. THE DANISH INGOLF-EXPEDITION. VOL. Ill, PART 1. CONTENTS FR. ME INERT: PYCNOGONIDA. PUBLISHED AT THE COST OF THE GOVERNMENT BY THE DIRECTION OF THE ZOOLOGICAL MUSEUM OF THE UNIVERSITY. ^cyjAs^- COPENHAGEN. H. HAGERUP. BIANCO I.UNO IP. DREYER), PRINTER TO THE COURT. 1899. THE DANISH INGOLF- EXPEDITION. VOLUME III. PYCNOGONIDA. BY FR. MEINERT. WITH 5 PLATES AND 2 FIGURES IN THE TEXT, i CHART, AND A LIST OF THE STATIONS. TRANSLATED BY TORBEN LUNDBECK. ->4K2XK- COPENHAGEN. BIANCO LUNO (F DREYER), PRINTER TO THE COURT. 1899. L CONTENTS. Pycnogonida. Page Introductory remarks I Terminology i The History of Development 1 1 Systematism 31 I. Fain. Xymphonidse 33 1. Subfam. Nymphonini 34 Gen. Xymphon (Fabr.) 34 grossipes Fabr 35 Sluiteri Hoek 36. brevitarse Kr 37 serratum G. O. Sars 37 megalops G. O. Sars 37 Sarsii n. sp 38 Hoekii n. sp 39 Stroemii Kr 40. longitarse Kr 4r Groenlandicum n. sp 41 elegaus Hans 42 leptocheles G. O. Sars 43 macrum Wils 43 macronyx G. O. Sars 43 — spinosum Goods 44 tenellum G O. Sars 45 robustum Bell 45 Gen. Paranymphon Caull 46. spinosum Caull 46 2. Subfam. Pallenini 4S Page Gen. Pallene (Johust.) 48. Pallene acus n. sp 48 — hastata n. sp 49, Gen. Cordylochele G O. Sars 50 malleolata G. O. Sars 50 — longicollis G. O. Sars 50, Gen. Pseudopallene Vils 50. circularis Goods 50. Gen. Pallenopsis Wils 51 plumipes n. sp 51 — fluminensis Kr 52 II. Fam. Ascorhynchida; 54. Gen. Ascorhynchus G. O. Sars 55 — tridens n. sp 55 III. Fam. Colossendeidte 56 Gen. Colossendeis Jarz 57 proboscidea Sab 57 clavata n. sp 57 colossea Wils 5S angnsta G. O. Sars 59 macerrima Wils 60. IV. Fam. Phoxiehilida; 60, 2. Subfam. Pvcuogonini 60. Gen. Pycnogonum (Briin.) 60, crassirostre G. 0. Sars 61 List of Literature 62 Explanation of the Plates 65 418^ Pycnogonida. By Fr. Meinert. The species represented in the following treatise have, with the exception of one only, been all taken on the Ingolf -expedition. The said one species is Pallcnopsis flituiiiiriisis Kr., which has been included in order to elucidate the genus, and throw light on this much disputed species, the original of which is still found at the Zoological Museum. The material for the «developmental history has likewise mostly been taken on the said expedition, although some few species have been taken from earlier collections. The number of species taken on the « Ingolf <;• -expedition is 31, of which 8 are new to science. When 43 species are drawn and described by G. O. Sars in «Den norske Nordhavs-Expedition, 1876 — 78:, it is to be remembered that only 20 out of these 43 species are due to the collections of the expedition. Terminology. Although the terminology of a group of animals chiefly depends on the systematic position of the group, and the homologies and analogies founded on this position, on the other hand it will be necessary to begin with definite appellations for each of the organs, though these appellations can only be justified by the later examination and the systematic position founded thereon. I therefore shall begin with giving a list of the names I have chosen; and as I here chiefly follow the appella- tions given by Sars, so I also take the liberty to copy his figure, Pycnogonidea, 1891, p. 3, which will be found on the other side. From the two lists it will immediately be seen that I have not thought myself justified in following Dohrn, when he, more particularly after Saviguy, gives to the limbs a continuous numerical order, Extremitas I — VII. This way of designing the limbs has several advantages, and has also been followed by later authors, as Adlerz and Schimkewitsch, but it has also important defects, which make themselves strongly felt. It is an advantage of the terminology of Dohrn that it is independent of all systematism; to this terminology it is all the same, whether the Pycnogonida are Crustacea or Arachnida; it has not to be altered to-day, that to-morrow, when another systematic taste is ruling, it may return to the expressions of yesterday, more or less altered in the interval. It is, however, inconvenient, when one or more of the seven pairs of limbs (extremities) are specially The Ingolf-Expedition. III. I. I ction to the others, "i when one or more pairs have disappeared, mi that be understood, now .1- the first, now as the second, third, or fourth pair of the the imago. The greatest drawback by Dohrn's way of designation is to me that with the developmental history, the embryonal legs (fig.2 6, c) not being Ithough thej are not to be regarded as the predecessors of the two foremost pairs ol neither the predecessors of the second and third typical pairs ol limbs of the imago, the imagiual fore-limbs, 01 oi the palpi and the ovigerous legs. I hope that it will appeal from mj examination of the larval development that these 1 pairs of limbs are not identical with, the embryonal legs, to which examination th eader is referred. Now, it the embryonal legs are neither identical with the two first pairs of ambulatory legs (Kroyer), imr with the palpi and ovigerous legs (Dohrn's Extrem.Il and IIIi, there will be typically 9, and 7. pairs of limbs, as supposed by Dohrn and all naturalists, excepting Semper, Pycnog. und Larveni, [874 (who lias 8 pairs). Even if it be supposed that the embryonal legs are peculiar limbs, it would, of course, be possible to use the appellation of Dohrn, the list of limbs then only being increased from VII to IX; but on the other hand it would be very untoward to be always obliged to subtract several, sometimes more than the half, from the number, which is got b) adding the embry- ' r. e*. o. cl. apo. cK ci. sc. pel. clif. s. eh. plm. dim. dm. pa. cxi. /■ ft'. /a'. .'.;■'. pip, po. pi,: Proboscis rostrum). First segment of trunk (segmentum corporis prinium). Oculiferous tubercle (tuber ocular Neck (collum). Lateral process of the En aent for the insertion of the ovigerous legs (protuberantia pedis oviferi - nd segment of trunk segmentum corporis secun- dum . Third segment of trunk (segmentum corporis tertium), th segment of trunk (segmentum corporis quar- tuim. Cauda] segment segmentum caud Lateral process of the body for the insertion of the anibulaton U -- i processus corporis lateralis). Cheliforus (cheliforus . Scape sea]. Us . Chela, 1 11 1 land 1 tiela v. manus). Palm (palma . Immovable finger acumen v. digitus immobilis). Movable Emgei pollex v. digitus mobilis), Ambulator} legs pes ambulatorius . First coxal joint (articulus coxalis primus). coxa! joint (articulus coxalis secundus Third coxal joint articulus coxalis tertius). Femoral joint (femu First tibial joint (articulus tibialis pi nl tibial joint (articulus tibialis alt First tarsal joint articulus tarsalis prioi Second tarsal joint (articulus tarsalis alter). Claw (unguis . Auxiliary claw (unguiculus auxiliai Palpus palpus Ipiformis i rvigerous leg (pes ovifi Terminal part of the ovigerous leg (pars terminalis pedis ovifi ri Egg-globe globus ovorum). PYCNOGONIDA. onal legs to the pairs of limbs found in the imago. In the genus Pycnogonum the first pair of ambu- latory legs, according to this, would be called Extrem. VI, the first five pairs of limbs having to be subtracted. The foregoing list and figure apply to the grown larva, the young, and the imago; with regard to the young larva the following short list together with the figure of this larva, seen from the under side, must suffice. a. Cheliforus. b. First pair of embryonal legs. c. Second pair of embryonal legs. d. Proboscis. e. First pair of ambulator)' legs. f. Second pair of ambulatory legs. Fig. 2. Nymphon robustum. Larva. I shall now proceed to notice the outer organs, giving a short description of each as well as the reason of the terms I have chosen, and at the same time I shall quote as synonyms the corre- sponding appellations by the chief earlier authors. Proboscis (rosfritw), fig. i r, and 2 d. O. Fabricius: tubulus v. rostrum ; Latreille: tuyau ou siphon d'une seule piece; later (Regn. anim. ed. II): bouche; Leach: os tubulosum, or rostrum; Savigny: premier anneau du corps allonge et remplacant la tete (vestiges de machoires); Johnston: rostrum; Milne-Edwards: tete; Erich- son: Zunge; Kroyer: Nseb (in the larva), later: Snabel (rostrum); Wilson: proboscis, or rostrum; Dohrn: Schnabel ; Bohm: Rostrum; Hoek: trompe (proboscis); Adlerz: snabel; Hansen: Snabel, or Proboscis (proboscis); Sars: Snabel (proboscis), or Mundsegment. The proboscis is the conical or almost cylindrical organ protruding from the anterior margin of the body, or from the lower side of it; it is always large or especially so in proportion to the body, and has at the point a trilobate mouth, leading to the trilateral pipe, which is closed behind by a kind of plait, protruding to a rather sharp angle and working as a filtering apparatus. The pro- boscis is commenced at a very earlv stage of the embryonal life (pi. 1, fig. 1) as a ball or tubercle without any trace of mouth, contemporary with the embryonal limbs (the chelifori and embryonal legs). It is no segment or metamere, and still less corresponding to, what in other animals is called the head, or to part of the head. Neither can it in any way be supposed to have arisen by a coal- escing of gnathites. First segment of trunk {segmentum corporis prinnti)i\ fig. 1 cl. O. Fabricius: caput et thorax v. primus articulus corporis; Leach: segmentum anticum; Latreille (Regn. an. ed. II): le premier segment du tronc; Johnston: the anterior segment of thorax; Erichson: Kopf; Kroyer: 0iering og forste Brystriug (annulus ocularis et annulus thora- l*Vt S'OGOXIDA uliferous segment; Dohrn: das erste Rumpfsegment; I'.ohm: Augenring; phalothorax Hansen: farste Kropring; Sars: Hovedsegment (seg- ilicum). Tin mi, when viewed Erom above, presents a simple surface without any bra« articulation, and Kroyer, when he nevertheless divides ii into an oculai segment and segment of thorax, has not been able to point out any traci m 01 anj other arti- ition, but has evidently started Erom the a priori reason that eyes cannot be Found on a thoracic [lowing). It' the animal, however, is seen Erom before, several seams or lines maj some- tinii en nunc- 01 less distinctly, as marking the boundarj oi peculiar skeletal parts, originally independent, but now united with the first segment of the thorax. Thus under the fore-edge of the ment of the trunk in Pallenopsis plumipes the common skeletal part (metamere) of the cheli- 111. i\ be seen a> a transverse band (pL I\', Kg. 3). To understand the first segment of the trunk, it is quite necessary to follow the larval development from the embryo. It will then be seen that the and foremost chief part of the embryo is formed by the proboscis and the three pairs of embry- onal lim ninding this latter, while the other chief part is not developed till later, the ambula- legs and the four segments of the trunk together with the caudal segment not being partitioned off at first The first chief part, most frequently with the exception of the chelifori, shrinks by and by, loses its independence of the other chief part, and is, as it were, swallowed up by the foremost part of this latter, the first segment of the trunk; not until this has taken place, and the embryonal have fallen off, do the imaginal fore-limbs, palpi and ovigerous legs, spring forth on the lower of this segment, when they are developed at all. The further details of this growth will be found in the following in the section treating of the larval development If we suppose that the four segments with the ambulators- legs of the Pycnogonida corresj with the thorax of the other Arthropoda, especially with that of the Arachnida and Insects, and the first principal segment of the embryo with its three pairs of limbs likewise corresponding with the head of those animals, the name of Cephalothorax (Hoek, Adlerz) for the first segment of the trunk would be very good; but as I consider this comparison as wrong, or, at all events, as inde- monstrable, I shall prefer another, less marked appellation, and as such I consider the one I have sen. I, for my part, think it to be most probable, or at all events possible, that the second princi- pal segment of the Pycnogonida with its four pairs of ambulatory legs and the caudal segment can red with the abdomen of the Arachnida, in which this part in its development has, or may have a similar division into somites, and similar rudimentary limb-, as in the I\ cuo^onida, cp. L-ocy: ■ii. Agelena, 1885, pi. II, fig.9 11, and pi. Ill, Kg. 13 15. The position of the genitals then won rally is the case, be in the abdomen, and in the processes of the abdomen, that is, the ambulat 1 »n the other hand, the eves would be placed on the fore edge of the abdomen, but ■ in the pedunculated Crustacea) do not form a typical part of the body in animal, belonging to or constituting the head; and even if we, to avoid this difficulty, should call the ■ , in which the eyes are placed, cephalothorax, it is still in the hindmost part of this segment, in the thorax, or the first somite of it that the eyes would be placed and farther itself, they would never come. PYCNOGONIDA. The oculiferous segment of Wilson and the Augensegment> of Bohni is only another expression taken from the appellation of Kroyer, but applied to the whole of the first segment of the trunk. When Erichson uses the name of Kopf for this part of the body, it is exclusively with regard to the ambulatory legs and the comparing them to the limbs of the Arachnida, of which again the three last pairs were to correspond to the thoracical legs of the Insects, while all the correspond- ing' segments were to form the thorax. Oculiferous tubercle {tuber ocular r), fig. I, o. Kroyer: 0ieknude (protuberantia ocularis); Sars: Oieknude (tuberculum oculiferum). On the dorsal side of the first segment of the trunk, in the middle of it, but more or less backward, is found a knob-like protuberance, the oculiferous tubercle. The shape of this knob is very different, varying in the different genera and species, growing from a low, rounded swelling to a height of almost the length of the trunk, and ending with a tapering point. It is not until the second larval stage of development that the oculiferous tubercle begins to be seen as an excrescence on the first segment of the trunk after this segment being distinctly separated. The eyes make their appearance prior to the oculiferous tubercle on the spot of the first segment of the trunk, from which this latter rises, and during the growth of the tubercle the eyes are raised with it more or less, so that in the imago they are placed in a square round the tubercle, more or less distant from its top. The tubercle bears typically four single eyes, ocelli, but frequently the eyes are not, or only a little, developed, so that as well blind species as seeing ones may be found in the same genus (Colosscudeis). Neck (coll urn), fig. I cl. I have thought it best, like Sars, to keep this name for the middle part of the first thoracical segment, when it is more or less strongly marked off, as I regard this appellation as so little marked, that it is no necessary consequence to look upon or denominate as head the thickened part of the trunk King before the segment in question. Lateral process of the first segment for the insertion of the ovigeroiis legs (protuberantia pedis ovzferi), fig. I apo. Sars: Halsfortsats (processus colli) til Fseste for de falske Fodder. This process originates from the under side of the first segment of the trunk just before the process of the trunk; it is very short, inconspicuous, and from its outer side or point arises the ovigerous leg. When the segment of the trunk is short, so that there is no neck, the palpi get towards it, and in some genera (Colosscudeis) the palpi do apparently arise from the fore side of this process. Second segment of trunk {segmentum corporis secundum), fig. i c2. Third segment of trunk (segmentum corporis tertium\ fig. i d. . Fourth segment of trunk (segmentum corporis quartum\ fig. i c4. No synonyms are here necessary to explain the opinion of the authors as to these segments. It is a matter of course, and everybody agrees that they are homonomous with the first segment of trunk, or, at all events, with the large upper and hinder part of it. Caudal segment (segmentum caiidale), fig. i sc. I»Y< DA l.i: ■■ uda; Latreille: le dernier segment du corps; Lamarck: domen; Johnston: abdomen; Milne-Edvards: abdomen; Hinterleib; Kroyer: Bagkrop, abdomen; Wilson: abdomen; Dohrn: Hinterleib; hi: Abdomen; II . ■ i k : abdomen; Adlerz: abdomen; Hansen: Bagkrop (abdomen); Sars: Hale- ntum caudale). The appellation of thi^ part of the trunk was in the early authors (L i n n e and O. Fabricius) simph cauda, tail; but Latreille having pointed out that it was a part, a segment, of the trunk If, the first name was displaced liy the appellation abdomen and the translations of it (Hinterleib, krop), which was adopted by all authors until Sars, the opinion being, I suppose, that it corre- the abdomen of tla- other Arthropoda, especially that of the [nsects and the Arachnida. wire, bas meant to adopt the "Id name of tail, hut on account of the prevalent aversion this appellation, lie has altered it to the mediate one of caudal segment, and I have followed him partly ol similar reasons. As to its development the caudal segment is the hindmost part of the hindmost principal division of the embryo, and until a far advanced stage in the larval development it forms a hindmost, gradually more protruding, process of tin- fourth segment of trunk. If upon the whole it is separated from this segment by a dermal suture, this does not take place until the third larval stage. It never hears limbs, hut the intestinal canal opens in the end of it with a weak squir- ting apparatus. Thus the caudal segment no doubt belongs to and makes the hindmost [■art or segment of the same principal portion to which the four preceding segments belongs; it is no separate part of the body, different from the foregoing segments of the trunk, no abdomen in contradistinction to a thoracical part, lying before it. The caudal segment can be pro- portionally very long, almost as long as the body, and then it is also well separated from the fourth lent of thf trunk and very slender; there is no trace of division in joints, not even in Zetes [/in- is has been maintained. On tin- other hand this segment may also be quite small, as it were, rudimentary, as I know from ,i not described genus among the collections, which the Smithsonian Institute has given me for examination. Lateral process of the body for the insertion of the ambulatory leys [processus lateralis), fiy. i pel. Sars: Legemets Sidefortsatser (processus laterales corporis) til Faeste tor Gangfodderne. Thi 5Ses of the body and the ambulator) legs attached to them, are structures charac- oida, as they are not formed by germinating or growth of a particular cellular ip but, as is distinctly seen from my drawings of the embryo, by a bag-like constriction of the m, in the same manner as the embryonal limbs (the chelifori and embryonal legs). They are in • i of the body, and so it will easil) be understood, that the intestinal canal and :ii continue far into the ambulator) legs as processes of tin body. C helifi i. Kg, i , /// and i nly prolongations of these processes, constricted into the number of nine joints, inclusive of the claw, which is common to all Pycnogonida. First coxal joint (articulus coxalis primus], fig. 1 <•'. and coxal joint (articulus coxalis secundus), fig. 1 c2. Third coxal joint [articulus coxalis tertius), fig. I f3. ; Hofteled (articuli coxales). These three joints Eonn the proximal end of the ambulatory Ic.l;; they belong to the shortest joints of the leg, and form a series "I homonomous joints, being of one set; therefore they may all ther correctly be termed the coxa. moral joint (femur), fig. 1 rs: I.aarlcd (articulus femoralis). In the Arthropoda, especially the Insects, the femoral joint follows upon the coxa and coxal banter, which in these animals is only a subordinate joint I think it, however, im- the terminolog] of th< the Insects to those of the Pycnogonida, and tli I have red it advisable to follow Sars in his appellations of the joints of the leg, only with -Dine variation in the special nanus. st tibial joint [articulus tibialis prior), fig. 1 I/". tibial joint [articulus tibialis alter), Kg. 1 tb-. (articuli bbiales). Thi closely united, and there is no reason to give any prominence PYCNOGONIDA. to either of them, and so I agree with Sars in not using unnecessary appellations, taken from the Araehnida or other Arthropoda. There is thus no reason to call one of the joints patella. First tarsal joint (articulus tarsalis prior), fig. i fa1. Sars: Tarsalled (tarsus). Second tarsal joint (a rt '/cuius iarsalis alter), fig. i fa2. Sars: Fodled (propodus). These two tarsal joints are closely united like the two tibial joints; often they are almost uniform without any particular difference as to length or structure. If there is any difference, it con- sists most frequently in the first joint being shortened, often much shortened in contrast to the second one. If we should choose to distinguish between the joints, and give each of them a separate name, I think that appellations as metatarsus and tarsus would be proper; but to avoid too many names and all confusion with the appellations of Sars, I have only numbered the joints. The names given by Sars, seem to me to be too unfortunate at all events; the name of tarsus meaning always the outermost joint, or — if the tarsus is divided — joints of the leg. Claw (t<)?gitis), fig. i u. Sars: Endeklo (unguis terminalis). The claw, as mentioned above, is only the last terminal joint of the leg (corresponding to the claw in the larva of the Staphyliuids and of most Coleoptera), but is not included in the foot. It is very much varying as to shape and size, often in the same genus (for inst. in Colossendeis); as it cannot be mistaken for any other claw, I have thought it unnecessary to use a more particular appellation. Auxiliary Claws (unguiculi auxiliarcs), fig. i ua. Sars: Bikloer (unguiculi auxiliarii). These auxiliary claws are really the terminal claws of the foot, originating from and attached to the last joint (the claw) of the foot. In so far they are real claws, and correspond to the claws in the Araehnida and most Insects. Corresponding claws are wanting in the Crustacea, and therefore their presence in the Pycnogonida is of no small systematic importance; it is to be remarked, however, that they often become rudimentary or quite disappear, but nevertheless they may be said to be typical in this group of animals. As to their importance in assisting the claw, it evidently cannot be great, and therefore their Latin name of auxiliares or auxiliarii is not very appropriate. Palp (palpus v. pes palfiiformis), fig. i pip. Linne: antennas; O. Fabricius: antennae; Latreille: palpes ; Leach: palpi; Savigny: pedes tertii; Lamarck: autennules; Johnston: palpi; Milne-Edwards: palpes; Erichson: zweites Kieferpaar, Maxillen, Tasten; Kroyer: Palper; later: first pair of jaws or Maxiller (maxillae primi paris); Wilson: palpi; Bolim: Palpen; Hoek: palpes; Hansen: Palper; Sars: Foler (palpi). After Latreille, more particularly, perhaps, founded on his theory of the proboscis being formed by a composition of gnathites, having introduced the appellation palpes for the word antenna used by Linne, this name (palpi — palpes) has now been used by almost all later authors; some (Erichson, Kroyer) have thought, however, that this pair of limbs do not correspond to the palps of the other Arthropoda only, but to the whole corresponding pair of gnathites, and have named The Ingolf-Expedition. III. t. 2 PYl IDA ipinion (Kiefer, Maxiller). In Dohrn, Adlerz and Schimkewitsch it oi Extrem II As I. as well as Dohrn, reject the tli<"i\ ol Latreille, I have retained Tlu- pal] the first pah ol the imaginal fore limbs; they do not arise, until tin- embryonal ■ in throw u off, and have ii" continuous connection with tin- latter. They always originate : tlu- anterioi edge of tlu- lower ^i-l<-- of tlu first segment of tlu- trunk, often at a great distance ••■us legs; hut when tin- segment is shortened the) approach tin- ovigerous legs, even ::tl\ originating from tlu- lateral process, on which those legs an- inserted [Colos- It is t" be supposed that the) are oi no great importance in tlu- life of the animal, ami thej also form tlu- pair of imaginal limbs, which are liable to tin greatest changes as to length, number •ints etc, ami soonest become rudimentarj or are thrown off In Ascorhynchus tridens 1 have in tin- fourth joint of these limbs found a particular organ of sense i?k as to details see the following ■;.'ii "ii tlu- ovigerous legs. Ovigerous leg [pes orwYm, fig. i /". I.iniu-: tentacula pectoris; O. Fabricius: pedes spurii ii'ila ovifera); Latreille: pattes; later gn. an. ed. Hi: fausses pattes; I, each: organa ovifera; Savigny: pedes epiarti; Johnston: ovife- legs; Milne-Edwards: appendices pediformes; Erichson: drittes Kieferpaar; Kroyer: andet ParKjseber, 55ggetraad; Wilson: accessory legs; Bohm: Eitrager; Hock: pattes oviferes; Hansen: pedes ovigeri; Sars: falske Fodder (pedes spurii). The most common appellations of this second pair of imaginal lore limbs are owing to the fact that they are used for carrying the eggs. Another starting point may he found in the peculiar tion of these limbs, as seemingl) they can he classed neither among the gnathites nor anion- the ambulatory legs, a fact already pointed out by ( ). Fabricius. The ovigerous legs are the latest developed limbs, even if their development takes place only a little later than that of the palps. They arise mi a level with and behind the palps on a particular hut their position in relation to the palps, especially with regard to distance, has already been mentioned. They are of a more considerable length ami most frequently have more joints than the palps. The number of joints is typicalh ten, exclusive of the claw, that is to say, one more than the number irrive at in the ambulatory legs, when in these we count the claw as a joint, and considei the auxiliary claws . sponding to tlu- claw of the ovigerous legs. Their most important function is in the male to carry the eggs, for which purpose some of the joints are often thickened or provided with particular hair-formations especially in the male. Besides I have in different species of Nym- phonidse [Nymphon groenlandicutn n. sp. pLIII, fig. j«w/; /',///,■//<■ hastata n. sp. pl.IV, fig. 17 a) and as well in the male as in the female, found in the fourth joint of these limbs an inner organ consisting lengthened bag, divided, as it were, into two parts by a constriction in the middle; this bag is ligament nnective tissue, arising from its anterior and posterior end, attached to the 'on: a broad nerve runs along the longitudinal side of tlu bag. No doubt this bay is an I suppose, of hearing. In the Ascorhynchus quite a similar organ is found, only that animal it is not found in the ovigerous legs, but in the palps (cp. above). But besides ser- in the male and bearers of an organ of sense, they serve, as 1 suppose, PVCNOGONIDA. 1 1 in both sexes as combs or cleansing apparatus for the other limbs of the animal, all of which can presumably be brought within the sphere of action of the rows of dermal leaves1) (the comb) with which the last joints of the ovigerous legs are provided. The terminal part of the ovigerous leg (Pars terminalis pedis oviferi), fig. i ptr. Sars: Endeled (pars terminalis). I have, as Sars, given a special name to these four last joints of the ovigerous leg, bearing the comb or cleansing apparatus, just mentioned. The comb consists of a greater or lesser number of daggershaped dermal leaves with deeply incised edges, arising in one or more rows from the inner side of these four joints. The claw, with which the leg terminates, is closely joined to the comb, and as it is often deeply incised in its inner edge it also partakes in the work of the comb. The egg-globe (globus ovorum), fig. i glov. Sars: JEggeklump (globa ovorum). The male, as it is well known, (Cavanna, Studi Picnog. , 1877) carries the deposited eggs, placed in lumps around one or more of the middle joints of the ovigerous legs. As the size of the eggs is very different in the different Pycnogonida, so it is also with that of the lumps, but most frequently the size of the lumps and of the eggs stands in an inverse ratio to each other. As a rare exception the males of some species carry the eggs in one cake on the lower side of the body (Pyc- nogonum), while the males of other species have some few, very large eggs attached singly to the ovigerous legs (Pallene). The number of egg-globes most frequently is two, one globe on each of the two legs, but frequently this number is doubled or increases further to 4—5 globes on each leg. Very rarely only one leg has one single egg-globe; I have, however, found this to be the case in by far the most of the males of Nymphon robustum , that I have had for examination. The preceding survey of the limbs and parts of the body of the Pycnogonida applies also to the young larvce, in so far as those limbs and parts have been developed; but besides these larva; have particular limbs, and to show these limbs I have on p. 3 given a contour-drawing of such a larva, fig. 2. Especially are to be mentioned : Embryonal leg of the first pair (Pes embryonalis prion's pans), fig. 2 b. Embryonal leg of the second pair (Pes embryonalis alferiits pan's), fig. 2 c. These two pairs of limbs develop at the same time as the chelifori (or the first pair of embry- onal legs) and the proboscis on the first chief part of the embryo; they soon attain to their full devel- opment, but are also early thrown off during the second or third larval stage. Only rarely they are not developed at all (Pallene haslata, pi. I, fig. 18 — 19) or grow only to short, tap-like processes (Pseu- dopallene spiuipes, pi. I, fig. 8, and Pseud, circularis, fig. 10, as well as Pallene brevirostris, fig. 16). The History of Development. On the development of the Pycnogonida there exists a rather considerable literature. The attention must first be drawn to the fact that the common distinction, also used in this work, which M By Sars these leaves or blades are rather unluckily named Raudtorner >, in English marginal spines». 2* !'\> IDA mbryonal and the larval stage, cannot be fully kt].t up with regard to the ■ ■ i u.i.il mark ol distiuctiou (whethei the embryo has or has ery little importance, and nearl) rel rms, even species of the ttain to a different, sometimes very different development in the egg. Accordingly it w m\ the metamorphosis in such forms as do not leave the egg until the) have ined their permanent shape This opinion and the interpretation of the larval development now irrent have been expressed bj Korschelt a. Heider (1890) p. 662 seq: J >i ^ meisten Pantopoden entwickeln sich mittelst Metamorphose thre Larven weisen gewohnlich drei Extremi- st, doch verlassen einige in hoherei Ausbildung das Hi; so besitzen diejungen Pallenen') beim Ausschlupfen bereits sammtliche Extremitaten und auch einige Arten der Gattung Nymphon ichen schon im Ei diese hohere Entwickelungsstufe. Die verschiedenen Arten der letztgenannten g differiren ubrigens in dieser Beziehung, da die Larven einiger beim Ausschlupfen nur vier funf Extremitatenpaare aufweisen (Hoek). As will be seen from this quotation, Korschelt and Heider found their statement especially on the examinations by Hoek, or recapitulate the principal nts "i the description of Hoek as it is given in his last great work: Nouvelles etudes sur les Pycnogonides (1881), p. 482 seq. But before I pass to my own representation of the developmental history I shall give a short historical view of the most important works in this branch of study, and as we have already in irn: Die Pantopoden des Golfes von Neapel (1881) a very copious literary survey, I may limit myself t<> the following four authors: Kroyer, Dohrn, Hoek and Morgan. K. rover is the author to be named first, not only because he first of all has studied and de- scribed larvae of the Pycnogonida, but also on account of his contributions being the most important • we hitherto have got concerning the development of these animals. Already his 1 >m Pycnogo- nidernes Forvandlinger 1 On the metamorphoses of the Pycnogonida 1 (1840) is of great importance, but still more so is the series of representations of larval forms given on pi. 39 of the great, unfinished French work of travel: Gaimard, Voyages en Scandinavie etc. (1849) to which never appeared any text or explanation. As such an explanation may with regard to the Pycnogonida be taken Kroyer's Contributions to our knowledge of the Pycnogonida , Bidrag til Kundskab om Pycnogo- niderne eller Sospindlerne (1845). I" l'K' close of the third section of this treatise, on the metamor- phoses of the Pycnogonida, I.e. p. 136 seq. Kroyer collects the laws that seem to regulate the devel- opment of the Pycnogonida under 5 principal heads which may briefly be rendered thus: 1 The -s through 3 stages. 2 The first stage is of a thick, swollen shape; filled with yolk without any abdomen; with a proboscis; with cheliferous Kindbakker (mandibles); with 2 pairs of feet. Eyes seem to be wanting. 3 In the second stage a third pair of feet found, but they are short, and have only an indistinct articulation, or none at all. Eyes as well as the cond pair of Kjseber (maxilles) can be distinguished, at least in some species. Some- tin* Ik substance- of the body is present, in which case tin young one passes this stage under I'll, species • >» this genus tli.it 1 have examined, .is will be when tin thi ol ambulati have been developed and before the legS. PYGNOGONIDA. J3 the belly of the mother' (the father it ought to be); sometimes the yolk is consumed, and then the young one has to find its food. 4 In the third stage the larva gets the fourth and last pair of (ru- dimentary) feet. The two preceding pairs (the three preceding must be meant) are very much devel- oped. The maxillae (i.e. palps and ovigerous legs) on the contrary, are still, in the species where they are found, quite rudimentary. 5 After a new casting of the skin the animal nearly gets its permanent shape, although the length of the body and the limbs is altered not a little. Doh r 11 in a couple of works has given important contributions to the history of development, first in his: Untersuchungen iiber Bau und Entwickelung der Arthropoden > (1870) in the second sec- tion of which, with the sub-title Ueber Entwickelung der Pycnogoniden , he treats of the develop- ment of the larva of Pycnogonum litterale, Achelia hrvis and Phoxichilidium sp. Still more important, however, is the contribution, he has given in the monograph entitled: Die Pantopoden des Golfes von Neapel (1881), in which, besides descriptions and figures of many different genera as Barana, Ammothea, C loft nia, Phoxichilus , Phoxichilidium and Perflate, he gives an account of the larva? known to him, and their development I.e. p. 69 — 80. The principal progress in our knowledge of the devel- opment given by Dohrn is that he justly shows how Kroyer has been wrong in his interpretation of the development of the two foremost pairs of ambulatory legs, as if those pairs had arisen by an uninterrupted development of the two hindmost pairs of limbs in the first form of the larva, the em- bryonal legs as I have called them. Kr oyer's error is, I suppose, principally due to the fact that in the very young larva of Pallene (or Pseudopallene] these limbs are almost or entirely wanting, and so Kroyer has taken the two foremost pairs of legs (i.e. ambulatory legs) to be corresponding to the two foremost pairs of legs (i. e. embryonal legs) in the larva of the other species. In the following I shall again recur to this subject. The works on the Pvcnogonida by Hoek are well known. The two most important are: Report on the Pvcnogonida in the Voyage of H. M. S. Challenger (1881) in which he on the plates XIX and XX represents the larva? from their earliest development; and next his «Nouvelles etudes sur les Pycnogonides (1881) where on pi. XXX the different larvae are represented. Besides figures of well known forms, as Phoxichilidium, Ammothea and Pycnogonum, he especially draws different species of the genus Nymphon. In the lastmentioned treatise, I.e. p. 481 seq. Hoek gives the results of his examinations in the following way: v Void en pen de mots le resultat auquel je suis arrive: on trouve toujours, a quelques exceptions pres, comme premiere forme larvaire, un animal avec trois paires d'extremites, dont la premiere se termine en une piuce et dont les deux suivantes sont formees de deux articles et se terminent par des griffes allongees (larve Protonymphon). Les deux deruieres paires d'extremites sont -- comme la premiere paire — des appendices simples, e'est-a-dire qu'elles ne sont pas divisees en deux branches comme celles des larves Nauplius. La bouche est placee a la fin dune excroissance de forme cylindrique ou conique, qui est implantee entre la pre- miere et la seconde paire d'appendices: cette excroissance, e'est la trompe, qui au moment de l'eelosiou de la larve est toujours tres courte, mais possede deja cette forme conique ou cylindrique. La maniere dont l'animal adulte se developpe de cette forme larvaire est des plus simples. Tandis que les trois appendices originaux se metamorphosent dans les trois paires d'appendices cephaliques ou disparaissent (soit une, soit deux, soit — et ceci n'arrive jamais chez les individus r\ iida • in-- thoraciques se developpent successivemenl an bord post£- sit6t mi nouveau segment form£, une paire de pattes se montre egalement mces laterales d un-iit. Quand quatre paires de pattes se ^..ut ainsi deVelopp. ments thoraciques (notous que I'ordre de deVeloppement des pattes correspond tout a dans l( de I'animal adulte), l'excroissance terminale se change en un abdomen in. >ins rudimentaire. Morgan has given a little series of essays <>n the Pycnogonida, of which especiall} the last mentioned, entitled : A Contribution to the Embryonalog} and l'h\ logenj of the Pj cnogonids In this Morgan gives the development of Phoxichilidium maxillare [= femoratum Rathke?), of Pallene empusa, and of Tanystylum orbiculare. He has more than his two above nn.ii- boned pred< paid attention to the first development of the embryo, an examination that K. rover did not enter upon at all, and gives furthermore a verj handsome series of the developmental stages of '.'. . especially the larva of Tanystylum; on the other hand I do not think his represen- 11 of the larval development of Pallene empusa to be correct In his introduction I.e. p. 2 Morgan many reasons the present paper attempts in no way to give a complete answer from the embi side The very great difficulties of a suitable technique had slowly to be overcome, and the time at command prevented a detailed description of the different organs arising from the germ- so that much remains that might be done, but nevertheless his essay is a very important advance in «.ur knowledge of the development of these animals, as also his representation of the structure and development of the eye in the Pycnogonida is rather exhaustive. sing now to my own description of the larval development I have to begin with the usual complaint of not having had fresh material at my disposal; but on the other hand the Ingolf-Expe- dition has brought home so rich a material well preserved in spirit that I suppose I shall be able to a more detailed and continuous description of the different stages of development in the larva. I have been able to follow the development for a shorter or longer way in a considerable number .>t mida, belonging to the different families and g. is Nymphon grossipes, Sluiteri, elegans, .'hi//, spinosum, macronyx\ Paranymphon spi/iosiiiiixy. Zetes (Eurycyde) hispidus; Pseudo- pallcne circularis and spinipes; Pallene hastata and brcvirostris\ Phoxichilidium femoratum\ Pycnogonum littorale, altogether 7 genera with 15 species. The species, the development of which I have most complete, are Nymphon grossipes, .V. robustum and Pseudopallene circularis, of which three species the first and the last are those that have been particularly examined by Kro\er; but besides corrobo- rating 1 ids statements and drawings il have partly examined his original pieces) I have also n able to increase and partly to cornet some of them, which corrections especiall} appl) to Pseu- The segmentation, yolk-division, of the Pycnogonid ovum is complete, some- times equal, sometimes unequal. I this thesis I must refer to Morgan, Contrib. EmbryoL, 1891, and I have nothing t.. add. It is, I think, t<> be supposed, .is Morgan does I.e. p. 23, that the difference ;.d and unequal segmentation, which latter is also continued in the difference between li .1 Bpinipes in stead ..1 spinosum. PYCNOGOXIDA. 15 large and small yolk parts, the maeromeres and micromeres of Morgan, must be of a considerable influence for the later development, and that it is connected with or proportioned to the mass of the alimentary volk in the egg; this fact again plays a very great part in the biology of the larva, as this latter may exist without any other food, and keep enclosed in the safe egg-shell the longer, the more alimentary yolk it brings along with it. Kroyer already has referred to this reciprocal relation in his Contributions to the knowledge of the Pycnogonida* (1845), comp. especially the third of the five principal heads, under which he collects the results of his examinations, I.e. p. 137, and to which I have referred at p. 12 seq. A germinal stripe as in the other Arthropoda, especially the Insecta, is not formed. The ganglia as well as the separate pairs of limbs are formed or constricted by degrees, from before backward, and, with the exception of the three foremost ganglia and pairs of limbs, one after the other. In the Arthropoda, especially the Insecta, the first germ of the embryo, as is well known, is distinctly seen as a smaller or broader longitudinal band, the germinal stripe, along the under side of the egg, and from this band the formation of the abdominal nerve cord and the pairs of limbs take their rise almost at the same time; besides the formations are only small, and, as far as they really are developed, they grow in size and length by a rapid multiplying, proliferation, of the cells. In the Pycnogonida, on the contrary, a germinal stripe is never found, but the whole yolk mass is immediately enclosed by a blastoderm, and all the limbs arise, if anything, from the sides of the bla- stoderm bv a segmentation of corresponding parts of the blastoderm with enclosed yolk mass. Further- more onlv the three first pairs of limbs, the embryonal legs, are formed at the same time, while the following four pairs, the ambulatory legs, are segmented off by degrees from before backward, most frequently one pair after the other and with longer or shorter intervals of time. The ganglia seem to develop contemporaneously with the embryonal limbs, and the ganglia of the abdominal side are divided into two principal sections, a foremost one for the embryonal legs, and a hindmost one for the ambulatory legs; but this latter mass of ganglia is not till a later stage separated into four or five pairs of ganglia by degrees as the ambulatory legs develop. I may refer to my figures pi. I, fig. 11 and pi. II, fig- iS, both representing what I call the second larval stage; the first figure repres- ents Pseudopallene circularise in which the whole mass of ganglia is seen still undivided, and only the nerve mass belonging to the segments of the embryonal legs, has been slightly separated; the other figure represents Nymphon Sluiteri, in which the two pairs of ganglionic centra may be distinctly discerned united to a common mass, while the nerve mass of the first pair of ambulatory legs is well separated from the following mass representing the ganglionic mass of the three following pairs of ambulatory legs, in which mass, however, as yet only two pairs of ganglionic centra are to be seen. The larva of Nympkon Sluiteri upon the whole is more developed than that of Pscudopalh'iie. Between the embryonal and the larval stage there is no distinct boundary, in so far as this boundary is to be determined by the embryo's leaving the egg; but the embryo leaves the egg sometimes on an earlier, sometimes on a later stage. I have already before mentioned that according to the common view the limit of the embryo- nal stage is formed by the embryo breaking the egg shell or egg membrane, and that the whole • " .' iNIll \ ;.niw p]a ckoned to th< embryonal stage, but that I cannot aj with th th( embryo, however, in the different Pycnogonida , breaks the egg shell some- tiui, .1 shorter, sometimes after a longer development, nay, sometimes not even, until all the limb mbulator) legs included, have been developed, it will be underst 1 thai Korschell and Heider, Lehrb. Entwick wirbell. Thier. [890, in their large, well known text 1 k can sa) ol the inida that only » 1 i <-- meisten Pantopoden entwickeln sich mittelsl Metamorphose . Lc p. 662, were anj important difference between the different Pycnogonida; Dohrn, Pantop. Golf, even says i.e. p. 77: Pallene hal die ganze Larvenentwickelung vollkommen unter- driiekt, das junge Thier, welches die Eischale verlasst, besitzt bereits alle definitive Extremitaten, wenn audi aoch nicht in definitiver Gestalt < >n the following page we find: Wenn der Embryo seine Reife erreicht hat, gleicht er in vielen Beziehungen der Larve von Phoxichilidium , welche den Hydroidpolypen verlasst . In mj opinion the peculiarity in Pallene emaciata, the species mentioned bj Dohrn, is "illy to be found in the fact that the larva completes its development in the egg, in- I g shell; and that this fact is not t<> be underst 1 as something general in the genus, but onl) as a peculiarity in this species among known forms I infer from the fact that in another Pallene- ies, Pallene haslata, 1 have found all larvae free with only three pairs of developed ambulatory », pi. 1, Kg 18 in. In the nearly related genus Pseudopallene I have even found the larva free in its first stage with the two foremost pairs of ambulatory legs not yet quite developed, pi. I, fig.8. In the following I shall enter into further details as to this fact. Also in other genera, for inst in .Vvw- phon, it may he found in the different species that the larvae leave the egg shell sooner or later, with- out an) other difference in the course of development. It is quite another thing that a good bound- really exists, but it can as usual he placed at the origin of the first larval form, here according- ly it i^ to he applied to the form that has been called Protonymphon (Hoekj or the Pantopod- larva 1 Dohrn). Alreadj in the introduction to this section on the larval development, I spoke of the usual misconception with regard to the duration of the embryonal life, and gave a quotation frem the text- hook b) Korschelt and Heider. I have here tried by demonstration on my figures to maintain more in detail that all Pycnogonida pass through the same scries of larval stages, whether the larva Protonymphon frees itself at once, or remains in the egg till all the ambulator) legs ar< developed, even if it has not attained its full length, segmentation, or all its appendages. When the yolk-division is equal the whole blastoderm, onl) excepting the middle and hinder parts of the dorsal side, participates in the form a t ion of the em- bryonal limbs and the proboscis. The embryo is free at once, is considered to be a full) devi larva in the first stage, and is called Protonymphon (Hoek) or Pan- larva kat' exochen 1 Dohrn, Morgan). It is the enormous, overriding development of the embryonal limbs and the proboscis that is this larval form, and this feature is found spread through the whole system nida, and has been known and described in different genera, as Phoxichilidium, Pycno- iltts, Ammothca (Achelia), Ascorhynchus, and Tanystylum. It is also this larval form which I inall) played the greatest | to tin- question of the systematic position of the PYCNOGONIDA. 17 Pycnogonida in a so-called natural system (phylogenesis), several authors, and especially Dohrn, having thought to find the Nauplius-type in it, a conception that Dohrn, however, as is well known, has again abandoned, comp. his Pantopoden des Golfes von Neapel (1889), the section « Phylogenie der Pantopoden , especially p. 87 seq. When the yolk-division is unequal, only the foremost part of the blastoderm participates in the formation of the embryonal limbs and the proboscis, while the hindmost part of this latter with enclosed macromeres appears as a bag-like dilation behind. The embryo remains wholly or partly in the egg, or, if it leave it, the em- bryo remains at or on the father. This larva which is to be regarded as the close of the first larval stage, has hitherto been drawn from a less number of genera than the Protonymphou; besides from the large genus Nymphoii it is also known from the genera Pallene, Pseudopallene , and Zetes (Eitrycydc), and I shall also be able to add some new forms. It may, however, sometimes be questioned whether this larval stage here is to be regarded as Protonvmphon or not. Thus for instance in the hitherto known species of the genus Nymphon a yolk-sack is always found at the close of the first larval stage, but this sack sometimes is so very small, that one may be tempted to regard the larva in this stage as Protonvm- phon, as has been done by Hoek with regard to Nymphon gallic it 111. In both forms this larval stage begins with a contemporaneous development of the three pairs of embryonal limbs, i.e. the chelifori and the embryonal legs, each pair of the limbs representing its metamere with the ganglia, and besides an inter- jacent process with an oral orifice at the point, i.e. the proboscis. A peculiar position is here occupied by the genera Pallene and Pseudopallene , which will be bespoken more in detail at the close of this section. The embryonal limbs accordingly appear at the same time as three pairs of large, flat protuber- ances, warts, or processes on the under side of the blastoderm, anteriorly enclosing the single protuber- ance of the proboscis, comp. my figure of the ovum of Pycnogonum littorale pi. I, fig. 1. All seven lumps are prolonged in a tubiform manner to lengthy processes, pi. I, fig. 2, the foremost free ends of which in the embryonal limbs are segmented by two consecutive segmentations. Of these three pairs of limbs the foremost pair, the chelifori, are almost from the beginning larger than the others, and grow disproportionately, when compared with those, and the hindmost part, the part arising from the trunk, is also more or less distinctly constricted from this as an independent joint, the scape. Further- more the fact has also to be mentioned that the two terminal joints of the chelifori always in the larva form a chela or a pair of pincers, so that these limbs get a very great resemblance to the chelse of the Arachnida. It is a matter of course that this congruity with the said organ of the Arachnida must be carefully taken into consideration when the question is of the systematic affinity of the two groups; another question, however, is, how much importance we shall have to attach to it. Finally is here to be mentioned the gland which is most frequently found in the basal part or the scape of the chelifori, and the shorter or longer thorns, arising from this joint. The two hindmost pairs of limbs, the embryonal legs, are uniform, always much smaller than the chelifori. Their basal part is comparatively short, and never constricted from the bod}-; the first The Ingolf-Expedition. III. 1. J PY< DA. :nl and slender, and the second, or outermost, joint is always still thinner, mosl I, .mil of about the same length as the preceding joint; sometimes, however, this to a long, thin thread more than twice the length of the body, as for inst . p] I. Kg |. The growth of the embryonal legs soon and even if ften the re kept in the following larval stages, the) show no alteration. The pr< like the embryonal legs, begins a> a low protuberance, soon growing im<> •cess with tnon > tapering sides, but without trace of any inner or outer division, ilescing "I" constituent parts. The pharynx, however, is early developed, already in ad it is seen as a dark hue stretching from the point of the proboscis towards its tphofi longitarsey pL II, fig. 20, and in Nymphon macronyxy pi. II, fig. 9. The chitinous serving for the insertion of the Musculi retractores of the pharynx, arc also early developed. With regard to the interpretation of the proboscis I shall take the liberty to state my opinion ady in this place, although my interpretation is chit-fly due to the structure of this organ found in a much more advanced stage of development and especially in the imago. It is the unhapp) note Uatreille to his description of the Pycnogonida, Regne animal, cd. II. Tom IV (1829) which is found again and again The note. I.e. p. 276, note 3, runs thus: I„c siphon . . . m'a offert des sutures ,itudinales, de maniere qu'il me parait compost du labre, de la languette et de deux machoires, le de ensemble . It was to be thought thai Dohm1) had succeeded in demolishing this notion, and I can with all my heart agree with him, when in Pantopoden des Golfes von Neapel (1881) he 5: W'ir wurden . . . keinenfalls aber an eine Verschmelzung von extremitatenartigen Mnndtheilen zu denken haben , I.e. p. 109. We find nevertheless that Adlerz in his fine little essay, Contributions be Morpholog) of the Pantopoda 1 Bidrag till Pantopodernes Morfologi (1888)) tries to maintain the old view of I.atreille. Adlerz founds his arguments especially on the fact that the two low- ermost antimeres (Dohrn) of the proboscis receive nerves from special centra in the first abdominal glion, comp. his fig. 2 on pi. I, and the letters a and ug in this figure. For these two foremost centra with their fibrillous punctuous mass (Leydig: Punktmasse) in connection with the two centra behind them in the same ganglion should show, how this ganglion is composed of three original pairs of ganglia, but it is well known that to each pair of ganglia belongs a metainere with a pair of limbs, which metamere could not then lie anything but the two lowermost antimeres I.e. p. id. To this is to be answered that, as qo trace oi limbs has ever been seen that might corre- be merged in the two antimeres, as little has any trace been found of a pair of foremost, - it has to be remembered that the supply of nerves for tin- two lowermost meta- llic:' perly must be said to arise from the foremost oik- of the two, originall) separated, of ganglia, in which, but not until a later stage, the corresponding foremost ped This view would also agree with my examinations, as I have also riginally uniform, and not until later showing distinct centra with their punctuous mass running into or stretching into the nerves of the Limbs. I think upon ■ the morpholog) t< 1 stress is at present laid upon the ganglia, and mj leer in Untersuchungeti Qber