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THE

VOYAGE’ OF’ H.M.8. CHALLENGER. ZOOLOGY.

REPORT on the Pycnoconipa, dredged by H.M.S. Challenger during the

years 1873-76. By Dr P. P. C. Hoek, Assistant at the Zootomical

Laboratory of Leiden University.

Tue beautiful and rich collection of Pycnocontpa formed during the expedition of

the Challenger has been placed in my hands by Professor Sir Wyville Thomson, F.R.S., for description in the official report of the voyage.’

Our knowledge with regard to the Pyenogonids in general, their systematic arrange- ment, their geographical distribution, &c., is still very insufficient ; and with respect to those of the greater depths of the ocean hardly anything is known.

The first attempt towards a monograph of the Pycnogonida is that of George Johnston.” His paper was published in 1837, and treats of the British species known up to that time. Though no special paper on Pycnogonids seems to have been published. previous to Johnston’s, yet there are several works of an older date, in which descrip- ‘tions of species and genera belonging to this group occur, as well as discussions as to their place in the Zoological System. But as the descriptions are for the greater part very incomplete and the species therefore not to be recognised, these works are interesting only in so far as they show how much uncertainty has always been felt as to the place of the Pycnogonids among the Arthropoda.

Linneus (1767) * brings the forms known to him under the genus Phalangium, in which also numerous land-spiders are placed, and which he ranges between Hydrachna and Aranea under his Insecta aptera.

* T wish to tender my sincere thanks to Professor Sir Wyville Thomson, F.R.S., &e., who liberally trusted to me— though a stranger—the drawing up of this report ; at the same time to Mr John Murray who has kindly given me much valuable assistance.

* George Johnston.—An Attempt to ascertain the British Pycnogonide, in The Magazine of Zoology and Botany,

conducted by W. Jardine, P. J: Selby, and G. Johnston, vol. i., 1837. > Carolus Linnzus, Systema Nature, editio xii. rev., 1766.

(ZOOL. CHALL, EXP,—PART x.—1881.) ® KI v3

2 THE VOYAGE OF H.M.S. CHALLENGER.

Otho Fabricius (1780)! assigns to them the name Pycnogonwm proposed by Briinnich, and places the Cyamus ceti with them in the same genus. He believes them to be most closely allied to Crustaceans.

J. C. Fabricius (1794)? places the two genera Pyenogonum and Nymphon along with Pediculus, Acarus, &e., in the eleventh class (the Antliata) of his entomological system.

Lamarck (1801) ® gives the same genera (Pycnogonum and Nymphon) a place in the class of the Arachnida, order of the Palpistes, together with Bdella, Acarus, and Hydrachna.

Savigny (1816) * proposes to place the Pycnogonida among the Crustacea, an opinion afterwards embraced by Milne-Edwards (1834)*’ and Johnston (1837). According to Johnston, Savigny arrived at this conclusion by a very ingenious analysis of their organs. He pointed out that the proboscis of the Pycnogonum is a head, whereas the mandibles, palpi, and ovigerous organs are merely modifications of the legs, so that the Pyenogonida, like the Crustaceans, really have seven pair of legs, &c.

Johnston ° himself, taking the assertions of Savigny as decisive, disagrees with those naturalists who object to the Pycnogonids being placed among the Crustaceans on account of the great simplicity of their anatomy. With Milne-Edwards he considers the Pyenogonids, although imperfect and even degraded, as formed on the same general plan as that of all the numerous other animals rightly placed in the class Crustacea.

There can be no doubt that Johnston’s publication is one of the most important in the history of the knowledge of the group. Johnston gives a very clear descrip- tion of the body of a Pyenogonid, fully discusses the systematic position of the order, proposes good characteristic marks for the genera, and enters into detailed descrip- tions of the species. The number of genera in his paper amounts to five (Nymphon, Pallene, Orithyia, Phoxichilus, Pycnogonum), each with one species, with the exception of the genus Nymphon, to which two species are assigned.

Of the authors who come after Johnston, Milne-Edwards is the first to be mentioned. In the third volume of his Histoire naturelle des crustacés (1840), he gives a very short description of the body of a Pycnogonid, and enumerates, but without paying special attention to the group, the species and genera known to him. Following Johnston as nearly as possible, he has the same five genera‘ and almost the same species. His descrip- tions are very insufficient ; his work derives importance only from the circumstance that he places—as I have already mentioned above—the Pycnogonids among the Crustaceans

as a distinct order, viz., that of the Araneiformes.

Othonis Fabricii Fauna Groenlandica, Hafniz et Lipsie, 1780.

* Joh. Christ. Fabricii Entomologia Systematica emendata et aucta, tom. iv., 1794.

3 J. B. Lamarck.—Systime des animaux sans vertebres, 4 Paris, an. ix., 1801.

* J. C. Savigny—Mémoires sur les animaux sans vertébres, premidre partie, 1816.

° H. Milne-Edwards.—Histoire naturelle des Crustacés, tom, i.-iii., 1834-40.

® In this introduction only the most important authors are meuupcele a much fuller list is given by J obnston i in his An Attempt, &c., and by Milne-Edwards, loc. cit.

7 The name Orith, yia of Johnston étant déja employé pour un autre genre de Crustacé,” is changed by Milne iaceneede into Phoxichilidiumd|.c., p. 535).

I].—Report on the Pycnoconipa dredged by H.M.S. CuaLtencer, during the years 1873-1876.

By Dr P. P. C. Horx, Assistant at the Zootomical Laboratory of Leiden University.

(Received February 20, 1881.)

REPORT ON THE PYCNOGONIDA. 3

The species of the English coast found (1842—44) a new monographer in Goodsir,! who in three consecutive papers enumerates a large number of species new to the fauna of the British Isles and to science in general. Two new genera (Pephredo and Pasithoe) are proposed by him, but owing to the want of detail Mr Goodsir’s papers are of little

value, for it is absolutely impossible to recognise either his new genera or his new species from such descriptions as he gives.

Of as little value is the list given by base (1864), in which all Goodsir’s species are found, in addition to some new Ammotheas and species of his new genus Achelia. Since Hodge’s list—though occasionally in English periodicals short descriptions of new species. have been published—no special paper on the Pycnogonids of the English coast has appeared.

Those of the Norwegian coast found a very able describer in Kréyer (1845),’ who gives very clear diagnoses of the genera and species. As a new genus he proposes Zetes, and the total number of species described by him is twelve. These descrip- tions were published without illustrations; but illustrations to the text may be found in Quoy and Gaimard’s Voyages en Scandinavie, Laponie, &c., Zoologie, Crustacés, pl. xxxix. (1840).

For the Pyenogonids of Northern Europe and the coasts of the Arctic Ocean, besides Kréyer, the following authors must be mentioned :—Otho Fabricius‘ for the coast of Greenland, as mentioned above. Sabine® (1824) describes two Nymphons (N. grossipes and N. hirsutum) and a species of Phoxichilus (P. proboscideus—a true Colossendeis, Jar- zyusky), found on the shores of the North Georgian Islands. Bell (1855),° in Belcher’s Last of the Arctic Voyages, gives descriptions and drawings of two new species of Nym- phon (N. hirtipes and N. robustwm) common in higher northern latitudes. Jarzynsky (1870)' enumerates the species of Russian Lapland and the White Sea. A new genus (Colos- sendeis) is proposed by him. Buchholz (1874),* in the narrative of the second German North Polar Expedition, enumerates three species of Nymphon, but none of these are new.

1 Harry D. S. Goodsir.—Edinburgh New Philosophical Journal, vol. xxxii., 1842; ibid., vol. xxxiii., 1842; On the Specific and Generic Characters of the Araneiform Crustacea, Annals and Mag. of Nat. Hist., vol. xiv., 1844.

? George Hodge.—List of the British Pycnogonoidea, with descriptions of several new species, Ann. and Mag. of Nat. Hist., vol. xiii., 3d series, 1864.

3 Henrik Kroyer.—Bidrag til Kundskab om Pyknogoniderne eller Sospindlerne, Natur-historisk Tidskrift, Ny Raekke, i., 1845,

4 Loe. cit. ;

5 A Supplement to the Appendix of Captain Parry’s Voyage for the Discovery of a North-West Passage in the years 1819-20, containing the Zoological and Botanical Notices, London, 1824; Marine Invertebrate Animals, by Captain Edward Sabine.

6 Thomas Bell—Account of the Crustacea of the Last of the Arctic Voyages in Search of Sir John Franklin, under the command of Captain Sir E. Belcher, C.B., &c., in two volumes, vol. ii., 1855.

7 Th. Jarzynsky.—Promissus catalogus Pyenogonidarum inventarum in mari glaciali ad oras Lapponie rossice et in Mari albo, anno 1869 et 1870, Annales de la Soe. des Natur. de St Petersb., 1870.

8 R. Buchholz.—Crustaceen der Zweiten Deutschen Nordpolarfahrt, Anhang; Pycnogonida, Die Zweit Deutsche Nordpolarfahrt, ii. 396, 1874.

+ THE VOYAGE OF H.M.S. CHALLENGER.

Heller (1875) ? proposes two new species of the same genus gathered during the Austrian North Polar Expedition ; both are identical with species described before under other

names.

In 1877 and again in 1879 G. O. Sars* published lists of the Pyenogonids gathered during dredging cruises in the northern part of the North Atlantic, on the coast of Norway, &. There are in all four new species of Nymphon (N. megalops, N. macronyx, N. serratum and N. pallenoides), a new genus, Ascorhynchus, with the species Ascorhynchus abyssi, a new species of Colnseqimiss (C. angusta), and a. new Pallene, P. malleolata.

Miers (1877)°* treats of the Pycnogonids collected during the last English Arctic Expedition. He gives two species, neither of which is new, and describes a variety of Nymphon hirtum.

In regard to the coast of Germany and the Netherlands not a single species has been recorded which is not found on the English coast. Occasionally enumerations of species have been published by Frey and Leuckart,* and Bohm.’ In a paper I published myself (1877) ° I described the four genera, species of which are found on the Dutch coast.

The Pycnogonids of the French coast have been studied by Quatrefages (1844),’ Claparéde (1863),° Hesse (1867-74),’ and Grube (1868-72).” Their studies resulted in the proposal of a new species of Ammothea (A. pycnogonoides, Quatr.), of a new Phoxichilidivin (2) (P. cheliferum, Claparéde), a new species of Phowichilus (P. levis, Grube), and two new genera (?) Oiceobathes, Hesse, and (?) Oomerus, Hesse, both very insufficiently described. The Pycnogonids found on the coasts of France, the British Isles, Germany, &c., are not yet sufficiently well known to allow of their geographical distribution being discussed.

About the species of the Mediterranean very little is known. Philippi (1843) " and

1 Camil Heller.—Die Crustaceen, Pycnogoniden, und Tunicaten der K. K. Oester. Ungar. Nordpol. Expedition, Denkschriften der Mathematisch-Naturwiss. Classe der K. Akad. der Wissensch., Bd. xxxy., Wien, 1875.

2 G. O. Sars.—Prodromus descriptionis Crustaceorum et Pycnogonidarum, quae in expeditione Norvegica, anno 1876, observavit, Arch. f. Math. og Naturvid., ii., 1877 ; Crustacea et Pyenogonida nova, quae in itinere 2 et 3tio expeditionis Norvegice, anno 1877 et 1878, collecta (Prodromus descriptionis), ibid., iv., 1879.

3 Edward J. Miers.—Report on the Crustacea collected by the Netairaliats of the Arctic Expedition in 1875-76 Annals and Mag. of Nat. Hist., fourth series, vol. xx., 1877.

4 Frey und Leuckart. —Beitrige sur Kenntniss qaxbellgser Thiere, 1847.

5 R. Bohm.—Ueber die Pyonvgoniden des Konig]. Zool. Museums zu Berlin, Monatsber. der Konigl., Akad. der Wiss. 1879.

5 Pp. P. C. Hoek.—Ueber Pyenogoniden, Niederl. Archiv. f. Zoologie, iii., 1877.

7 A. de Quatrefages.—Mémoire sur Vorganisation des Pyenogonides, Ann. d. Sc. Natur., 3™¢ Série, Zoologie, tom. iv., 1845.

8 A. René Edouard Claparéde.—Beobachtungen tiber Anatomie und Entwickelungsgeschichte wirbelloser Thiere an der Kiiste von Normandie angestellt, 1863.

® Hesse.—Annales des Sciences naturelles, 5!™¢ Série, vii., 1867 ; ibid. 5!me Série, xx., 1874.

© Edward Grube.—Mittheilungen iiber St Malo und Roscoff und die dortige Meeres besonders die Anneliden-fauna 1869 ; Mittheilungen tiber St Vaast la Hougue, und seine Meeres, besonders seine Anneliden-fauna, Verhandl. der Schlesischen Gesellsch. f. vaterl. Cultur., 1869. 1 A, Phillipii—Ueber die Wenpalitaniscte n Pyenogoniden, Arch, f. Naturgesch, ix., 1843.

REPORT ON THE PYCNOGONIDA. 5

Costa (1838—61)* published short notes on the Pycnogonids found there. Philippi proposed a new genus(Hndeis), which is perhaps identical with Pasithoe, Goodsir; and a second genus (Pariboea), with the species Pariboea spinipalpis. Costa introduces (1838) the genus Phanodemus, in all probability identical with Pephredo, Goodsir; in his Microdoride medi- terranea (1861) he proposes three new genera: Rhynchothorax, Platychelus, and Aleynous. From the Gulf of Naples Costa knows in all seven species, whereas the total number of species of the Mediterranean found in Philippi’s paper is only four. A monograph on _ the Pycnogonids of the Mediterranean, and especially of the Gulf of Naples, will very pro-

bably soon appear ; it will form the second part of the Studi e Ricerche di Cavanna (1877),”

and will also be published by Dohrn, as announced in his Neue Untersuchungen (1878).”

Of all Pycnogonida, those found on the west coast of North America are best known. Careful attention was paid to them by Stimpson (1852),* Verrill, Smith (1874),’ but especially by Wilson (1878-80),° who in his Pyenogonida of New England, enumerates fourteen species belonging to nine genera, two of which (Psewdopallene and Anoplo- dactylus) are new to science. Though I do not believe that these new genera after a careful examination will hold good, and though I think it a pity that Wilson in his researches has not taken advantage of recent investigations (especially those of Cavanna), yet there can be no doubt, I believe, that his paper is one of the best descriptive publi- cations after those of Johnston and Kroyer.

For the other countries of our globe, a very brief enumeration may suffice. As far as I have been able to ascertain, by far the greater number of the species described are littoral ; from the open ocean very few species are recorded. ‘Two species described by White (1847),’ inhabiting the South Sea, are exceptions. White describes them as species

‘of Nymphon, whereas I believe that they ought to be considered as Phoxichilidiums. From the open ocean are also those species (one of Mymphon, another of Phowichilidium) mentioned by Grube (1869)* as occurring in the China Sea. Grube’s descriptions as well as those of White are extremely incomplete.

Wood-Mason (1873)° described a species of a genus which he believed to be new,

1 QO. G. Costa.—Fauna del Regno di Napoli, Crostacei et Aracnedi, Napoli, 1838 ; Microdoride mediterranea, tomo primo, Napoli, 1861.

2 G. Cavanna.—Studi e Ricerche sui Picnogonidi, parte prima (Publicazioni del R. Istituto di Studi superiori pratici et di perfezionamento in Firenze, Sezione di Scienze fisiche e naturali), Firenze, 1877.

3 A. Dohrn.—Neue Untersuchungen iiber Pyenogoniden, Mittheil. a. d. Zoologischen Station zu Neapel, i., 1879.

# William Stimpson.—Synopsis of the Marine Invertebrata of Grand Manan, Smithsonian Contributions to Know- ledge, January 1853.

5 Smith in Report on the Invertebrata of Vineyard Sound. In Part I. of the Report on the Condition of the Sea- Fisheries of the South Coast of New England, 1873.

6 E. B. Wilson.—Descriptions of Two New Genera of Pycnogonida, American Journal of Science and Arts, vol. xv., 1878 ; Synopsis of the Pycnogonida of New England, Transactions of the Connecticut Academy, vol. v., 1880.

7 Adam White——Descriptions of New or Little-Known Crustacea in the Collection at the British Museum, Pro- ceedings of the Zoological Society of London, part 15, 1847.

8 E. Grube in Jahresbericht der Schlesischen Ges. fiir vaterlandische Cultur, Breslau, 1869.

® James Wood-Mason.—On Rhopalorhynchus kréyert, a new Genus and Species of Pycnogonida, with plate xiii., Journal of the Asiatic Society of Bengal, part 2, 1873.

6 THE VOYAGE OF H.M.S. CHALLENGER.

and called Rhopalorhynchus: There can be no doubt that this is the same as the genus formerly (1870) described ‘by Jarzynsky * as Colossendeis. Wood-Mason’s species is an inhabitant of Port Blair, Andaman Islands.

Miers (1875 and 1879) ° mentions two species of Nymphon, and one of a new genus, which he calls Tanystylum, and which is nearly allied to Achelia. These species were collected at Kerguelen Island during the visit of the English and American Transit of Venus expeditions to that Island. Béhm (1879)° has made a very careful study of the Pyenogonids of the Royal Zoological Museum at Berlin. He describes two species of Nymphon and one of Achelia, as collected at Kerguelen; one species of Nymphon col- lected south of the Cape of Good Hope, one Pallene (?) taken in the Straits of Magellan, another Pallene from Mozambique, a Phowichilidium and a Phoxichilus collected in the neighbourhood of Singapore ; finally, besides some species from Northern Europe, three species found near Enosima (Japan); one species of a new genus, which Bohm calls Lecithorhynchus, one Ascorhynchus (Gnamptorhynchus, Bohm), and one species of Pallene. Slater (1879)* published a short paper on a new genus of Pyenogonids (Para- zetes) found in Japan, and described in the same paper a variety of Pycnogonwm litorale from the same country.

In the Boston Journal of Natural History, Eights (1836 ?) mentions the genus Decalo- poda, but I have not been able to ascertain whether this is a good genus, nor where it has been found.’ <A species of Pasithoe described by Dr Gould’ is, according to Wilson (loc.cit. p. 2), “indeterminable.” To Mr Wilson’s paper I am also indebted for the men- tion of a species of Pycnogonid found on the coast of Chili: it seems to be a species of Pycnogonum.’

In this enumeration the reader will not find a complete list of the descriptive litera- ture of Pyenogonida, but all the more important publications, together with the greater number of the minor papers on our group are mentioned. With a few exceptions the zoological publications about Pyenogonids are very superficial, and this I believe is owing partly to the circumstance that many authors who have had no opportunity of comparing large collections of different forms have published descriptions of species and even of genera from the examination of such species only. To describe new species, however, ought

1 Th. Jarzynsky, loc. cit.

2 E. J. Miers.—Descriptions of new species of Crustacea collected at Kerguelen’s Island, by the Rev. A. E. Eaton. Annals and Magazine of Natural History, fourth series, vol. xvi., 1875 ; Crustacea of Kerguelen Island, Philosophical Transactions, London, vol. elxviii. ; extra volume, pp. 200-214, 1879, pl. xi.

5 R. Bohm, loc. cit.; the same in Sitzungsberichte der Gesellschaft naturforschender Freunde in Berlin, 1879, pp. 53 and 140,

* Henry H. Slater.—On a new genus of Pyenogon (Parazetes) and a variety of Pycnogonwm littorale from Japan Ann. and Magaz. of Nat. History, 5th series, vol. iii., 1879.

® Boston Journal of Natural History, i. 204, t.7. (See Cuvier’s Animal Kingdom, London, Wm. S. Orr & Co., 1840, p. 468.)

® Proc. Boston Society Nat. Hist., vol. i. p. 92. 7 Gay.—Historia fisica y politica de Chile, Zoologia, p. 308, pl. iv. fig. 8, 1854.

REPORT ON THE PYCNOGONIDA. t

not to be the work of one who begins to study a group, as is often the case, but can only be done properly after laborious and continuous research. Moreover, the study of the literature is enormously encumbered by the circumstance, that descriptions of single species often lie buried in obscure periodicals. This circumstance, I hope, will be considered, when my report is found to be far from complete.

The collection of Pyenogonida brought home by the Challenger and need in my hands numbers about 120 specimens. They were in an excellent state of preservation, and to facilitate the work, the bottles of spirit in which they were put, were furnished with labels indicating the station, latitude, longitude, bottom temperature, and the nature of the’ sea-bed where they were dredged. Some of the specimens were not obtained from any of the 361 dredging stations, but were collected on the shore (near Cape Town, e.g.), or dredged in shallow water (Bahia, Kerguelen). Over a course of 68,890 miles the dredge was let down at 361 stations, and Pycnogonids were procured on only twenty-six occasions. The 120 specimens of Pyenogonida brought home belong to thirty-six species, and thirty-three of these I have been obliged to consider and describe as new to science. The greatest depth where a Pycnogonid was found was 2650 fathoms ; the greatest depth dredged during the cruise was 4575 fathoms.

- In the following list I have given the range in depth at which species of Pycnogonida were found by the Challenger, and also recently during the cruise of the Knight Errant” :—

Shore, . : : A Discoarachne brevipes, Hoek. re : c 6 Hannonia typica, Hoek. ' 7 to 20 asee : : Phoxichilidium fluminense, Kroyer. “6 3 y : 5 Phoxichilidium insigne, Hoek. 10%0:120 _,, : : Nymphon brachyrhynchus, Hoek. 25 +0120 ,, - : Nymphon brevicaudatum, Miers. 25 4 : c Nymphon fuseum, Hoek. 38 oF é : Ascorhynchus minutus, Hoek, op 5 ; Fi Pallene languida, Hoek. 38 to 40 ,, ; 3 Pallene laevis, Hoek. 38 to 120 _ =r, . . Pallene australiensis, Hoek. 45, 55,175 ,, : ; Phoxichilidium patagonicum, Hoek. 53 5 5 3 Pycnogonum litorale, Strom. 55, 70, 120 ,, . : Colossendeis megalonyx, Hoek. 83 ¢ 7 9 : Nymphon brevicollum, Hoek. 83 to 540 _—s—*,, ; és Nymphon grossipes, Oth. Fabr., sp. 120 x 5 : Colossendeis robusta, Hoek. 150 : op : ; Ascorhynchus orthorhynchus, Hoek. 375 to 540, 0 . Nymphon robustum, Bell, 400 to 1600 _,, . ; Colossendeis leptorhynchus, Hoek. 515, 530, 540 ,, . Nymphon strémii, Kroyer. 540 : x ; 0 Nymphon macronyx, G. O. Sars. + ; Colossendeis proboscidea, Sab., sp.

600 . op . ; Phoxichilidium patagonicum, var. elegans, Hoek.

8 THE VOYAGE OF H.M.S. CHALLENGER.

700 fathoms, A . Oorhynchus aucklandie, Hoek.

825 : as é : Nymphon perlucidum, Hoek. 1100 ° op : 4 Nymphon longicoxa, Hoek.

: A} : A Nymphon compactum, Hoek. 1250 5 x , : Colossendeis minuta, Hoek. 1375 : n : 5 Ascorhynchus glaber, Hoek. 1375 to 1600 _,, : 5 Nymphon hamatum, Hoek.

iS . of - Colossendeis gigas, Hoek.

- 35 5 ; Colossendeis gracilis, Hoek. 1600 to 1950 _,, Phowichilidium pilosum, Hoek. 1675 5 " - : Nymphon meridionale, Hoek.

+ 4 a 2 : Phowxichilidium oscitans, Hoek. 1875 F o) : : Phoxichilidium mollissimum, Hoek. 2160 - 5 : ; Nymphon procerum, Hoek. 2225 IS ; 3 Nymphon longicollum, Hoek.

ee : =F : 5 Collossendeis media, Hoek. 2650 : $ a : Colossendeis brevipes, Hoek.

The number of times at which Pycnogonida were dredged at certain depths is shown in the following table :—

99 dredgings in depths of from lto 500 fathoms, . : 26 times. Y

30 5 3 501 to 1000 so, : : a) >

47 7 5 1001 to 1500 =, 2 Ee 3} op

47 x, op 1501 to 2000 _—S—,, : : A 55

93 5 x 2001 to 2500 _—ti, 3 : Ph

83 2501 to 3000 - . Once (at 2650 fathoms). 11 = Ay 3001 to 4575 35 ; ; None. :

It thus becomes apparent that what Davidson has shown for the Brachiopoda, holds also in the case of the Pycnogonida, that they are very seldom found in depths exceeding 500 fathoms ; out of about 100-dredgings in depths of from 1 to 500 fathoms, Pycnogonids were brought up twenty-six times, while in depths varying from 501 to 3000, they were obtained only thirteen times out of 300 dredgings.

The following statement shows the range in depth at which the genera of Pyenogonida hitherto known have been found. The total number is twenty-seven genera, of which eleven are true littoral forms. Of the sixteen remaining genera there are five of which I am quite uncertain as to the depth at which they are found, and four for which the depth does not exceed 50 fathoms. Then there are two (Pallene and Pycnogonum), which, as a rule, inhahit depths not exceeding 120 fathoms, but which in a single case were found at depths almost reaching 500 fathoms (Pallene malleolata, G. O. Sars, at a depth varying between 191 and 459 fathoms, and Pyeno- gonum litorale, dredged by Smith and Harger, at a depth of 430 fathoms). Hence there remain only five genera of Pycnogonida, species of which may truly be called

deep-sea inhabitants; they are the genera Nymphon, Ascorhynchus, Oorhynchus, Colos- sendeis, and Phowichilidium.

REPORT ON THE PYCNOGONIDA.

List oF THE GENERA OF PYCNOGONIDA HITHERTO KNOWN.

Name of the Genus.

Nymphon, Fabr., Ammothea, Leach,

‘| Bohmia, Hoek, . Phanodemus, Costa, Rhynchothorax, Cos., . Pephredo, Goodsir, Platychelus, Cos., Oiceobathes, Hesse, : Ascorhynchus, G. O. Sars, .

Zetes, Kroyer, Parazetes, Slater, Pariboea, Philippi, Achelia, Hodze, .

Alcinous, Cos., . Tanystylum, Miers, Lecithorhynchus, Bohm, Oorhynchus, Hoek, Colossendeis, Jarzynsky, Pasithoe, Goodsix, Endeis, Philippi, Discoarachne, Hoek, . Pallene, Johnston,

Phoxichilidium, M.-Kdwards,

Oomerus, Hesse, . Hannonia, Hoek, ° : Phoxichilus, Laty.,

Pycnogonum, Briinnich,

Number of Depth in Fathoms

Species | at which they have Geographical Distribution. De- been found.

scribed,

38 Shore to 2225. | Mundane—Pacific Ocean excepted.

5 Shore to 5. American and European Coasts of the North Atlantic.

1 (2) (?)

3 Shore. Coast of Italy.

1 Q North Coast of Africa,

1 Shore. Coast of England.

1 (2) Coast of Sardinia.

1 Shore. Coast of France.

D 38 to 1539 North Atlantic, Indian Ocean, South Coast of Australia, North of New Guinea, Coast of Japan.

1 Shore. Coast of Greenland,

1 (2) Japan.

1 Shore. Coast of Italy.

4 Shore to 35. American and European Coasts of the North Atlantic, Coasts of the Mediterranean, Ker- guelen,

2 (2) Coast of Italy.

2 5 to 7 Kerguelen, East Coast of North America.

2 3 to 4 Japan.

1 700 Auckland.

12 55 to 2650 Mundane—Pacific Ocean excepted.

1 Shore. Coast of England.

2 Shore. Coast of Italy.

i Shore. Coast of Cape Colony.

16 Shore to 459.* | Coast of Northern Europe, Greenland Sea, Coast of Greenland, East Coast of North America, Coast of Mozambique, off Australia, | China Sea, Coast of Japan.

15 Shore to 1950. Coast of Northern Europe, Greenland, North | America, North Atlantic, Coast of Brazil, Patagonia, South Atlantic, Indian Ocean, Coast of Lower Siam, off Japan.

1 Shore. Coast of France.

1 Shore. Coast of Cape Colony,

4 Shore. Coasts of Northern Europe, Mediterranean Coast, Coast of Lower Siam.

2 Shore to 480,? Coasts of Northern Europe, East Coast of North

America, Coast of Chili, Coast of the Mediter- ranean, Coast of Australia,

1 Teste G. O. Sars.

(ZOOL. CHALL, EXP,—PART x,—1881.)

2 Smith and Harger, teste Wilson.

K 2

10 THE VOYAGE OF H.M.S. CHALLENGER.

When comparing the bathymetrical range of the different genera with their geographical distribution, it is easily remarked that it is the genera most widely spread over the bottom of the sea which are capable of existing at the greatest variety of depth. This is, for instance, the case with Nymphon, Colossendeis, and Phowichilidium. Some species of Nymphon are found at low-water mark, others inhabiting shallow water in the immediate neighbourhood of the coast are dredged at a depth of under 100 fathoms ; others again are never found at a depth exceeding 800 fathoms, and finally, there are some which are true deep-sea species. Some species of Colossendeis were dredged at a depth of under 100 fathoms, other species inhabit the ocean at a depth not exceeding 800 fathoms and others were dredged at depths varying from 800 to 2800 fathoms. The genus Phowxichilidiwm shows almost the same bathy- metrical range as Nymphon. Now the geographical range of these three genera is, as far as I could ascertain from the facts at my disposal, nearly the same ; this distribution is mundane. With the exception of the Pacific Ocean, from which as yet not a single species of Pyenogonid has been obtained, representatives of these three genera are found almost in every sea.

Of the genus Ascorhynchus only five species are known as yet. They were collected at depths varying from 38 to 1539 fathoms, and at widely distant places, viz., in the Greenland Sea, between the Cape of Good Hope and Kerguelen Islands, off Australia, to the north of New Guinea, and off Japan; and as the different species of this genus form a very natural group, it is, I think, very probable, that later investigations will show also for interjacent places the occurrence of forms belonging to this same group. Oorhynchus is as yet the only genus which seems to inhabit depths exceeding 800 fathoms exclusively ; but as only a single specimen of the one species known of this genus has been collected, I do not think it expedient to pay much attention to this fact.

Hence, with regard to the bathymetrical range, a close study of the material brought home by the Challenger, added to what was previously known on the subject, has shown :—

(1) That those genera which range most widely geographically are also those which range most widely in depth; and (2), that there does not seem to exist a single true deep-sea genus of Pycnogonids.*

As for the influence of the increasing depth on the form and the structure of our animals, this is by no means easily traced. As far as the structure of the integu- ment and of the eyes is concerned, I will treat the question at some length when speak- ing of their structure. As a rule the true deep-sea species are more slender, the legs very long and brittle, and the surface of the body smooth, whereas the true shore-inhabitants are much more concentrated, have shorter legs, and are often densely covered with

1 From the study of deep-sea forms in general, Mr Moseley and others came to the conclusion that these animals have a world-wide range. Of this the Pycnogonids give a fair instance, I believe (Moseley in Nature, April 8, 1880, p. 546).

REPORT ON THE PYCNOGONIDA. 11

hair. However, these rules admit of a great many exceptions. Thus the most common shallow-water species of the English, French, and Dutch coasts is Nymphon gracile, Leach, an exceedingly slender animal with very long legs, and moreover almost smooth. Colossendeis proboscidea, Sab., sp., is a blind species occurring only at a considerable depth ; yet it has a highly concentrated body with short legs. Two species of Phoai- chilidium, for which I have proposed the names Phoxichilidium pilosum and Phowichili- dium mollissimum, are true inhabitants of the depths of the ocean; yet they are not smooth at all, but covered by avery hairy integument. The case of Phoxichilidium pata- gonicum and its variety elegans, which I describe hereafter, must probably be considered as a trifling instance of the effect of depth on the slenderness of the body.

The scientific and trustworthy material at our disposal is by no means suflicient to enable us to discuss thoroughly the question of the geographical distribution of Pyenogonids. Judging from what is known of the European and North American coasts, it is most probable that on all coasts, and everywhere in shallow water in the neighbourhood of the shore, forms of Pycnogonids will be found occurring ; and as I think it improbable that any true shore-inhabitant will be found which shows a very wide range, it is also highly probable that the number of rittoral forms at present known is very small in comparison with the number really existing.

The distribution of those Pycnogonids which are not to be considered as shore- inhabitants, but which have never been dredged yet at depths exceeding 500 fathoms, is best known in the northern part of the Atlantic and the seas corresponding with it (North Sea, Greenland Sea, Barents Sea). The species of the genus Nymphon, which occur in the neighhourhood of the coast of New England, are found to the north and east as far as Greenland, Spitzbergen, and Novaja Semlja; but these Arctic Seas are, moreover, inhabited by some forms of the same genus occurring there only. As this point has been more fully discussed by me in another paper, it will suffice merely to mention it here.

Among the Pycnogonids of the Challenger Expedition, Colossendeis megalonyx, Hoek, is the only species, which, though found at a depth of from 55 to 120 fathoms, has a wide range; about the 58th south parallel it was dredged off Kerguelen Island, and also between Patagonia and the Falkland Isles.

With respect to the true deep-sea species the material is by no means sufticient for the study of their geographical range. Of the thirty-six species of Pycnogonids brought home by the Challenger, nineteen are true deep-sea species. Of these only three belong to the northern hemisphere, viz., Colossendeis minuta, Hoek, south of Halifax ; Phowichi- lidium oscitans, Hoek, west of the Azores; and Phowchilidium mollissimum, Hoek, off Yeddo; they were only dredged once and were new to science. Of the remaining sixteen, which belong to the southern hemisphere, one was dredged at lat. 65° 42’ §. (Nymphon meridionale, Hoek) and one almost under the equator (Nymphon per-

12 THE VOYAGE OF H.M.S. CHALLENGER.

lucidum, Hoek, at lat. 48’ S.). The fourteen remaining species were all dredged between lat. 33° 31’ S., and lat. 53° 55’ S.; and it is a remarkable fact, that those two latitudes limit a zone of about 20°, in which Pycnogonids seem to be rather common. However, even in this zone they are again much localised, being almost in every instance from near the coast of an island or continent. For miles the dredge was let down without bringing up a single specimen; whereas six species were found occurring at Stations 146 and 147, off the Crozets Islands (these Stations being very near to one another, I take as one); one at Station 157; three east of New Zealand, at Stations 168 and 169; five between Juan Fernandez and Valparaiso (Stations 298, 299, and 300); and two east of Buenos Ayres (Stations 320 and 325). |

These facts indicate, I think, that the number of places inhabited by deep-sea Pyenogonids are not very numerous, and that where Pycnogonids do occur, many forms are, as a rule, found living together. This also ought to be observed when considering that between Stations 237 (off Yeddo) and 298 (between Juan Fernandez and Valparaiso), throughout a course of 11,775 miles, the dredge was let down sixty times and not a single Pycnogonid was obtained. This of course may partly be ascribed to the circumstance, that on an average the depth of that part of the ocean is too considerable to be inhabited by Pycnogonids; but as the depth at many stations during that part of the voyage did not exceed the depths of other stations at which Pycnogonids were dredged, this cannot be considered as the only reason. Also when the same circumstance is found to be the case in that large part of the South Atlantic between the Azores and Station 146, where during a course of more than 9000 miles the dredge was let down at 76 stations without a single return of Pycnogonids, and this although the depth at these stations is less, and at most of them much less, than some of the greater depths at which Pycnogonids were found, it is quite evident that the depth of the sea alone cannot be held responsible for it. Nor do I consider it yet proved that Pycnogonids are totally wanting in these oceans, as only a very small area of these oceanic abysses has been explored; so I think the only conclusion which at present may be drawn is this, that as yet only a few of the places where Pycnogonids occur in great numbers have been found out.

In regard to the nature of the bottom from which the Pyenogonids of the Challenger Expedition were obtained, conclusions must be also somewhat uncertain. The bottoms on which they occur seem to be extremely different. We find that one species was brought up from a bottom of gravel and stones, one from hard ground, one from rocky ground, five species are recorded as having been brought up from a muddy bottom, one from diatom ooze, five from a sandy bottom, three from a bottom of grey ooze, three from grey mud, and three from globigerina ooze. The other species were obtained from rocky bottoms in the neighbourhood of the shore.

More particulars about the geographical and bathymetrical distribution of the

REPORT ON THE PYCNOGONIDA. 13

Pycnogonids may be found in the list of the species hitherto described, which I append to this report. I have tried to make it as complete as possible; yet it contains many species of which no information is given as to the depth at which they were found ; others of which even the locality they inhabit is not accurately stated; and furthermore, there are genera and species—and of the latter no small number—about which we are totally left in the dark. To explain this the reader must keep in mind (1) that this is the first

Immovable claw

WASTAN) cee ac an ar ? A a ae ig aa aan nnn nwenennmrms 3rd coxal joint of the leg f Palpus

POoBO8CI8 <a-nennesnveen 0 ee Ist joint of the mandible

Cephalic part of the cephalothoracic segment ) 4 eT Skea ene yf / 2nd tibial joint

t 2nd coxal joint 3rd

Thoracic part of th cephalothoraci:

Ist tarsal joint -------------- 2nd thoracic segment

3rd thoracic segment I}

2nd tarsal joint.--- 4th thoracic segment

Abdomen ...--. = (fe ee

aM TSN / < ceeeneeaeen Anus

OvigerOUs Veg ma----o-----------enenn---fof 2 Claw

RA ___... Ist tibial joint

ola 2nd tibial joint

Nymphon, sp. * attempt to make such a list, with the exception of a very incomplete and superficial enumeration published in 1874 by Semper,’ and (2) that there is as yet no paper published which discusses the relative value of distinguishing marks, So it is evident that the making of this list has been an exceedingly troublesome affair, and that some

allowance may be made for its incompleteness. 1 For reasons easily to be understood I have taken a species of Nymphon as the type.

2 ©, Semper, Ueber Pyenogoniden und ihre in Hydroid-Polypen schmarotzenden Jugendformen., Arbeiten des Zool. Zoot. Instituts in Wirzburg, Band i., 1874,

14 THE VOYAGE OF H.M.S. CHALLENGER,

Before inserting this list I wish to give a short description of the body of a Pyenogonid, and at the same time to state the nomenclature I have made use of.

The body of every Pycnogonid consists of four segments, the first of which is to be considered as formed by the connection of the head with the first thoracic segment. At the anterior end this first segment is furnished with a long and stout proboscis. This proboscis is situated either about the front of the first segment, as in Mymphon, and in this case is capable of very limited motion, or as in Ammothea and Ascorhynchus, though also situated about the front, it is connected with the segment by means of an articulation, and for that reason is highly movable, or it is, as in Phowichilidiwm, situated on the ventral surface of the first segment, and bent forward ; or finally, it is situated about the ventral side, and at the same time lapped over it (Béhmia, mihi). The form and size of this proboscis varies greatly. . At its extremity it is furnished with a triangular mouth. It is to be considered as an unpaired outgrowth of the region surrounding the mouth, and has nothing to do with a true head, as was supposed by Savigny. Neither is there anatomically or embryologically any real ground for the opinion, suggested by Huxley,’ that the proboscis represents the united chelicers and pedipalpi like that of Acarina.?

The cephalic part of the cephalothoracic segment is generally furnished with three pair of appendages, which long ago received the names of mandibles, palpi, and ovigerous legs. As far as has been ascertained till now, there is not a smgle genus of Pycnogonid, which does not show these three pair of appendages either in the adult state, or during its embryological development. Yet cases are not rare, in which in the adult animal, either the first (the mandibles) or the second pair (the palpi) or both are deficient. With respect to the third pair of appendages (the so-called ovigerous legs), on the contrary, they are never found wanting, as far as we know, in the adult animal of either sex. Whoever studies different forms of Pycnogonids, will soon discover what a difference may be caused in the appearance of the cephalic part of the body by the presence or absence of the cephalic appendages; hence it is that the various authors who have proposed a classification of the group have largely made use of this presence or absence of cephalic appendages. Although there is no doubt, I believe, that good characteristics may be derived from the number of these appendages, the following may show how extremely necessary it is to be cautious in this matter.

' Huxley, Anatomy of Invertebrated Animals, p. 386, London, 1877.

? On a transverse section, the proboscis of the Peynogonids always shows a more or less distinctly triangular shape, the mouth is also triangular, &e. The total form, therefore, is to be compared with the fruit of a monocotyle- donous plant, composed of three carpels. Of these one is placed dorsally, the two others meet longitudinally in the middle of the ventral side. If anybody should feel inclined to try again to homologise the proboscis with cephalic ap- pendages, he will have to eall the dorsal piece the labrum, and the two others the homologues of mandibles. However, in the earliest stages of development I have observed, the proboscis has already the form of a short cylindrical appendage,

and I must point out the anatomical fact that the proboscis for the greater part is innervated from the supraceso- phageal ganglion.

REPORT ON THE PYCNOGONIDA. 15

The mandibles in some genera are two-jointed (Nymphon, Pallene, &c.), in others three-jointed (Phoxichilidium). As a rule the second or third joint terminates in a pair of pincers, with a movable and an immovable claw. Now there are genera, some species of which show the mandibles small, yet furnished with true pincers, whereas other species of the same genus show the mandibles in a much more rudimentary state, as if, for instance, represented only by a single joint terminating abruptly (Ascorhynchus glaber, Hoek, and A. minutus, Hoek). In other genera the mandibles are in the adult animal always rudimentary, represented only by short stumps (Lecithorhynchus, Bohm, Oorhynchus, Hoek, &c.); whereas in a fourth category the mandibles have totally disappeared (Colossendeis, Phowichilus, Pycnogonum, &c.). Among the specimens of a species of one of these genera (Colossendeis gracilis, Hoek), dredged during the cruise of H.M.S. Challenger, I have, however, found one specimen furnished with a pair of distinctly three-jointed mandibles, terminating in a pair of pincers; and this specimen was the largest of the three obtained.

The palpi when present show very different numbers of joints. Thus there are only three in Pephredo, five in Nymp