-o cm. long. In the smaller specimen the stalk is only 0-3 cm. in length and the head is globular, with a diameter of about 1 -o cm. In each the stalk is encrusted with white shelly debris but the head is bare. The zooids, which are confined to the head, are seen through the test as orange-brown bodies. The test is semi-transparent and firm, but contains no 'kotballen' (masses of foreign matter) which Brewin found in her specimens. Zoom (Text-fig. 24 C). Large zooids in which the abdomen is well developed reach a total length of 3-4 mm.; zooids with a short abdomen are little more than half that length. The siphons are both provided with six distinct lobes. Eighteen to twenty longitudinal muscles are present on each side of the thorax, and converge to form a more compact band of muscle which extends down the whole length of each side of the abdomen. Some zooids have a short vascular process (v.pr.) at the lower end of the abdomen. A small thin-walled projection from the base of the dorsal side of the thorax (b.p.) is present in some zooids and may represent the brood pouch described by Brewin. The whole body is of an orange-brown colour when preserved in alcohol. Branchial sac. Details are difficult to distinguish owing to the contraction of the thorax. The oral tentacles are closely spaced and number at least twenty. There are three rows of stigmata but the number in each row could not be determined; they probably exceed twenty. The hooked dorsal languets on the two transverse bars are quite prominent. Gut. The oesophagus (oe.) is nearly twice as long as the stomach, and in this respect differs from Brewin's type specimens most zooids of which had a short oesophagus. The stomach (st.) is smooth- walled and the intestinal loop short, without any apparent divisions. In the type specimens the anus was smooth-edged; in the 'Discovery' material the anus (a), which lies opposite the second row of stigmata, has two lips. Gonads. Gonads were not developed in the present specimens. 84 DISCOVERY REPORTS Remarks. The genus Atapozoa was erected by Brewin (1956c) for a species found at Trigg Island, near Perth, Western Australia. Atapozoa differs from Endistoma in having a stalked brood pouch, and only two anterior papillae in the larva instead of three. There were no larvae in the ' Discovery ' specimens, and the brood pouch, if present at all, was in a rudimentary state. The identification therefore rests on the other characters of the zooid and on the structure of the colony, in all of which features there is close agreement with the type specimens. Distribution. Western Australia ; North Island, New Zealand. Text-fig. 24. Atapozoa marshi Brewin (St. 935): A, B, two colonies; C, zooid. Suborder PHLEBOBRANCHIATA Lahille, 1886 Family DIAZONIDAE Garstang, 1891 Genus Tylobranchion Herdman, 1886 Tylobranchion speciosum Herdman (Text-fig. 25; PI. Ill, fig. 1) Tylobranchion speciosum Herdman, 1886, p. 157, pi. 22, figs. 1-17. For synonymy see Kott (1954), p. 152. DESCRIPTION OF SPECIES 85 Occurrence. St. 123: S. Georgia, 230-250111. St. 144: S. Georgia, 155-178111. St. 160: Shag Rocks, 177 m. St. 371 : S. Sandwich Islands, 99-161 m. St. WS 27: S. Georgia, 104 m. St. WS 243 : Patagonian Shelf, 144-141 m. St. WS 841 : Patagonian Shelf, 110-121 m. Colony. The largest specimen in the collection is one from the Patagonian Shelf (St. WS 841), measuring 9 cm. tall, 1-5 cm. thick, and 7 cm. long. The original colony must have been still larger, as the specimen is only a portion. In form the colonies (PI. Ill, fig. 1) are generally pillar-like, wedge- shaped, or club-shaped and are often markedly flattened from side to side. The test is firm but not hard, sometimes almost clear and occasionally nearly opaque. Some of the colonies from South Georgia and the Patagonian Shelf are reddish brown in colour. In most specimens the zooids are A _ d.p. H 0.2 mm 2.0 mm Text-fig. 25. Tylobranchion speciosum Herdman: A, zooid (St. WS 27); B, C, D, branchial papillae from different specimens (Sts. WS 27, 371, WS 243); E, gonads; F, transverse section of zooid at level of heart ; and G, below level of heart; H, larva (St. 144). readily visible through the test. Attachment of the colony is usually to a small group of pebbles embedded in the basal test. Zoom (Text-fig. 25 A). The general structure of the zooid is already known, and the principal variations in the ' Discovery ' specimens are tabulated on page 86. Certain points regarding the lower part of the zooid, however, have remained doubtful. Berrill (1935) described a true post-abdomen containing the heart and gonads, but Arnback (1927, 1950) showed that the heart is much farther forward than Berrill's figure indicated. A careful examination of the ' Discovery ' specimens allows me not only to confirm Arnback's findings, but also to add details concerning the epicardium and the nature of the posterior part of the zooid. The epicardium is a flattened tube forming a partition across the abdomen. Extending from just below the base of the thorax, it reaches the pericardium (pc.) but instead of ending there it continues into the lower, narrow part of the zooid where it forms a partition separating the two blood channels (Text-fig. 25 G, b.c). This part of the zooid behind the heart also 86 DISCOVERY REPORTS contains muscles of the body wall and is not homologous with the vascular process which occupies a similar position in the related Diazona. In Diazona the vascular process has a mesenchymatous septum and no extension of the epicardium. Gonads (Text-fig. 25 E). Specimens collected in July (St. WS 243, Patagonian Shelf), and March (St. 371, South Sandwich Islands) had well-developed gonads consisting of bunched testis follicles (t.) at the lower end of the intestinal loop, and an elongated ovary (ov.) below the testis. Larva (Text-fig. 25 H). Two of the specimens carry larvae. One colony from the Patagonian Shelf (St. WS 243), collected in July, has only three larvae in the zooids, and one colony from South Georgia (St. 144) collected in January, has many larvae in each breeding zooid. Only the latter Species or material T. antarcticum T. speciosum T. weddelli ' Discovery ' St. 144 (4 colonies) ' Discovery ' St. WS 27 (18 colonies) Height of colony (cm.) Up to 2 •6-27 1-6-s-o 3-o. 3'5 'Discovery' St. 371 (2 colonies) ' Discovery ' St. WS 243 (1 colony) ' Discovery ' St. WS 841 (piece of i colony) 'Discovery' 4-5, 4-0 St. 160 (2 colonies) 4'5 Piece, 7 by 9 Length of zooids (mm.) Thorax 2, abdomen 2-75 Thorax 4-5, abdomen 7-8 Thorax 7-8, abdomen 7 Thorax 3-5-5-0, abdomen 3-0- 5-5 Thorax 2-0-6-0, abdomen 3-0- 7-0 Thorax 6-7, abdomen 7-9 Thorax 4, abdomen 5 Thorax 3, abdomen 3 Thorax 5-6, abdomen 3-5 Table 25 Thoracic muscles 7 or 8 Numerous (about 11?) 9 or 10 6-8 7-12 7-10 6-8 Branchial papillae Tall; processes long Flattened; pro- cesses short Flattened; pro- cesses short Short; processes quite long Short with short processes or long with long processes Long; processes long Long; processes long Short; processes short Short; processes short Stomach folds Sinuous and narrow About 17, slightly sinuous 14, straight 17-19; mostly straight 12-18, mostly straight, but some sinuous in some zooids 12-16, straight Apparently smooth 10-12 15 or 16 Distribution or occurrence E. and W. Antarctic Kerguelen W. Antarctic S. Georgia S. Georgia S. Sandwich Is. Patagonian Shelf Patagonian Shelf Shag Rocks specimen has fully developed larvae. These measured about 0-55 mm. from the end of the papillae to the base of the tail. There are two short dorsal papillae (d.p.) placed close together, and one short ventral papilla (p.p.), the three arranged to form a triangle. The trunk is deep and rounded. Within the cerebral vesicle the black otolith projects from the floor, but there is no trace of a pigmented ocellus. Remarks. Three species of Tylobranchion have been described from southern waters, T. speciosum, Herdman, T. antarcticum Herdman, and T. zveddelli Arnback. Van Name (1945) doubted whether they are distinct, and Kott (1954), after examining material from the B.A.N. Z. Antarctic Research Expedition of 1929-31 decided that they all represent one species. But Arnback (1950) still maintained their separation. I have to record, however, that in her personal notes, to which I have had access, she seemed to have found less clear distinctions between the species represented in the 'Discovery' collections. The characters shown in Table 25 include those used by Arnback to separate the three species. They show such a degree of overlapping that I am accepting Kott's (1954) view of the identity of the species, the name T. speciosum having priority. DESCRIPTION OF SPECIES 87 The systematic position of the genus has been much discussed. Originally placed in the family Polyclinidae by Herdman (1886), it is now generally regarded as a phlebobranchiate ascidian, related to, or actually within, the family Diazonidae. The larva, with its triangular arrangement of the papillae, also shows that the genus should be removed from the Polyclinidae. The ' Discovery ' records are of special interest as they extend the known range northwards to the edge of the Antarctic and beyond into the Subantarctic (Patagonian Shelf). Arnback (1950) had already recorded the species (as T. antarcticum) from South Georgia, at that time the most northern locality. Distribution. Antarctic (Cape Adare, MacRobertson Land, Kaiser Wilhelm II Land, Graham Land, South Georgia, South Shetland Islands, South Sandwich Islands), Subantarctic (Patagonian Shelf). Family ASCIDIIDAE Adams, 1858 Genus Ascidia Linnaeus, 1767 Ascidia translucida Herdman (Text-fig. 26) Ascidia translucida Herdman, 1880, p. 466. ? Ascidia plicata Kott, 1954, p. 150, fig. 31. Occurrence. St. 39: S. Georgia, 179-235 m. St. WS25: S. Georgia, 18-27 m. St. MS 10: S. Georgia, 26-18 m. St. MS 65: S. Georgia, 39 m. St. MS 68: S. Georgia, 220-247 m- External appearance (Text-fig. 26A). The largest of the six specimens is 19-0 cm. long and the Text-fig. 26. Ascidia translucida Herdman (St. MS 68): A, external appearance; B, specimen with test removed; C, D, E, dorsal tubercles of small, medium and large specimens, respectively. 88 DISCOVERY REPORTS smallest 1-5 cm. long. The size of the largest animal is greater than any yet recorded for this species, unless we accept A. plicata Kott as a synonym, Kott having recorded specimens of that species up to 29 cm. in length (see below for a discussion of A. plicata). Dorsal tubercle. The species is distinguished mainly by the very complex form of the opening of the dorsal tubercle. The large specimens in the ' Discovery ' collection show this feature but in smaller ones the opening is much simpler, and a series of increasing complexity can be seen (Text- fig. 26C-E). Oral tentacles and branchial bars. The numbers of oral tentacles and of longitudinal branchial bars are given in Table 26, for specimens of different sizes. Table 26 Length of body No. of No. of longi- {cm.) tentacles tudinal bars 19-0 18 39 8-5 16 36 8-2 21 25 7-5 25 40 29 36 27 i-5 19 20 These figures give the total numbers of tentacles, including the smallest visible ones. If the larger and more conspicuous tentacles only are counted, the numbers would be reduced by one-third to one half. The number of tentacles does not increase steadily with growth of the body ; in fact there is a tendency for large animals to lose tentacles. Branchial sac. The wall of the branchial sac is plicate, as noted by Herdman (1882). I have found that in large specimens the plication is complex, as the walls of each fold are thrown into a series of lesser folds, as described by Kott (1954) in her species A. plicata. Correlated with this folding there has developed immediately external to the perforated wall, a flat sheet of tissue extending over the whole outer surface of the wall. This sheet represents an expansion of the outer part of the transverse bars, and serves to support the folded stigmatic wall. The sheet is pierced by transverse rows of slit- like openings by which alone the water may escape from the branchial cavity to the surrounding peri- branchial cavities. The papillae of the branchial sac are large, and in some places intermediate papillae may be seen, but these seem usually to be associated with the growth of new transverse bars. Remarks. A. translucida is readily distinguished by its dorsal tubercle from other Antarctic and Subantarctic species except A. plicata Kott (1954) in which a similar tubercle has been described. Kott states that this species is distinguished from A. translucida by (1) the branchial wall with primary and secondary folds, (2) the atrial siphon one-third to one half of the body length from the oral siphon, and (3) the absence of secondary branchial papillae. I believe that the branchial wall of A. translucida is essentially the same as that described for A. plicata. The type specimen of A. translucida, which Herdman described and illustrated, was only 2-2 cm. in length, and a specimen of this small size might be expected to have a simple type of folding in the branchial sac. The 'Discovery ' specimen of 2-9 cm. length has only slight folding of the wall, and the smallest specimen available, of length 1-5 cm., shows no folding at all. There is, therefore, a gradual increase in complexity with increasing age and size. The second feature used to distinguish A. plicata, the distance of the atrial siphon from the anterior end of the body, does not in fact separate the two species, in each of which the distance is between one-third and one half of the body length. DESCRIPTION OF SPECIES 89 The third criterion, the presence or absence of intermediate papillae in the branchial sac, is also an unreliable character. In A. translucida, Hartmeyer (1912) found that secondary papillae were present in older specimens but not in younger ones. Arnback (1938) also noted that in A. translucida these papillae exist in some parts of the branchial sac but not in others. For these reasons I regard A. plicata as very probably a synonym of A. translucida. Distribution. Antarctic (South Georgia), Subantarctic (Kerguelen). Ascidia challenged Herdman (Text-fig. 27) Ascidia challengeri Herdman, 1882, p. 102, pi. 30. Ascidia charcoti Sluiter, 1905, p. 471. Ascidia dispar Arnback, 1938, p. 48; text-fig. 11. Occurrence. St. 145: S. Georgia, 26-35 m. St. 156: S. Georgia, 200-236 m. St. 160: Shag Rocks (S. Georgia), 177 m. St. 164: S. Orkneys, 24-36 m. St. 195: S. Shetlands, 391 m. St. 1652: Ross Sea, 567 m. St. 1660: Ross Sea, 351 m. St. WS 27: S. Georgia, 107 m. St. MS 71 : S. Georgia, 110-60 m. B.G.L.E., 1934-7, Stella Creek. p.bd Text-fig. 27. Ascidia challengeri Herdman (St. 145): Oral tentacles. External appearance. The specimens range in length from 1-3 cm. to n-o cm., the largest being from the Ross Sea. They vary from a regular oval and laterally flattened form to an irregular pear- shaped form. The siphons are generally, but not always, inconspicuous, the oral one terminal and the atrial about one-third of the body length from it. No. of tentacles Dorsal lamina No. of longitudinal branchial bars per side Intermediate branchial papillae Branchial stigmata Table 27 A. dispar About 50 Extends far beyond oesophageal mouth 40-50 Absent Short and irregular A. challengeri Few, usually up to 20 Scarcely extends beyond oesophageal mouth 30-32 Usually present Long and regular Remarks. Arnback (1938) described a new species A. dispar, based on a single specimen from South Georgia. She recognized the strong similarity to A. challengeri, but gave as main distinctions those shown in Table 27. Of these characters the ones which, judging by distinctions between other species of Ascidia, are likely to be the most reliable are (1) the number of tentacles, (2) the number of longitudinal branchial go DISCOVERY REPORTS bars, and (3) the presence or absence of intermediate branchial papillae. In Table 28 I have shown the variation in the ' Discovery ' specimens in respect of these three characters. A fourth character which I have added is the presence or absence of a rib running forward along the inner siphonal wall from the base of each tentacle (Text-fig. 27, rb.). This is a feature which I noticed in some specimens and which is illustrated but not mentioned by Herdman (1923, pi. 13, fig. 1) in A. challengeri. Inspec- tion of the way in which these characters are distributed among the specimens shows that it is im- possible to maintain the distinctions made by Arnback in establishing A. dispar, which I therefore regard as a synonym of A. challengeri. Table 28 Station ... Locality ... 156 S. Georgia 160 Shag Rocks WS 27 5. Georgia 156 S. Georgia MS 71 S. Georgia H5 S. Georgia No. of tentacles No. of longitudinal branchial bars 40-43 50-53 30 60 48-50 About 39 26 28 50-55 About 40 29 32 Intermediate branchial Present Present ? Absent Present in Absent papillae Tentacle ribs Absent Absent ? ? places Present Present Station ... 164 1652 1660 195 B.G.L.E. Locality ... 5. Orkneys Ross Sea Ross Sea S. Shetlands Stella Creek No. of tentacles 18 12-15 26 11-16 12-14 No. of longitudinal branchial bars 38-40 54-58 36 33 27-32 Intermediate branchial Present Present Present Present Present papillae Tentacle ribs Absent Present ? ? in places Present or absent Two other species seem to be closely related, if distinct: A. placenta Herdman, and A. meridionalis Herdman. Herdman (1923) himself suggested that A. meridionalis might prove to be the same as A. challengeri. Distribution. Antarctic (South Georgia, Graham Land, South Orkneys, South Shetlands, Kaiser Wilhelm II Land, Wilkes Land, King George V Land, Ross Sea), Subantarctic (Kerguelen). Ascidia interrupta Heller (Text-fig. 28) Ascidia interrupta Heller, 1878, p. 89, pi. 2, fig. 9. For synonymy see van Name, 1945, p. 182. Occurrence. St. 279 : French Congo, West Africa, 58-67 m. External appearance (Text-fig. 28A). The three specimens are 7-3 cm. long by 3-0 cm. wide, 7-4 by 5-0 cm., and 7-6 by 2-8 cm. The shape is long and rather narrow, but the outline is irregular and the surface of the body has swellings and depressions. At the anterior end the body is slightly narrowed towards the oral siphon (o.s.). The atrial siphon (a.s.) is scarcely marked externally. It is situated between one half and two-thirds of the body length from the anterior end. Test. The test is fairly thick, hyaline and cartilaginous in appearance, and is semi-transparent. Body wall. The left side of the body has few muscles, and on the right side the muscles form a loose irregular, but mainly transverse, mesh of slender strands. When the test has been removed, the oral siphon is seen to be a narrow, but not very long tube, and the atrial siphon a short conical tube pro- jecting almost at right angles to the long axis of the body. Tentacles. There are from eighty to no oral tentacles in the 'Discovery' specimens. They are slender and closely crowded. DESCRIPTION OF SPECIES 91 Dorsal tubercle. In one of the specimens examined, the dorsal tubercle is of a simple U -shape, with the right limb a little turned inwards (Text-fig. 28 C). In another specimen the opening is broken up into a number of irregular pieces, but is still basically U-shaped (Text-fig. 28 D). Branchial sac. There are fifty to sixty longitudinal bars on each side of the branchial sac. Gut. The gut (Fig. 28 B) is very like that illustrated by van Name (1945, fig. 97). Gonads. In all three specimens the testis is poorly developed, and the ovary is a small slightly lobed body lying within the intestinal loop (Text-fig. 28 B, ov.). 20cm Text-fig. 28. Ascidia interrupta Heller (St. 279): A, external appearance; B, specimen with test removed; C, D, dorsal tubercles of two specimens. Remarks. These animals from the French Congo, West Africa agree very closely with the detailed description given by van Name (1945) of the species as it occurs on the tropical coasts of the American side of the Atlantic. So far as I am aware, it has not been recorded hitherto from the African coast and the ' Discovery ' specimens are from deeper water than previous records. This is a further example of the distribution of a tropical species on both sides of the Atlantic. Distribution. East coast of tropical America; French Congo, West Africa. Ascidia sydneiensis Stimpson (Text-fig. 29) Ascidia sydneiensis Stimpson 1855, p. 387. For synonymy see van Name 1945. p. 189. Occurrence. St. 90: False Bay, S. Africa, 0-2 m. St. 1686: Victoria, Australia, o m. External appearance. The specimen from False Bay, South Africa is 5-0 cm. long and 3-0 cm. wide. The specimen from Victoria, Australia is 9-2 cm. long and 6-9 cm. wide. Internal structure. Both specimens are quite typical of this species. Each shows the charac- teristic bands of muscles on the right side (Text-fig. 29 B), the large number of oral tentacles (150-200), and the complex dorsal tubercle. Remarks. In the South African individual the gut is full of food, consisting largely of algal cells, diatoms and peridineans with a certain amount of coarser inorganic matter. Distribution. Widely distributed throughout the warmer and temperate waters of the world. 92 DISCOVERY REPORTS Family AGNESIIDAE Huntsman, 1912 Genus Agnesia Michaelsen, 1898 Agnesia glaciata Michaelsen (Text-fig. 30) Agnesia glaciata Michaelsen 1898, p. 370. Agnesia krausei Michaelsen, 1912, p. 181, figs. 24, 25. Agnesia capensis Millar, 1955, p. 191, fig. 19. Occurrence. St. 91 : False Bay, S. Africa, 35 m. St. 939: N. Island, New Zealand, 87 m. St. WS 775: Patagonian Shelf, 115-uom. External appearance. The two specimens from the Patagonian Shelf have lengths of 17 and 10 mm. The single specimen from False Bay, South Africa, is 9 mm. long and the largest of those from north of New Zealand is 12 mm. long. In most cases the body is rectangular in outline. In all specimens the test is thin and very transparent, but is hidden to a variable degree by the sand or broken shell 2.0 cm 3.0 cm Text-fig. 29. Ascidia sydneiensis Stimpson (St. 1686): A, external appearance of specimen; B, same specimen with test removed. which adheres to it. This coating of sand is most complete in the specimens from New Zealand and least in those from the Patagonian Shelf. Test hairs are sparsely developed in the specimens from the Patagonian Shelf and South Africa, but appear to be absent in the New Zealand specimens. Musculature (Text-fig. 30A). The same arrangement of muscles is found in all the specimens, but the degree of development varies. Longitudinal muscles radiate out from the two siphons and pass downwards across the upper part of the body. Strong circular muscles are present on both siphons, round which they form complete rings. Posterior to the siphons the circular muscles are represented by four longitudinal series of short transverse bands (t.m.), one series near the dorsal and one near the ventral margin of each side of the body. When the body is contracted these short trans- verse bands are inconspicuous, and this may possibly account for the omission of any reference to them by Michaelsen (1898, 1900) in his descriptions of A. glaciata and A. krausei. Remarks. A. glaciata, the type species of the genus, was found off Tierra del Fuego and described by Michaelsen (1898, 1900); he subsequently described another species, A. krausei, from the Pata- gonian Shelf. A single specimen from Table Bay, South Africa, was made the type of a third species, DESCRIPTION OF SPECIES 93 A. capensis (Millar, 1955). The three descriptions are very similar, as may be seen by the comparison of the diagnostic characters given in Table 29. Details of the 'Discovery' specimens are included. It is evident from the table below that both the number of turns of the stigmata, and whether the stigmata are undivided (Text-fig. 30 B) or divided (Text-fig. 30 C) depend on the size of the specimen. The distinctions between A. krausei and A. glaciata therefore break down. As van Name (1945) pointed out A. krausei is to be regarded as a young stage of A. glaciata, because division of the stigmata is likely to occur in older specimens. Having now been able to examine a second specimen 5.0 mm Text-fig. 30. Agnesia glaciata Michaelsen : A, specimen from Patagonian Shelf (St. WS 775); B, stigma of specimen from False Bay, S. Africa (St. 91); C, stigma of specimen from St. WS 775. Table 29 'Discovery' St. WS 775 A. krausei A. glaciata A. capensis (type specimen) 'Discovery' St. 91 (S. Africa) (Patagon ian Shelf) ' Discovery ' St. 939 (New Zealand) Specimen 1 Specimen 2 Length of body (mm.) Up to 9 Up to 18 11 9 10 17 12 No. of turns of stigmata Nature of stigmata 4-5 Undivided 7-9 Divided 3-5 Divided 4 Undivided 5 Divided 9 Divided 5 Undivided Radial stigmatic vessels Present Present Absent Present Present Present Present of Agnesia from Table Bay, South Africa, I find that this one possesses radial vessels across the stigmata (Text-fig. 30 B, r.v.), and conclude that my earlier observation (Millar, 1955) was incorrect or based on poor material. The distinction between A. capensis and A. glaciata also disappears, and one species, A. glaciata, remains. All specimens of Agnesia in the 'Discovery' collection can be referred to A. glaciata, which appears to be a species of wide distribution in southern waters. Distribution. Subantarctic (Magellan region); South Africa; north of New Zealand. 94 DISCOVERY REPORTS Genus Caenagnesia Arnback, 1938 Caenagnesia bocki Arnback (Text-fig. 31) Caenagnesia bocki Arnback, 1938, p. 41, pi. 2, figs. 20-22. Agnesia complicata Kott, 1954, p. 151, figs. 32, 33. Occurrence. St. 42: S. Georgia, 120-204 m. St. 181: Palmer Archipelago, 160-335 m- St. 182: Palmer Archipelago, 278-500 m. External appearance. The shape of these specimens is very much as described by Arnback (1938). In some of them there is a coating of fine sand or mud on most of the test. One specimen (St. 182) has fine test processes arising from the lower part of the body, as in the type specimen. The largest specimen is only 15 mm. in length, as compared with 20 mm. in Arnback's material, and 30 mm. in Kott's material. 4.0 mm Text-fig. 31. Caenagnesia bocki Arnback (St. 42): A, specimen with test removed; B, dorsal tubercle. Internal structure. The 'Discovery' specimens show remarkable agreement with Arnback's detailed account. The numerous oral tentacles are arranged in five distinct circles. The rectum appears to be a little shorter than that shown in Arnback's fig. 20. Remarks. This species has been recorded only twice before; off Graham Land (Arnback, 1938), and off Enderby Land (Kott, 1954) if we accept Agnesia complicata Kott as a synonym of C. bocki. Kott's description of the specimens which she examined from near Enderby Land agrees very closely with Arnback's description of the type specimens, except in having a better developed branchial sac. In A. complicata there were twenty-four transverse rows of infundibula each with seventeen infundi- bula, as compared with twelve rows each with thirteen or fourteen infundibula in C. bocki. This difference can be accounted for by the larger size of the specimens from Enderby Land. Kott mentioned ' bifid languets ' alternating with each transverse row of infundibula and not with each two rows (cf. A. septentrionalis Huntsman, A. glaciata Michaelsen, van Name, 1945, p. 201). These ' bifid languets ' are in fact the bifid papillae which are present on the transverse vessels. True languets, to which Huntsman referred in A. septentrionalis, are present only along the roof of the branchial sac. Caenagnesia, having a continuous dorsal lamina, has no languets. Distribution. Antarctic (Graham Land, South Georgia, Enderby Land). DESCRIPTION OF SPECIES 95 Family CORELLIDAE Lahille, 1887 Subfamily Corellinae Herdman, 1882 Genus Corella Alder & Hancock, 1870 Corella eumyota Traustedt Corella eumyota Traustedt, 1882, pp. 271, 273, pi. 4, figs. 2, 3; pi. 5, figs. 13, 14. For synonymy see van Name, 1945, p. 212. Occurrence. St. 55: Falkland Islands, 10-16 m. St. 1652: Ross Sea, 567 m. Remarks. I have nothing to add to the descriptions already existing of this well-known species. Van Name (1945) discusses the problems involved in determining the probable synonyms of the species. Distribution. Antarctic (Graham Land, Kaiser Wilhelm II Land, Ross Sea, PWilkes Land), Sub- antarctic (Falkland Islands, coast of Chile, Magellan region, Auckland Islands, Macquarie Islands), South Africa, St Paul (Indian Ocean), New Zealand (North and South Islands), south and west Australia, Tasmania. Order PLEUROGONA Perrier, 1898 Suborder STOLIDOBRANCHIATA Lahille, 1886 Family STYELIDAE Sluiter, 1895 Subfamily Botryllinae Adams, 1858 Genus Botryllus Gaertner (in Pallas), 1774 ? Botryllus separatus Sluiter (Text-fig. 32) Botryllus separatus Sluiter, 1904, p. 100, pi. 15, fig. 22. Occurrence. St. 934: North Island, New Zealand, 98-92 m. External appearance. The single example is a brown colony approximately 8-o by 4-5 cm., soft and thick. There are numerous round, oval or somewhat elongated systems of zooids. Groups of vascular ampullae lie between the systems and also form a fringe round the margin of the colony. 1.0 mm Text-fig. 32. ? Botryllus separatus Sluiter (St. 934) : Zooid. Zoom (Text-fig. 32). The zooids attain a maximum length of 3 mm. and are golden-brown in colour in the preserved state. The oral opening (0.0.) is sessile and without lobes, and the atrial opening (a.o.) is large, exposing part of the dorsal surface of the branchial sac. 96 DISCOVERY REPORTS Tentacles. Only four tentacles (tn.) were seen, although Sluiter noted eight. Branchial sac. There are twelve rows of stigmata in most zooids examined, each row with about eighteen stigmata. The three longitudinal branchial bars customary in the genus are present. The dorsal lamina is a narrow membrane. Gut. The gut is confined to the posterior part of the zooid. It consists of a short curved oeso- phagus (oe.), a conical stomach (st.) with nine folds but completely lacking a pyloric caecum, and an S-shaped intestine and rectum. The anus (a), which lies opposite the 7th row of stigmata, has a plain margin. Gonads. No gonads were present in any of the zooids examined. Remarks. Few species of either Botryllus or Botrylloides have been described from the North Island of New Zealand or the Australian coasts, and the present specimen does not agree well with any of them. The main points on which I base identification are the absence of a pyloric caecum and the presence of nine folds on the stomach. But there must remain some doubt about this identification because reliable characters are few in the botryllids, and the nearest record of B. separatus is from the vicinity of Borneo. Distribution. Indonesia; North Island, New Zealand. Genus Polyzoa Lesson, 1830 Polyzoa opuntia Lesson (Text-fig. 33 A; PI. V, fig. 1) Polyzoa opuntia Lesson, 1830, p. 437. For synonymy see van Name 1945, p. 236. Occurrence. St. 145: S. Georgia, 26-35 m. St. I23°: Magellan Strait, 27 m. St. 1902: Pata- gonian Shelf, 50-80 m. St. WS71: Falkland Islands, 82-80 m. St. WS75: Falkland Islands, 64-104 m. St. WS86: Patagonian Shelf, 151-147111. St. WS95: Patagonian Shelf, 109-108 m. St. WS221: Patagonian Shelf, 76-91 m. St. WS788: Patagonian Shelf: 82-88 m. St. WS798: Patagonian Shelf, 49-66 m. St. WS 834: Patagonian Shelf, 27-38 m. St. WS 837: Patagonian Shelf, 95-102 m. St. MS 33: S. Georgia, 40 m. St. MS 64: S. Georgia, 7-15 m. St. Port Stanley, Falkland Islands, on shore. External appearance (PI. V, fig. 1). The colony of this species, although variable, is well known and characteristic, and needs no further description. Larva (Text-fig. 33 A). The larva has an ovoid trunk measuring about o-8 mm. from the anterior end of the papillae to the base of the tail. Behind the three papillae is a number of ampullae forming a complete ring round the anterior end of the trunk. There is a single black sense organ. The tail is about 1-5 mm. long, excluding the fin of test which projects about o-6 mm. beyond the end of the tail. Biology. Larvae were found in colonies from the Patagonian Shelf and Falkland Islands in December, February, March and June, and in colonies from the Magellan Strait in December. No larvae were present in the colonies from S. Georgia. Remarks. Arnback (1950) separated P. opuntia Lesson and P. coccinea Cunningham, which van Name (1945) regarded as synonymous species. The distinctions which Arnback proposed are: (1) the difference between seven longitudinal bars (P. opuntia) and eight bars (P. coccinea) on the left branchial wall ; and (2) differences in the form of the colony. The colony is very variable and I doubt whether these distinctions are sufficiently great or constant in the genus to justify this course. Distribution. Subantarctic (coast of Argentine, Falkland Islands, Kerguelen, Tierra del Fuego), Antarctic (South Georgia, Heard Island). DESCRIPTION OF SPECIES 97 Polyzoa reticulata (Herdman) (Text-fig. 33B; PI. V, fig. 6) Chorizocormus reticulatus Herdman, 1886, p. 346, pi. 46, figs. 1-8. For synonymy see van Name 1945, p. 237. Occurrence. St. 42: S. Georgia, 120-204111. St. 51: Falkland Islands, 105-115111. St. 58 Falkland Islands, 1-2 m. St. 140: S. Georgia, 122-136 m. St. 141: S. Georgia, 17-27 m. St. 148 S. Georgia, 132-148 m. St. 474: S. Georgia, 199 m. St. 1230: Magellan Strait, 27 m. St. WS 25 S. Georgia, 18-27 m. St. WS27: S. Georgia, 107 m. St. WS 71 : Falkland Islands, 80-82 m. St. WS82: Falkland Islands, 140-144 m. St. WS85: Falkland Islands, 79 m. St. WS823: Pata- gonian Shelf, 80-95 m. St. MS 10: S. Georgia, 26-18 m. St. MS 14: S. Georgia, 190-nom. St. MS 62: S. Georgia, 31m. St. MS 71 : S. Georgia, 110-60 m. St. MS 74: S. Georgia, 22-40 m. 7.0 mm Text-fig. 33. Larvae of A, Polyzoa opuntia Lesson (St. WS 221), B, P. reticulata (Herdman) (St. MS 74), and C, Alloeocarpa incrustans (Herdman) (St. 388). External appearance (PI. V, fig. 6). The colonies vary in form, some having closely united zooids with little or no stolon, and in others the zooids are widely separated with long narrow stolons. Larva (Text-fig. 33B). In form this is very like the larva of P. opuntia. The trunk is from 0-72 to 0-90 mm. long, and the tail from i-o to 1-5 mm. excluding the projecting fin of test material. There are three papillae, about fourteen ampullae in a ring round the anterior end of the trunk, and a single black sense organ. Biology. Larvae were present in colonies collected at Falkland Islands in February and March, and at South Georgia in November, December, February and March. Distribution. Subantarctic (Falkland Islands, Patagonian Shelf, Magellan Strait, Kerguelen, Campbell Islands, Macquarie Islands), Antarctic (South Georgia). I3 DM 98 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. DESCRIPTION OF SPECIES 99 Larvae were found in the colonies from the Patagonian Shelf and Falkland Islands in February, March, April, May and June, and in colonies from South Georgia in November, January and February. Distribution. Subantarctic (Falkland Islands to Tierra del Fuego), Antarctic (South Georgia). Table 30 V VI VII VIII IX X XI XII / // /// II No. of colonies with larvae 3 i 0 — — 0 I 0 2 1 1 2 No. of colonies without larvae 4 0 1 — — 1 0 2 1 4 1 0 Genus Amphicarpa Michaelsen, 1922 Amphicarpa diptycha (Hartmeyer) (Text-fig. 34, PI. V, fig. 3) Distomus diptychos Hartmeyer, 1919, p. 87, pi. 2, fig. 48. Occurrence. St. 1686: Victoria, Australia, o m. External appearance (PI. V, fig. 3). The colony, which is about 5 cm. long, and rather less in width, had been growing on the shell of a living mussel. For the most part the zooids are close as 3.0 Text-fig. 34. Amphicarpa diptycha (Hartmeyer) (St. 1686): Zooid. 13-2 ,oo DISCOVERY REPORTS together, only those on the margins of the colony lying some distance apart. Where the zooids are separated the narrow basal stolons which unite them can be seen. Sand almost completely covers both zooids and stolons. The zooids are ovoid, upright, may be slightly narrowed at the base, and bear the two inconspicuous siphons at the upper end. The largest zooids are about i cm. long. Tentacles. The oral tentacles, although closely spaced, number only about 50, whereas Kott (1952) found about 100. Dorsal tubercle. The opening of the dorsal tubercle is a simple longitudinal slit. Branchial sac. In a large zooid the longitudinal branchial bars have the following arrangement: dorsal line o (12) 5 (9) 6 endostyle. Gut. The gut is just as Kott described it, including the series of ligaments (Text-fig. 34, Ig.) attached to the intestine. Gonads. Only the ovaries are present in zooids of the ' Discovery ' colony, there being no trace of testes. On the right side there is a slightly curved row of about eight very small ovaries; on the left side two rows diverge from the postero-ventral part of the body wall, one parallel to the endostyle and the other following the course of the intestine (ov.). Endocarps. Large and small endocarps (en.) are scattered over much of the body wall. Distribution. Western and southern coasts of Australia; Tasmania. Subfamily Styelinae Herdman, 1881 Genus Cnemidocarpa Huntsman, 191 3 Cnemidocarpa pfefferi (Michaelsen) (Text-figs. 35A-C) Styela pfefferi Michaelsen, 1898, p. 367. Occurrence. St. 42: S. Georgia, 120-204 m. St. 123: S. Georgia, 230-250 m. St. 159: S. Georgia, 160 m. St. 1952: S. Shetlands, 367-383 m. External appearance. The largest specimen is 5-2 cm. high and 2-5 cm. wide, and the smallest one 2-2 by 2-2 cm. The body is generally upright with the two quite prominent siphons a little distance apart at the upper end. Shallow furrows divide the surface into large irregular areas. All the examples in the ' Discovery ' collection are pale grey in the preserved state, with a fairly smooth surface which is almost free of encrusting matter. Tentacles. These vary from ten to thirty-two according to the size of the specimen. Dorsal tubercle. The dorsal tubercle of the ' Discovery ' specimens is constant in form, having a C-shaped slit with inrolled horns and the open interval facing forward. Gut. The stomach has twenty-four to thirty-one complete folds. Gonads (Text-figs. 35 A, B, C). In all specimens dissected there were two gonads on each side. Each consists of a sinuous ovary (ov.), the sides of which have swellings, knobs, or short branches. These short lateral branches are generally in pairs with the two limbs curved in towards each other. The testis follicles (t) are arranged on the sides of the branches in a very characteristic manner (see Text-fig. 35 B) and are closely united to the ovarian branches from the sides of which they scarcely project even when well developed. The gonad is therefore of the Cnemidocarpa type, in which the testis is bound closely to the ovary, within a common membrane. Remarks. This species has been confused with Styela paessleri, and van Name (1945) considered them to be probably identical. The structure of the gonads is, however, quite different, although when S. paessleri is at full maturity the testis is so large that it presses closely round the sides of the ovary (see p. 115). The difference in the gonads of the two species will be best understood by reference to DESCRIPTION OF SPECIES 101 Text-figs. 35 A-C and D-F which show the close union of testis and ovary in C. pfefferi and their separation in S. paessleri. Distribution. Antarctic (South Georgia, South Shetland Islands). Text-fig. 35. Cnemidocarpa pfefferi (Michaelsen) (St. 123): A, gonad; B, lobe of gonad enlarged; C, transverse section of lobe of gonad. Styela paessleri Michaelsen (St. 53): D, gonad; E, part of gonad enlarged; F, transverse section of part of gonad. Cnemidocarpa nordenskjoldi (Michaelsen) (Text-figs. 36 A, C, D) Styela nordenskjoldi Michaelsen, 1898, p. 365. Occurrence. St. 53 : Falkland Islands, 0-2 m. St. WS 71 : Falkland Islands, 82-80 m. St. WS94: Patagonian Shelf, 1 10-126 m. St. WS221: Patagonian Shelf, 76-91 m. St. WS243: Patagonian Shelf, 144-141 m. St. WS247: Falkland Islands, 172 m. St. WS582: Magellan Strait, 12 m. St. WS583: Magellan Strait, 14-78 m. St. WS784: Patagonian Shelf, 170-164 m. St. WS805: Patagonian Shelf, 148-150 m. St. WS 847: Patagonian Shelf, 51-57 m. External appearance. The many specimens range from very young ones, little over 1 mm. in length, to a large one 5 cm. long and 2-6 cm. high. They are variable in shape, either ovoid, almost globular or low with an expanded base. The siphons are not very far apart and may be quite prominent or rather small. Small mammillations break up the surface of the test, giving it a slightly rough I02 DISCOVERY REPORTS appearance. Although preserved specimens are brown, a collector's note describes one specimen as ' orange ' in life. Internal structure. The anatomy of the species has already been described in detail, particularly by Michaelsen (1900), van Name (1945) and Arnback (1950). The specimens in the 'Discovery' collections are in close agreement with these accounts. But three specimens from the Palmer Archi- pelago which I have assigned to the closely related C. drygalskii (Hartmeyer) require that these species be compared, particularly as van Name (1945) considered them to be possibly synonymous. In Table 31 I have shown their main characters, including those of 'Discovery' specimens. Table 31 C. nordenskjoldi A C. drygalskii A t Michaelsen (1900) 'Discovery' specimens Hartmeyer (191 1) 1 'Discovery' specimens Tentacles About 44 28-36 30-40 26-35 Dorsal tubercle C-shaped or closed ring C-shaped Half-moon or ring- shaped C-shaped Branchial folds 10-12 bars per fold; 10-20 bars per fold; 8-20 or more bars per 5-20 bars per fold ; 4-6 bars between 4-14 bars between fold ; 4-6 bars 3-10 bars between folds folds between folds folds Parastigmatic bars Present in places Present Present Present Dorsal lamina A few irregular teeth Smooth Smooth Smooth Stomach folds About 21 20-26 About 14 12-15 Intestinal loop Crosses endostyle Crosses endostyle, Does not cross endo- Does not cross endo- except in very small style style specimens Anus 3 lips each sub- 2 or 3 lips, more or 2 lips ; smooth margin 2 or 3 lips, more or divided less subdivided less subdivided Gonads One on each side ; One on each side ; One on right, one or One on each side; testis follicles closely testis follicles closely two on left ; testis testis follicles closely bound to ovary bound to ovary follicles closely bound to ovary bound to ovary It appears from the comparison that only two characters separate the species: (1) the number of folds on the wall of the stomach ; and (2) whether or not the intestinal loops cross the endostyle into the right half of the body (Text-fig. 36A, B). The number of folds on the stomach seems to be a valid distinguishing character, as shown by the following comparison of ' Discovery ' specimens of approximately the same size : C. nordenskjoldi C. drygalskii Body length (cm.) 1-3 i-8 2-1 1-5 2-3 2-5 No. of folds on stomach 20 24 26 12 12 15 The course of the intestinal loop is also generally a reliable character and only breaks down in young specimens of C. nordenskjoldi, in which the loop has not yet grown across the endostyle to the right side of the body. The two species also differ in distribution, C. nordenskjoldi being confined to the Subantarctic and C. drygalskii to the Antarctic. Gonads. Cnemidocarpa and Styela are distinguished from each other mainly by differences in the structure of their gonads. That these distinctions are not entirely satisfactory is shown by C. norden- skjoldi. In this species the testis follicles are closely applied to the sides and parietal surface of the gonad and are enclosed along with the ovary within a common membrane (Fig. 36 C, D), thus agreeing with the condition in Cnemidocarpa (see van Name, 1945, pp. 262-3). When the testis is fully developed, DESCRIPTION OF SPECIES jo3 however, the follicles project slightly from the sides of the gonad, which then approaches the condi- tion typical of Styela. In fact van Name (1945) placed the species in Styela, but pointed out that 'the gonads approach the Cnemidocarpa type'. Arnback (1950), however, suggested that the species should be placed in her genus Ypsilocarpa, which, she says, ' agrees with the genus Cnemidocarpa as regards the general structure of the reproductive organs, the ovary and testis not being separated '. The genus Ypsilocarpa (Arnback, 1921) was characterized as follows: 'Branchial sac. Four folds on each side; three are well developed, and one — the second — is in a rudimentary state. Text-fig. 36. Cnemidocarpa nordenskjoldi (Michaelsen) and C. drygalskii (Hartmeyer) : A, B, comparison of the intestinal loop, ventral view; C, gonad of C. nordenskjoldi (St. WS 805); D, transverse section of the same. Gonads. One elongate cylindrical gonad on each side, bent into the shape of the letter U, and made up of both ovary and testis. Atrial tentacles. The atrial tentacles are thickly scattered over the narrow velum.' Arnback evidently regarded the gonads and the atrial tentacles as the best characters for separating Ypsilocarpa from Cnemidocarpa, but as mentioned above found the structure of the gonad basically similar. There remains only the number of the gonads, their considerable length, and their shape, together with the distribution of the atrial tentacles, to distinguish the two genera, but I do not consider that these characters, even in combination, are of generic value. The proper genus for nordenskjoldi is therefore thought to be Cnemidocarpa. 104 DISCOVERY REPORTS Biology. In Text-fig. 37 are shown the size-distribution and state of the gonads in all specimens, adding together all material from different years. Only large specimens were present in December, January, February and April. Material collected in May shows a number of very small specimens representing the new generation. The breeding season probably occurs between the end of February and the beginning of May. This is confirmed by the state of the gonads which are full from December until February in those animals large enough to be mature. In July animals of a similar size have empty gonads, showing that these animals have spawned. Distribution. Subantarctic (Falkland Islands to Tierra del Fuego). NUMBER OF SPECIMENS JULY 5 1 JUNE MAY APRIL MARCH FEB JAN DEC I 'If I I 1 1 I vttut\ □ NO GONADS GONADS DEVELOPING GONADS MATURE GONADS SPAWNED "I ' 1 1 1 1 2 3 4 5 6 BODY LENGTH CM Text-fig. 37. Cnemidocarpa nordenskjoldi (Michaelsen) : Size distribution and condition of the gonads of specimens collected in different months. Cnemidocarpa drygalskii (Hartmeyer) (Text-fig. 36 B) Styela drygalskii Hartmeyer, 191 1, p. 452, pi. 45, fig. 6, pi. 50, figs. 6-10. Occurrence. St. 187: Palmer Archipelago, 259-354 m- External appearance. The body is dorso-ventrally flattened into a low dome-shape, with a broad base of attachment. A roughened surface is produced by the presence of many small raised plates on the test. The colour is pale brown. Internal structure. The diagnostic characters of the species, and details of the 'Discovery' specimens, have been given in the comparison with Cnemidocarpa nordenskjoldi (see Table 31). Remarks. I believe that this species, like the previous one, is best placed in the genus Cnemidocarpa, DESCRIPTION OF SPECIES 105 and for the same reasons relating to the structure of the gonad which is similar in both species (see p. 102). Distribution. Antarctic (Graham Land; Kaiser Wilhelm II Land). Cnemidocarpa verrucosa (Lesson) (Text-fig. 38 ; PI. V, fig. 5) Cynthia verrucosa Lesson, 1830, p. 151, pi. 53, fig. 2. For synonymy see van Name 1945, p. 272. Occurrence. St. 39: S. Georgia, 179-235 m. St. 42: S. Georgia, 120-204 m. St. 45: S. Georgia, 238-270 m. St. 51 : Falkland Islands, 105-115 m. St. 53: Falkland Islands, 0-2 m. St. 55: Falkland Islands, 10-16 m. St. 58: Falkland Islands, 1-2 m. St. 123: S. Georgia, 230-250 m. St. 140: S. Georgia, 122-136 m. St. 143: S.Georgia, 273 m. St. 148: S. Georgia, 132-148 m. St. 159: S. Georgia, 160 m. St. 160: S. Georgia, 177 m. St. 190: Palmer Archipelago, 93-126 m. and 315 m. Text-fig. 38. Cnemidocarpa verrucosa (Lesson) (St. 366): A, gut of specimen 0-4 cm. long; B, gut of specimen 4-0 cm. long. St. 366: S. Sandwich Islands, 332-155 m. St. 370: S. Sandwich Islands, 80-18 m. St. 371 : S. Sand- wich Islands, 99-161 m. St. 474: S. Georgia, 199 m. St. 599: S. Shetlands, 203 m. St. 1159: between Bouvet Island and Crozet Island, 230-0 m. St. 1952: S. Shetlands, 367-383 m. St. WS 25 : S. Georgia, 18-27 m- St- WS 71 : Falkland Islands, 82-80 m. St. WS 81 : Falkland Islands, 81-82 m. St. WS 85 : Falkland Islands, 79 m. St. WS 823 : Patagonian Shelf, 80-95 m. St. MS 68: S. Georgia, 220-247 m. St. MS 71 : S. Georgia, 110-60 m. British Graham Land Expedition, 1934-7: St. Stella Creek, 10 m. External appearance (PI. V, fig. 5). The appearance of this species is well known and characteristic (see van Name, 1945, p. 272). The largest specimen in the collection has a length of 16 cm. and a breadth of 6-7 cm. Branchial sac. In large individuals the wall of the branchial sac is minutely plicate with the folds running parallel to the longitudinal bars. Gut. Hartmeyer (191 1) found a small pyloric caecum in young specimens, although there is none in large ones. This is confirmed by examination of the ' Discovery ' material ; specimens of greatest 14 106 DISCOVERY REPORTS diameter about 0-4 cm. possess a small caecum (Text-fig. 38 A, p.c), but all specimens over about 2-0 cm. in diameter lack a caecum (Text-fig. 38 B). There are about twenty-four folds on the wall of the stomach, but they are internal and are visible from the outside only in small specimens (see Text-fig. 38 A, B). Biology. Text-fig. 39 shows the size-distribution, in different months, of the specimens from two collecting areas: (1) the Falkland Islands and Patagonian Shelf; and (2) South Georgia, the South Shetland Islands, the South Sandwich Islands and Graham Land. In both populations breeding had probably started before March, as indicated by the presence of young individuals in that month. In the more southerly localities no very young specimens were taken in April, but it must be pointed out that the total numbers collected at this time were very small. The samples from the Falkland Islands and Patagonian Shelf, taken in May, include quite a high proportion of young individuals, suggesting a breeding season extending farther into the southern autumn in the Subantarctic population, than in the Antarctic population. The histograms for March (Antarctic) and May (Subantarctic) point to the presence of at least two year-classes, and the animals may possibly live for two years or more. These are only very tentative suggestions, however, as the numbers of specimens are small and the months of collection limited. Distribution. Subantarctic (Falkland Islands, Patagonian Shelf, Kerguelen) ; Antarctic (Graham Land, Kaiser Wilhelm II Land, South Georgia, South Shetland Islands, South Sandwich Islands, Enderby Land, Queen Mary Land, MacRobertson Land). Cnemidocarpa tricostata sp.n. (Text-fig. 40) Diagnosis of species. Ventral half of body with a thick coat of test hairs, dorsal half without hairs. About twenty-two oral tentacles, and a single circle of atrial tentacles. Dorsal tubercle with a straight opening. Branchial sac without folds, but with three longitudinal bars on each side. Stomach with about thirteen folds. One gonad on the left side and none on the right. Occurrence. St. 27: S. Georgia, nom. External appearance (Text-fig. 40 A). The single specimen is 1-2 cm. high and 0-9 cm. across at the widest point. In the preserved state it is pear-shaped with a swollen base which apparently rested on a soft substratum. The upper part of the body narrows towards the siphons which are close together and project as short tubular papillae with 4-cleft openings. The test on the upper half of the body is broken up into rounded wart-like swellings, which in some places have the appearance of being arranged in circles passing round the body. No test hairs or foreign particles are present on the upper part of the body, which is yellowish grey in colour. The lower half bears a thick coat of test hairs to which a few sand grains adhere. These hairs are unbranched and not very long. They arise either singly or in groups of two or three. Test. The test is rather thin but tough. Body wall. The muscles of the body wall are arranged in two layers, an external one of weak circular muscles and an internal one of strong longitudinal muscles. A few large clear endocarps are attached to the inner surface of the body wall. Tentacles. There are about twenty-two simple oral tentacles and a single circle of many slender atrial tentacles. Dorsal tubercle. The dorsal tubercle is rather small, with a simple oval transverse opening (Text-fig. 40 D). Branchial sac. There are no folds on the branchial walls, each side having only three tall longi- tudinal bars (Text-fig. 40 C, Lb.). The meshes are therefore long, and each accommodates up to thirty stigmata (Text-fig. 40 E). Slender parastigmatic transverse bars pass across the centres of the rows io7 DESCRIPTION OF SPECIES of stigmata. At the anterior end of the branchial sac the dorsal lamina (d.la.) is narrow, and it increases gradually in width towards the oesophageal mouth; the margin is plain and slightly rolled in. Gut. The oesophagus (oe.) is short, curved and rather wide. About thirteen longitudinal folds mark the walls of the large ovoid stomach (st.). A very small straight pyloric caecum is hidden in the bend NUMBER OF SPECIMENS 10 _ MARCH ■ 10 _ JAN &. FEB -i 1 1 r < JAN &. FEB 10 _ DEC - ~i 1 P 4 5 6 DIAMETER CM I 1 8 OVER 8 i X Text-fig. 39. Cnemidocarpa verrucosa (Lesson): Size-distribution of specimens collected from different areas and in different months. 14-2 io8 DISCOVERY REPORTS between the stomach and the intestine. The intestine bends sharply back after leaving the stomach, lies close to the left side of the stomach, then bends forwards near the oesophagus. The rectum is of moderate length and ends in a wide anus (a.) with about twelve shallow lobes. Gonad (Text-fig. 40 C, F). Only a single gonad was found in this specimen, and that is on the 1.0 cm 0.4 Text-fig. 40. Cnemidocarpa tricostata sp.n. (St. 27) : A, external appearance ; B, specimen with test removed ; C, specimen with right half of the body removed, seen from the right ; D, dorsal tubercle ; E, part of branchial wall ; F, transverse section of gonad. DESCRIPTION OF SPECIES 109 left side. The gonad starts ventrally a little to the right of the endostyle, and curves across the posterior half of the left side of the body to end rather far back in the atrial cavity. In structure the gonad is of the typical Cfiemidocarpa-type, with the testis (t) occupying that part of the gonad which is attached to the body wall, and the ovary (ov.) on the free or mesial side. The testis consists of long narrow follicles arranged in a series along the length of the gonad. The ovary occupies the superficial part of the gonad and shows oocytes of various sizes. No oviduct could be seen. Two short slender sperm ducts were found along the length of the gonad, projecting from its free (ovarian) surface. Remarks. This is a very distinctive species not readily confused with any Cnemidocarpa yet described. In the formation of the branchial sac it is most like Styela insinuosa (Sluiter), but in having only three bars on each side shows a still greater simplification. A few species of Cnemidocarpa and Styela have a reduced number of branchial folds. Thus in C. mortenseni (Hartmeyer) there is only one on each side, and in the deep-sea species S. sericata Herdman there are no folds but twenty to thirty longitudinal bars on each side. The presence of only one gonad in C. tricostata is also a remarkable case of simplification. Distribution. Antarctic (South Georgia). Genus Styela Fleming, 1822 Styela schmitti van Name f. simplex n. (Text-fig. 41) Styela schmitti van Name, 1945, p. 298, text-fig. 195. Diagnosis of form simplex. Characters as in the species but with about eight tentacles, a simple slit-like opening of the dorsal tubercle, and only one well-developed fold and a rudimentary one on each side of the branchial sac. Occurrence. St. 388: off Cape Horn, Tierra del Fuego, 121 m. External appearance (Fig. 41 A-C). The shape of the body is much as described by van Name (1945) except that it is generally rather narrower and more nearly cylindrical. The sizes of the body and stalk in the ' Discovery ' specimens are : Body length (mm.) 7 7 5 5 5 5 Stalk length (mm.) 433321 A light coating of sand and broken shell covers the body of all the specimens, but does not extend to the stalk. Two small projections close together at the upper end of the body mark the scarcely visible siphons. Internal structure (Text-fig. 41 D). The main internal characters of the form simplex are shown in Table 32 along with those of van Name's type material of the species. Body-wall muscles Tentacles Dorsal tubercle Branchial folds No. of stomach folds Anus Gonads Occurrence Table 32 5. schmitti f. simplex ('Discovery' material) External circular and internal longitudinal muscles forming sheets of fine strands 8-16; short Simple transverse slit Well-developed dorsal fold, rudimentary second fold, other folds absent About 20 2 simple or slightly frilled lobes 2 each side ; ovaries tubular ; testes grouped round blind ends of ovaries Off Tierra del Fuego; 121 m. 5. schmitti (type material, van Name) Diffuse Probably 35-40 Modified C-shaped slit, with open interval to left 4 folds, dorsal one highest, ventral one sometimes reduced About 20 A number of deep rounded lobes Normally 2 each side ; ovaries elongate sinuous ; testes along both sides and round blind ends of ovaries Off Montevideo, Uruguay; about 21 m. no DISCOVERY REPORTS In the branchial sac only the dorsal fold is present on each side and a second one is represented merely by the closer spacing of some of the longitudinal bars. The arrangement of the bars on one side in a large specimen was : dorsal line 4 (6) 3 (6) 3 endostyle. It will be seen from the above table that f. simplex is principally distinguished from the type material 4.0 cm 2.0 cm - t Text-fig. 41. Styela schmitti van Name f. simplex n. (St. 388) : A, B, C, external appearance of three specimens; D, specimen with right side of the body removed, seen from the right ; E, dorsal tubercle of two specimens. DESCRIPTION OF SPECIES in by: (i) the smaller number of tentacles; (2) the simpler dorsal tubercle; and (3) the greater reduction of the branchial folds. The similarities between the 'Discovery' specimens and those described by van Name are too great to justify specific distinction. The degree of distinctness is best indicated, I believe, by a separate form, f. simplex, the name referring to the tendency towards simplification in several organs. Distribution. Off Uruguay (typical form) ; off Cape Horn, Tierra del Fuego (f. simplex). Styela insinuosa (Sluiter) (Text-fig. 42) Tethyum insinuosum Sluiter, 1912, p. 24, pi. 2, figs. 28-32; pi. 3, figs. 33-35; pi. 4, fig. 44. Occurrence. St. 156: S. Georgia, 200-236 m. St. 474: S. Georgia, 199 m. External appearance (Text-fig. 42 A). The specimens are all more or less cylindrical, with the siphons fairly close together at the upper end. The whole surface is covered with low wart-like swellings, and the colour in the preserved state is brown. The largest specimen is 5-3 cm. high by 2-0 cm. wide, and the smallest is 2-2 cm. by 1-5 cm. 2.0 cm Text-fig. 42. Styela insinuosa (Sluiter) (St. 474): A, external appearance; B, gut; C, left gonad. Body wall. The body wall is quite thick, owing to the existence of powerful muscles which constitute an inner longitudinal, a middle circular, and an outer longitudinal layer. Tentacles. There are twenty-four oral tentacles in the largest animal and about sixteen in the smallest; Sluiter (1914) found up to thirty-two. The atrial tentacles are numerous and stand in a single circle on the margin of a low velum within the atrial siphon. Dorsal tubercle. The slit of the dorsal tubercle is C-shaped with inrolled horns, the open interval facing forward. ii2 DISCOVERY REPORTS Branchial sac. The complete absence of branchial folds constitutes the most remarkable and characteristic feature of the species. There are only four large longitudinal bars on each side of the branchial sac. Plication of the branchial wall increases the surface area, as it does in several species of Ascidia. Gut (Text-fig. 42B). Sluiter has already described the course of the gut, noting the longitudinal position of the stomach and double intestinal loop. All the 'Discovery' specimens confirm his description, but I find more folds on the wall of the stomach, about thirty-five even in a small specimen instead of the twenty which he found, and the stomach sometimes lies obliquely or almost vertically. The margin of the anus has about twelve distinct lobes. Gonads. In the type specimens Sluiter described one gonad on the left and two on the right, but Kott (1954) found only one on each side. In the 'Discovery' material also there is a single gonad on each side. The anterior part of each ovary (Text-fig. 42 C, ov.) is straight and the posterior part variously bent. In the largest specimen the right gonad is distinctly curved upwards to form a U with unequal limbs. Groups of testis follicles (t) are situated along the length of the ovaries, but are more plentiful at their posterior ends and are sometimes confined to this region. Remarks. This is a species which has seldom been taken by expeditions, only Sluiter and Kott having examined material so far as I know. Very few styelid ascidians, other than compound forms, have carried the reduction of branchial folds, and even branchial bars, so far. I would point to the similarity between the present species and the Arctic styelid species Pelonaia corrugata Goodsir & Forbes, which also has flat branchial walls. The form of the gonads is another point of similarity, particularly in the specimen of S. insinu- osa with a U-shaped gonad. Both are aberrant species of the family Styelidae, but it is doubtful whether the resemblance is due to convergence or to close relationship. Distribution. Antarctic (South Shetlands, King George V Land; South Georgia). Styela magalhaensis Michaelsen (Text-fig. 43) Styela canopus var. magalhaensis Michaelsen, 1898, p. 367. ?5. melincae Arnback, 1929, p. 2. Occurrence. ?St. 123: S. Georgia, 230-250 m. St. WS 776: Patagonian Shelf, 110-99 m. External appearance. The single specimen from St. WS 776 is of a squat conical shape with the siphons forming low projections close together on the upper narrow side. Irregular rounded swellings are present on the surface. The general colour is creamy grey. The length and height are both i-i cm. Test. The test, although tough, is not very thick. It is raised in irregular wart-like swellings. Body wall. Longitudinal and circular muscles are evenly spread over the rather thin body wall, which is brown in the preserved state. Tentacles. There are about sixty-four of various sizes. Dorsal tubercle. The dorsal tubercle has a simple U-shaped opening facing forward. Branchial sac. Each side of the branchial sac is thrown into four quite distinct folds, with the following distribution of longitudinal bars: dorsal line 4(14)4(15)6(12)5(13)4 endostyle. The dorsal lamina is a simple membrane with a plain inrolled edge. Gut. Most of the gut lies in the lower part of the body. The oesophagus is curved, and the walls of the long stomach have about twenty-four longitudinal folds. There is a very small pyloric caecum. The first part of the intestine lies parallel to the stomach, and the rectum bends upwards towards the atrial siphon. Gonads. One of the most characteristic features of this species is the form of the gonads (Text- fig. 43 G). In ripe specimens these constitute two long tubular sinuous ovaries (ov.) on each side, with DESCRIPTION OF SPECIES a 113 t Text-fig. 43. ? Styela magalhaensis Michaelsen (St. 123): A, external appearance; B part of test; C, gut; D, E, F, gonads. Styela magalhaensis Michaelsen (St. WS 776) : G, gonads. 15 DM ii4 DISCOVERY REPORTS a compact mass of testis follicles (t) at their lower ends; this is the condition in the 'Discovery' specimen from St. WS 776. Van Name (1945) is a little doubtful if these gonads are sufficiently different from those of S. paessleri to justify specific distinction, but on the whole thinks that they are. From a study of the 'Discovery' specimens of S. paessleri (see p. 115), and the present specimen I have no hesitation in regarding these as separate species. There are two specimens from South Georgia (St. 123) which I include in S. magalhaensis with some hesitation. Details are as follows. External appearance. The larger specimen (Text-fig. 43 A) is i-6 cm. high and 0-9 cm. wide, and the smaller one is 1-2 by o-8 cm. The body is ovoid to conical in shape with the siphons fairly close together at the upper end. Small tag-like processes are present on the lower part of the body. Else- where the surface of the test is divided indistinctly into polygonal plates, each of which has a few brown pigment spots (Text-fig. 43 B). Body wall. This is thin and semi-transparent, with weak muscles. A few finger-like endocarps are scattered on the inner surface of the body wall. Tentacles. There are about thirty-three simple curved oral tentacles, which are quite long and alternate in length. Long fine thread-like atrial tentacles are present scattered over a wide area at the base of the atrial siphon. Dorsal tubercle. The opening of the dorsal tubercle is crescentic and faces forward. Branchial sac. The longitudinal bars on the four folds are arranged as follows in the larger specimen: dorsal line 3 (14) 4 (12) 5 (13) 8 (11) 8 endostyle. Gut (Text-fig. 43 C). The oesophagus (oe.) is curved. The stomach (st .) which lies horizontally, near the base of the body, is oval to diamond-shaped in outline, and has about twenty-four longi- tudinal folds. Both the intestine and rectum are wide, but immediately before the anus (a.) the rectum abruptly narrows. About twelve reflected lobes subdivide the margin of the anus. Gonads (Text-fig. 43 D-F). Both specimens have two gonads on each side. The ovaries (ov.) vary from rather short and straight to quite long and sinuous. At the lower end of each ovary are two, three, or four rounded masses of testis follicles (t.), lying at some distance from the ovary. Remarks. Although I have provisionally included these two specimens in S. magalhaensis, the pigmentation and sculpturing of the test, and the failure of the testicular masses to coalesce, are differences which might indicate some systematic distinction. But at present there is too little material, and the similarities to typical specimens of S. magalhaensis are too great, to permit separating those two specimens from that species. A number of other species have been described from the southern part of the South American coast, which are sufficiently like S. magalhaensis to raise some doubts regarding their validity. The characters of these species are shown in Table 33 for comparison with the present species. Conclusions regarding the validity of Herdman's three species must be cautious, as the descriptions are not sufficiently detailed. It does seem, however, that S. oblonga differs sufficiently from S. magal- haensis to avoid confusion. As nothing is known regarding the gonads or gut of S. flava, the species must remain of uncertain value. 5. glans appears to be very like 5. magalhaensis, especially in the structure of its gonads. Here again details of the gut are wanting, but S. glans might well prove to be a synonym of S. magalhaensis. Van Name (1945) has argued that S. melincae is identical with S. magal- haensis, and the above comparison shows the similarities on which his conclusion rests. Only the numbers of tentacles and of branchial bars on the folds differ markedly and these are both characters varying with body size ; Michaelsen's specimens were larger than Arnback's specimens. Distribution. Subantarctic (southern part of Argentine coast; Magellan region; PGuaitecas Islands, Chile); Antarctic (MacRobertson Land, South Georgia). DESCRIPTION OF SPECIES i'5 Table 33 5. magalhaensis S. melincae S. gians S. oblonga S. flava Michaelsen Arnback Herdman Herdman Herdman Tentacles About 60 About 24 'Few' 12 About 60 Dorsal tubercle Arc-shaped, facing C-shaped, facing ' Simple ' 'Cup-shaped' ' Irregular' forward forward Branchial sac Well developed. Well developed. Rudimentary. Rudimentary. Low. 10 bars per About 20 bars per 5-9 bars per fold ; 5 bars per fold ; 6-9 bars per fold ; fold; 10 between fold ; 4 between 2-5 between 5 between 3 between Stomach folds About 24 About 25 ? p ? Gonads 2 each side (some- 2 each side ; testis 2 each side ; testis One each side ; ? times only one) ; masses fused near masses fused near testis masses in testis masses fused proximal end of proximal end of clusters near near proximal end of ovary ovary proximal end of ovary ovary Styela paessleri Michaelsen (Text-fig. 35D-F) Styela paessleri Michaelsen, 1898, p. 368. Occurrence. St. 53: Falkland Islands, 0-2 m. St. WS 841 : Patagonian Shelf, no- 121 m. External appearance. The largest specimen in this collection is 4-0 cm. high and 2-2 cm. wide, and the smallest one 2-5 by 1-4 cm. The body is irregular, varying from dome-shaped to tall and columnar, with the siphons close together at the upper end. The test is wrinkled, leathery and generally some shade of brown. Tentacles. The oral tentacles are numerous, and I have counted thirty-five and fifty-eight respec- tively in two specimens of moderate size; Michaelsen (1898) noted about sixty tentacles. Dorsal tubercle. In two specimens examined the dorsal tubercle was C-shaped with the open interval posterior, and in a third specimen it was in the form of a horizontal S. According to Michaelsen the opening is either a straight slit or a slit with the left end turned back. Gonads (Text-fig. 35D-F). The gonads are very characteristic in this species. There are two on each side, each consisting of a branched ovary (ov.) and many round or pear-shaped testis follicles (t) grouped round the ends of the ovarian branches. The gonads are of the Styela type, in which the testis follicles are separate from the ovary instead of being closely united to it within a common membrane as in Cnemidocarpa. When fully developed the testis follicles of S. paessleri may become closely crowded together to form large irregular masses pressed against the sides of the ovary and to some extent overlapping it. In this way the basic structure of the gonads is to some extent obscured. Remarks. Kott (1954) records the species from Kerguelen but is a little doubtful about the identification. Van Name (1945) considered that S. paessleri probably includes Michaelsen's species S. pfejferi, but as I have pointed out (see p. 100) the latter species is clearly distinguished by its gonads and is in fact a Cnemidocarpa. Distribution. Subantarctic (Falkland Islands to Tierra del Fuego; PKerguelen). Styela partita (Stimpson) (Text-fig. 44) Cynthia partita Stimpson, 1852, p. 231. For synonymy see van Name 1945, p. 290, and Tokioka, 1953, p. 262. Occurrence. St. 2 : Ascension Island, o m. External appearance. The larger of the two specimens has a height of i-i cm. and a greatest width 15-2 n6 DISCOVERY REPORTS of o-6 cm., and the smaller specimen is 0-4 cm. high and 0-5 cm. wide. The surface is smooth, shining and slightly wrinkled. Internal structure. This is a well-known species and I shall merely summarize the main characters of the larger of our two specimens. Oral tentacles thirty; atrial tentacles many, short, resembling papillae, and spread over a narrow belt at the base of the atrial siphon. Dorsal tubercle very small with an indistinct opening. Branchial sac — dorsal line 2 (10) 2 (7) 3 (8) 3 (5) 3 endostyle. Stomach with twenty-one folds; anus with six lobes. Gonads two on each side, of the shape shown in Text-fig. 44 B. Distribution. Warm waters of Atlantic American coast; English Channel to West Africa; Mediter- ranean; Japan. ov Text-fig. 44. Styela partita (Stimpson) (St. 2): A, gut; B, left gonad. Family PYURIDAE Hartmeyer, 1908 Genus Pyura Molina, 1782 Pyura stolonifera (Heller) Cynthia stolonifera Heller, 1878, p. 10, pi. 2, fig. 10. For synonymy see Kott, 1952, p. 274. Occurrence. St. 90: False Bay, S. Africa, 0-2 m. External appearance. The larger of the two specimens is 5-5 cm. high, including a basal extension of test, and 5-0 cm. wide. On the upper side the siphons are close together and prominent. The surface of the body bears some knob-like swellings. Internal structure. In one specimen there are eight and in the other about fourteen dorsal languets. The dorsal tubercle has a complex and much convoluted slit which is basically C-shaped with the open interval directed back to the left. The complex dorsal tubercle, and the shortening of the dorsal side of the branchial sac with consequent reduction in the number of dorsal languets are two characteristic features of the species. Distribution. South Africa; western, southern and eastern Australia; Tahiti. DESCRIPTION OF SPECIES 117 Pyura setosa (Sluiter) (PI. IV, fig. 2) Halocynthia setosa Sluiter, 1905, p. 472. For synonymy and references see Kott (1954), p. 126. Occurrence. St. 175: S. Shetlands. External appearance (PL IV, fig. 2). The single specimen is ovoid, 3-5 cm. long and 2-6 cm. high, and almost completely covered with a thick coat of long stiff bristles. These bristles, which reach 13 mm. in length, bear many short pointed spines. Tentacles. There are about twenty-one compound tentacles of various sizes and a few small almost unbranched ones. Dorsal tubercle. The dorsal tubercle is C-shaped with the open interval facing forward and a little to the right. Branchial sac. The anterior part of the dorsal lamina is a toothed membrane, and for most of its length the lamina is represented by long pointed closely crowded languets united basally by a narrow membrane. The longitudinal bars on the six branchial folds are arranged thus: dorsal line 3 (31) 3 (16) 3 OS) 5 06) 5 (29) 2 (3°) 2 endostyle. Gonads. The left gonad is within the intestinal loop, and the right gonad is a long horizontal sac. The sperm duct and oviduct are short and turned upwards towards the atrial siphon. Test spines Tentacles Dorsal tubercle Dorsal lamina Branchial folds Occurrence P. setosa Up to 21 mm. long About 16 Horse-shoe with inrolled horns; facing forward Series of languets, anterior ones small, posterior large 6 each side Western and eastern Antarctic Table 34 P. stubenrauchi Up to 5 mm. About 30 Horse-shoe ; facing forward A membrane toothed at posterior end 4 each side Strait of Magellan P. echinops 'Short' About 38 Horse-shoe, inrolled horns, facing forward A membrane toothed except at anterior end 4 each side North coast Argentine Remarks. P. setosa is a very distinctive species, but two other species P. stubenrauchi (Michaelsen) and P. echinops Arnback have been described with similar characters, and the important features of the three are shown in Table 34. It appears from this comparison that P. stubenrauchi and P. echinops are the same species as sug- gested by van Name (1945); the name P. stubenrauchi has priority. P. setosa is distinguished from P. stubenrauchi by several characters, but principally the subdivision of the dorsal lamina into languets and the presence of six branchial folds on each side. The two species are nevertheless obviously closely related, having been derived from a common ancestor by geographical speciation. Distribution. Antarctic (Graham Land, South Orkney Islands, Kaiser Wilhelm II Land, McMurdo Bay, Adelie Land, Enderby Land, MacRobertson Land). Pyura discoveryi (Herdman) (Text-fig. 45; PI. IV, fig. 1) Halocynthia discoveryi Herdman, 19 10, p. 9, pi. 4, figs. 6-12. Occurrence. St. 27: S. Georgia, 110 m. St. 42: S. Georgia, 120-204 m. St. 140: S.Georgia, 122-136 m. St. 144: S. Georgia, 155-178 m. St. 148: S. Georgia, 132-148 m. St. 152: S. Georgia, 245 m. St. 159: S. Georgia, 160 m. St. 160: S. Georgia, 177 m. St. 170: S. Shetlands, 342 m. n8 DISCOVERY REPORTS St. 177: S. Shetlands, 1080 m. St. 187: Palmer Archipelago, 259-354 m. St. 190: Palmer Archi- pelago, 93-126 m. St. 474: S. Georgia, 199 m. St. 1948: S. Shetlands, 490-610 m. External appearance (Text-fig. 45 A). This species is generally found in groups of several indi- viduals growing together, attached basally to bottom material, and to each other by irregular areas of their sides. In some cases there is little or no encrusting matter on the test, but in others the whole body except the siphons is covered with sand, small stones and broken shell. The shape is variable, often upright and sometimes rather squat, and the siphons may be short or remarkably long (Text- fig- 45 A). Text-fig. 45. Pyura discoveryi (Herdman) (St. 474) : A, specimen with long siphons ; B, the same with test removed ; C, dorsal tubercle; D, oral tentacle; E, hepatic tubules; F, showing position of left gonad (St. 1948); G, right gonad of same specimen. Siphons. According to Kott (1954) there are no spines in the lining of the siphons, and I also can find none. Tentacles. The tentacles number sixteen to twenty and are only slightly branched (Text-fig. 45 D). Dorsal tubercle. The opening of the dorsal tubercle is basically U-shaped with the ends of the limbs variously bent ; usually both are turned outwards, or the left one outwards and the right one inwards, or one or other may point forward (Text-fig. 45 C). Branchial sac. Some authors have said that there are six branchial folds on each side (Herdman, 1910; Hartmeyer, 191 1; Kott, 1954) and others that there are seven (Sluiter, 1914; Arnback, 1938; van Name, 1945). In all the specimens from the 'Discovery' collection that I have examined there are seven folds, and although the ventral fold is lower than the others, it is unmistakably present. This finding agrees with Arnback's careful review of the question (see Arnback, 1938, pp. 30-2). In DESCRIPTION OF SPECIES 119 a specimen of length 3-4 cm. the longitudinal bars have the following arrangement: dorsal line 4(16) 2 (16) 2 (22) 2 (24) 2 (17) 2 (13) 3 (8) 1 endostyle. There is, in some specimens, a slight tendency for the longitudinal bars to project at the posterior ends of the branchial folds, as in P. jacatrensis. Gonads. I have nothing to add to the existing accounts of the gonads, except to note that in one specimen (St. 1948) the right gonad is Y-shaped, having two branches (Text-fig. 45 G). Distribution. Antarctic (McMurdo Bay, Kaiser Wilhelm II Land, Alexander I Land, Graham Land, South Shetlands, Wilkes Land, South Georgia, near Shag Rocks). Pyura squamata Hartmeyer (Text-fig. 46) Pyura squamata Hartmeyer, 1909-11, p. 1337 (nomen nudem); 1911, p. 439, pi. 45, fig. 12, pi. 50, figs. 1-5. Occurrence. St. 187: Palmer Archipelago, 259 m. External appearance. The single specimen is 1-7 cm. long, i-o cm. broad and 0-5 cm. in height. It is yellow-grey in colour and patterned all over with small, mainly hexagonal plates into which the test is divided (Text-fig. 46 A). Text-fig. 46. Pyura squamata Hartmeyer (St. 187): A, part of test; B, oral tentacle; C, dorsal tubercle. Internal structure. Owing to the damaged condition of the specimen certain details of structure could not be seen. But the form of the tentacles (Text-fig. 46 B) and dorsal tubercle (Text-fig. 46 C), the arrangement of branchial bars, and the shape of the gonads all conform closely to Hartmeyer's description of the type specimen. The anus is divided into seven rounded lobes; in the type specimen the anus was destroyed. Remarks. This species is characterized principally by the polygonal plates of the test, and the presence of only five well-developed branchial folds, with a rudimentary 6th fold. In spite of the damaged state of the only specimen in the ' Discovery ' collection I have no hesitation in assigning it to P. squamata. Distribution. Antarctic (Kaiser Wilhelm II Land, Charcot Land, Palmer Archipelago). Pyura legumen (Lesson) (Text-figs. 47 A, B, C; 48; PI. IV, fig. 6) Boltenia legumen Lesson, 1830, p. 149, pi. 53, fig. 1. For synonymy see van Name, 1945, p. 326. Occurrence. St. 52: Falkland Islands, 17 m. St. 53: Falkland Islands, 0-2 m. St. 55: Falkland Islands, 10-16 m. St. 56: Falkland Islands, 10-5-10 m. St. 57: Falkland Islands, 15 m. St. WS 71 : 120 DISCOVERY REPORTS Falkland Islands, 82-80 m. St. WS 84: Falkland Islands, 75-74 m. St. WS 89: Tierra del Fuego, 23-21 m. St. WS 90: Patagonian Shelf, 82-81 m. St. WS 788: Patagonian Shelf, 82-88 m. St. WS 811: Patagonian Shelf, 99 m. St. WS 834: Patagonian Shelf, 27-28 m. St. WS852: Patagonian Shelf, 86-88 m. External appearance (Text-fig. 47 A; PI. IV, fig. 6). The general appearance of this species is already well known. In almost all the ' Discovery ' specimens the point of origin of the stalk is at the anterior ventral part of the body, but in some small ones it is mid-ventral. The proportion of body 2.0 cm 2.0 cm V//&///S Text-fig. 47. Pyura legumen (Lesson) (St. 57) : A, intact specimen; B, test-spine; C, part of dorsal lamina. Pyura georgiana Michaelsen (St. MS 14): D, intact specimen; E, test-spine; F, part of dorsal lamina. Pyura bouvetensis (Michaelsen) (St. 181): G, intact specimen; H, test-spines; J, probable attitude in life with body resting lightly on the bottom. length to stalk length bears no direct relation to the total size of the animal, that is, to its age (see Text-fig. 48). Irregular longitudinal furrows mark the surface, and in some animals these break the test into rectangular or polygonal areas each bearing a group of spines. The degree to which spines are developed is very variable. They may be numerous and short, forming a kind of fur, or few and scattered. When well developed the spines reach 2 mm. in length, are sharply pointed, and bear small thorn-like processes (Text-fig. 47 B). Atrial organs. The three pads, called atrial organs, which lie within the atrial siphon, at its base, have been noticed by several workers, especially Michaelsen (1900) and Arnback (1938). The structure and function of the organs, however, have never been clarified. Sections show that the atrial organs are thick pads of test substance richly provided with blood spaces. As these spaces are lined with 121 DESCRIPTION OF SPECIES epidermis they are to be regarded as specially developed test vessels. Great numbers of blood cells, many of them phagocytes, lie in the test matrix. The function of the atrial organs is still unknown. Parietal organs. Michaelsen (1900) noted the existence of other enigmatic structures which have become known as the parietal organs. These were described as a pair of swellings of the body wall, one on each side, and containing vacuolated cells. I have examined many specimens of P. legumen without finding parietal organs, although they are easily seen in related species (see p. 122), and I can only conclude that they are not always present or recognizable in P. legumen. Branchial sac. In a specimen with body 3-9 cm. and stalk 3-2 cm. the branchial sac has the following arrangement of longitudinal bars: dorsal line 2 (22) 2 (13) 3 (20) 3 (20) 3 (15) 4 (12) 1 (3) 1 endostyle. Biology. There are not enough specimens to indicate the breeding season of this species. s 54 4 3 2 I 5 6 TOTAL LENGTH CM Text-fig. 48. Pyura legumen (Lesson). Relation between the ratio body-length/stalk-length and the total length. In some animals the intestine is filled with plankton organisms, mainly small algal cells and Globigerina sp. together with diatoms. Remarks. I discuss this and the two related species P. georgiana and P. bouvetensis on p. 124. Distribution. Subantarctic (Falkland Islands, Patagonian Shelf, Magellen region). Pyura georgiana (Michelsen) (Text-figs. 47D-F; 49; 50; PI. IV, fig. 7) Boltenia georgiana Michaelsen, 1898, p. 364. Occurrence. St. 39: S. Georgia, 179-235 m. St. 42: S. Georgia, 120-204 m> St. 123: S. Georgia, 230-250 m. St. 140: S. Georgia, 122-136 m. St. 144: S. Georgia, 155-178 m. St. 145: S. Georgia, 26-35 m- St. 148: S. Georgia, 132-148 m. St. 152: S. Georgia, 245 m. St. 156: S. Georgia, 200- 236 m. St. WS 62: S. Georgia, 26-83 m- St- ws 567: s- Georgia, 145 m. St. MS 14: S. Georgia, 190-110 m. St. MS 68: S. Georgia, 220-247 m. External appearance (Text-fig. 47 D ; PI. IV, fig. 7). This species differs from P. legumen in having the stalk originating from near the middle, or somewhat towards the anterior end, of the ventral side, instead of at the extreme anterior end of that side, and passing down ventrally from the body and not 16 DM 122 DISCOVERY REPORTS as an oblique continuation of the long axis of the body, as in P. legumen. If the ratio of the height (i.e. dorso-ventral diameter) of the body to the length of the stalk is plotted against the total length of the specimen, it is seen that this ratio decreases with increase of total length, that is presumably with age (Text-fig. 49). Old animals may have a stalk from three to eight times the dorso-ventral diameter of the body, whereas in young animals the stalk may barely equal the diameter of the body. As in P. legumen the surface of the body bears a sparse but variable coating of spines (Text-fig. 47 E). In P. georgiana however, the spines usually lack the secondary thorn-like processes commonly found in P. legumen. Parietal organs. This species has no atrial organs within the base of the atrial siphon, but in every specimen dissected a parietal organ was found on the middle of each side of the body. Sections show 7-1 6- 5- Hl-J ca\