ae ys Tyle ¥ " Ai, er ee Cre Ae: t AL Can iP - A he * Rape ey ny Silda) # Dy isi ee) 4 -- QR a oo, GY } v.) be no FAUNA NORVEGIA¢ _Bd. 1 BESKRIVELSE AF DE HIDTIL KJENDTE NORSKE ARTER AF UNDERORDNERNE PHYLLOCARIDA 0¢ PHYLLOPODA VED 41 = ns— ay G. O. SARS MED 20, TILDELS FARVETRYKTE PLANCHER — CHRISTIANIA TRYKT 1 AKTIE-BOGTRYKKERIET (Forhen: Det Mallingske Bogtrykkeri.) 1896 aA ee! r FAUNA NORVEGIA DESCRIPTIONS OF THE NORWEGIAN SPECIES AT PRESENT KNOWN BELONGING TO THE SUB-ORDERS PHYLLOCARIDA ayn PHYLLOPODA BY G. O. SARS WITH 20 PLATES, COLOURED AND UNCOLOURED CHRISTIANIA PRINTED BY THE JOINT-STOCK PRINTING COMPANY (Formerly: Det Mallingske Bogtrykkeri.) 1896 FORTALE, ! Neerverende Verk, til hvis Udgivelse Staten har bevilget de fornodne Midler, blev paabegyndt for mere end et Decennium siden; men forskjellige uforudseede Omstendigheder har bevirket, at Ud- arbeidelsen af samme i lengere Tid har maattet standses, saa at forst nu Verket kan udkomme i sin Helhed. Oprindelig var Bevillingen givet til den fortsatte Udgivelse af Fauna littoralis Norvegia, hvoraf tidligere er udkommet 3° Bind, forfattede dels af min Fader alene, dels af ham i Forening med nu afdode Overlege Danielssen og Konservator ‘Koren. Da det forekom mig, at denne Titel paa en mindre heldig Maade vilde komme til at begrendse Stoffet, tillod jeg mig at foreslaa, at Benzvnelsen littoralis udgik og at Verket herefter skulde ud- komme under den her anvendte Titel. Det af mig til neerverende Bind valgte Stof er ogsaa af den Art, at det vanskeligt vilde passe indenfor Rammen _af den tidligere Titel, da jo her ikke blot Sadyr, men ogsaa en Del wegte Ferskvandsdyr er omhand- lede. Idethele syntes mig, at den mere omfattende Titel, Fauna Norvegie, bedre maatte kunne svare til sin Hensigt, da der herunder vil kunne leveres Bidrag til Belysning af hvilkensomhelst Branche af vor Fauna, der maatte frembyde en seerlig Interesse. I Overensstemmelse med de 3 udkomne Bind af Fauna littoralis, tror jeg at nerverende Verk bor indeholde Afhandlinger af en mere udforlig ana- tomisk-biologisk Character, behandlende visse ud- valgte Dele af vor Fauna og udstyrede paa en saa- vidt muligt tidsmessig Maade, saavel hvad Text som Plancher angaar. I et andet, paa engelsk skre- vet Verk har jeg paabegyndt en Bearbeidelse af vor Fauna efter et herfra temmelig forskjelligt Prin- cip, idet dette Verk er nermest beregnet paa at PREFACE. The present work, for the publication of which the Government has granted the necessary funds, was begun more than ten years ago; but various unforeseen circumstances having combined to put a stop to the preparation of the work for a considerable time, it is only now that it can be published in its entirety. The grant was originally given for the continued publication of Fauna littoralis Norvegia, of which three volumes had already been published, written partly by my father alone, partly by him in conjunction with the late Dr. Danielssen, and Curator Koren. As it seemed to me that this title would limit the subject-matter somewhat infelicitously, I ventured to suggest that the desig- nation Jittoralis should be struck out, and that the work should hereafter appear under the title here employed. The matter chosen by me for the pre- sent volume, is also of such a kind, that it could hardly be included under the former title, as not only marine animals, but also some true fresh-water animals are here treated of. Upon the whole, it seemed to me that the more comprehensive title, Fauna Norvegie, would better answer its purpose, as under it, contributions might be made to the infor- mation concerning any branch of our fauna that might offer special interest. In accordance with the 3 published volumes of Fauna littoralis, I think that the present work should contain treatises of a more exhaustive anatomical-biological character, dealing with certain parts of our fauna, and got up as far as possible in a manner suitable to the times, as regards text and plates. In another work, written in English, I have begun an account of our fauna on a very different principle to this, as it is rather calculated to give, as far as possible, a brief, VI give en saavidt muligt kortfattet systematisk Over- sigt af samtlige hidtil kjendte norske Arter, hvor- ved der er lagt hovedsagelig Vegt paa dets prak- tiske Anvendelighed ved Artsbestemmelsen, mindre paa det ydre Udstyr eller paa en mere indgaaende anatomisk Behandling af de enkelte Former. Jeg tror, at zoologiske Arbeider udarbeidede efter ethvert af disse Principer har sin fulde Berettigelse og Nytte Side om Side, og skulde ogsaa af denne Grund onske, at Fauna Norvegie blev forbeholdt mere udforlige Monographier af enkelte mindre kjendte Dyreformer eller af begrendsede Grupper, der maatte frem- byde en serlig Interesse i anatomisk-biologisk Hen- seende. Plancherne til nerverende Bind er i sin Tid udforte paa nu afdode Lithograf Lynghs Officin, og ved deres Udforelse er anvendt al den Omhyggelig- hed og Kunst, som da kunde presteres, saavel hvad Lithographering som Farvetrykning angaar. Texten er i Lighed med de 2 sidste Bind af Fauna littoralis og med Nordhavs-Expeditionens Generalberetning, dobbeltspaltet, den ene Spalte norsk, den anden en- gelsk. Oversettelsen af de 6 forste Ark er besorget af nu afdode Translateur Wilson, Resten af Miss Jessie Muir. Idet jeg herved fremlegger for Offentligheden Iste Bind af Fauna Norvegie, sker det med det Haab, at der maa gives vore fremtidige Zoologer Anledning til at fortsette dette- Verk med flere paafolgende Bind udstyrede paa en for vort Land verdig Maade. Forfatteren. systematic survey of all the hitherto known Nor- wegian species, whereby special importance is laid on its practical applicability in the determination of species, and less on its external get-up, or on a more detailed anatomical treatment of the various forms. I think that zoological works written on these two principles are perfectly legitimate and useful side by side; and I therefore wish that Fauna Norvegie could be kept for more detailed mono- graphs on certain less familiar animal forms, or of limited groups that offered special interest in an anatomical-biological direction. The plates to the present volume were executed, in their time, in the late lithographer Lyngh’s printing-office, and all the care and art of which that time was capable, both as regards lithography and colour-printing, were employed in their execu- tion. The letter-press is similar to that of the last 2 volumes of Fauna littoralis, and to the General Report of the North Atlantic Expedition, being in two columns, the one column Norwegian, the other Eng- lish. The translation of the first 6 sheets was made by the late Mr. Wilson, translator, the remainder by Miss Jessie Muir. 5 In now presenting the first volume of Fauna Norvegie to the public, I do so in the hope that opportunity may be given to our future zoologists to continue this work with successive volumes, got up in a manner worthy of our country. The Author. ; i INDHOLD. ener ge st 3)! Fae Phyllocarida .... Fam. Nebaliide. _ Gen. Nebalia, Leach 1. Nebalia bipes (Fabr.) 2. Nebalia typhlops, G. O. Sars. Phyllopoda . ue. Sectio I. Anostraca . Fam. 1. Branchipodide .. Gen. Branchinecta, Verrill . . Branchinecta paludosa (Miller) Fam. 2. Polyartemiide Gen. Polyarlemia, Fischer _ Polyartemia forcipata, Fischer Sectio II. -Notostraca Fam. Apodide 1¢ Gen. Lepiduwrus, Leach Lepidurus glacialis (Kroyer) Sectio III. Conchostraca Fam. 1. Limnadiide . Gen. Limnadia, Brogniart Limnadia lenticularis (Lin.) . Fam. 2. Limnetide Gen. Limnetis, Lovén . _Limnetis brachyurus (Mall. CONTENTS. Introduction .. . Phyllocarida. . . Fam. Nebaliide . Gen. Nebalia, Leach ; 1. Nebalia bipes (Fabr.) . 2. Nebalia typhlops, G. O. Sars . Phyllopoda Section I. Anostraca Fam. 1. Branchipodide . Gen. Branchinecta, Verrill . Branchinecta paludosa (Miller) Fam. 2. Polyartemiide Gen. Polyartemia, Fischer Polyartemia forcipata, Fischer Section IT. Notostraca Fam. Apodide Gen. Lepidurus, Leach ; Lepidurus glacialis (Kroyer) Section III. Conchostraca Fam. 1. Limnadiide Gen. Limnadia, Brogniart Limnadia lenticularis (Lin.) . Fam. 2. Limnetide . Gen. Limnetis, Lovén . . Limnetis brachyurus (Miill.) 2ThITHOA bal Hie 2 a NT Be NaN VE es. aa orn re a oa ee td ap sasinh Wier ty Aiwa f an yaa Rope 3 hr th Kt om Snbebad eh ee ea veer iA a aR” Soe <2 _itiesé Ranier sis ie * poaey Fi 9 Shh Soa wae ee dane Aa “ea e* a ee telat. A War, Eee my } Sn eae aeke 1 s od Pikes igre {Shes "Ve ey thi n. Sj ; ey te ‘% j INDLEDNING. Crustaceernes vidtloftige Classe inddeles, som bekjendt, ialmindelighed i to store Afdelinger, Mala- costraca, eller de hoiere Krebsdyr, og Entomostraca, eller de saakaldte Smaakrebse. LEnhver af disse Afdelinger lader sig igjen dele i 4 Grupper eller Ordener. Til den forste herer 1) Podophthalmata, eller de stilkoiede Krebse (Decapoda, Schizopoda og Stomatopoda), 2) Cumacea, 3) Isopoda og 4) Amphi- -poda; til den sidste: 1) Branchiopoda, 2) Ostracoda, 3) Cirripedia, og 4) Copepoda. Hertil kommer endnu den i mange Henseender meget anomale, og i visse Punkter med Arachniderne beslegtede Gruppe, Xipho- suré, eller Dolkhalerne, som dog af flere Natur- forskere ikke henregnes til Crustaceerne, men be- tragtes som Typen for en egen Arthropodeclasse. Naar undtages denne sidste Gruppe, er alle de evrige ovenanforte Ordener vel repreesenterede i vor Fauna. For det forste vil vi alene komme til at beskjeeftige os med den forste af de til Entomostra- ceerne horende Ordener, Branchiopoda. Denne Orden har faaet sit Navn deraf, at et storre eller mindre Antal af de bag Munddelene felgende Lemmer an- tager en eiendommelig bladdannet Structur, der gjor dem fortrinlig skikkede til at fungere som Respira- tionsorganer, om de end i enkelte Tilfelde paa samme Tid kan fungere som Svemmeapparater. Undertiden, saaledes hos visse Cladocerer, kan disse Lemmers saavel respiratoriske som motoriske Func- tion vere meget reduceret, hvorimod de faar sin vesentligste Betydning som Griberedskaber, der understetter Munddelene ved at fastholde og bringe til Munden de Fodemidler, hvoraf disse Dyr lever, en Function, som imidlertid ogsaa for en Del kan paavises hos Former med forevrigt normalt udvik- lede Branchialfodder, f. Ex. Apus. Ogsaa hos fuld- 1— G. 0. Sars: Fauna Norvegiz. INTRODUCTION. As is known, the extensive class Crustacea is, in general, classified into two great divisions viz., Malacostraca, or the higher Crustaceans, and En- tomostraca, or the so-called lower Crustaceans. Each of those divisions may be subdivided, again, into 4 groups or orders. To the first division per- tain: — 1) Podophthalmata or the stalk-eyed Crusta- ceans (Decapods, Schizopods and Stomapods), — 2) Cumacea, — 3) Isopoda, and — 4) Amphipoda. To the second division pertain: — 1) Branchiopoda, — 2) Ostracoda, — Cirripedia, and — 4) Copepoda. To them is added the Xiphosure, or sword-tails — in many respects very anomolous, and in certain cha- racters relat«d to the group Arachnida — which are by several naturalists, however, not assigned to the Crustaceans, but is considered to be the type of a special class af Arthropods. With the excep- tion of that last-named group all the other above- mentioned orders are well represented in the Nor- wegian Fauna. At present we shall only occupy ourselves with the first of the orders pertaining to the Entomostracans viz: Branchiopoda. This. order has obtained its appellation from the circumstance, that a larger or smaller number of the appendages behind the oral parts assume a peculiar foliaceous structure, which causes them to be admirably adapted to serve as respiratory organs, even although they, in a few cases, may at same time serve as swimming apparatuses. Occasionally, as in certain Cladocerans, both the respiratory and motoric func- tions of these appendages may be greatly diminished; and their essential importance becomes that of a prehensile-apparatus which aids the oral parts in securing and carrying to the mouth the nutriment upon which these animals feed; a function which kommen typiske Branchiopoder vil vi finde, at Lem- | ‘4 . ‘ : . : | merne, ved Siden af sin Function som Respirations- | organer, altid er af vesentlig Betydning for Til- veiebringelsen af Foden, idet de ved sine rythmiske Bevegelser frembringer en continuerlig Stremning af Vandet ind mod Munden, hvorved de Smaa- partikler, hvoraf Dyret lever, bringes indenfor Mund- delenes Omraade. I ethvert Fald maa den oven- omtalte eiendommelige Modification af Lemmerne, hvortil vi egentlig ikke har noget tilsvarende hos andre Crustaceer, .betragtes som den for de her om- handlede Dyr vigtigste og mest udpregede Cha- racter. ' Branchiopoderne indtager i flere Henseender en central Stilling inden Crustaceernes Classe, og Prof. Claus har endog fremsat den Hypothese, at alle nulevende Crustaceer i sidste Instans nedstammer fra en phyllopodeagtig Dyreform (Protophyllopod). Skjondt denne Hypothese af andre Zoologer (Packard) har veret bestridt, er der dog al Grund til at an- tage, at disse Dyr har conserveret adskillige Cha- racterer/ der efter al Sandsynlighed er i hoi Grad primitive og maaske endog skriver sig fra de eldste paa vor Klode optreedende Arthropoder. Allerede det i hai Grad varierende og ofte excessivt foragede Antal Kropssegmenter, samt disses ialmindelighed mindre skarpt udpreegede Gruppering til distincte Kropsafsnit, synes at vise, at vi her har at gjore med Former af en kun lidet udarbeidet Character, hos hvem endnu ikke det for Nutidens Crustaceer typiske Forhold rigtigt har festnet sig; og hvad Lemmernes Bygning angaar, saa er vel alle enige i at de, ialfald hos de typiske Branchiopoder, repre- senterer et mere primitivt Standpunkt end hos nogen af de ovrige Crustacegrupper. Ogsaa hvad den indre Organisation angaar, findes hos de herhen horende Former kun lidet fixerede Forhold, men derimod en Mangfoldighed af Modificationer i Bygningen af snart sagt alle Organer, hvad der ligeledes giver denne Crustacegruppe et ganske eiendommeligt Preeg lige- overfor de ovrige Ordener. Endelig vil vi i disse Dyrs Levevis, Forplantning og Udvikling stede paa baade characteriske Forskjelligheder mellem de for- skjellige Former og tildels ogsaa hoist eiendomme- lige, fra samme hos andre Crustaceer afvigende For- hold. Et neiere Studium af denne Crustacegruppe vil derfor ogsaa veere af serlig Interesse, saavel i phylogenetisk som biologisk Henseende og vil pas- sende kunne tjene som Udgangspunkt ved Bearbei- delsen af den her omhandlede Dyreclasse. may also, to some extent, be demonstrated in forms with otherwise normally developed branchial-legs e. g. Apus. Also in perfectly typical Branchiopods we may observe that the appendages, besides their function as respiratory organs, are always of mate- rial importance in the procuring of the nutriment, as they by their rhythmical movement produce a continuous current of the water in towards the mouth, by which the minute particles upon which the animal exists are brought within the range of the oral parts. At any rate, the above mentioned peculiar modification of the appendages, to which we meet with nothing really correspondent in other Crustaceans, must be considered to be the most important and prominent characteristic of the ani- mals here spoken of. The Branchiopods occupy, in several respects, a central position in the class of the Crustaceans, and _ Prof. Claus has even proposed the hypothesis, that all the now-existent Crustaceans may descend, in the final instance, from a phyllopodous animal-form (Protophyllopod). Although that hypothesis has been rejected by other zoologists (Packard), there is still every reason to assume that those animals have retained several characteristics which are, in all probability in a high degree primitive, and perhaps even emanate from the-oldest Arthropods that have appeared on our Earth. The extremely vari- able and frequently excessively increased number of body-segments, as well as in general their less distinctly prominent grouping into distinct’ sections, at once appears to point to the circum- stance that we have here to do with forms of only vaguely developed character, in which the typical fea- tures characteristic of the modernly existent Crusta- ceans, have not yet become permanently established: and as regards the structure of the appendages all unite, we believe, in the opinion that it, at any rate in the typical Branchiopods, represents a more pri- mitive condition than in, any of the other groups of Crustaceans. Also in regard to the internal or- ganization there is found, in the forms belonging to this order, only little of permanent features but, on the other hand, a multitude of modifications in the structure of, it may be said, all the organs, a circumstance that also imparts to this group of Crustaceans a quite peculiar imprint compared with the other orders. Finally we meet in these ani- mals’ mode of life, propagation and development, both characteristic differences between the various forms and partly, also, highly peculiar features differing from those in other Crustaceans. eller «Thorax», men som maaske mere passende bor kaldes Midtkroppen (mesosome), bestaar af 8, i sin hele Omkreds tyde- ligt sondrede, og ensformigt udviklede Segmenter, der hvert berer et Par Branchialfodder. Omvendt hvad Tilfeldet er med Hovedet, har. dette Afsnit sin sterste Udstrekning ventralt, idet begge Afsnit forbinder sig med hinanden langs en meget skraat gaaende Linie. Maalt langs Dorsalsiden er det her omhandlede Afsnit derfor neppe lengere end Hove- det, medens det ventralt er nesten dobbelt- saa langt. Bagtil forbinder det sig med Bagkroppen, uden at vere afsat fra samme ved nogen merkbar Indknibning. Det forreste Afsnit af Bagkroppen («, urosome) which forms the immediate continuation of the anterior one’) and diminishes evenly and ra- pidly backwards (see Pl. I figs. 1 and 2) consists also of 2 segments, of which the 2 foremost ones are furnished with rudimentary ventral appendages, while the 2 hindmost ones are quite devoid of such appendages. It is cylindrical in form, almost twice as long as the foremost section, and has the po- sterior edge of the 3 foremost segments regularly 1) In the gen. Paranebalia this section is sharply defined from the preeabdomen. skilte, tilspidsede Plader, der delvis dekker Anal- aabningen nedentil (se Tab. III, Fig. 12). @inene (Tab. II, Fig. 1 og 7, 0, Fig. 3 og 4), der er feestede temmelig ner sammen ved den forreste Ende af Hovedet, lige under Pandepladens Basis, er vel udviklede og omtrent af Pandepladens halve Lengde. De er tydeligt stilkede og meget frit be- vegelige, saa at de snart kan rettes ud til hver Side, snart legges tet ind mod hinanden og boies nedad, i hvilket Tilfeelde de ganske skjules mellem den forreste Del af Rygskjoldets Valvler. Af Form er de noget sammentrykte, aflangt ovale, eller new- sten halvmaanedannede, med den ydre Del noget udvidet og skjevt afrundet, endende nedentil i et vinkelformigt Hjerne. Forkanten af Oiet er ganske glat, uden Spor af de sterke Sagtakker, som findes her hos Sl. Paranebalia. Qiepigmentet, der hos det levende Dyr er af en vakker purpurrod Farve, fyl- der nesten ganske den ydre Halvpart af Qiet, og fra det udstraaler til alle Kanter talrige Synsele- menter, i Form af smaa sterkt lysbrydende Legemer (Krystalkegler) af kort peredannet Form. Derimod mangler den @iet omgivende Hud (Cornea) ganske ethvert Spor af nogen egentlig Facettering som hos ‘de heiere Crustaceer. Hvert Qie dekkes ved Roden af en fra Pandedelen udspringende skjelformig, i en skarp Spids udgaaende Plade, der nesten rekker til Midten af Wiets Leengde (se Fig. 3, 4). De ovre Folere (Tab. II, Fig. 1, a’, Fig. 5), der udspringer lige under Winene, er af kraftig, nesten fodformig Bygning og, lige udstrakte, omtrent af af Forkroppens Lengde. Man kan paa dem adskille et tykkere, dobbelt vinkelbsiet Skaft og 2 terminale Vedheeng af ulige Form, hvoraf det ene har Ud- seendet af en skjelformig Plade, det andet af en forlenget, mangeleddet Svebe. Skaftet bestaar af 4 Segmenter, hvoraf de 2 yderste er fast forbundne med hinanden, medens det foregaaende (2det) Led har en meget bevegelig Articulation saavel med iste som 3die Led. iste Led af Skaftet er, som det synes meget fast forbundet med Hovedet og kun lidet bevegeligt, hvorfor det ved Dissection vanske- ligt kan erholdes i Forbindelse med den ovrige Del. Det er (se Fig. 1, Fig. 7 a‘) af oval Form, uden en- hver Borstevebning og opfyldt med sterke Muskel- 13 serrated, as in the posterior segments of the former. The caudal rami are articulated to the extremity of the last segment; they appear. to correspond to the so-called furca of the Copepods, and may, therefore, be most properly considered to be a bifurcated terminal segment. Below the base of the candal ‘rami the last segment projects into 2, by a narrow median incision, separated acuminate lamella which partly cover the anal aperture beneath (see Pl. IIT fig. 12). The eyes (Pl. II, fig. 1 and 7, 0, figs. 3 and 4), which are secured pretty closely together at the foremost extremity of the head, just below the base of the frontal plate, are well deyeloped and about half the length of the frontal plate. They are distinctly stalked and very freely mobile, so that they may be directed, now to each side now laid close in to each other and bent downwards, in which case they become quite concealed between the foremost part of the valves cf the carapace. In form they are somewhat compressed, oblongo- oval, or almost semi-lunar, with the outer part somewhat expanded and obliquely rounded, ter- minating below in an angular corner. The anterior edge of the eye is perfectly smooth without trace of the powerful sawteeth found in the gen. Paranebalia. The ocular pigment, which, in the liv- ing animal, has a beautiful purple-red colour, occu- pies almost completely the outer half of the eye, and from it radiate numerous visual elements in all directions, in the form of small, strongly re- fractive bodies (crystal cones) of short pyriform shape. On the other hand the enclosing integument (cornea) of the eye is quite deficient in every trace of any real facets such as exist in the higher Cru- staceans. Hach eye is covered at the base by a squamiform plate that issues from the frontal part, and terminates in a sharp point which reaches nearly to the middle of the length of the eye (see figs. 3, 4). The superior antenne (PI. II, fig. 1 a‘, fig. 5), which issue just under the eyes, are of powerful, almost pediform structure, and when straightly extended are about same length as the anterior division of the body. We can in them distinguish a thickish doubly geniculated peduncle and 2 terminal appen- dages of dissimilar form, of which the one has the appearance of a squamiform plate, the other of a pro- longed multi-articulate flagellum. The peduncle con- sists of 4 segments, of which the two outermost ones are firmly attached to each other, while the preceding joint (2nd) has a very flexible articulation both with the Ist and 3rd joints. The Ist joint of the peduncle is, apparently, very firmly connected to the head and but little flexible, hence it can with difficulty be obtained on dissection, in union with the remaining part. It is oval in form (see fig. 1, knipper, der tjener til at bevege den ovrige frie Del af Foleren. 2det Led, der ialmindelighed er rettet lige fortil, dannende med Iste en mere eller mindre tydeligt udpreget albuformig Boining, er omtrent saa langt som de 2 folgende tilsammen og noget forstykket paa Midten, nesten tendannet. Det beerer i Midten af den ovre Kant en enkelt sterk Fjerborste og i den nedre Kant, nermere Enden, en Rad af omkring 8 saadanne, der hurtigt aftager i Leengde udad; ved Spidsen af Leddet findes des- uden et Knippe af divergerende simple Borster. 3die Led, der sedvanlig med det- foregaaende danner en meget sterk, retvinklet kneformig Boining, er noget indknebet ved Basis, men udvides successivt mod Enden, der er skjevt afskaaret i Retningen forfra bagtil.. Det har i hver Kant, ner Enden, en Rad at cilierede Borster, hvoraf de i Bagkanten er leengst. ade Led er meget kort og bredt, nesten triangulert vg ligesom foregaaende skjevt afskaaret i Enden, men i modsat Retning, hvorved dets Bagkant bliver meget kort. Forkanten er bevebnet med en Rad af» korte Torner og ender med et noget sammentrykt, kort triangulert Fremspring, der ved Spidsen berer en noget sterre Torn’). Af de 2 terminale Vedheng har det forreste Formen af en oval Plade, omtrent af samme Leengde som Skaftets 3die Led, og langs Yderkanten og Spidsen tet besat med fine haar- formige Borster ordnede i to Rader. Det bagre Vedheng, der repreesenterer den egentlige Svobe, er omtrent af Skaftets Lengde og afsmalnes successivt mod Enden. Den bestaar af omtrent 15 Led, hvoraf dog de 3 forste ikke er tydeligt sondrede fra hin- anden. Hvert Led berer ved Enden i Forkanten et Knippe af smaa Borster, hvoraf nogle har Charac- teren af Sandsevedheng (Lugtepapiller), og i Bag- kanten en enkelt simpel Berste. Hos den endnu ikke slegtsmodent udviklede Han (Fig. 1) ligner disse Falere temmelig samme hos Hunnen, alene med den Forskjel, at Sveben er mere opsvulmet ved Basis og delt i et noget storre Antal Led. De nedre Folere (Fig. 1, a?, Fig. 6), som ud- springer tet bag de ovre, mangler ganske det blad- formige Vedheng, men er forovrigt byggede efter samme Type som hine og har ligeledes Skaftet dob- belt geniculeret. 1ste Led er, som paa de ovre, meget fast forbundet med Hovedet, sterkt musculost ') Hos Sl. Paranebalia er dette Fremspring betydelig storre og grovt sagtakket i Forkanten. 14 fig. 7, a1), without trace of any setaceous armature, and filled with strong muscular bundles,{which serve to move the remaining free part of the antenna. The 2nd joint — which is usually directed straight forward, forming with the 1st a more or less dis- tinctly marked elbow-shaped bend — is about as long as the 2 succeeding ones together and some- what tumefied at the middle, almost fusiform. It carries in the middle of the upper edge a single strong, plumose bristle, and on the lower edge, nearer the extremity, a series of about 8 similar bristles that rapidly diminish in length outwards: at the tip of the joint there is, further’ observed a bundle of divergent simple bristles. The 3rd joint, which with the preceding one usually forms a very strong right-angled geniculate bend, is somewhat con- stricted at the base but gradually expands towards the extremity, which is obliquely truncated in a direc- tion from before backwards. It has on each edge, near the extremity, a series of ciliated bristles, of which those on the posterior edge are the longest. The 4th joint is very short and broad, almost triangular, and like the preceding one obliquely truncated at the extremity but in the opposite direction, causing its posterior edge to be very short. The anterior edge is armed with a series of short spines and termin- nates in a somewhat compressed short triangular prominence, which at the point carries a somewhat largish: spine’). Of the two terminal appendages the foremost one has the form of an oval lamella, about the same length as the 3rd joint of the pe- duncle, and along the outer edge and at the point it is closely beset with delicate capilliform bristles arranged in two series. The posterior appendage, which represents the flagellum proper, is about same length as the peduncle and tapers gradually towards the extremity. It consists of about 15 joints, of which, however, the 3 first ones are not distinctly separated from each other. [ach joint carries at the extremity, on the anterior margin, a bundle of small bristles, of which some have the nature of sensory appendages (olfactory papille), and on the posterior edge a single simple bristle. In the still incompletely sexually developed male (fig. 1) these _antenne resemble pretty much those of the female, with the sole difference, that the flagellum is more tumefied at the base and divided into a somewhat. larger number of joints. The inferior antenne (fig. 1 a®, fig. 6) which issue close behind the superior ones, are completely without the foliaceous appendage, but are constructed, other- wise, according to the same type as those, and have also the peduncle doubly geniculated, The 1st joint is, as in the superior ones, very firmly united to ') In the gen. Paranebalia, this prominence is considerably larger and coarsely serrated on the anterior edge. og uden enhver Borstebevebning. 2det Led, der omtrent er af samme Storrelse som liste, mangler ligeledes Borster, men gaar fortil ud i et kort tand- formigt Fremspring. Den ydre Del af Skaftet dan- ner ogsaa her en steerk kneformig Boining med fore- gaaende Led, men bestaar kun af et enkelt Led, paa hvilket dog en oprindelig Tvedeling er antydet ved en skarpt markeret Afsats baade fortil og bagtil ’). Til den bagre Afsats er festet en sterk Fjerborste, og langs Forkanten af Leddet findes en hel Del saa- danne Borster, tildels af betydelig Leengde, navnlig ved Enden, hvor de delvis er krandsformigt’ stillede omkring Leddet. Desuden findes langs den ovre Halvpart af Forkanten en Rad af Smaatorner, der nedad successivt tiltager i Lengde, og en Del lig- nende Torner bemerkes ogsaa ved Enden af Leddet fortil mellem Borsterne. Sveben er betydelig (ne- sten dobbelt) lengere end paa de ovre Folere og bestaar af omkring 20 berstebesatte Led, hvoraf dog de 3 eller 4 inderste er mindre tydeligt begrendsede. Hos den endnu ikke slegtsmodent udviklede Han skiller disse Folere (Fig. 1, a”) sig vesentlig kun derved, at Svoben er meget tet ringet, eller delt i et stort Antal, endnu ufuldstendigt begreendsede Led. Overleben (Fig. Ps L, Fig. 8), der til Siderne ganske dekkes af de nedre Foleres Basalled, danner et tydeligt convext Fremspring af afrundet Form og med den bagre Kant svagt indbugtet i Midten samt her besat med fine Haar. Underleben (Fig. 7, 1, Fig. 9) ‘er meget liden og vanskelig at isolere. Den har imidlertid fore- kommet mig at frembyde det Fig. 9 fremstillede Udseende af en i Midten dybt indskaaret og delvis cilieret Plade. Kindbakkerne (Fig. 1, M, Fig. 10) har et for- holdsvis meget lidet Corpus, hvis ydre Del er baad- formig og ender opad i en Spids, hvormed det arti- culerer til Rygskjoldets indre Flade. Dets indre Hule er fyldt med de strke, i Midten ved en chitin- agtig Sene forbundne Adductormuskler (se Fig. 10), og fra den bagre Kant udgaar en tynd Chitinsene, hvyortil Kindbakkernes Rotationsmuskler fester sig. Den nesten under en ret Vinkel med det ovrige Corpus indboiede Tyggedel er (se Fig. 11) i Enden delt i 2 Grene, hvoraf den ydre har Formen af en liden trianguler Lamelle, der svarer til det tandede Parti (cutting edge) hos andre Crustaceer, medens ') Hos Sl. Nebaliopsis bestaar denne Del af 2 tydeligt be- grendsede Led. 15 the head, strongly musculous, and without any ar- mature of bristles. The 2nd joint, which is about the same size as the 1st one, is also quite deficient in bristles, but passes, in front, into a short denti- form projection. The outer part of the peduncle also forms here a strongly geniculated bend with the preceding joint, but consists of only a single joint, upon which, however, there is an indication of an original subdivision in the shape of a sharply defined ledge both in front and behind’). Attached to the posterior ledge there is a powerful plu- mose bristle, and along the anterior edge of the joint quite a number of such bristles may be observed, partly of considerable length, especially at the ex- tremity, where they are partly arranged in a ver- ticillate manner around the joint. Further, there may be observed along the upper half of the an- terior edge a series of small spines, which gradu- ally increase in length below; and a number of similiar spines are also observed at the extremity of the joint in front, between the bristles. The fla- gellum is considerably longer (nearly double) than on the superior antenne, and consists of about 20 joints beset with bristles, of which, however, the 3 or 4 innermost ones are less distinctly defined. In the not yet sexually fully developed male these_ antenne distinguish themselves chiefly (fig. 1, a”), only by the circumstance that the flagellum is very closely annulated, or divided into a large number of still imperfectly defined joints. The anterior lip (fig. 7 L, fig. 8) which, at the sides, is quite covered by the basal joints of the inferior antennz, forms a distinctly convex promi- nence of rounded form, with the posterior margin faintly hollowed in the middle and beset here with delicate hairs. The posterior lip (fig. 7 1, fig. 9) is very small and difficult to isolate. It appears, however, to me, to present the appearance of a partly ciliate lamella, deeply incised in the middle, as shown in fig. 9. The mandibles (fig. 1, M, fig. 10) have, relati- vely, a very small corpus, whose outer portion is navicular in form and terminates above in a point, by which it articulates with the inner surface of the carapace. Its inner cavity is occupied by the pow- erful adductor, muscles, which are connected in the middle by a chitinous tendon (see fig. 10), and from the posterior margin a thin chitinous tendon issues, to which the rotatory muscles of the mandibles are attached. The masticatory part, which is bent inwards almost at a right angle to the remaining corpus (see fig. 11), is divided at the extremity into 2 rami, of which the outer has the form of a *) In the gen. Nebaliopsis this part consits of 2 distinctly defined joints. den indre og betydelig sterre Gren svarer til Molar- processen. Den forste er ganske simpel og har kun strax indenfor Spidsen et yderst lidet tandformigt Fremspring. Den sidste er af cylindrisk Form, lidt buet, og har som sedvanlig Enden fint riflet samt mere tvert afkuttet paa hoeire end paa venstre Kindbakke. Palpen (Fig. 1, 7, Mp, Fig. 10), der ud- gaar fra Corpus noget fortil paa det Sted, hvor Tyggedelen forbinder sig med den ydre, baadformige Del, er af serdeles betydelig Storrelse, nesten 3 Gange saa lang som selve Corpus, og viser en Byg- ning idethele overensstemmende med samme hos hoiere Crustaceer, navnlig Amphipoderne. Den be- staar af 3 skarpt begreendsede Segmenter eller Led, alle omtrent af ens Sterrelse, eller kun ganske lidt tiltagende i Leengde udad. 1ste Led er simpelt cylin- driskt, dog noget fortykket i hver Ende, og mangler ganske Borster. Det forbinder sig med 2det Led paa en ganske egen Maade, saa at begge med hin- anden danner et Slags Knee. 2det Led er i sit ba- sale Parti noget opsvulmet og danner umiddelbart indenfor Ledfoiningen med iste, en albuformig Ud- vidning. Det afsmalnes successivt mod Enden og har i Midten af Yderkanten 3—5 tynde Borster. Sidste Led, der er meget bevegeligt forbundet med Zdet, er temmelig smalt, sterkt. sammentrykt fra Siderne og ganske lidtbredere i sit ydre Parti, som er jevnt tilrundet i Enden. Det berer langs den nedadvendte skarpe Kant en tet Rad af fint cili- erede, toleddede Borster og har desuden ved Spid- sen nok en Rad af meget fine og sterkt krummede Borster. Leddets svre Kant mangler Borster, men viser i sit bagre Parti en serdeles fin Ciliering. I sin normale Situs convergerer de to Palper sterkt ved Basis (se Fig. 10), saa at 2det Led paa begge kommer til at ligge tet sammen i Juxtaposition, indenfor Basalleddene af de 2 Par Folere. Sidste Led paa hver divergerer igjen noget og treeder frit frem enten foran eller mellem Folernes Rod (se Fig. 1, Mp). ° ; Iste Par Kjever (Tab. I, Fig. 1 & 7, m', Tab. II], Fig. 1) er af afrundet Form og gaar indad ud i to korte, stumpt afrundede Tyggelappe, hvoraf den ydre er storst, nesten af oxedannet Form og, foruden med nogle tildels cilierede Berster, beveebnet i sit bagre Parti med en Gruppe af smaa, i Enden tve- delte Torner (Fig. 1a). Den indre Tyggelap er for- holdsvis liden, af membranes Beskaffenhed og paa den nesten tvert afkuttede Ende forsynet med en tet Rad af seerdeles fine cilierede Borster, foruden en Del korte Torner. Fra Enden af disse Kjever i] 16 small triangular lamella, which corresponds to the denticular portion (cutting edge) in other Crusta- ceans; while the inner, considerably larger ramus. corresponds to the molar expansion. The first-named is quite simple, and has, immediately inside the point, only an extremely small dentiform prominence. The last-named is cylindrical in form, slightly curved, and, as usual, has the extremity finely fluted and more obtusely truncated on the right than on the left mandible. The palp, (fig. 1, 7, Mp. fig. 10), which issues from the corpus a little in advance of the place where the masticatory part is con- nected to the outer navicular- part, is of parti- cularly large size, almost 3 times as long as the corpus itself, and exhibits a structure corresponding, upon the whole, with that of the higher Crustaceans, especially the Amphipods. It consists of 3 sharply defined segments or joints, all of about the same size, or only quite slightly increasing in length out- wards. The 1st joint is simple cylindric in form but. somewhat tumefied at each extremity, and is quite devoid of bristles. It is connected to the 2nd joint in quite a peculiar manner, so that they form with each other a kind of knee. . The 2nd joint is some- what tumefied in its basal part, and forms imme- diately inside the articulation to the 1st joint an elbow-shaped expansion. It diminishes gradually towards the extremity, and has 4—5 slender brist- les on the middle of the outer margin. The ter- minal joint, which is very flexibly connected to the 2nd one, is pretty narrow, strongly compressed from the sides and quite slightly broader in its outer part, which is evenly rounded at the extremity. It bears along the downward bent sharp margin a close series of delicate double-jointed bristles, and has, further, at the point, yet another series of very delicate and strongly bent bristles. The upper mar- gin of the joint has no bristles, but exhibits a parti- cularly delicate ciliation in its posterior part. In its normal situs the 2 palpi converge strongly at the base (see fig. 10), so that the 2nd joint of each — lies in close juxtaposition inside the basal joints — of the 2 pairs of antenna. The terminal joint of each diverges again a little, and appears freely forward either in front of or between the bases of the antenne (see fig. 1, Mp). The 1st pair of maxille (Pl. LI, figs 1 and 7, m!; Pl. III, fig. 1) are rounded in form and pass over, inwards, into two short, obtusely rounded mastica- tory lobes, of which the outer one is the largest, almost securiform, and armed, besides with some partly ciliate bristles, also, in its posterior part, with a group of minute spines bifurcated at the ex- tremity (fig. 1a). The inner masticatory lobe is relatively small, of membranous nature, and fur- nished on the. almost obtusely truncated extremity with a close series of delicate ciliate bristles besides udgaar et besynderligt, sterkt forlenget Vedheng (Tab. ILI, Fig. 1, p), som ifolge sit Udspring aaben- bart representerer en eiendommeligt modificeret Palpe. Den bestaar af en noget tykkere, med en Del tynde Muskelbundter fyldt Basaldel, og en tynd Endesnert, som dog begge gaar ganske umerkeligt over i hinanden. Basaldelen, der paa 2 forskjellige Steder har et Bundt af tynde divergerende Borster, viser strax ved sit Udspring en abrupt dobbelt vinkelformig Boining udad og bagtil, hvorfor den tynde, nesten bersteformige Endedel bliver rettet skraat bagtil og opad langs Siderne af Truncus, rekkende med sin Spids lige op til dennes dorsale Flade (se Tab. II, Fig. 1, m'). Langs den ene Kant af denne Endedel er med korte Mellemrum festet circa 16 lange og tynde, ucilierede Borster og til Spidsen 3 lignende; alle Borster viser i Enden en eiendommelig, nesten korketreekkerformig Krumning og er temmelig stive, samt vende ialmindelighed nedad og indad. Angaaende dette eiendommelige Vedhengs Function, er der ingen Tvivl om, at det tjener til at rense Rygskjoldets Hule, og dermed ogsaa de tandre Branchialfedder, for fremmede i den indtreengende Dele, i Lighed med hvad Tilfeeldet er med det bagre Fodpar hos visse Ostracoder (Cypri- dinider, Cyprider). 2det Par Kjever (Tab. II, Fig. 1 og 7, m?, Tab. III, Fig. 2) er udpreget pladeformige og af temme- lig compliceret Bygning, mest mindende om samme hos de heiere Crustaceer (Podophthalmia). Man kan paa dem adskille en af 2 utydeligt begrendsede Segmenter bestaaende Basaldel og 2 fra denne fortil udgaaende Grene. Basaldelen har indad 4 borste- besatte Lappe, der utvivlsomt svarer til Tyggelap- pene paa Iste Par, med den Forskjel, at hver Tygge- lap her altsaa er dobbelt eller delt i to. Den for- reste af disse 4 Lappe er imidlertid meget liden, knudeformig og berer 6 lange, cilierede Borster. De 3 evrige Lappe er ligeledes borstebesatte paa den tvert afkuttede Ende; men Borsterne er her meget kortere og tettere samt delvis ordnede i flere Rek- ker. Den midterste af disse 3 egentlige Tyggelappe er betydelig smalere end de 2 ovrige, som omtrent indbyrdes er af ens Storrelse. Af de 2 Endegrene er den indre (p), der forestiller Endognathen eller Palpen, af betydelig Storrelse, noget afsmalnende mod Enden og delt i 2 vel begreendsede Led, hvoraf det Iste er storst. Begge Led er i Inderkanten be- _ satte med talrige cilierede Borster, delvis ordnede i 2 Rekker, og en af de fra Spidsen udgaaende ud- merker sig ved betydelig Lengde. Den ydre Gren (ex), eller Exognathen, er betydelig mindre end den indre og rekker neppe udover dennes Iste Led. Den har Formen af en meget smal elliptisk Plade, der langs hele Inderkanten og Spidsen er forsynet 3 — G. 0. Sars: Fauna Norvegiz. 17 ally of about the same size. a number of short spines. From the extremity of these maxille a strange, greatly prolonged appen- dage issues (Pl. III fig. 1, p.) which judged by its origin evidently represents a peculiarly modified palp. It consists of a somewhat thickish basal part occupied by a number of thin bundles of muscles, and a slender terminal lash which, however, pass imperceptibly the one into the other. The basal part, which in two different places lias a bundle of slender divergent bristles, exhibits, ifimediately at its origin, an abrupt double-kneed bend outwards and back- wards, which causes the thin, almost setiform ter- minal part to become directed obliquely backwards, and upwards along the sides of the truncus reaching, with its point, quite up to its dorsal surface (see Pl. II, fig. 1 m’). Along the one margin of this terminal part there are secured at short inter- vals, about 16 long, slender, non-ciliate bristles, and 3 of the same kind at the tip: all the brist- les exhibit at the extremity a peculiar, almost cork- serew-shaped bend and are rather stiff, and generally turn downwards and inwards. Reyarding the func- tion of this peculiar appendage, there is no doubt that it serves to clean the cavity of the carapace, and at same time the delicate branchial legs of foreign, to it penetrating, substances, like what is the case with the posterior pair of legs in certain Ostracods (Cypridinids, Cyprids). The 2nd pair of maxille (Pl. II, fig. 1 and 7, m?; Pl. IIT fig. 2) are of distinguished lamelliform shape, and of rather complex structure, reminding one most of the same maxille in the higher crustaceans (Po- dopthalmia). We can in them distinguish a — of 2 indistinctly defined segments constructed — basal part, and two branches issuing from it in front. The basal part has, inwards, 4 lobes beset with bristles which indubitably correspond to the masti- catory lobes of the ist pair, with this difference, that each masticatory lobe is here double or bifur- cated. The foremost of these 4 lobes is, however, very small, nodiform, and carries 6 long ciliated bristles. The 3 remaining lobes are also beset with bristles on the obtusely truncated extremity; but the bristles are here much shorter and closer and, also, partly arranged in several series. The mesial one of those. 3 masticatory lobes proper is consider- ably narrower than the 2 others, which are mutu- Of the 2 terminal branches, the inner one (p) which represents, the endognath or the palp, is of considerable size, dimi- nishing somewhat towards thie extremity, and divided into 2 well defined joints, of which the Ist one is the largest, Both joints are on the inner margin beset with numerous ciliated bristles, partly arranged in 2 series, and one of them issuing from the point distinguishes itself by its great length. The outer branch (ex), or the exognath, is considerably smaller med en regelmessig Rad af temmelig lange, fint cilierede Randborster. De 8 Par Branchialfodder, som umiddelbart folger efter Kjewverne, er alle byggede efter samme Type og ligger tet ind mod hinanden i Form af tverstillede Plader, noget mere convexe fortil end / bagtil (se Tab. II, Fig-1). De tiltager noget i Stor- relse indtil 4de Par og aftager saa igjen successivt bagtil. Paa dem alle kan man (se Tab. III, Fig. 3—6) adskille 3 fra en felles Basis udgaaende Ho- veddele, som vi, i Lighed med hvad man pleier hos andre Krebsdyr, kan benevne: Endopodit (p), Exopodit (ex) og Epipodit (ep).. Den felles Basaldel bestaar, som paa 2det Par Kjever, af 2 ufuldkom- ment sondrede Segmenter, der i Inderkanten har en dobbelt Rad af Borster, hvoraf de paa 1ste Segment delvis udmerker sig ved betydelig Langde. Endo- poditen (p), der danner den umiddelbare Fortsettelse af Basaldelen, danner en mod Enden successivt af- smalnende Stamme, paa hvilken der er en svag An- tydning til Segmentering. Denne Del er hos den zgberende Hun betydelig sterkere forlenget end hos yngre Individer af begge Kjon og har sidste Led vel sondret, noget omboiet og besat med ser- deles lange divergerende Fjerborster, der delvis rager frem nedenfor Rygskjoldets Valvler (se Tab. I, Fig. 1). Forovrigt er Endopoditen langs hele Inder- kanten besat med Borster, der fordetmeste er ord- nede i en dobbelt Rad og umiddelbart fortsetter de paa Basaldelen forekommende Borstereekker. Exo- poditen (ex), der er festet til Basaldelens 2det Segment, udenom Endopoditen, har Characteren af en bred, langs Midten med en noget fortykket _ Ribbe forsynet Plade, noget forskjellig i Form paa de forskjellige Branchialfodder. Paa Iste Par (Tab. III, Fig. 3) er den regelmessig oval og i Yderkanten besat med en Rad af circa 18 tynde Borster, til- tagende i Lengde mod Spidsen. Paa de folgende Par (Fig. 4, 5) bliver den successivt noget sterre og sterkere udvidet i Enden, som er skjevt afrundet og kun besat med faa og spredte Randborster. Paa sidste Par endelig (Fig. 6) har den antaget en tem- melig smal elliptisk Form. Epipoditen (ep), der ved en kort Stilk er festet til Ydersiden af Basaldelens Iste Segment, er af serdeles betydelig Storrelse, saa. at den mere eller mindre fuldstendigt dekker de evrige Dele, naar disse Lemmer sees in situ fra Ydersiden (se Tab. II, Fig. 1). Den har Formen af en elliptisk eller nesten halvymaanedannet Plade og gaar ud i en dorsal og en ventral Lap, adskilte i Midten ved en tvers over Epipoditen fra dennes Feste lobende fortykket Ribbe. Ligesom Tilfeldet var med Exopoditen, er der ogsaa nogen Forskjel i | Epipoditens Storrelse og Form paa de forskjellige 18 than the inner one and scarcely extends beyond its Ist joint. It has the form of a very narrow ellip- tical lamella which, along the entire inner mar- gin and at the point, is furnished with a regular series of pretty long finely ciliated marginal bristles. The 8 pairs of branchial legs which immediately succeed the maxille, are all constructed on the same type, and lie close in to each other in the form of transversally placed lamelle, rather more convex in front than behind (see Pl. I, fig. I). They increase somewhat in size as far as to the 4th pair and then gradually diminish backwards. In all of them 3 chief portions issuing from a common base (see PI. III, figs. 3—6) may be distinguished, which we, like what we are accustomed to do with other crusta- ceans, may term endopodite (p), exopodite (ex) and epipodite (ep). The common basal part consists, as in the 2nd pair of maxille, of 2 imperfectly sepa- rated segments which have a double series of brist- les on the inner margin, of which those on the first segment are distinguished by their great length. The endopodite (p) which forms the immediate con- tinuation of the basal part forms a trunk, dimi- nishing gradually towards the extremity, upon which there is a faint indication of a segmentation. This part is, in the ovigerous female, considerably more prolonged them in young individuals of both sexes, and has the terminal joint well separated, somewhat recurvate and beset with particularly long divergent and plumose bristles, which partly project below the valves of the carapace (see Pl. I, fig. 1). The endo- podite is, otherwise, beset with bristles along the entire inner margin, which are chiefly arranged in a double series, and are immediate continuations of the bristle series appearing on the basal part. The exopodite (ex), which is attached to the 2nd seg- ment of the basal part, outside the endopodite, has the character of a broad lamella, furnished along the middle with a somewhat thickened rib, and is a little different in form in the various branchial legs. In the 1st pair (PI. JII, fig. 3) it is regularly oval and beset on the outer edge with a series of about 18 slender bristles increasing in length towards the point. In the succeeding pairs (figs. 4.5) it becomes gradu- ally somewhat larger and more strongly expanded at the point, which is unevenly rounded and beset with only few and scattered marginal bristles. Fin- ally, in the last pair (fig. 6) it has assumed a pretty narrow elliptical form. The epipodite (ep), which is attached by a short stem to the outer side of the 1st. segment of the basal: part, is of particularly large size, so that it more or less completely covers the remaining parts when those appendages are viewed in situ from the outer side (see Pl. II, fig. 1). It has the form of an elliptical, or almost semilunar plate, and passes out into a dorsal and a ventral lobe divided in the middle by a thickened rib which —- or ee —— Par Branchialfodder. _kraftige Torner. Dens Storrelse tiltager noget indtil 4de Par, hvor den er storst, og aftager saa igjen successivt paa de bagenfor liggende Par (se Tab. Il, Fig. 1). Paa iste Par (Tab. III, Fig. 3) er dens ventrale Lap betydelig storre end den dor- sale og smalt tillobende i Enden, medens ‘hin er jevnt afrundet. Paa de folgende Par (Fig. 4, 5) bliver Forskjellen mellem de 2 Lappe efterhvert mindre, og paa sidste Par (Fig. 6) er Forholdet det omvendte af hvad det er paa lste Par, idet den dor- sale Lap her er den storste og mere smalt udlobende end den ventrale. Saavel Exopoditen som Epipoditen, men iseer denne sidste, viser den for Gjelleelemen- terne hos andre Krebsdyr characteristiske spongiose Structur, idet der mellem de 2 Lameller, hvoraf begge disse Vedheng begrendses, findes et compli- ceret System af med hinanden anastomoserende Hul- ’ rum, hvori der hos det levende Dyr foregaar en livlig Blodcirculation. At begge disse Vedheeng der- for er af respiratorisk Betydning, er ganske utvivl- somt, skjondt, som senere skal vises, ogsaa selve Rygskjoldet spiller i denne Henseende en vigtig Rolle. De 4 forreste Par Bagkropslemmer (se Tab. I, Fig. 1) er overordentlig kraftigt udviklede Svommeappa- rater, der i flere Henseender, og ogsaa i den Maade, hvorpaa de beveges, minder om Copepodernes Svom- mefedder. De er alle byggede efter samme Type og bestaar hvert (se Tab. III, Fig.7 og 9) af en med talrige sterke Muskelbundter fyldt, noget affladet Basaldel, og to fra dennes Ende udgaaende, med cilierede Svommeborster forsynede, enleddede Grene eller Aarer, hvoraf den ydre ialmindelighed er ret- tet sterkt udad og i Yderkanten bevebnet med Paa alle Par findes ved Enden af Basaldelen paa den indre Side en eiendommelig indadrettet Fortsats (Fig. 8), der moder den tilsva- rende paa den anden Side og i Spidsen er beveebnet med et Antal, sedvanlig 4, krogformige Torner (Fig. 8a). Ved disse Torner hegtes de 2 til samme Par herende Fodder ligesom sammen, saa at deres Bevegelser kun kan ske samtidigt. iste Par Svommefodder (Fig. 7) skiller sig kjen- _ deligt fra de ovrige, saavel ved Basaldelens Form og Bevebning som ved Beskaffenheden af den ydre Gren. Basaldelen, der ligesom paa de ovrige Par har et ganske kort Rodled, er her forholdsvis len- gere og smalere, noget aftagende i Brede mod En- den, og beveebnet med 4 lange Torner, hyoraf en er 19 crosses the epipodite from its point of attachment. As was the case with the exopodite, there is also some difference in the size and form of the epipo- dite in the various pairs of branchial feet. The size inereases somewhat until the 4th pair, where it is greatest, and it then diminishes again, successively, in the pairs situated behind (see Pl. II, fig. 1). In the 1st pair (Pl. ITI, fig. 3) the ventral lobe is con- siderably greater than the dorsal one, and projects in a narrow pointed form at the extremity, while the latter is evenly rounded. In the succeeding pairs (figs. 4,5) the difference between the two lobes becomes gradually less, and in the last pair (fig. 6) the relation is the reverse of what it was in the Ist pair; as the dorsal lobe is here the largest one and more narrowly projecting than the ventral one. Both the exopodite and the epipodite, but especially the last-named, exhibit the characteristic spongy structure for the gill-elements in other crustacea; as between the 2 lamella by which the appendages of both are limited, there is found a complicated system of cavities, anastomosing with each other, in which, in the living animal, an active blood cir- culation proceeds. That both these appendages are therefore of respiratory importance is perfectly indu- bitable, although, as will be subsequently shown, the carapace itself also plays an important part in that respect. The 4 foremost pairs of the posterior appen- dages of the body (see Pl. II, fig. 1) are extremely powerfully developed swimming legs which, in several respects as well as in the manner in which they are moved, remind us of the swimming feet of the Copepods. They are all constructed on the same type, and consist, each (see Pl. III, figs. 7 and 9), of a somewhat flattened basal part filled with nu- merous strong bundles of muscles, and two branches or oars, issuing from its extremity and furnished with ciliated swimming-bristles. Of these branches the outer one is usually directed strongly outwards, and is armed on the outer edge with powerful spines. In all the pairs there is found, at the extremity of the basal part on the inner side, a peculiar projec- tion directed inwards (fig. 8), which meets the corre- sponding one of the other side, and is armed at the point with a number — usually 4 — uncinate spines (fig. 8a). The 2 feet pertaining to the same pair are, as it were, hooked together by these spines, so. that their movements can only take place simul- taneously. The Ist pair of swimming feet (fig. 7) are per- ceptibly distinguished from the others, both by the form and armature of the basal part as well as by the nature of the outer branch. The basal part which, as upon the other pairs, has a quite short basal joint, is here relatively longer and narrower, somewhat narrowing in breadth towards the extre- feestet helt oppe ved Basis til Yderkanten, en anden helt nede ved det ydre Hjorne, medens de 2 ovrige udgaar fra den nederste Del af Inderkanten. Den ydre Gren er temmelig smal, men successivt noget bredere mod Enden, og har langs Yderkanten en regelmessig Rad af circa 20 korte Torner, hvorpaa folger, festet til en seregen Afsats, en betydelig steerkere saadan. Fra den noget skraat afkuttede Ende udgaar 3 sterke divergerende Torner, hvoraf den yderste er lengst, den midterste kortest. Hele den indre Kant af Grenen er forovrigt besat med en tet Rad af lange og tynde cilierede Borster. Den indre Gren er betydelig lengere og ogsaa sma- lere end den ydre, nesten lineer, og viser ved Basis et ufuldstendigt sondret lidet Rodled. Den er i begge Kanter forsynet med en Rad af lignende Svommeborster som paa den ydre Gren og gaar ved Enden ud i en kort dolkformig Spids, indenfor hvil- ken en lang bagudrettet Torn er festet. Paa de ovrige Svommefodder (Fig. 9) er Basal- delen kortere og bredere, mere affladet, og har Yder- kanten tilskjerpet samt endende nedad med et spidst udtrukket Hjorne. Inderkanten er ligesom Yder- kanten uden Torner, men har 2 Knipper af meget fine Borster, skilte ved et lengere Mellemrum. Mel- lem de 2 Grene danner Basaldelen et lancetformigt tilspidset Fremspring. Den ydre Gren er forholds- vis storre og bredere end paa iste Par og har langs Yderkanten 7 Afsatser, hvet beveebnet med 2 teet sammenstillede divergerende Torner; fra Spidsen ud- gaar, som paa Iste Par, 3 Torner, som her succes- sivt tiltager i Lengde indad. Den indre Gren er kun lidet lengere end den ydre, men betydelig sma- lere, forovrigt af samme Beskaffenhed som paa Iste Par. Det bagerste Par skiller sig neppe fra de 2 foregaaende uden derved, at det er noget mindre. De 2 Par rudimentere Bagkropslemmer, der er feestede til Bugsiden ved Enden af 5te og 6te Seg- ment (se Tab. I, Fig. 1), er begge af meget enkel Bygning og som det synes ganske ubevegelige. [ste Par (Tab. III, Fig. 10) er det storste og be- staar hvert af 2 Segmenter, et kort Basalled og et mere langstrakt, i sin ydre Del lidt udvidet Ende- led. Dette sidste er langs Inderkanten besat med fine Berster og har langs den skraat afskaarne Ende- rand en Rad af 7 Torner, hvoraf den yderste er leengst; mellem Tornerne bemerkes ogsaa en Del fine lige udad rettede Borster. — 2det Par (Fig. 11) er neppe mere end halvt saa lange som Iste og be- staar hvert af et enkelt ovalt Led, hvis Inderkant er ret, medens Yderkanten er noget buet. Til den 20 mity, and armed with 4 long spines, of which one is secured to the outer edge, quite up at the base; another quite down at the outer corner, whilst the 2 others issue from the lowest part of the inner edge. The outer branch is pretty narrow, but is somewhat more successively broad towards the ex- tremity, and has a regular series of about 20 short spines along the outer edge, succeeded by a consi- derably more powerful one secured to a special pro- jection. From the somewhat obliquely truncated extremity there issue, 3 strongly divergent spines, of which the outermost one is the longest, and the medial one shortest. The entire inner edge of the branch is otherwise beset with a close series of long and slender ciliated bristles. The inner branch is con- siderably longer and also narrower than the outer one, almost linear, and exhibits at the base an imperfectly separated, small basal joint. It is fur- nished on both edges with a series of similar swim- ming bristles as on the outer branch, and at its extremity passes into a short lanceolate point, inside of which a long spine, directed backwards, is secured. : On the other swimming feet (fig. 9) the basal part is shorter and broader, more flattened, and has the outer edge sharpened and terminating down- wards in'an acutely drawn out corner. The inner edge, like the outer one, is devoid of spines, but has two bundles of very fine bristles, separated by a longish interval. Between the two branches the basal part forms a lanceolate pointed projection. The outer branch is relatively larger and broader than in the Ist pair, and has 7 projections along the outer edge, each of which is armed with 2 diver- gent spines placed closely to each other; from the point thére issue, as in the 1st pair, 3'spines, which increase here successively in length inwards. The inner branch is only a little longer than the outer one, but considerably narrower; otherwise of the same character as in the Ist pair. The last pair are scarcely distinguished from the 2 preceding ones, unless in that they are somewhat smaller. The 2 pairs of rudimentary, posterior append- ages of the body, which are secured to the ventral side at the extremity of the 5th and 6th segments (see Pl. I, fig. 1), are both of very simple structure, and, as it appears, quite immobile. The 1st pair (Pl. ITI, fig. 10) are the largest, and each consists of 2 seg- ments, a short basal joint and a more: elongated, in its outer part slightly widened, terminal joint. This last is beset along the inner edge with fine spines, and along the obliquely truncated terminal margin has a series of 7 spines, of which the outermost one is the longest; between the spines there are observed, also, a number of fine bristles directed straight outwards. The 2nd pair (fig. 11) are scarcely more than half as long as the Ist, and each consist of a se lat ea eel 21 sidste er festet 4 sterke Torner, og fra Spidsen | single oval joint whose inner edge is straight, udgaar 2 lignende, hvoraf den inderste er lengst. Imellem Tornerne findes ogsaa her fine udadrettede Borster, medens Bersterne i Inderkanten er steerkt redncerede. Halegrenene (Fig. 12) er omtrent saa lange som de 2 sidste Bagkropssegmenter tilsammen og ialmin- delighed sterkt divergerende. De er af smal lineer Form, ganske lidt afsmalnende mod Enden og rundtom forsynede med en Rad af korte ucilierede Torner, der ved Spidsen antager Formen af sterkt forlengede Borster. Foruden disse findes langs Inderkanten en Rad af betydelig lengere og finere, tet cilierede Borster. Dyrets Farve er noget varierende fra meget bleg gulagtig til temmelig intens redbrun. De mest udpreget farvede Exemplarer har jeg observeret i vor arktiske Region. Beskrivelse af den slegtsmodne Han. Medens den endnu ikke slegtsmodne, skjondt forevrigt fuldt udvoxede Han (se Tab. II, Fig. 1) kun lidet skiller sig i sit Udseende fra Hunnen, er Forskjellen mellem de to Kjon i den slegtsmodne Tilstand saa skarpt udpreeget (se Tab. I, Fig. 1 og 3), at man uden en noiere Undersogelse knapt en- gang skulde tro, at de tilhorte samme Art. Kjons- “forskjellen er udtrykt saavel i den hele Habitus som i Structuren af enkelte af Lemmerne, iseer de 2 Par Felere, der er modificerede paa en meget lig- nende Maade som hos Hannerne af de fleste Amphi- poder. De storste Hanner, jeg har fundet, havde en Lengde af omtrent 12 mm.; men jeg har ved vor Sydkyst truffet Hanner af knapt mere end den halve Storrelse, skjondt fuldstendigt slegtsmodent ud- viklede. Legemets Form er (se Tab. I, Fig. 3) paafaldende smekrere end hos Hunnen, og navnlig er Rygskjol- det kjendelig smalere, seet fra Siden af elliptisk Form, med Hoiden neppe halvt saa stor som Leeng- den. Fremdeles er Bagkroppen noget lengere i Forhold til Forkroppen, og- dens forreste Afsnit kraftigere udviklet end hos Hunnen. Endelig giver de enormt forlengede Halegrene Dyret et fra Hun- nen meget afvigende Udseende. Minene er fuldkommen af samme Bygning som hos Hunnen, men synes noget storre og har det ydre Parti sterkere udvidet. whilst the outer edge is somewhat curved. To the last named 4 strong spines. are secured, and 2 simi- lar ones issue from the point, of which the inner- most one is the longest. Between the spines there are also found here fine bristles directed outwards, whilst the bristles on the inner margin are greatly reduced. The caudal rami (fig. 12) are about same length as the two last posterior segments of the body taken together, and are usually strongly diver- gent. They are of narrow, linear form, quite slightly narrowed towards the extremity, and furnished roundabout with a series of short non-ciliated spines, which at the tip assume the form of greatly pro- longed bristles. Besides these there are found, along the inner edge, a series of considerably longer and finer, closely ciliated bristles. The colour of the animal is somewhat variable, from very pale yellowish to pretty intense red- brown. I have observed the most distinguished co- loured. specimens in the Norwegian Arctic region. Description of the sexually ripe male. Whilst the not yet sexually ripe male, al- though in other respects fully developed (see PI. I, fig. 1), distinguishes itself in appearance only slightly from the female, the difference between the two sexes in the sexually ripe condition is so sharply defined (see PI. I, fig. 1 and 3), that without a close examination the observer would scarcely even believe that they pertained to the same species. The sexual difference is expressed both by the en- tire habitus, as well as in the structure of some of the appendages, especially the two pairs of antenna, which are modified in a very similar manner to that of the males of most Amphipods. The largest males I have found had a length of about 12 mm; but on our south coast I have met with males of scarcely more than half the size, although completely sexually developed. The form of the body (see Pl. I, fig. 3) is con- spicuously more slender than in the female, and the carapace, especially, is perceptibly narrower; viewed from the side the shape is elliptical, the height being scarcely half so great as the length. Further, the posterior division of the body is somewhat longer in relation to the anterior one, and its fore- most section more powerfully developed than in the female. Finally, the enormously prolonged caudal rami impart to the animal a very different appear- ance from the female. The eyes are of exactly the same structure as in the female, but appear to be somewhat larger, and have the outer portion more dilated. De ovre Folere (Tab. IV, Fig. 1) er betydelig lengere end hos Hunnen og, lige udstrakte, omtrent saa lange som Forkroppen og «Preabdomen» tilsam- men. Skaftet skiller sig ikke vewsentligt i sin Byg- ning fra samme hos Hunnen, hvorimod begge de ter- minale Vedheng er kjendelig forskjellige. Det blad- formige Vedheeng er forholdsvis betydelig storre og mere forlenget, omtrent 4 Gange saa langt som bredt, eller paa det nermeste af samme Lengde som de to sidste Led af Skaftet tilsammen. For- ovrigt viser det den samme characteristiske teette, kostformige Borstebesetning som hos Hunnen. Svo- ben er serdeles sterkt forlenget, mere end dobbelt saa lang som Skaftet og sterkt afsmalnende mod Enden. Den er sammensat af 17 vel begrendsede Led, hvoraf det Iste egentlig representerer 3 med hinanden sammensmeltede Led. De 9—10 forste Led er steerkt opsvulmede i sit ydre Parti og her besatte med en tet Krands af yderst fine gjennem- sigtige Sandseborster. De ydre Led bliver efter- haanden overordentlig tynde og forlengede; dog er sidste Led noget kortere end de umiddelbart fore- gaaende. De nedre Folere (se Tab. I, Fig. 3) er af hele Legemets Leengde, Halegrenene iberegnede, og ud- meerker sig iser ved den overordentlig tynde og forlengede, af talrige korte Led bestaaende Svobe, der ialmindelighed er lige bagud rettet. Derimod skiller Skaftet sig (se Tab. IV, Fig. 2) kun lidet fra samme hos Hunnen. Dog er dets sidste Led noget tykkere og mangler de lange Fjerborster, der hos Hunnen udgaar fra Enden, i hvis Sted der blot fin- des nogle meget fine Haar. Kindbakkerne og Overleben viser fuldkommen samme Udseende som hos Hunnen. Ogsaa de 2 Par Kjever (Fig. 3 og 4) er byg- gede paa samme Maade som hos Hunnen; men begge Par er forholdsvis mindre og har navnlig Tygge- lappene meget svagere udviklede samt kun forsynede med yderst smaa, simple Borster. Branchialfodderne (Fig. 5) har den egentlige Stamme, eller Endopoditen, betydelig svagere ud- viklet end hos Hunnen og neppe overragende Exo- poditen. Ogsaa er de paa den festede Borster kor- tere og alle af ens Udseende, uden at de i Spidsen feestede udmerker sig ved en paafaldende Lengde. I Modsetning hertil er saavel Exopoditen som Epi- poditen seerdeles store og deres Gjellestructur endnu mere udpreeget end hos Hunnen. Bagkroppens Svommefodder er idethele kraf- tigere udviklede end hos Hunnen (se Tab. I, Fig. 3), WS The superior antenne (Pl. IV, fig, 1) are con- siderably longer than in the female, and when straightly extended are about as long as the anterior division of the body and the preabdomen taken together. The peduncle does not particul- arly distinguish itself in structure from that of the female while, on the other hand, both the terminal appendages are perceptibly. different. The lamelliform appendage is, relatively, considerably larger and more prolonged, about 4 times as long as it is broad, or nearly of the same length as the two last joints of the peduncle together. It exhibits otherwise the same characteristic, close, brush-like, bristly armature as in the female. The flagellum is particularly greatly: prolonged, more than twice as long as the peduncle, and is greatly narrowed towards the extremity. It is composed of 17 well-defined joints, of which the first one really represents 3, which are coalescent with each other. The 9—10 first joints are greatly thickened in their outer portion, and are here covered with a close wreath of estremely fine, transparent sensory bristles. The outer joints become gradually extraordinarily slender and prolonged; but the last joint is some- what shorter than the immediately preceding ones. The inferior antenne (see Pl. I, fig. 3) are as long as the entire body, the caudal rami included, and are especially distinguished by the extraordi- narily slender and prolonged flagellum, consisting of numerous short joints, which is usually directed straight backwards. On the other hand, the peduncle (see Pl. IV, fig. 2) distinguishes itself only little from the same part in the female. Still its last” joint is somewhat thicker, and is without the long plumose bristles which, in the female, issue from the extremity; in place of them there are only found a few very fine hairs. ?, The mandibles and upper lip exhibit exactly the same appearance as in the female. . The 2 pairs of maxille also (fig. 3 and 4) are constructed in the same manner as in the female; but both pairs are relatively smaller, and have, especially, the masticatory lobes much more faintly developed and only furnished with extremely small simple bristles. The branchial feet (fig. 5) have the stem-proper, or endopodite, considerably fainter developed than in the female, and scarcely reaching beyond the exo- podite. The bristles attached to it are also shorter and all alike in appearance, without those attached to the point distinguishing themselves by any re- markable length. “In contrast herewith the exopo- dite as well as the epipodite are particularly large, and their gill-structure more distinguished than in the female. , The swimming feet of the posterior division of the body are altogether more powerfully developed 23 men skiller sig forevrigt ikke synderligt i sin | than in the female (see PI. I, fig. 3), but do not other- Bygning. ‘De 2 Par rudimentere Bagkropslemmer (Fig. 6 og 7) er ligeledes noget storre end hos Hunnen, og sidste Par (Fig. 7) har her et tydeligt afsat lidet Rodled, ligesom 1ste Par. I sin Form og Bevebning stemmer iovrigt begge Par temmelig noie overens med samme hos Hunnen. Halegrenene udmerker sig (se Tab. I, Fig. 3) ved en i Forhold til samme hos Hunnen meget paa- ‘faldende Leengde, idet de endog er saa lange som de 5 bagre Bagkropssegmenter tilsammen, eller ne- sten af Legemets halve Lengde. De er (Tab. IV, Fig. 8), som hos Hunnen i hver Kant bevebnede med en Rad af korte Torner, hvoraf dog de i Yder- kanten her er meget talrigere og finere end de i Inderkanten. Desuden findes, som hos Hunnen, langs den indre Kant en Rad af temmelig lange og tynde - Fjzrborster. Farven er i levende Tilstand gjennemgaaende blegere end hos Hunnen og Legemet halvt gjennem- sigtigt. Indre Organer. Undersogelsen af den indre Organisation er hos nerverende Dyreform forbunden med ganske ser- lige Vanskeligheder. Dyret er ialmindelighed ikke gjennemsigtigt nok til at at man kan umiddelbart stu- dere denne paa det levende Dyr, og ved Dissection af opbevarede Exemplarer kommer man ikke meget langt, paa Grund af det complicerede System af Muskler, som omgiver og tildels fylder den i og for sig meget trange Kropshule. Hertil kommer endnu et meget sterkt udviklet, og med talrige Fedtkugler fyldt Bindeveev, som omspender de forskjellige Or- ganer og kun vanskeligt lader sig skille fra samme. Heller ikke Snitmethoden har givet mig fuldt ud tilfredsstillende Resultater. Bedst har jeg kunnet faa undersogt den indre Bygning i sin Helhed ved af et stort Antal Exemplarer at udvelge enkelte ualmindelig gjennemsigtige og helst’ ganske unge _ Individer og undersoge disse directe under Mikro- skopet i levende Tilstand. Ved at combinere disse Undersogelser med hvad jeg har kunnet fremstille ved Dissection, har jeg endelig efter meget Besveer troet at faa nogenlunde Rede. paa den indre Orga- nisation hos denne merkelige Dyreform. Forst efterat disse Undersogelser forlengst var afsluttede, erholdt jeg Prof. Claus’s fortjenstfulde Arbeide: «Untersuchungen zur Erforschung der genealogischen Grundlage des Crustaceen-System», hvori den indre Organisation hos Nebalia i Korthed omtales, med Vedfoielse af steerkt forstorrede Figurer af Han og Hun, fremstillede som transparente Objecter. De wise distinguish themselves particularly in their structure. The 2 pairs of rudimentary, posterior append- ages of the body (figs. 6 and 7) are likewise some- what larger than in the female, and the last pair (fig. 7) have here a distinctly defined, small basal joint like the 1st pair. In their shape and armature both pairs correspond otherwise pretty exactly with the same organs in the female. The caudal rami distinguish themselves (see Pl. I, fig. 3) by a very striking length in relation to the length of the same in the female, as they are even as long as the 5 backmost segments of the posterior body taken together, or nearly half the length of the body. They are (PI. IV, fig. 8), as in the female, armed on each edge with a series of short spines, of which, however, those on the outer edge are here much more numerous and finer than those of the inner edge. There are found, besides, as in the female, along the inner edge, a series of pretty long and thin plumose sete. The colour, in the live state, is, pervadingly, paler than in the female, and the body is semi- transparent. Internal organs. The investigations of the internal organization is in the present animal form attended with quite special difficulties. The animal is generally insuffi- ciently transparent to enable us to study it directly in the living state; and on dissection of preserved specimens we make no great progress on account of the complicated muscular system which surrounds and partly fills the, in itself very narrow, body- cavity. To that is added still, a very strongly developed, and with fatty globules filled, connective- tissue, which encloses the various organs, and per- mits itself with difficulty to be separated from them. Neither has the sectional method afforded me completely satisfactory results. I have been enabled to investigate the internal structure in its entirety best, by choosing from among a large number of specimens some more than usually trans- parent, and preferably quite young, individuals, and by investigating these in the live state directly under the microscope. By combining these investigations with what I have been able to present by dissec- tion, I have finally after much difficulty, I believe, been able to obtain in some measure an elucidation of the internal organization of this remarkable ani- mal form. First after these investigations had long previously been concluded, did I obtain Prof. Claus’s admirable work «Untersuchungen zur Erforschung der genealogischen Grundlage des Crustaceen Sy- stem» in which the internal organization of Nebalia is shortly mentioned, and illustrated by greatly mag- . 24 Resultater, hvortil jeg er kommet, stemmer idethele temmelig vel overens med hvad Claus her har med- delt. Paa Tab. V fremstiller Fig. 1 en Hun seet fra Siden og sterkt forstorret, med de forskjellige Organer indtegnede i samme og anlagte med for- skjellige Farver. Fig. 2 fremstiller et Tveersnit af Legemet omtrent over Midten af Truncus; de indre Organer er anlagte med samme Farve som paa Hovedfiguren. Tarmtractus. Spiseroret er meget kort og stiger fra Mund- aabningen lodret i Veiret, forbindende sig under en nesten ret Vinkel med den forreste, i Hovedet lig- gende Del af Tarmen. Dette forreste Afsnit af Tarmtractus er forsynet med et temmelig compli- ceret Chitinskelet (Tab. V, Fig. 3, 4) og danner saa- ledes et Slags Tyggemave, noget lignende den hos Amphipoderne forekommende. Paa Chitinskelettet kan adskilles 3 Hoveddele, en forreste, en midterste og en bagerste Del. Den forreste Del er noget ‘affladet og indeholder 2 fortil divergerende Lister, besatte med en dobbelt Rad af fine, tet sammen- treengte Chitinpigge. Lige ved Indgangen til Spise- roret findes desuden ventralt 2 parvise Forhoininger, besatte med indadrettede Borster. Den midterste Del er temmelig steerkt opsvulmet og bagtil skraat afskaaret, dannende her en nesten klokkeformig Udvidning, hvorfra rager frem et Par tet haarede Flige. Det er her at de tilTarmen horende Lever- sekke forener sig for at udmunde i Tyggemavens Lumen. Den bagerste Del, endelig, danner en lang skedeformig, og i de frie Kanter med fine Borster besat tynd Flig, der kun indtager Dorsalsiden af Tarmen og med sin i en fin Spids udtrukne Ende rekker langt ind i selve Truncus. Tarmen danner forevrigt et simpelt cylindriskt, med steerke Rimg- muskler forsynet Ror, der strekker sig igjennem hele Midtkroppen. Bagkroppen og Mesteparten af Halen. Ved Enden af nestsidste Halesegment for- binder den sig med en kort, sterkt muskulos Ende- tarm, der aabner sig nedenunder Basis af Halegre- nene. Af Leversekke findes ikke mindre end 4 Par, alle seerdeles tynde og saa fast forbundne med Tar- men med fedtholdigt Bindevev, at de yderst vanske- ligt lader sig isolere fra samme. Det forreste af disse Par er meget korte og rettede fortil over Tyggemaven, medens de 3 ovrige Par folger Tarmen bagud og ender omtrent ved Begyndelsen af Halen. - Paa Tveersnit (Fig. 2) viser disse sidste (ed, ev) sig grupperede nesten i Form af en Rosette omkring og tet ind mod Tarmen, med et noget sterre Mel- lemrum mellem det dorsale Par. nified figures of male and female, presented as transparent objects. The results at which I have arrived agree, upon the whole, pretty well with what Claus has here stated. Plate V, fig. 1 repre- sents a female viewed laterally and greatly magni- fied, with the various organs drawn in the repre- sentation and coloured with different colours. Fig. 2 represents a transversal section of ‘the body across nearly the middle of the truncus; the internal organs are coloured with the same colours as in the chief figure. The intestinal tract. The oesophagus is very short and rises per- pendicularly from the oral aperture, connecting itself at almost a right angle with the foremost part of the intestine situated in the head. That foremost section of the intestinal tract is fur- nished with a pretty complicated chitinous skeleton (Pl. 4, fig. 3, 4) and forms thus a kind of mastica- tory stomach, somewhat like what is present in the Amphipods. Three chief parts may be distinguished in the chitinous skeleton, a front one, a medial one, and a back one. The front portion is somewhat flattened and contains 2 fillets which diverge to the front and are beset with a double series of fine, closely crowded chitinous spikes. Exactly at the mouth of the oesophagus there are further found, ventrally, 2 prominences in pairs, beset with bristles directed inwards. The medial part is pretty greatly swollen out and obliquely truncated behind, forming here a nearly bell-shaped dilation, from which a pair of densely hirsute flaps project. It is here that the liver-sacs pertaining to the intestine unite, in order to debouch into the cavity of the masticatory stomach. The posterior part finally forms a long sheath-like thin flap which is, on its free edges, beset with fine bristles, and only occupies the dorsal side of the intestine; and which, with its extremity drawn out to a fine point, extends far into the truncus itself. The intestine forms, other- wise, a plain cylindrical tube furnished with strong ring-muscles, which extends itself through the entire mesosome, the metasome, and the greater part of the urosome. At the extremity of the pen-. ultimate caudal segment, it connects itself to a short, strongly muscular rectum which opens below the base of the caudal rami. Of liver-sacs there are no less than 4 pairs found, all of them particularly slender, and so firmly connected to the intestine by fatty connective-tissue ‘that it is extremely difficult to isolate them from it. The foremost pair of these sacs is very short and directed forwards above — the masticatory stomach, while the 3 other pairs follow the intestine backwards and terminate at about the beginning of the urosome. In trans- versal sections (fig. 2) these last show themselves —-_ _ Blodkarsystemet. Hjertet (Fig. 1, Fig. 2, c) er af langstrakt spindel- dannet Form og strekker sig, umiddelbart ovenfor Tarmen, igjennem hele Midtkroppen og Storsteparten af Bagkroppen, endende omtrent ved Enden af den- nes 3die Segment. I Midtkroppens 5te Segment har det sin sterste Vidde og viser her til hver Side en meget iginefaldende Tverspalte. En lignende, men betydelig mindre Spaltaabning sees til hver Side helt fortil, ved Hjertets Begyndelse. Claus har desuden afbildet, mellem begge Par, 4 meget smaa dorsale Spaltaabninger, som det dog ikke er lykkets mig at faa se tydeligt. Fra Hjertets forreste Ende udgaar en, ialfald i sit inderste Parti tydelig Arterie, og ogsaa Hjertets bagre Ende har forekommet mig at fortsette sig i en lignende bagudlobende Arterie. Noget virkeligt udviklet Blodkarsystem synes dog neppe at vere tilstede, og Blodet circulerer, som hos andre lavere Crustaceer, vesentlig kun i veg- lose Hulrum mellem Bindevevet og Musklerne. I Branchialfodderne er allerede omtalt Tilstedeve- relsen af saadanne med hinanden anastomoserende Blodgange, navnlig i de 2 ydre Vedheeng (Exopodit og Epipodit). Et lignende System af veglose Blod- kanaler findes ogsaa mellem Rygskjoldets 2 Lamel- ler, og da Cirkulationen her er meget livlig, har man Grund til at antage, at Rygskjoldet spiller en ikke uvesentlig Rolle ved Dyrets Respiration. Nervesystemet. At undersoge Nervesystemet i sine Detailler, er forbundet med serdeles store Vanskeligheder, da dets Centraldele ligger.saa tet omgivne af Muskler og Bindeveev, at de yderst vanskeligt lader sig isolere ved Disection. Paa Tversnit af Kroppen (Pl. V,Fig. 2) kan man dog let orientere sig angaaende Buggangliekjedens Beliggenhed (g), og kan herefter bestemme dens Plads ogsaa i Profil af Dyret (se Fig. 1). Hjernegangliet har det kun lykkets mig at se temmelig ufuldstendigt, Det synes ikke at’ vere af nogen betydelig Storrelse, og udsender, for- uden Synsnerverne, sterke Nervestammer til de 2 Par Folere. I Midtkroppen ligger de enkelte Knuder af Buggangliekjeden tet sammen, kun for- bundne med meget korte og tykke Lengdecommis- surer, mellem hvilke der knapt er noget Mellemrum. Selve Ganglierne er forholdsvis smaa og alle af ens Storrelse, deres 2 Halvdele fuldkommen -sammen- 4—G. 0. Sars: Fauna Norvegie. (ed, ev), grouped nearly in the form of a rosette, around and close in to the intestine, with a somewhat largish interval between the dorsal pair. The blood-vessel system. The heart (fig. 1, fig. 2 c) is of elongate, fusi- form shape, and extends, immediately above the intestine, through the entire mesosome and the greater part of the metasome, terminating at about the extremity of the 3rd segment of the latter. It has its greatest breadth in the 5th segment of the mesosome, and exhibits here on either side a very prominent transversal fissure. A similar. but considerably smaller fissure-aperture is seen on each side, quite in front, at the commencement of the heart. Claus has illustrated besides, between both pairs, 4 very small dorsal fissure-apertures, which I have, however, not been fortunate enough to ob- serve distinctly. From the foremost extremity of the heart there issues a, at least in its innermost portion, distinct artery; and also the posterior ex- tremity of the heart has appeared, to me, to con— tinue itself in a similar backward running artery. Any real, developed blood-vessel system scarcely appears, however, to be present; and the blood circulates, as in other lower Crustaceans, princi- pally, only in cavities, without walls, between the connective-tissue and the muscles. In the branchial feet, the presence of such blood pasages, anastom- osing with each other, has already been mentioned; especially in the 2 outer appendages (exopodite and epipodite). A similar system of blood-ducts, without walls, is also found between the 2 lamelle of the carapace, and as the circulation is here very active there is reason to suppose that the carapace plays a not unimportant part in the respiration of the animal. The nervous system. To investigate the nervous system in its details is a matter of particularly great difficulty, as its central portions lie so closely surrounded by muscles ~and connective tissue that it is excessively difficult to isolate them by dissection. In transversal sec- tions of the body (Pl. V, fig. 2) we can, however, easily obtain information concerning the situation of the ventral ganglial chain (g), and can from this deter- mine its situation also in a side-view of the animal (see fig. 1). I have not been fortunate enough to observe the ganglion of the brain very perfectly. It does. not appear to be of any considerable size, and sends off, besides the optical nerves, powerful ner- vous stems to the 2 pairs of antenne. In the meso- some, the individual knots of the ventral ganglial chain lie close together, only connected by very short and thick longitudinal commissures, between which there is scarcely any interval. The ganglia 26 smeltede med hinanden og udsendende 2 sterke | themselves are relatively small and all alike in Sidestammer, der udbreder sig dels i Branchial- fedderne, dels i Kroppens Muskulatur, De 4 i Bag- kroppen beliggende Ganglier er betydelig storre og ogsaa mere fjernede fra hinanden, med lengere og mere tydeligt skilte Commissurer. I Halen lober 2 Nervestammer langs ad Bugsiden lige til Hale- grenene, og danner for hvert Par af de smaa Hale- fodder en liden ganglios Opsvulmning. En lignende synes ogsaa at findes ved Basis af Halegrenene. Generationsorganerne, Ovarierne er til sine Tider meget let at obser- vere hos det levende Dyr, da de med stor Tydelig- hed skinner igjennem Integumenterne paa Grund af sin intense redgule Farve. De danner (se Pl. V, ‘Fig. 1, Fig. 2, ov) 2 langstrakte Sekke, der streek- ker sig, til hver Side af Tarmen, igjennem hele Midtkroppen og Bagkroppen og rager endog et Stykke ind i Halen. I enhver af Sekkene findes kun en enkelt Rekke sig udviklende Adg, alle med tydelig Kimblere og grovkornet Blommemasse. Aigge- lederne har det ikke lykkets mig at faa se saa tyde- ligt, at jeg med Bestemthed kan angive deres Plads. Det har imidlertid forekommet mig, at de udmunder ved Basis af 6te Par Branchialfodder.. Testes har omtrent samme Beliggenhed som Ovarierne og dan- ner ligesom disse simple Sekke, men er betydelig smalere end disse. De munder, ifolge Claus ved Basis af sidste Par Branchialfedder. Udvikling. JEggene optages, som ovenfor nevnt, efter at vere komne ud af Adglederne, i et Slags Rugehule, der ligger ind under Midtkroppen, omgiven af Ryg- skjoldets Valvler og delvis begreendset af Branchial- ° fodderne, hvis talrige krummede Endeborster hindrer dem fra at falde ud af Rygskjoldets Hule. De undergaar her sin hele Udvikling, og forst naar Un- gerne er saa vidt komne, at de med Lethed kan be- ‘vege sig i Vandet, forlader de Klekkehulen. Ud- viklingen er ngiere studeret af den russiske Natur- forsker Kowalewsky, og mine Undersogelser stemmer i alt vesentligt overens med hvad der af denne ud- merkede Forsker er meddelt. ggene er umiddel- bart efter at vere optagne i Klekkehulen, af redgul Farve og noget oval Form, Senere antager de lidt efter lidt en noget lysere Couleur og bliver ogsaa mere gjennemsigtige. De er, som hos Flerheden af Crustaceerne, meroblastiske, idet Storsteparten af size; their 2 halves are completely coalescent with each other, and send off 2 powerful lateral stems which distribute themselves partly in the branchial feet and partly in the muscles of the body. The 4 ganglia situated in the metasome are considerably larger and also situated farther apart from each other, with longer and more distinctly separated commissures. In the urosome 2 nerve-stems pass along on the ventral side, right to the caudal rami, and form, for each pair of the small caudal feet, a small gangliar swelling. A similar swelling ap- pears also to be present at the base of the caudal rami. The reproductive organs. The ovaries are at times very easy to observe in the living animal, as they shine through the inte- guments with great distinctness, owing to their intense red-yellow colour. They form (see Pl. V, fig. 1, fig. 2, ov) 2 elongate sacs which extend them- selves to each side of the intestine through the entire mesosome and metasome, and reach even some way into the urosome. In each of the sacs there is found only a single series of developing ova, all having a distinct germinative vesicle and coarsely granular yolk substance. The ovarial ducts I have not been fortunate enough to observe so distinctly that I can with precision state their situation. It has, however, appeared to me that they debouch at the base of the 6th pair of branchial feet. The testicles have nearly the same situation as the ovaries and, like these, form plain sacs, but are considerably narrower than them. According to Claus they debouch at the base of the last pair of branchial feet. Development. The ova are received, as above stated, after having been discharged from the ovarial ducts, in a kind of hatching cavity, which is situated in below the mesosome, surrounded by the valves of the carapace and partly limited by the branchial feet whose numerous bent terminal bristles prevent them from falling out of the cavity of the carapace. They undergo here their entire development, and first when the young ones have advanced so far ‘that they can move themselves with ease in the water do they abandon the hatching cavity. The development has been closely studied by the Russian naturalist Kowalewsky, and my investigations agree in all material points with what has been stated by that eminent investigator. The ova are, imme- diately after having been received into the hatching cavity, red-yellow in colour, and somewhat oval in shape. Subsequently they, little by little, assume i i re ll ee ia. Aiggets Blommemasse ikke undergaar nogen Kloy- ning. Ifolge Kowalewsky dannes det blastodermale Cellelag ved den successive Klovning af en enkelt stor Polarcelle. Paa et temmelig tidligt Udviklings- stadium, som er fremstillet Pl. V, Fig. 6, finder vi, at Blommemassen i den ene Halvdel af Agget er begerformigt omgivet af et Lag af klare Cellier, der naynlig i Kanten af Agget tydeligt hever sig af fra den mere ugjennemsigtige redgule Blommemasse. Dette er den sig dannende Blastoderm. Det forste Anleg til Embryonet antydes ved en svag trans versal Indbugtning i Blastodermen, begreendset af 2 noget fremspringende Vulster. Den ene af disse Vulster forestiller Overleben, den anden Haleenden (se Fig. 7 og 8). Til, hver Side af den ovenomtalte Indbugtning viser sig noget senere 3 tverstillede langagtige Forhoininger, der forestiller Anlegget til de 2 Par Folere og Mandibularpalperne, og foran dem sees til hver Side en utydeligt begrendset rundagtig Udvidning, der aabenbart er Anlegget til Oienstilkene. Embryonet, der endnu er omgivet af ggehinden, befinder sig nu i det saakaldte Nauplius- stadium. Senere optreder, bag de 3 Par ovenomtalte Lemmeanleg, successivt en dobbelt Rekke af min- dre Forhoininger, der antyder Anlegget til de fol- gende Lemmer (se Fig. 7). Samtidigt bliver den transversale Indbugtning dybere, Haleenden sondrer sig tydeligere og streber at fjerne sig fra Over- leben, hvad der tilsidst, i Forbindelse med Embry- onets Veext, har tilfolge at Aiggehinden brister og skaller af. Det Stadium, som nu folger, er det saa- kaldte Puppestadium, som er fremstillet Fig. 9 og 10. Embryonet, som nu kun er omgivet af en over- ordentlig tynd og gjennemsigtig Membran, Larve- huden, viser ikke lengere den oprindelige ventrale Krumning, men har strakt sig fuldt ud i Lengden og endog antaget en svag dorsal Boining. Formen er nesten kolledannet, idet Legemet fortil ligesom er opblest, paa Grund af en betydelig Rest af Blommemassen, der fylder det her dorsalt. Man kan saaledes egentlig paa Legemet adskille to tem- melig skarpt sondrede Hoveddele, en nesten kugle- formigt opsvulmet forreste Del, og en betydelig smalere, nesten cylindrisk og bagtil i.en stump ' Spids udgaaende Del. Den forste svarer nermest til Hovedet hos det voxne Dyr, medens den. sidste i sig indbefatter baade Midtkrop, Bagkrop og Hale. Saavel paa den forreste som bagerste Del kan der nu adskilles en dobbelt Rekke af lemmelignende Fremspring, men af et endnu yderst ufuldkomment Udseende, kun dannende. simple koniskt tillobende Fortsatser. Storst og tydeligst sondrede er de 2 forreste Par (a', a*) som forestiller de 2 Par Folere. De har en nesten poelsedannet Form og er boiede bagud langs Siderne af Forkroppen. Imellem dem i Midten sees et tydeligt klapformigt Fremspring (L), som er Overleben, og foran dem til hver Side en 27 a somewhat lighter colour and also become more transparent. They are, as in most of the Crustacea, meroblastic, as the greater part of the ovum’s yolk does not undergo any segmentation. According to Kowalewsky, the blastodermatic cellular layer is formed by the successive segmentation of a single large polar cell. In a pretty early stage of devel- opment, which is represented in PI. 4, fig. 6, we find that the yolk in the one half of the ovum is sur- rounded by a cup-shaped layer of clear cells which, especially on the edge of the ovum, distinguish themselves from the more opaque red-yellow yolk. That is the Blastoderm in course of formation. The first rudiments of the embryo is indicated by a faint transversal incurvation of the blastoderm, limited by 2 projecting swellings. The one of these swellings represents the upper lip, the other the caudal extremity (see fig. 7 and 8). On each side of the above-mentioned in-curvature there, somewhat later, appear 3 transversally placed, elongate pro- minences which represent the rudiments of the 2 pairs of antenne and the palpi of the mandibles; and in front of them there is seen on either side an indistinctly limited, roundish dilatation, which is evi- dently the rudiment of the ocular peduncles. The embryo, which is still surrounded by the skin of the ovum, finds itself now in the so-called Nauplius stage. Subsequently there appears, behind the rudi- ments of the 3 pairs of appendages above mentioned, successively, a double series of smaller prominences, which indicate the rudiments of the succeeding appen- dages (see fig. 7). At the same time the transversal in-curvature becomes deeper, the caudal extremity separates itself more distinctly and endeavours to remove itself from the upper lip, with the eventual effect, in connection with the growth of the embryon, that the skin of the ovum bursts and scales off. The stage which now succeeds is the so-called pupa stage, represented in fig. 9 and 10. The embryo, which is now only surrounded by an extraordinarily thin and transparent membrane, the larval skin, no longer exhibits the original ventral curvature, but has stretched ‘itself fully out in length, and even as- sumed a faint dorsal curvature. The shape is almost clavate, as the body in front is, as it were, blown out, owing to a considerable remnant of the yolk substance which here occupies it dorsally. We can thus in the body really distinguish two pretty sharply separated chief parts, an almost globularly shaped swollen front part, and a considerably .narr- ower, almost cylindrical, part passing out in a blunt point behind. The first named corresponds closest to the head of the adult animal, while the last- named contains within itself the mesosome, the metasome and the urosome. In the front, as well as in the posterior part, there can now be dis- tinguished a double series of limb-like prominences 28 temmelig stor rundagtig Forhoeining (0), Anlegget til Gienstilkene. Bag Folerne folger 3 Par ligeledes polsedannede, men betydelig mindre Vedheeng, hvori man let erkjender Anlegget til Mandibularpalperne (Mp) og de 2 Par Kjever (m', m*). Langs Siderne af den bagre Del af Legemet sees en uafbrudt Rekke af ialt 11 Par simpelt koniske Fortsatser, hvoraf de 8 forreste er af fuldkommen ens Udseende og staar nesten ret ud til Siderne, medens de 3 ba- gerste Par er mindre tydeligt fremragende og mere nedadrettede. Alle disse Fortsatser er egentlig kun simple poseformige Udkrengninger af Larvehuden, og ferst indenfor dem sees Anlegget til et til- svarende Antal Lemmer. De forstnevnte 8 Par Fortsatser (brp) synes at svare til et lignende Antal Branchialfodder, medens de 3 bagerste Par (pl) aabenbart antyder ligesaamange Svommefodder. Den bagenfor liggende Del af Puppens Legeme er uden ethvert Spor af Fortsatser og simpelt koniskt tillobende. Indenfor den gjennemsigtige Larvehud, som temmelig lost omgiver den bagre Del af Em- bryonets Krop, er allerede en tydelig Segmentering bemerkelig, og man kan herved temmelig ngie be- stemme Greendsen mellem de forskjellige Kropsafsnit. Kun det bagerste Afsnit, Halén er endnu ufuldkom- ment segmenteret. I den forreste Del af Legemet sees til hver Side, ligeledes indenfor Larvehuden, en utydelig halvcirkelformigt buet Linie (c), der fore- stiller den frie Kant af det sig udviklende Ryg- skjold, og helt fortil, umiddelbart ovenover Anlegget til Gienstilkene, er der et lidet knudeformigt Frem- spring (R), der aabenbart forestiller den sig udvik- lende Pandeplade. I Axen af den bagre Del af Le- gemet har allerede Tarmen anlagt sig i Form af en med et klart lysegult Inhold fyldt simpel Kanal, der dog endnu er lukket i sin bagre Ende, medens den fortil staar i aaben Kommunication med den rummelige, af Blommemasse fyldte Hule, der ind- tager den dorsale Del af Hovedet. Fig. 11 forestiller det umiddelbart efter Puppestadiet folgende Udvik- lingstrin. Hvad der vesentlig adskiller dette Sta- dium fra det foregaaende, er, at Larvehuden nu er afkastet, saa at de forskjellige Kropsvedheng alle er frit fremragende, ligesom Legemets Segmentering ogsaa udvendigt er tydelig. Den dorsale Krumning af Embryonet er nu saa sterk, at Legemet nesten beskriver en fuldsteendig Halvcirkel. De til Hove- det herende Lemmer har voxet adskilligt i Storrelse, men er forevrigt kun lidet ‘forandrede. Dog bemer- kes paa det forreste Par (a') en Jiden Bigren, som antyder det bladformige Appendix. Branchialfedderne (brp) er tilstede i sit fulde Antal (8 Par) og viser sig alle dybt tvekleftede, samt lige nedadrettede. Derimod findes der endnu kun anlagte 3 Par Svomme- fodder (pl), idet det 4de Par ferst meget senere ud- vikler sig. Heller ikke sees noget Spor af Hale- fodder. Halen selv har imidlertid nu sit fulde Antal | which however have, as yet, an extremely im- perfect appearance, forming‘only plain conically shaped prolongations, The 2 foremost pairs (a', a*) which represent the 2 pairs of antenne, are the largest and most distinctly separated. They have almost a sausage-shape, and are curved backwards along the sides of the anterior body. Between them, in the middle, there is seen a distinct flap-shaped pro- minence (L.), which is the upper lip, and in front of them, on either side, a pretty large roundish pro- minence (QO), the rudiments of the ocular stems. Be- hind the antenne succeed 3 pairs, likewise sausage- shaped, but considerably smaller appendages, in which we easily recognize the rudiments of the man- dibular palps (Mp) and the 2 pairs of maxille (m', m?*). Along the sides of the posterior part of the body there is seen a continuous series of 11 plain, conical projections in all, the 8 foremost ones of which-are of exactly the same appearance and stand almost straight out at the sides, while the 3 backmost pairs are less distinctly projectant and directed more downwards. All these projections are really only plain bag-shaped bulgings of the larval-skin, and first to the inside of them is there seen the rudi- ments of a corresponding number of appendages. The first named 8 pairs of projections (brp) corre- spond, it would seem, to a similar number of branchial feet; whilst the 3 backmost pairs (pl) evi- dently indicate the same number of swimming feet. The portion of the body of the pupa situated behind is without the least trace of projections and runs out in plain conical form. Inside of the transparent larval skin, which pretty loosely surrounds the pos- terior portion of the body of the embryot, there is already a distinct segmentation noticeable, and we can by it pretty distinctly determine the demarcation between the various divisions of the body. The backmost division only, the urosome, is as yet imper- fectly segmented. In the anterior part of the body there is seen on either side, likewise inside the larval skin, an indistinct, semicircular curved line (c), which represents the free edge of the carapace in course of development; and quite in front, immediately above the. rudiments of the ocular stems, there is a ~ small nodular prominence (R) which evidently re- ° presents the frontal plate in course of development. In the axis of the posterior part of the body the — intestine has already begun to appear in the form of a plain canal, filled, with a clear light yellow substance, which is still closed at its posterior ex- tremity, whilst, in front, it stands in open commu- nication with the roomy cavity filled with yolk substance which occupies the dorsal part of the head. Fig. 11 represents the stage of development imme- diately succeeding the pupa stage. What chiefly dis- tinguishes this stage from the preceding one is, that the larval skin is now thrown off, so that the various 29 Segmenter, og Halegrenene er tydeligt afsatte samt hver i Spidsen forsynet med en kort Borste. Pande- pladen (R) er nu tydeligt fremragende, og Gienstil- kene (O) har antaget en noget konisk Form samt viser i sin ydre Del den forste svage Antydning til Dannelse af Synselementer. Til hver Side af Tar- men bemerkes i Midtkroppen en temmelig plump og kort eylindrisk Sek, der aabenbart forestiller en af Leverseekkene. Den dorsale Del af Forkroppen er endnu sterkt opblest og fyldt af redgul Blomme- masse. Umiddelbart nedenfor denne Del sees nu tydeligt de frie Kanter af Rygskjoldet. De Foran- dringer, Embryonet endnu har at gjennemgaa, er ganske successive. Den tilbageverende Rest af Blommemassen opbruges lidt efter lidt, og samtidigt aftager den dorsale Opsvulning af Hovedet i Stor- relse, medens Rygskjoldets Valvler mere og mere voxer ud over Siderne af Midtkroppen. De forskjel- lige Kropsvedheng udformes og indtager den for dem characteristiske Stilling i Forhold til Legemet, hvorved ogsaa meget snart Nebalia-Habitusen bliver fremtredende. Fig. 12 fremstiller Ungen, naar den er ferdig til at forlade Klekkehulen. Man har ingensomhelst Vanskelighed med i den at erkjende en ung Nebalia. Den eneste vesentlige Afvigelse er, at der fremdeles kun er 3 Par Svommefodder tilstede. Af det 4de Par sees kun et ubetydeligt Anleg bag de ovrige, i Form af et Par smaa knude- formige Fremspring (p'). Ungen kan nu bevege sig frit i Vandet og ernere sig selv; men det varer endnu adskillig Tid, inden de forskjellige Vedheng -opnaar sin fulde Udvikling og faar sin normale rige- lige Borstebeseetning. Af alle Vedheng er 4de Par Svemmefedder de, som udvikler sig senest. appendages of the body are all freely projectant, while, also, the segmentation of the body is distinct externally. The dorsal curvature of the embryo is now so great, that the body almost describes a com- plete semi-circle. The appendages pertaining to the head have considerably increased in size, but are otherwise only little changed. Still there may be noted on the foremost pair (a') a little sub-branch that indicates the lamelliform appendage. The branchial feet (brp) are present in their full number (8 pairs) and show themselves to be all deeply fissured and directed straight downwards. On the other hand, there are as yet only found 3 pairs of swim- ming feet (pl) in a rudimentary state, as the 4th pair only much later becomes developed. Neither is there any trace of caudal feet observed. The urosome itself has now, however, its full number of segments, and the caudal rami are distinctly projected and each furnished with a short bristle at the tip. The frontal plate (R) is now distinctly projectant, and the ocular stems have now assumed a somewhat conical form and in their external part exihibit the first faint indication of the formation of visual elements. In the mesosome, on each side of the intestine, there is noticed a pretty stout and short cylindrical sac, which evidently represents one of the liver sacs. The dorsal part of the an- terior body is still greatly blown out and filled with red-yellow yolk substance. Immediately below that part the free edges of the carapace are now dis- tinctly seen. The changes that the embryon has yet to undergo are quite successive. The remains of the yolk substance are little by little used up, and the dorsal swelling of the head becomes at same time reduced in size, while the valves of the carapace grow more and more out over the sides of the mesosome. The various appendages of the body become fully formed and occupy the characterstic position in relation to the body pe- culiar to them, causing thus the Nebalia habitus very soon to become prominent. Fig. 12 represents the young one when it is ready to abandon the hatching cavity. We have no difficulty whatever, in recognizing in it a young Nebalia. The only material divergence is, that there are still only 3 pairs of swimming feet present. Of the 4th pair there is only seen a faint rudiment behind the others, in the shape of a pair of small nodular prominences (p'). The young one can now move itself freely in the water, and nourish itself; but some time still passes, before the various appendages attain their full development and acquire their nor- mal, abundant bristle-covering. Of all the append- ages, the 4th pair of swimming feet are those which develope themselves latest. Forekomst og Levevis. Den her omhandlede merkelige Dyreform fore- kommer ikke sjelden langs vor hele Kyst, fra Chri- stianiafjorden til Vadse, men synes idethele at op- trede baade hyppigst og kraftigst udviklet i vor arktiske Region. I stor Mengde har jeg saaledes fundet den paa en Plads i Lofoten, Brettesnes, hvor mange hundrede Individer indsamledes i Lobet af et Par Dage, og ogsaa ved Finmarken har jeg paa sine Steder truffet den i meengdevis, Den pleier at holde til paa maadeligt Dyb, fra 10 til 30 Favne, og helst paa saadanne Steder, hvor Bunden er dekket af forraadnende Tangarter, hvoraf den for en veesent- lig Del synes at ernere sig. Ligesom Tilfeldet er med flere andre Crustaceer, synes Hannerne kun til visse bestemte Tider af Aaret at opnaa fuld Slegts- modenhed, og optreeder da kun ganske enkeltvis. Der- imod er endnu ikke slegtsmodent udviklede Hanner - at finde til enhver Tid af Aaret og nesten i samme Antal som Hunnerne. I Maaden at bevege sig paa, ligesom i sin hele ydre Habitus, har dette Dyr en umiskjendelig Lighed med en colossal Copepode; navnlig er den habituelle Overensstemmelse med visse Harpacticider meget paafaldende. Ligesom hos disse sidste, er Legemet overordentlig boieligt, navn- lig i dorsal Retning, og kan ofte krummes saa steerkt, at Halegrenene kommer i Contact med Pandepladen. Bevegelsen sker stodvis ved kraftige og temmelig rythmiske Slag af Svommefodderne, hvorved Lege- met drives frem med temmelig betydelig Fart. De slegtsmodne Hanner er overotdentlig raske i sine Beveegelser og foretager ofte lengere Udflugter i Vandet. Derimod holder Hunnerne og de endnu ikke fuldt udviklede Hanner sig i Regelen ved Bunden og beveger sig her mellem Bundmaterialet, ialmin- delighed paa Siden. De forstaar herunder med stor Behendighed at skjule sig mellem Mudret eller de hensmuldrende Tangrester, som bedekker samme, saa det slet ikke er saa let at finde dem frem, trods den ikke ubetydelige Storrelse. Lettest opdager man dem ved at slaa det optagne Bundmateriale ud i et fladt Kar, med en ubetydelig Kvantitet af Sjo- vand. De tilstedeverende Exemplarer vil da, iser naar man rorer lidt om i Bundsatsen, snart vise sig paa Overfladen af Vandet, og da de i Lighed med forskjellige andre Crustaceer ikke formaar at komme — ned i Vandet igjen, efterat de forst er komne i Be- rorelse med Luften, kan de med Lethed opsamles i levende Tilstand. Bringer man et helst yngre In- divid i en passende Kvantitet Sjovand under Mikro- skopet, kan man saa noiere studere de forskjellige Livsytringer og kan gjennem de halvt gjennemsigtige Integumenter observere Hjertets Pulsationer, Tar- mens perestaltiske Bevegelser og Branchialfoddernes Spil. Disse sidste, der ingensomhelst Inflydelse har paa Locomotionen, vil man i Regelen finde i en Distribution and habits. The remarkable animal form spoken of here appears not rarely along our entire coast, from the Christianiafiord to Vadse, but seems, on the whole, to appear most frequently, and most powerfully de- veloped in our Arctic region. I have thus found it in great abundance at a place, Brettesnes in Lo- - foten, where many hundreds of individuals were col- lected in the course of a couple of days; and also in Finmark I have, in certain places, met with it in great abundance. It is accustomed to keep itself at a\moderate depth, from 10 to 30 fathoms, and preferably in those places where the bottom is co- vered with decomposing sea-weed of which it appears, to a material extent, to nourish itself.’ Like what is the case with several other Crustaceans, the males appear to only attain full power of reproduction at certain fixed seasons of the year, and are then met with only quite solitary. On the other hand, not fully reproductively ripe developed males are to be found at all seasons of the year, and almost in equal number to the females. In manner of movement, as well as in entire external habitus this animal has an unmistakable likeness to a colossal Copepod, especially is the habitual agree- ment with certain Harpacticide very striking. Like as in those last, the body is extraordinarily flexible, especially in dorsal] direction, and may ofen be so strongly bent that the caudal branches come into contact with the frontal plate. The movement takes place in jerks, with powerful and tolerably ryth-~ mical strokes of the swimming feet, by which the body is drawn forwards with pretty considerable speed. The reproductively ripe males are extra- ordinarily active in their movements, and frequently make long excursions in the water. On the other hand, the females and the not yet fully developed males remain, as.a rule, at the bottom, and move here among the material of the bottom, generally on the side. In doing this they understand to con- ceal themselves with great dexterity in the mud, or the decomposing remains of sea-weed which covers it, so that it is not at all easy to search them out, in spite of the not inconsiderable size. We find them easiest by pouring the collected bottom mate- rial into a flat vessel, along with an inconsiderable quantity of sea-water. The specimens present will then, especially if the bottom stuff is stirred a little up, soon show themselves on the surface of the water, and as they, like several other Crustaceans, are unable to swim downwards in the water again after they have first come into contact with the air, they may with ease be collected in the live state. If we place, preferably a young individual, in a suitable quantity of sea-water, under the microscope, we can then more closely study the various features Tow regelmessig svingende rythmisk Bevegelse, som kun for kortere Tid ganske kan stoppes. Denne Be- vegelse har vesentlig respiratoriske Formaal, men er ogsaa af stor Betydning for Neringsoptagelsen. Ved disse Lemmers Spil frembringes nemlig inden- for Rygskjoldets Valvler en fortil gaaende Strom- ning af Vandet, hvormed de Smaapartikler, der tje- ner Dyret til Fede, hvirvles indenfor Munddelenes Omraade. Vandet strommer herunder i en conti- nuerlig Strem ud fra Rygskjoldets forreste Ende, nedenfor Pandepladen. Derfor holdes denne altid, under Branchialfoddernes Beveegelse, lige fortil strakt, medens den i Regelen, saasnart Beveegelsen stopper, beies nedad, hvorved den som en Klap tillukker den forreste Aabning af Rygskjoldet. Udbredning. Arten synes at have en ganske overordentlig vid geographisk Udbredning. Foruden ved Norges Kyster er den observeret i de arktiske Have, ved Gronland, Spitsbergen og Island, frem- deles ved Nordamerikas Ostkyst, ved de britiske Wer, og idethele langs hele, Europas Nordso- og Atlanterhavskyst, ligesom den ogsaa forekommer i Middelhavet, hvor den paa sine Steder, som i Golfen ved Neapel, ikke er ualmindelig. 2. Nebalia typhlops. G. O. Sars. (Pl. 1, Fig. 4, Pl. IV, Fig. 9—19). Nebalia typhlops, G. O. Sars, Nye Dybvandscrustaceer fra Lo- foten; Chr. Vid. Selsk. Forh. f. 1869. Artscharacteristik. Meget lig foregaaende Art i sin almindelige Habitus, skjondt maaske lidt mere undersetsig af Form.. Rygskjoldet, seet fra Siden, af oval Form, lidt lavere fortil og med de nedre Kanter jevnt buede paa Midten. Pandepladen vel udyiklet, aflang oval, sterkt hvelvet oventil og for- synet i Enden med et spidst tornformigt Fremspring, @Minene yderst smaa og rudimentere, koniskt til- lebende i Enden, og uden Spor af Pigment eller Synselementer. De ovre Folere (hos Hunnen) for- holdsvis kortere end: hos foregaaende Art, med Svo- ben neppe lengere end Skaftet og kun sammensat af 10 Led, det bladformige Appendix temmelig for- lenget, nesten halvt saa langt som Svoben. De nedre Folere omtrent som hos N. bipes. Branchial- fodderne med Endopoditen meget tynd og sterkt forlenget, omboiet i Spidsen og forsynet med lange divergerende Fjerborster; Epipoditen med den dor- of life, and may through the semi-transparent inte- guments observe the pulsations of the heart, the peristaltic movements of the intestine, and the play of the branchial feet. These last, which have no influence whatsoever on the locomotion, we will usually find in a regular, swinging, rythmical mo- tion, which only for a short time may be quite stopped. That motion has chiefly a respiratory func- tion, but is also of great importance in securing the nourishment. By the play of these appendages there is produced, namely, inside of the valves of the carapace, a forward current of the water by which the small particles that serve the animal for food are drawn within the area of the oral parts. The water during this flows out in a continuous stream from the foremost extremity of the carapace below the frontal plate. It is therefore always held stretched straight forward during the motion of the branchial feet, whilst, as a rule, as soon as the motion ceases, it is bent downwards, by which action it, like a cover, closes the foremost aperture of the carapace. Distribution. The species seems to have quite an extraordinarily extensive geographical distribu- tion. Besides on the Norwegian coasts, it is ob- served in the Arctic seas, at Greenland, Spitzbergen and Iceland; further, off the east coast of North America, at the British Islands, and, as a whole, along the entire North sea and Atlantic coasts of Europe; and, it likewise occurs in the Mediter- ranean, where it, in certain places, such as the Gulf of Naples, is not uncommon. 2. Nebalia typhlops. G. 0. Sars. (Pl. I, fig. 4, Pl. IV, figs 9—19). Nebalia typhlops, G. O. Sars, Nye Dybvandscrustaceear fra Lo- Aoten; Chr. Vid. Selsk. Forh. f. 1869. Specific Characters. Very like the preceding species in its general habitus, although, perhaps, a little more stumpy in shape. Carapace, viewed laterally, oval in form, a little lower in front, and with the lower edges evenly curved at the middle. Frontal plate well developed, oblongo-oval, — strongly arched above, and furnished at, the extre- mity with a pointed spiniform prominence. Eyes extremely small and rudimentary, passing into co- nical form at the end, and without trace of pig- ment or visual elements. Superior antenne (in female) relatively shorter than in the preceding species, with the flagellum scarcely longer than the peduncle and only composed of 10 joints; ~ the la- melliform appendage rather prolonged, almost half the length of the flagellum. Inferior antenne about as in N. bipes. Branchial feet with the endopodite very slender and greatly prolonged, sale Lob betydelig storre end den ventrale. Forste Par Svommefodder med Yderkanten af den ydre Gren kun forsynet med 3 Smaatender, umiddelbart ovenfor den Iste Endetorn. Halegrenene noget kor- tere end de 2 bagerste Segmenter tilsammen, Far- ven hvidagtig, uden Pigmentering. ' Dyrets Leengde 9 mm. Bemerkninger. Den her omhandlede Art staar vistnok meget ner foregaaende, men er dog let kjendelig fra samme ved forskjellige vel udpregede Characterer, hvoraf navnlig maa fremheves den rudimentre Beskaffenhed af Oinene og Pandepladens Form og Bevebning. Ogsaa i Bygningen af de for- skjellige Kropsvedheeng vil man ved en ngiere Sam- menligning kunne paavise en Del mindre Differentser fra samme hos W. bipes. Beskrivelse. Legemets Form hos Hunnen (se Pl. 1, Fig. 4) stemmer idethele temmelig noie over- ens med samme hos foregaaende Art, skjondt den maaske er noget mindre slank. Hannen er endnu ubekjendt. Rygskjoldet er som hos .V. bipes steerkt sammentrykt og viser, seet fra Siden, en temmelig regelmessig oval Form, med den storste Hoide, der er noget storre end den halve Lengde, omtent paa Midten. De frie Kanter af Valvlerne er nedentil jevnt buede og danner helt fortil en sterk Krum- . ning, inden de steder sammen ved Basis af Pande- pladen. Bagtil viser de sig skraat afskaarne i Ret- ningen forfra bagtil, og de nedre bagre Hjorner af Rygskjoldet danner derfor, som hos foregaaende Art, til hver Side en smalt afrundet Lap, der dekker Siderne af Bagkroppen og nesten rekker til Begyn- delsen af Halen. Pandepladen (se Pl. IV, Fig. 9, 10) er vel udviklet og af meget smal tungedannet Form, temmelig sterkt hvelvet oventil, og forsynet i En- den med et spidst tornformigt Fremspring, der dan- ner Fortseettelsen af en langs den nedre Side lebende Kjel- Sidste Bagkropssegment har, som hos fore- gaaende Art, et Par smaa afrundede Epimerer og er ligesom de 3 folgende Halesegmenter grovt sag- _takket i den bagre Kant. Halegrenene er noget kortere end de 2 foregaaende Segmenter tilsammen, forovrigt af fuldkommen samme Bygning som hos toregaaende Art. Minene (se Pl. IV, Fig. 9, 11) udmerker sig i hoi Grad ved sin ringe Stoerrelse og rudimentere Beskaffenhed, og rager kun lidet frem fra Rygskjol- det, hvorfor de let kan forbisees. De er, som hos N. bipes, deekkede oventil af en skjelformig, spidst udlobende Plade. Selye Qienstilken er af konisk R2 recurved at the tip and furnished with long di- vergent plumose bristles; the epipodite with the dorsal lobe considerably larger than the ventral one. First pair of swimming feet with the ex- terior edge of the outer branch furnished only with 3 small teeth immediately above the 1st terminal spine. Caudal rami somewhat shorter than the 2 backmost segments taken together. Colour whitish, without pigmentation. Length of the animal 9 mm. Remarks. The species here spoken of is cer- tainly very nearly allied to the preceding one, but still is easily distinguishable from same by various well defined characteristics, of which may especially be noticed the rudimentary character of the eyes, and the shape and armature of the frontal plate. Also in the structure of the various appendages of the body, we may, on a closer comparison, be able to notice a number of smaller differences in the same from those of N. bipes. Description. The shape of the body of the female (see Pl. I, fig. 4) agrees, on the whole, pretty exactly with, that of the preceding species, although it is, perhaps, somewhat less slender. The male is yet unknown. The earapace is, as in WN. bipes, strongly compressed and exhibits, viewed laterally, ” a pretty regular, oval form; with the greatest height, which is ‘somewhat more than half the length, at - about the middle. The free edges of the valves are evenly curved below, and form, quite in front, a strong curvature until they unite at the base of the frontal plate. At the back they show them- selves obliquely truncated in a direction from back to front, and the lower posterior corners of the carapace form, therefore, as in the preceding species, on each side, a narrow rounded lobe which covers the sides of the metasome and extends almost to the commencement of the urosome. The frontal plate (see Pl. IV, figs. 9, 10) is well developed and of very narrow linguiform shape, pretty strongly arched above, and furnished at the extremity with a pointed spiniform prominence which forms the contin- uation of a carnia that runs along the lower side. The last segment of the metasome has, as in the preceding species, a pair of small rounded epimera, and are, as well as the 3 succeeding caudal segments, coarsely serrated on the posterior edge. The caudal rami are somewhat shorter than the 2 preceding segments taken together, otherwise of perfectly the same structure ‘as in the preceding species. The eyes (see Pl. IV, figs. 9, 11) distinguish themselves in a high degree by their small size and rudimentary character, and only project a little for- ward from the carapace; for which reason they may easily be overlooked. They are, as in N. bipes, covered above with a squamiform plate running "_”~C Form, uden nogen bemerkelig Opsvulmning i Enden. Af Pigment eller Synselementer er der ikke det ringeste Spor at opdage. _. De ovre Folere (se Pl. IV, Fig. 9) er forholds- vis kortere end hos foregaaende Art, forovrigt af en meget lignende Bygning. Svoben er kun lidet len- gere end Skaftet og kun sammensat af 10 Led. Det skjelformige Appendix er derimod forholdsvis storre end hos foregaaende Art, nesten halvt saa langt som Sveben, og af en mere aflang Form, forevrigt forsynet med en lignende kostformig Besetning af stive Borster. De nedre Folere (ibid.) stemmer idethele saa neie overens med samme hos foregaaende Art, at en neiere Beskrivelse er unodvendig. Ogsaa Munddelene viser en meget lignende Byg- ning, skjondt enkelte mindre Differentser ved noiere Sammenligning lader sig paavise. Saaledes er Man- diblernes Palper (se Fig. 12) forholdsvis noget min- dre, og deres 2det Led har kun en enkelt meget sterk Borste i den ydre Kant ner Spidsen. Forste Par -Kjever (Fig. 13) er ligeledes noget svagere ud- viklede, men forovrigt paa det nermeste af samme Udseende som hos N. bipes. Paa 2det Par Kjever (Fig. 14) er Endognathens 2 Led kun ufuldkomment - sondrede og nesten af ens Lenge; Exognathen er neppe mere end halvt saa lang og har et ringere Antal Randborster end hos N. bipes. Branchialfodderne (Fig. 15, 16) udmerker sig navnlig ved Endopoditens Leengde og Tyndhed. Paa de forreste Par overrager den betydeligt Exopoditen og har sidste Led sterkt omboiet samt besat med serdeles lange divergerende Fjerbjorster. Exopo- diten er af skjzvt oval Form og forsynet med flere Randborster, hvoraf de yderste er tydeligt cilierede. Epipoditen har paa alle Par den dorsale Lap be- tydelig mindre end den ventrale, medens det om- vendte var Tilfeeldet. hos foregaaende Art. Som hos denne, bemerkes nogen Forskjel i de forskjellige Hoveddeles indbyrdes Forhold paa de forskjellige Par Branchialfodder. Sidste Par (Fig. 16) har saa- . ledes et fra 1ste Par (Fig. 15) temmelig afvigende Udseende og skiller sig ogsaa kjendeligt fra det til- svarende hos N. bipes (Pl. III, Fig. 6). Endopoditen er her, i Modsetning til hvad Tilfeeldet er med de evrige Par, meget kort og uden nogen tydelig Led- deling, og Exopoditen er ligeledes forholdsvis min- dre end hos N. bipes og i Yderkanten forsynet med en Rad af cilierede Borster. Fem lignende Fjer- borster findes ogsaa paa den korte og tilrundede - ventrale Lap af Epipoditen. Svemmefodderne forholder sig i alt vesentligt som hos N. bipes; kun er de idethele af en noget 5 — G. 0. Sars: Fauna Norvegize. 33 out to a point. The ocular stem itself is of conical shape, without any noticeable swelling at the ex- tremity. There is not the slightest trace of pigment or visual elements to be discovered. The superior antenne (see PI. IV, fig. 9) are rela- tively shorter than in the preceding species, other- wise of a very similar structure. ‘The flagellum is only a little longer than the peduncle and is composed of only 10 joints. The squamiform appendage is, on the contrary, relatively larger than in the preceding species, almost half the length of the flagellum -and more oblong in form, otherwise furnished with a similar supply of stiff bristles. The inferior antenne (ibid.) agree, upon the whole, so exactly with those of the preceding species that a more detailed description is unnecessary. The oral parts also exhibit a very similar struc-. ture, although upon a closer comparison a few small divergencies may be observed. Thus the palpi of the mandibles (see fig. 12) are relatively some- what smaller, and their 21d joint has only a single, very strong bristle on the outer edge, near the tip. The first pair of maxille (fig. 13) are likewise some- what more faintly developed; but otherwise pretty — nearly of the samme appearance as in N. bipes. In the 2nd pair of maxilla the 2 joints of the endo- gnath are only imperfectly separated and almost equal in length; the exognath is scarcely more than half as long, and has a smaller number of marginal bristles than in N. bipes. The branchial feet (fig. 15, 16) especially dis- tinguish themselves by the length and slenderness of the endopodite. In the foremost pairs it considerably overreaches the exopodite, and has the terminal joint strongly recurved, and also beset with parti- cularly long, diverging plumose bristles. The exo- podite is of oblique, oval form, and furnished with several marginal bristles, of which the outermost are distinctly ciliated. The epipodite has, in all pairs, the dorsal lobe considerably smaller than the ventral one, whilst the opposite was the case in the preceding species. As in that, there is observed some difference in the mutual relations of the various chief parts of the different pairs of the branchial feet. The last pair (fig. 16) have thus a pretty divergent appearance from the Ist pair (fig. 15), and distinguish themselves perceptibly from the corres- ponding pair in N. bipes (Pl. IL, fig. 6). The endo- podite is here, in contrast to what is the case in the other pairs, very short, and without any distinct articular division; and the exopodite is likewise relatively smaller than in N. bipes, and is furnished on the outer edge with a series of. ciliated bristles. Five similar plumose bristles are also found on the short and rounded ventral lobe of the epipodite. The swimming feet have, in all essential respects, the same structure as in N. bipes;.only that they mere smeekker Form. Paa Iste Par (Fig. 17) er der dog den Forskjel, at Yderkanten af den ydre Gren kun har, umiddelbart ovenfor den yderste Torn, 3 Smaapigge, medens hos N. bipes hele denne Kant er tet og regelmessigt pigget. De 2 Par rudimentere Halefodder (Fig. 18, 19) viser ligeledes et Udseende, meget ner overens- stemmende med samme hos denne Art, alene med den Forskjel, at Tornernes Antal paa begge er noget ringere. Farven er hos det levende Dyr hvidagtig, uden nogen bemerkelig Pigmentering. Integumenterne er tynde og gjennemsigtige, saa de indre Organer tem- melig tydeligt skinner igjennem. ZEggene i Klekkehulen er forholdsvis store og af en meget bleg gulagtig Farve. Lengden af den w#gberende Hun er kun 9 mm., Sterrelsen er altsaa betydelig ringere en hos N. bipes. Forekomst. Jeg har hidtil kun seet 3 Expl. af denne Art, alle Hunner. De blev tagne til forskjel- lige Tider paa 3 vidt adskilte Punkter af vor Kyst, ‘det ene ved Hvitingso, udenfor Stavanger, det 2det i Trondhjemsfjorden, og det 3die ved Lofoten. Ex- emplarerne forekom paa alle 3 Steder i et Dyb af fra 150—200 Favne og paa bled Lerbund. Arten synes herefter at maatte betragtes som en udpreget Dybvandsform, hvad der ogsaa kan sluttes af de ufuldkomment udviklede Synsredskaber. Udenfor Norge er den endnu ikke bleven observeret. are altogether of a somewhat more slender form. In the 1st pair (fig. 17) there is, however, the diffe- rence, that the outer edge of the outer branch has, immediately above the outermost spine, only 3 small spikes, whilst in N. bipes the whole of that edge is closely and regularly spiked. The 2 pairs of rudimentary caudal feet (figs. 18, 19) likewise present an appearance very nearly correspondent with those in that species, with the difference only, that the number of spines on both is somewhat smaller, The colour in the living state of the animal is whitish, without any noticeable pigmentation. The integuments are thin and transparent, so that the internal organs are pretty distinctly visible through them. The ova in the hatching cavity are relatively large, and of a very pale yellowish colour. The length of the ovigerous female is only 9 mm. The size is thus considerably less than in N. bipes. b Distribution. I have hitherto only seen 3 spe- cimens of this species, all females. They were taken at different times, at 3 widely separated places off our coast; the one at Hvitingso, off Stavanger, the 2nd in the Trondhjemsfjord, and the 3rd at the Lo- foten isles. The specimens were obtained, at all ~ the 3 places, at a depth of from 150—200 fathoms and - on soft clay bottom. It appears from this, that the species must be considered as a distinguished deep- water form, which may also be gathered from the imperfectly developed visual apparatus. Out of Nor- way it has not hitherto been observed. - Subordo II. PHYLLOPODA. Character. Branchiopoder af meget forskjellig Kropsform, dels uden, dels med Rygskjold, det sidste undertiden udviklet i Form af 2 volumingse, det hele Dyr omsluttende Valvler. Legemets Segmenta- tion forskjellig hos de forskjellige Former. Ginene dels stilkede, dels sessile, undertiden neesten sammensmel- tede; et mediant Enkeltgie (ocellus) tilstede. Folerne i Regelen meget ulige udviklede; 1ste Par som oftest meget smaa og udelukkende sensitive; 2det Par af forskjellig Bygning, snart rudimentere (hos det voxne Dyr), snart udviklede til kraftige 2grenede Aarer, eller til tangformige Griberedskaber (hos Hannen). Overleben vel udviklet, klapformig; Under- leben i Regelen manglende. Kindbakkerne hos det udviklede Dyr uden Palpe. To Par Kjever tilstede, begge smaa og af forholdsvis simpel Bygning. Alle bag Munddelene folgende Lemmer respiratoriske, af tilnermelsesvis uniform Bygning og bladdannet lap- pet Form; deres Tal meget forskjelligt, undertiden abnormt stort. Udviklingen i Regelen en compli- ceret Metamorphose, begyndende med et frit Nauplius- Stadium. Indlandsdyr. Bemerkningér. Denne Underorden omfatter et ikke meget stort Antal Dyreformer, der imidlertid viser meget veesentlige Forskjelligheder, saavel hvad det ydre Udseende som den indre Bygning angaar. Hvad der hovedsageligt characteriserer denne Af- deling af Branchiopoder, og har givet dem sit Navn, er Structuren af de bag Munddelene folgende Lem- mer, der alle viser et lignende bladformigt og lappet Udseende som de til Midtkroppen hos Phyllocariderne horende saakaldte Branchialfodder. Da de tillige i sin Function er udpreget respiratoriske, benevnes Sudordo II. PHYLLOPODA. Characters. Branchiopods of very various shape, partly without and partly with carapace, the lastnamed sometimes developed in the form of 2 voluminous valves enveloping the entire animal. The. segmentation of .the body different in the various forms. Eyes partly pedunculated, partly sessile, sometimes nearly coalescent; a median single eye (ocellus) present. Antenne, as a rule, very unequally developed; Ist pair most frequently very small and exclusively sensitory; 2nd pair of vari- able structure, sometimes rudimentary (in the adult animal), sometimes developed to powerful, 2-branched oars, or to pincer-shaped prehensile apparatus (in the male). Anterior lip well developed, flap-formed; posterior lip, as a rule, wanting. Mandibles, in the developed animal devoid of palpi. Two pairs of max- ille present, both small and of relatively simple structure. All the appendages placed behind the oral parts respiratory, of approximately uniform structure and leaf-formed shape; their number -very variable, sometimes abnormally large. The de- velopment usually a complicated metamorphosis, commencing: with a free Nauplius-stage. Inland animals. Remarks. This sub-order includes a not very large number of animal forms, which exhibit, how- ever, very material divergencies, both in respect of the external appearante as well as in the internal structure. What chiefly characterizes this division of Branchiopods and has gevin to it its designation is, the structure of the appendages placed behind the oral parts, which all exhibit a similar leaf-shaped and lobed appearance as the so-called branchial-feet pertaining to the mesosome in the Phyllocarida. As they are, besides, in their function prominently 36 de ogsaa her paa samme Maade. Forskjellen er altsaa, at her alle bag Munddelene folgende Lemmer er wgte Branchialfedder, medens dette hos Phyllo- cariderne kun er Tilfeeldet med en Del af dem. I Folernes Bygning er der saa stor Forskjel hos de forskjellige Former, at intet andet bestemt feelles Charactertrek kan anfores end, at det iste Par ude- lukkende er sensitive og derfor af en meget tander Structur.. Ogsaa Minenes Bygning er meget forskjel- lig, idet de snart er stilkede som hos Phyllocariderne, snart sessile, snart sammensmeltede til et enkelt i det indre af Hovedet beliggende Organ. Characte- ristisk ligeoverfor Phyllocariderne er Tilstedeverel- sen af et mediant Enkeltoie (ocellus). Angaaende Munddelenes Structur, kan fremheves Mangelen af Palper paa Kindbakkerne, og den forholdsvis simple Bygning af de 2 Par Kjever. De hidtil bekjendte Phyllopoder vil passende ,kunne fordeles paa 3 storre Afdelinger, for hvilke jeg allerede i 18677’) har foreslaaet folgende Benzev- nelser: Anostraca, Notostraca og Conchostraca. For- skjellen mellem disse Afdelinger er saa stor og gjen- nemgribende, at de ikke, som af de fleste Forskere gjort, kan opfattes som blotte Familier, men. ube- tinget bor tillegges en langt hoiere systematisk Verdi (Tribus eller Sectioner). Til enhver af disse Grupper horer et meget begrendset Antal af Sleg- ter, som delvis lader sig fordele paa flere Familier. De herhen horende Slegttypers Faatallighed og i Regelen overordentlig skarpt udpreegede For- skjel, i Forbindelse med deres sporadiske Forekomst paa vidt adskilte Localiteter, synes at tyde hen paa, at vi i Phyllopoderne har. de sidste divergerende Grene af en uddsende Dyrgruppe, som rimeligvis, at domme efter flere paleontologiske Fund, har veret langt rigere representeret i tidligere Jordperioder. Ogsaa af disse Dyrs Organisation og Udvikling synes man at vere berettiget til at slutte, at de maa vere af meget gammel Oprindelse. Det yderlig variable Antal af Kropssegmenter og af Lemmer, disse sid- stes uniforme Bygning, den oftest kun .lidet skarpt udpregede Sondring af Legemet i tydeligt begrend- sede Kropsafsnit, alt dette er Characterer, der aaben- bart henpeger paa primitive Tilstande, hvori endnu ikke de hos de moderne Crustacegrupper gjeldende Forhold rigtigt har fixeret sig. Phyllopoderne min- der i denne Henseende ikke saa lidet om de #ld- gamle Trilobiter, ligesom der ialfald hos Afdelingen Notostraca er en umiskjendelig habituel Lighed med de ligeledes langt op i den geologiske Tid gaaende ') G. O. Sars, Histoire naturelle des Crustacés d’eau douce de Norvége, I. respiratory, they are also named here in the same manner. The difference, therefore, is, that here all the appendages placed behind the oral parts are real branchial feet, while in the Phyllocarida that is only the case with a part of them. ‘In the structure of the antenne there is such a great differ- ence in the various forms, that no other certain characteristic feature in common can be given, than that the Ist pair are exclusively sensitory and there- fore of a very delicate structure. The structure of the eyes also is very different, as they are some- times pedunculated, as in the Phyllocarida, sometimes sessile, sometimes coalescent to a single-organ situ- ated in the interior of the head. The presence of a single median eye (ocellus) is a characteristic feature in contrast with the Phyllocarida. Re- garding the structure of the oral parts may be mentioned, the absence of palpi on the mandibles, and the relatively simple structure of the 2 pairs of maxille. The Phyllopods hitherto known may suitably be assigned to 3 large divisions, for which the author, as early as 18671), proposed the following designations: Anostraca, Notostraca and Conchostraca. The differ- ence between those divisions is throughout, so great, that they cannot be regarded as families only, as has been done by most writers, but ought, evid- ently, to be assigned a far higher systematic value (Tribus or Sections). To each of these groups there pertain a very limited number of genera, which to some extent may be referred to several families. The paucity in number of the generic types pertaining hereto, and the, as a rule, extraordinarily sharply distinguished difference, in connection with their sporadic occurrenée in widely separated loca- lities, seems to give an indication that in the Phyllo- pods we have the last diverging branches of a van- ishing animal group, which, probably, judging by several paleontological discoveries, has been far more abundantly represented in earlier periods of our earth’s history. From the organisation and develop- ment, also, of these animals, it seems as if we were warranted in concluding that they must be of very old origin. The extremely variable number of body segments and of appendages; the uniform structure of the last-named; the usually only little sharply distinguished separation of the body in distinctly defined divisions, are all characteristics that evid- ently point to primitive conditions, in which the regulating relations of the modern groups of cru- staceans had not yet been thoroughly consolidated. The Phyllopods remind us in that respect, not so little of the ancient Trilobites, while, also, there, in ') G. O. Sars, Histoire naturelle des Crustacés d’eau douce de Norvége, I. Dolkhaler (Xiphosura). Det synes altsaa som om disse Dyr, uagtet deres Organisation idethele har naaet et forholdsvis meget hoit Udviklingstrin, dog ved Siden heraf har conserveret flere af de primitive Characterer, der maa antages at have udmerket de zldgamle Stamformer, hvorfra alle de moderne Cru- staceer i sidste Instans har taget sit Udspring. Ogsaa Udviklingen synes at stotte denne baade af Prof. Claus og Dr. Dohrn fremholdte Anskuelse. Saagodtsom hos alle Phyllopoder begynder nemlig den frie Udvikling med det overordentlig simple saakaldte Nauplius Stadium, og Larven gjennemgaar derpaa en Rekke af successive Omformninger, der lidt efter lidt forbereder Phyllopodestadiet. Det bor dog her bemerkes, at Dr. Packard i sit fortjenst- fulde Veerk over Nordamerika’s Phyllopoder heevder en herfra meget forskjellig Anskuelse. Efter denne Naturforskers Mening er Phyllopoderne tvertimod af meget ny Oprindelse og fremstaaet ved en videre Udvikling af Cladocer-Typen. Dette kunde maaske til Nod lade sig hore, hvor der er Sporgsmaal om den ene af Phyllopodernes 3 Sectioner, de saakaldte Conchostraca, der ganske sikkert viser en meget ud- preget Affinitet til Cladocererne. Men langt van- skeligere bliver det at faa udledet de 2 ovrige Phyl- lopode-Typer fra Cladocererne. Der gives ikke en eneste Cladocer, der viser den fjerneste Tilnermelse til de for Grupperne Anostraca og Notostraca cha- racteristiske Eiendommeligheder, og det gaar heller ikke an, at aflede disse 2 Typer fra den 3die Con- chostraca. De 3 Phyllopodetyper staar i Virkelig- heden paa en Maade helt isolerede og har rimelig- vis et meget forskjelligt Udspring. Langt natur- ligere end den af Packard fremsatte Hypothese om Phyllopodernes Afstamning fra Cladocererne, synes det mig at vere at vende Sagen helt om, og altsaa antage, at Cladocererne er af yngre Oprindelse end Phyllopoderne og har udviklet sig som en Sidegren fra Gruppen Conchostraca. Raadsperger vi Pale- ontologien, vil ialfald intet Modbevis mod en saadan Antagelse kunne hentes herfra; tvertimod. Medens man nemlig endnu ikke kjender en eneste Cladocer i fossil Tilstand, finder man talrige fossile Skaller af utvivlsomme conchostrake Phyllopoder, nermest henhorende til Slegten Estheria, lige op til den De- voniske Periode; noget der jo viser, at ialfald denne Gruppe af Phyllopoder ikke kan vere af saa ny Oprindelse, som man efter Packards Hypothese synes at maatte antage. Nu er der forskjellige morpho- logiske Forhold, der gjor det hoist usandsynligt at antage, at Gruppen Conchostraca skulde repreesen- tere de wldste og oprindeligste Phyllopoder. Vi kommer ad denne Vei snarere til en stik modsat . Slutning, nemlig at denne Gruppe er af en betyde- lig yngre Oprindelse end de 2 ovrige. At man ikke kjender nogen forverdenske Former af disse sidste Grupper, kan naturligt forklares af de herhen ho- 37 the division Notostraca, at any rate, is an unmistak- able habitual resemblance with the sword-tails (Xi- phosura), likewise passing far back in geological times It appears therefore, as if these animals, although their organisation has, upon the whole, attained, relatively, a very high stage of develop- ment, still have retained several of the primitive characteristics which must be assumed to have distinguished the ancient ancestors, from which all the modern crustaceans have finally had their origin. The development also seems to support that view, advocated both by Prof. Claus and Dr. Dohrn. In almost all the ~Phyllopods the free development begins, namely, with the extraordi- narily simple so-called Nauplius stage; and the larva thereupon undergoes a series of successive transformations, which, little by little, prepare the , phyllopod-stage. It ought to be noted here, how- ever, that Dr: Packard in his admirable work upon the Phyllopods of North America, maintains a very different view. According to the opinion of that naturalist, the Phyllopods are, on the con- trary, of very late origin, and produced by a further development of the Cladocera-type. That might per- haps, in the absence of anything better, be accepted, when the question concerns one of the 3 sections of Phyllopods, the so-called Conchostraca, which quite certainly exhibits a very distinguished affinity to the Cladocera. But far more difficult does it become, to trace the 2 other phyllopod-types from the Cla- docera. There is not a single Cladoceran that exhi- bits the slightest approximation to the characteristics peculiar to the groups Anostraca and Notostraca, and neither is it permitted for us to trace these 2 types trom the 3rd, the Conchostraca. The 3 types of Phyllopods stand in reality, in a measure, quite isolated, and probably have a very different origin. Far more natural than the hypothesis of the deri- vation of the Phyllopods from the Cladocera, pre- sented by Packard, does it appear, to me, to be, to quite reverse the case, and consequently assume that the Cladocera are of later origin than the Phyllo- pods and have become developed, as a lateral branch, from the group Conchostraca. If we consult pale- ontology, we will, at any rate, find no testimony rebutting such an assumption to be obtained there- from; on the contrary, while we do not yet know of a single Cladoceran in fossil condition, we find numerous fossil remains of indubitable conchostracan Phyllopods most closely approaching to the genus Estheria, even up to the Devonian period; a fact that certainly shows that that group of Phyllopods, at any rate, cannot be of such late origin as we, according to Packard’s hypothesis, seem obliged to suppose. Now there are various morphological rela- tions that make it extremely improbable to suppose that the group Conchostraca represents the oldest rende Dyrs lidet faste Integumenter, der neppe er egnede til at opbevares i fossil Tilstand. Dog maa det her bemerkes, at det langt fra er sikkert, at alle de eldgamle, fordetmeste siluriske Former, der af Packard henregnes til Phyllocariderne, virkelig horer herhen. Enkelte af dem har ialfald habituelt, ved sit flade Rygskjold og tildels Mangelen af den for Phyllocariderne characteristiske Pandeplade, en vel saa stor Lighed med notostrake Phyllopoder (Apus), og kan derfor muligvis ligesaa sandsynligt have hert herhen. Da man af ingen af disse fossile Former kjender Lemmerne, maa deres rette syste- matiske Stilling endnu blive at betragte som et aabent Spergsmaal. Alle egte Phyllopoder er Indlandsformer og forekommer som oftest i ganske smaa og grunde Ferskvandsansamlinger, der om Sommeren ganske eller delvis udtorres. Arterne af Slegten Artemia er eiendommelige for det sterkt saltholdige Vand i de saakaldte Saliner. I Havet existerer der derimod for Tiden ingen Phyllopoder. Angaaende disse Dyrs Forplantningsmaade og Udvikling, saa stoder vi her paa mange eiendomme- lige og interessante Forhold, ligesom deres sporadiske Forekomst, Udbredningsforhold og Levevis idethele frembyder yderst merkverdige Ting, som neppe endnu er tilstrekkeligt forklaret. Naar hertil kom- mer deres ofte meget bizarre Udseende, elegante Be vegelser og eiendommelige Organisation, synes der virkelig at vere Grund for med Packard at anse dem for de interessanteste af alle Crustaceer. Skjondt der til Norges Fauna kun horer ialt 5 Former, er dog alle de 3 ovenneyvnte Hovedgrup- per representerede, og enhver af de norske Former representerer desuden for sig en serskilt Familie. 38 and most original Phyllopods. We arrive in that way at, rather, a quite contrary conclusion, namely that that group is of considerably younger origin than the 2 others. That we are ignorant of any prime- val forms of these lastnamed groups may be natur- ally explained by the little firm nature of the inte- guments of the animals pertaining hereto, which are scarcely adapted for preservation in fossil condition. Still it must be noted here that it is far from cer- tain that all the ancient, chiefly silurian forms, which are assigned by Packard to the Phyllocarida, really pertain thereto. A few of them have, at any rate, in habitus, by their flat carapace and partly from the absence of the frontal plate characteristic of the Phyllocarida, a rather stronger resemblance to notostracan Phyllopods (Apus), and may therefore just as probably have possibly pertained thereto. As we do not know the appendages from any of these fossil forms, their correct systematic position must still be considered an open question. All genuine Phyllopods are inland forms, and usually appear in quite small and shallow collections of fresh-water, which in summer quite, or partially, dry up. The species of the genus Artemia is peculiar to the strongly salt water in the so-called salines. In the ocean there exist, on the other hand, at the present time, no Phyllopods. Regarding the method of reproduction of these animals and their development, we come here upon many peculiar and interesting relations, while also their sporadic appearance, distributive relations, and mode of life upon the whole, present extremely remarkable things which are scarcely yet suffici- ently elucidated. When to this is added their fre- quently very bizarre appearance, the elegance of their movements and the peculiar ‘organisation, there seems really to be reason for, like Packard, consi- ‘dering them to be the most interesting of all ern- staceans. Although there only pertain 5 forms altogether to the fauna of Norway, the 3 above named chief groups are, however, all represented; and each of the Norwegian forms represents of itself, besides, a separate family. ' Sectio I. Anostraca. (Negne Phyllopoder). Syn: Phyllopoda pisciformia. Character. Legemet forlenget, meget blodt og beieligt, mere eller mindre ormformigt, uden Spor af noget Rygskjold eller Skal. Legemets Segmen- tering temmelig uniform, dog med tydelig Adskillelse i Hoved, Midtkrop og Hale. Qinene tydeligt stilkede og beveegelige, af en lignende Bygning som hos Ne- balia. Forste Par Folere meget smaa, traadformige; 2det Par hos Hunnen mere eller mindre rudimentere, fligformige, hos Hannen omdannede til kloformige Griberedskaber. Kindbakkerne med stump riflet Tyggeflade, uden tydeligeTender. Branchialfodderne uden Coxallap, men med 1 eller 2 Deekblade ved Basis paa den ydre Side, alle af noget ner ens Byg- ning, udpreget respiratoriske, men samtidigt ogsaa locomotoriske. Halen uden Lemmer, dens forreste Segmenter delvis sammenvoxne og givende Udspring for de ydre Kjonsvedheng: hos Hunnen en enkelt, mere eller mindre sewkformig Agbeholder med ter- minal Aabning, hos Hannen 2 fuldsteendig skilte og meget smaa Copulationsredskaber. Udviklingen en compliceret Metamorphose begyndende med et frit Nauplius-Stadium. / Bemerkninger. De til denne Afdeling herende Phyllopoder er let kjendelige ved sit langstrakte og blede, nzsten ormlignende Legeme, ved Mangelen af et Rygskjold eller Skal, ved de tydeligt stilkede Mine, ved den eiendommelige Bygning af 2det Par Folere hos de to Kjon, endelig ved den eiendomme. lige Beskaffenhed af de ydre Kjonsvedheng. Man kan fordele de hidtil bekjendte Former paa 3 Fa- milier: Branchipodide, Thamnocephalide og Polyarte- miide. Kun den forste og sidste af disse Familier er representerede i Norges Fauna. Den 3die Fa- milie er opstillet af Packard for en merkelig nord- amerikansk Form, 7'hamnocephalus platywrus Packard,.- der, foruden ved de eiendommelige Frontalvedheng, udmerker sig i hoi Grad derved, at Halen ender med en enkelt bred horizontal Svommeplade. 39 Sectio I. Anostraca. (Naked Phyllopods). Syn: Phyllopoda pisciformia. Characters. Body prolonged, very soft. and flexible, more or less vermiform, without trace of any carapace or shell. The segmentation of the body pretty uniform, but with distinct division be- tween the head, the mesosome and the tail. Eyes distinetly pedunculated and moveable, of similar structure to these in Nebalia. First pair of antenne very small, filiform. Second pair more or less rudi- mentary in the female, flap-shaped; transformed in the male to claw-formed prehensile apparatus. Mandibles with blunt rifled masticatory surface, with- out distinct teeth. Branchial feet without coxal lobe, but with one or two covering plates at the base on the outer side; all of somewhat uniform structure, distinguished respiratory, but at same time also locomotive. Tail without appendages; the foremost segments partly coalescent and furnishing the origin for the outer sexual appendages: in the female a single, more or less sac-formed marsupium with terminal aperture; in the male 2 completely separated and very small copulative appendages. The development a complicated metamorphosis, com- mencing with a free Nauplius stage. Remarks. The Phyllopods belonging to this division are easily recognizable by their elongate and soft, almost vermiform body, by the absence of a carapace or shell, by the distinctly pedunculated eyes, by the peculiar structure of the 2nd pair of antenne in the two sexes and, finally, by the pe- culiar character of the outer sexual appendages. We may refer the hitherto known forms to 3 families: Branchipodide, Thamnocephalide and Polyartemiide. Only the first and last named of these families are represented in the fauna of Norway. The 3rd family is established by Packard, to include a remarkable ‘North American form, Thammnocephalus platyurus, Packard, which, besides by its peculiar frontal appendages, distinguishes itself in a high degree, in that the tail terminates in a single, broad hori- zontal swimming plate. 40 Branchipodide. Fam. 1. Character. Legemet smalt cylindriskt, noget tykkere fortil, med Halen vel udviklet og tydeligt segmenteret hos begge Kjon, endende med 2 borste- besatte Halegrene. Hannens Gribeantenner tydeligt segmenterede og i Regelen forsynede med en rudi- mentere Bigren. Frontalvedheng tilstede hos Han- nen eller manglende. 11 Par Branchialfodder til- stede, alle med en enkelt sagtakket ydre Dekplade. Hunnens Hgbeholder tydeligt seekformig og bagud- rettet, udspringende fra de 2 forreste Halesegmenter. Bemerkninger. Til denne Familie horer ialt 5 Slegter, nemlig: Artemia Leach, Branchinecta, Verrill, Branchipus Schiffer, Chirocephalus Prevost, og Streptocephalus Baird. Kun en af disse Slegter, Branchinecta, er representeret i vor Fauna. Fami- lien er hovedsageligt characteriseret ligeoverfor den felgende Familie, Polyartemiide, ved den forskjellige Bygning af Hannens Gribeantenner, ved det bety- delig ringere Antal Branchialfodder, ved Halens Form, endelig ved Beskaffenheden af Hunnens Egge beholder. Fra Familien Zamnocephalide, med hvem den kommer overens i Antallet af Branchialfodder, skiller den sig ved Legemets smekrere Form og navnlig ved Beskaffenheden af Halen. Gen. Branchinecta, Verrill, 1869. Syn: Branchipus, Milne-Edw. (ex parte). Slegtscharacter. Legemet af serdeles slank Form, med Halen tynd og forlenget, bestaaende af 9 Segmenter, foruden Halegrenene; de sidste for- holdsvis korte. Hannens Gribeantenner simple, be- staaende af et tykt cylindriskt.Skaft og en smal, kloformig, indadkrummet Endedel; Bigrenen meget liden, knudeformig. Ingen Frontalvedheng tilstede. Branchialfodderne forholdsvis brede, med Exopoditen af afrundet oval Form, og den ydre Dekplade sag- takket i Kanterne. Hunnens Eggebeholder serdeles smal og forleenget, nesten cylindrisk. Bemerkninger. Denne af den amerikanske For- sker, Prof. Verrill, opstillede Slegt er vesentlig characteriseret ligeoverfor Sl. Branchipus Schiiffer ved den overordentlig slanke Kropsform, ved Man- Branchipodide. Fame: Character. Body narrow cylindrical, somewhat thicker in front, with the tail well developed and distinctly segmented in both sexes, terminating in 2 bristle-beset caudal rami. Prehensile antenne of the male distinctly segmented, and usually furnished with a rudimentary sub-branch. Frontal appendages present in the male or awanting. 11 pairs of branchial feet present, all having a single serrated external covering plate. Marsupium of the female distinctly sac-formed, directed backwards, and i issuing from the 2 foremost caudal segments. Remarks. Five genera in all pertain to this family, namely: Artemia, Leach; Branchinecta, Verrill; Branchipus, Schaeffer; Chirocephalus, Prevost, and Streptocephalus, Baird. Only one of these genera, Branchinecta, is represented in our fauna. The family is principally characterised, in contrast with the following ‘family Polyartemiide, by the different structure of the prehensile antenne of the male, by the considerably smaller number of branchial feet, by the shape of the tail and, finally, by the cha- racter of the marsupium in the female. It distingu- ishes itself from the family Zamnocephalide, with which it agrees in the number of branchial feet, by the more slender form of the body, and se cially in the character of the tail. Gen. Branchinecta, Verrill, 1869. Syn: Branchipus, Milne-Edw. (ea parte). Generic characters. -Body of particularly slen-_ der shape, with the tail slender and prolonged, consisting of 9 segments besides the caudal rami; the last named relatively short. Prehensile an-_ tenn of the male simple, consisting of a thick, eyl-- indrical shaft, and a narrow, claw-shaped, incurved terminal part; the sub-branch very small, nodiform. No frontal appendage present. Branchial feet re- latively broad, with the exopodite of rounded oval form and the outer covering plate serrated on the edges. Marsupium of the female particularly narrow and elongated, almost cylindrical. Remarks. This genus, established by the Ame- rican naturalist, Prof. Verrill, is chiefly characteri- sed, in contrast with the gen. Branchipus, Schiffer, by the extraordinarily slender shape of the body, 4 gelen af Frontalvedheng hos Hannen, ved den meget forskjellige Form af Hunnens Aigheholder, endelig ved betydelig kortere Halegrene. Betydelig storre Affinitet har den til Slegten Artemia Leach, med hvilken den stemmer overens baade i Henseende til den almindelige Habitus og ved Mangelen af Frontal- vedheng hos Hannen. Den skiller sig imidlertid ogsaa fra denne Slegt ved visse vel udpregede Cha- racterer, sauledes ved den forskjellige Form af Han- nens Gribeantenner og af Hunnens Agbeholder, endelig derved, at Halen har et Segment flere. Man kjender ialt med Sikkerhed 6 herhen horende Arter, nemlig, foruden den nedenfor neermere beskrevne arktiske Form, 2 nordamerikanske Arter: B. colora- densis Packard og B. Lindahli Packard, en af Baird fra Jerusalem beskreven Form, B. eximia, og to russiske Arter fra Omegnen af Odessa, B. spinosa M. Edw. og B. feror M. Edw. Det var denne sidste Art, som den russiske Naturforsker Schmankewitch troede at se forvandlet til en Artemia ved paa kun- stig Maade at domesticeres i saltholdigt Vand, noget der vel egentlig er at forstaa saaledes, at Arten under de forandrede Forhold antog visse Charac- terer, der mindede om ovennevnte Slegt. Branchinecta paludosa (Miiller). (Pl. VI, VII, VIII). ° Cancer stagnalis, Fabr., Fauna gronlandica, No. 224 (non Linné). Branchipus paludosus, Miller, Zool. Danica II, 10, Pl. 48, Fig. 1—8. Branchipus middendorfianus, Fischer, Middendorf's Sibirische Reisen, Bd. II, p. 153, Pl. VII, Fig. 17--2% Branchinecta gronlandica, Verrill, Amer. Journ. Se. 1869, p. 253. ‘Branchinecta arctica, Idem, ibid. Artscharacteristik. Legemets Form slank og elegant, med de 3 Kropsafsnit vel markerede. Ho- vedet af middelinaadig Storrelse, jevnt afrundet for- til hos begge Kjon. Halen betydelig lengere end den foranliggende Del af Legemet, smalt cylindrisk, med nestsidste Segment det. lengste, og sidste Seg- ment omtrent halvt saa langt. Halegrenene nesten dobbelt saa lange som sidste Segment, smalt lancet- formige og tet kantede med cilierede Borster. 2det Par Folere hos Hunnen nesten-.af Hovedets Lengde, meget skraat afskaarne i Enden, med det bagre Hjorne udtrukket i en skarp Spids. Samme Folere hos Hannen mere end dobbelt saa lange, Skaftet noget krummet ved Basis, tykt cylindriskt, med en Rad af smaa Tender langs den indre Kant; Ende- delen lidt kortere, noget boiet paa Midten og jevnt afsmalnende mod Spidsen, som er stumpt tilrundet. Branchialfodderne med Endopoditens ydre Lap hos 6 — G. 0. Sars: Fauna Norvegiz. 41 by the absence of frontal appendages in the male, by the very different shape of the marsupium of the female, and, finally, by considerably shorter caudal rami. It has much greater affinity to the genus Artemia, Leach, with which it agrees, both in regard to the general habitus and in the absence of frontal appendages in the male. It distinguishes itself, how- ever, also from that genus by certain well marked characteristics; thus, by the different form of the prehensile antenne of the male and of the mar- supium in the female, and, finally, in the tail hav- ing an additional segment. We know with certainty of 6 species, altogether, pertaining hereto, namely, besides the Arctic form more particularly described below, 2 North American species: B. coloradensis, Packard, and B. Lindahli, Packard; a form from Jerusalem, described by Baird, B. eximia; and 2 Russian species from the neighbourhood of Odessa, B. spinosa, M. Edw. and B. ferox M. Edw. It was the last named species that the Russian naturalist Schmankewitch believed to have seen transformed to an’ Artemia, by being, in an artificial manner, do- mesticated in water containing salt; a fact which may be more properly understood in this manner, viz. — that the species, under the changed relations, assumed certain characters which reminded of the above-named genus. Branchinecta paludosa (Miiller). (Pl. VI, VII, VII). Cancer stagnalis, Fabr., Fauna gronlandica, No. 224 (non Linné). Branchipus paludosus, Miller, Zool. Danica II, 10, Pl. 48, figs 1—8. Branchipus middendorfianus, Fischer, Middendorf'’s Sibirische Reisen, Bd. Il, p. 153, Pl. VII, figs. 17—23. Branchinecta grgnlandica, Verrill, Amer. Journ. Se. 1869, p. 253. Branchinecta arctica, Idem, ibid. Specific characteristics. Form of body slender and elegant, with the 3 -body-divisions well mar- ked off. Head of moderate size, evenly rounded in front in both sexes. Tail considerably longer than the part of the body lying in ‘front of it, narrow cylindrical, with the penultimate segment the longest, and the last segment about half as long. Caudal rami almost twice as long as the last segment, narrow lanceolate in shape, and closely edged with ciliated bristles. Second pair of an- tenn, in female, almost the length of the head, very obliquely truncated at the extremity, with the posterior corner drawn out to a sharp point. Same antenne in male more than twice as long; shaft somewhat curved at the base, thick cylindrical, with a series of small teeth along the inner edge; terminal part a little shorter, somewhat curved in the middle, and narrowing evenly towards the point, Hunnen kort trianguler, hos Hannen betydelig ster- kere uddraget og nesten leformig indadkrummet. Hunnens Agbeholder serdeles forlenget, rekkende neesten til Enden af nestsidste Halesegment. Han- nens ydre Kjonsvedheng cylindriske, forsynede ved Basis fortil med 2 fremspringende Flige, mellem hvilke der er en dyb Indbugtning. Legemet hos begge Kjon gjennemsigtigt, med et mere eller min- dre tydeligt gronligt eller redligt Anstrog. Hun- nens Lengde indtil 18 mm:, Hannens 23 mm. Bemerkninger. Denne Art er allerede i 1780 af O. Fabricius anfort fra Gronland, men urigtigt identificeret med Br. stagnalis Scheeffer. ‘Senere er den under den oventor anforte Species-Benevnelse kjende- ligt beskrevet og afbildet af O. Fr. Miiller i hans bekjendte Veerk, Fauna danica. De af Prof. Verrill som B. grgnlandica og arctica opforte Former har senere vist sig at vere identiske med nerverende Art, og det samme er utvivlsomt ogsaa Tilfeldet med’ B. middendorfianus Fischer, Af de 2 nordame- rikanske Arter beskrevne af Packard, synes B. colo- radensis at komme meget ner den her omhandlede Art, medens B. Lindahli skiller sig mere kjendeligt, navnlig ved de betydelig sterkere forlengede Hale- grene. Generel Beskrivelse. Legemet er hos begge Kjon (se Pl. VE, Fig. 1—4) smalt og forlenget, ne- . sten ormformigt, med serdeles tynde og boielige Integumenter, samt inddelt i tydelige Segmenter, Man kan adskille 3 temmelig skarpt begraendsede Kropsafsnit, nemlig Hoved, Midtkrop og Bagkrop eller Hale. Hovedet bestaar igjen af 2 Partier, et forreste og et bagerste, skilte ved en tydelig over Rygsiden gaaende Tversutur. Det forreste Parti er noget opsvulmet, nesten kugleformigt, og mere eller min- dre sterkt nedboiet. Det berer Ginene og 2 Par Folere, samt fortseetter sig nedentil i Overleben. Til det bagre Parti eller Nakkedelen horer de ovrige Munddele. Af disse er mest ioinefaldende de kraf- tigt udviklede Kindbakker, der som et Par Boiler omgiver Hovedet paa Greendsen mellem dettes 2 Af snit, og hvis baadformige Corpora danner til hver | Side et tydeligt convext Fremspring, sely bemerke- ligt, naar Dyret sees ovenfra. lLige bag Kind- bakkerne sees til hver Side af Nakkesegmentet en S-formigt bugtet Figur, den saakaldte Skalkjertel, hvis bagre Del omsluttes af en lidt fremspringende Hudfold, den forste svage Antydning til det hos andre Phyllopoder saa sterkt udviklede Rygskjold eller Skal. Ventralt udgaar fra Nakkesegmentet de 2 Par Kjever. 42 which is bluntly rounded. Branchial feet with the outer lobe of the endopodite, in female, short tri- angular; in male considerably more drawn out, and almost falciformly curved inwards. Mar- supium of female greatly prolonged, reaching al- most to the extremity of the penultimate caudal segment. Outer sexual appendages of male eylin- drical, furnished in front, at the base, with 2 projecting flaps, between which there is a deep sinus. more or less distinct greenish or reddish tinge. Length of female up to 18 m. m.; that of male 23 m. m. Remarks. This species is, as early as 1780, recorded by A. Fabricius from Greenland, but errone- ously identified with Br. stagnalis, Scheffer. Subse- quently it has been, under the above-named specific designation, recognizably described and illustrated by O. Fr. Muller in his well-known work, Fauna danica. The forms established as B. grgnlandica and arctica by Prof. Verrill, have subsequently shown themselves to be identical with the present species, — and the same is also indubitably the case with B. middendorfianus, Fischer. Of the 2 North Ame- rican species described by Packard, B. coloradensis appears to approach pretty closely the species here described, whilst B. Lindahli distinguishes itself more noticeably, especially by the considerably more prolonged caudal rami. General description. The body is, in both sexes, (see Pl. VI, figs. 1—4) narrow and prolonged, almost vermiform, with particularly thin and flexible inte- guments, and is divided into distinct segments. © We can distinguish 3 pretty sharply defined divi- sions of the body, viz., the cephalon, the mesosome, and the metasome or tail. 3 The cephalon, again, consists of 2 parts, an an- terior and a posterior one, separated by a distinct transversal suture passing across the dorsal side. The foremost part is somewhat swollen, almost glo- bular, and more or less strongly bent downwards. It carries the eyes and the 2 pairsof antenne, and is continued downwards in the upper lip. The other oral parts pertain to the posterior, or cervical part. Of these, the most striking are the powerfully de- ‘veloped mandibles, which like a pair of bows sur- round the head on the limit between its 2 divisions, and whose cymbiform corpora form on either side a distinctly convex prominence, even noticeable when the animal is viewed from above. Just behind the mandibles there is seen, on either side of the cervi- cal segment, an S-formed flexuous figure, the so-called shell-gland, whose posterior part is enclosed by a slightly projecting integumental fold, the first faint indication of the, in other Phyllopods so strongly developed carapace or shell. The 2 pairs of Body transparent in both sexes, with a. Det paa Hovedet folgende Kropsafsnit, Midt- kroppen eller Truncus, er fortil omtrent af Hovedets ‘Brede og lidt nedtrykt, men afsmalnes lidt i sin bagerste Del. Det er sammensat af 11 paa hinanden folgende korte og ensformigt udviklede Segmenter, hvoraf ethvert berer et Par Branchialfodder. Disse sidste folger med regelmessige korte Mellemrum efter hinanden, dannende med sine forskjellige Lap- per og talrige Borster til hver Side en bred Breemme. Herved fremkommer langs Midtkroppens Underside en af samtlige Branchialfodder begrendset kanal- agtig Fordybning, der gradvis tiltager noget i Brede fortil, hvor den stoder op mod Mundregionen. Bagkroppen eller Halen er overordentlig slank, betydelig smalere end Midtkroppen, og af regelmes- sig cylindrisk Form. Den udgjor kjendeligt mere end Halvdelen af Legemets Totallengde, og er sam- mensat af 9 Segmenter foruden Halegrenene. Af disse Segmenter er de 2 forreste kun i den dorsale Del tydeligt sondrede, medens de ventralt gaar over i hinanden og danner her Udspringet for de ydre ‘Kjonsvedheng. Disse 2 forste Segmenter af Halen vil derfor passende kunne benevnes: «Kjonsringene». Hos Hunnen er det forreste af disse Segmenter noget opsvulmet fortil, og det bagerste danner nedentil, ved Basis af Hgbeholderen, 2 rundagtige Fremspring, der navnlig- er meget tydeligt fremtredende, naar Dyret sees ovenfra eller nedenfra (se Tab. VI, Fig. 4, Tab. VIL, Fig. 11). De folgende 5 Segmenter er alle af ens Udseende og ogsaa af tilnermelsesvis samme Storrelse, simpelt cylindriske, med Lengden betydelig sterre end Breden. Nestsidste Segment er derimod betydelig lengere end de ovrige, og sidste omvendt meget kort, neppe mere end halvt saa langt som nestsidste. Det er (se Tab. VI, Fig. 10) tveert afkuttet. i Enden og viser i Midten af den bagre Kant en ganske svag Indbugtning. Til hver Side _af denne, og adskilte i Midten ved et storre Mellem- rum, er festet de smalt lancetformige Halegrene, der maaske, i Lighed med den saakaldte Furca hos Copepoderne, kan betragtes som fremkomne ved Klov- ningen af et terminalt Segment, men som dog vel correctest vil kunne beskrives som et Par omformede Lemmer. : Hunnens Lengde gaar op til 18 mm. -Hannen er i, Regelen kjendelig storre og opnaar ofte en Lengde af indtil 23 mm. Begge Kjon er desuden let kjendelige ved den meget forskjellige Udvikling af 2det Par Foiere, samt ved Beskaffenheden af de ydre Kjonsvedheng. Disse vil tea gp kunne be- a paa dette Sted. 43 maxillee ment. The division of the body that succeeds the head, the mesosome or truncus, is about same breadth in front as the head, and a little flattened, but narrows a little in its backmost part. It is composed of 11 short and uniformly developed seg- ments, of which each carries a pair of branchial feet. These last follow after each other at regular issue ventrally from the cervical seg- . short intervals, forming with their various lobes and numerous bristles a broad fringe on either side. In this way there is produced along the un- derside of the mesosome a canalular cavity, borde- red by all the branchial feet, which gradually in- creases somewhat in breadth in front, where it joins up to the oral region. The metasome or tail is extraordinarily slen- der, considerably narrower than the mesosome, and of regular cylindrical shape. It occupies appreciably, more than half the entire length of the body, and is composed of 9 segments besides the caudal rami. Of these segments, the 2 foremost ones are only distinctly separated in the dorsal part, whilst they ventrally pass over into each other, and _ form here the origin of the outer sexual appendages. These 2 first segments of the tail may, therefore, sui- tably be named «the sexual segments». In the female the foremost of these segments is somewhat swollen in front; and the backmost forms downwards, at the base of the marsupium, 2 roundish prominences, which are, especially, very distinctly prominent when the animal is viewed from above or from below (see Pl. VI, fig. 4, Pl. VIII, fig. 11). The succeeding 5 segments have all a uniform appearance, and are also of approximately the same size, plain cylin- drical, with the length considerably greater than the breadth. The penultimate segment is, on the contrary, considerably ‘longer than the others, while, on the other hand, the last is very short, scarcely more than half as long as the penultimate one. It is (see Pl. VI, fig. 10) transversally truncated at the extremity, and in the middle of the posterior edge shows a quite faint sinus. -On either side of this, and separated in the middle by a lar- gish interval, the narrow lanceolate caudal rami are attached,” which, perhaps, like the so-called furca in the Copepods, may be considered as pro- duced by the splitting of a terminal segment, but which, however, probably more correctly may be described as a pair of transformed appendages. The length of the female reaches up to 18 m. m. The male is, as a rule, appreciably larger, and fre- quently attains a length of 23 m..m. Both sexes are, further, easily recognizable by the very different development of the 2nd pair of antenne, and by the character of the outer sexual appendages. These may be conveniently described here. Hos Hunnen (Tab. VI, Fig. 3,4) danner de ydre Kjonsvedheeng en enkelt bagudrettet, poseformig Be- holder af meget smal, nesten cylindrisk Form, dog gradvis noget tiltagende i Tykkelse mod Enden. I sin fulde Udvikling rekker den nesten til Enden af nestsidste Halesegment; men er ofte en Del kor- tere. Sedvanligvis sees i dens indre et storre eller mindre Antal af Ag af morkegron Farve, ordnede i 2 eller flere Rader. Enden «uf Aigbeholderen er noget koniskt tillobende og bestaar af 2 ved ser- - egne Muskler bevegelige Klapper, der begrandser en tverliggende spaltformig Aabning, hvorigjennem JEggene udstedes. Den ventrale Klap er noget mere fremragende end den dorsale og ender med et lidet papilleformigt Fremspring (se Tab. VIII, Fig. 11). Hos Hannen (Tab. VI, Fig. 1 og 2) er Kjons- heengene dobbelte og meget smaa. De udspringer (se Fig. 11) hvert med en temmelig bred Basis fra Siderne af de 2 Kjonsringe og retter sig skraat nedad og bagud. Fortil viser de ner sit Udspring en dybt indstikkende Bugt, som begrzendses oventil af en sammentrykt trianguler Lap, nedentil af en konisk tilspidset Fortsats. Den ydre Del af Ved- henget er simpelt cylindriskt, og fra dens stumpt tilrundede Ende sees undertiden en uregelmessig sagtakket Vorte at skyde frem, egentlig en Udkreng- ning af vas deferens. Legemet er hos begge Kjon i hoi Grad gjennem- sigtigt, saa at de indre Organer, navnlig den med rodgult Indhold fyldte Tarmkanal, tydeligt skinner igjennem de tynde Integumenter. Farven er noget vekslende efter Lokaliteterne, snart meget bleg, hvidagtig, snart med et mere eller mindre tydeligt redligt eller gronligt Anstrog. Beskrivelse af Kroppens Vedheng. Qinene (Tab. VI, Fig. 9; Tab. VII, Fig. 1 og 2, 0), der rager frem til hver Side fra den forreste Del af Hovedet, er stilkede og viser idethele en meget lignende Bygning som hos Nebalia, skjondt deres Bevegelighed er langt mere begreendset. Af Form er de nesten kelledannede, idet de gradvis udvides mod Enden, der er noget skjevt tilrundet. Den egentlige Gienglob, der indtager omtrent 1/3 af @iets Leengde, indeholder en oval eller elliptisk An- samling af moerkt Pigment, omgivet udad af en klar Zone, hvori de ydre lysbrydende Dele af Syns- elementerne har sin Plads (se Tab. VIII, Fig. 6). Nogen ydre Facettering er ligesaalidt tilstede her som hos Nebalia. — Midt imellem Minene sees i det Indre af Hovedet en dyb sort Pigmentplet, som er det saakaldte Ocellus eller enkle @ie. In the female (Pl. VI, figs. 3, 4), the outer sexual appendages form a single, bag-formed reservoir directed backwards, of very narrow, almost cylind- rical shape, but increasing gradually somewhat in thickness towards the extremity. In its full develop- ment it extends almost to the extremity of the pe- nultimate segment, but is often somewhat shorter. There is usually seen in its interior a larger or smaller number of ova of dark green colour, arranged in 2 or several series. The extremity of the mar- supium runs somewhat conically out, and consists of 2 flaps, moveable by means of peculiar mus- cles, which define a transversal fissure-like aper- ture through which the ova are expelled. The ventral flap is somewhat more projected than the dorsal one, and terminates in a small papilliform prominence (see Pl. VIII, fig. 11). . In the male (Pl. VI, figs. 1 and 2), the sexual appendages are double and very small. They issue, (see fig. 11), each with a pretty broad base, from the sides of the 2 sexual segments and are di- rected obliquely downwards and backwards. They exhibit in front, near their origin, a deep sinus, which is defined above by a compressed triangular lobe, and below by a conically pointed projec- tion. The outer part of the appendage is plain cylindrical, and from its bluntly rounded extremity an irregularly serrated nipple is sometimes seen to project, really a bulging out of the vas deferens. The body, in both sexes, is in a high degree transparent, so that the internal organs, especially the intestinal canal, filled with red-yellow contents, shine distinctly through the thin integuments. The colour is somewhat variable, according to the locality, sometimes very pale, whitish, sometimes with a more, or less distinct reddish or greenish tinge. Description of the appendages of the body. The eyes (Pl. VI, fig. 9; Pl. VII, figs. 1 and 2, 0), which project forwards on either side of the foremost part of the head, are distinctly peduncul- ated, and altogether exhibit a very similar structure to those of Nebalia, although their mobility is far more limited. They.are almost claviform in shape, as they become gradually dilated towards the extre- — mity, which is somewhat obliquely rounded. The real ocular globe, which occupies about 1/s of the eye, contains an oval or elliptical collection of dark pigment, surrounded outwards by a clear zone in which the outer refracting portions of the visual elements have their position (see Pl. VIII, fig. 6). Any external facetting is just as little present here as in Nebalia. Midway between the eyes there is seen, in the interior of the head, a deep black pigment-patch, which is the so-called ocellus or simple eye. Forste Par Folere (Tab. VI, Fig. 9, a'; Tab. VII, Fig. 1, 2, a') er meget smaa og simpelt byggede, dannende hver en meget smal cylindrisk, eller ne- sten traadformig Stamme, paa hvilken ingen tyde- ligt udpreget Leddeling kan paavises. De er sed- vanligvis rettede skraat fortil og udad (se Tab. VI, Fig. 1—4), men kan ogsaa til en vis Grad beveges i andre Retninger, ligesom de idethele er meget boielige. Paa Spidsen, der er noget skraat afskaa- ret, berer de (se Tab. VIII, Fig. 2) en Gruppe af 8 yderst smaa og delikate Sandsevedheng, som ved sterk Forsterrelse (Fig. 3) viser en stavdannet Form, med et kort, dobbelt contureret Fodstykke og en liden klar Blere ved den stumpt afrundede Spids. Ifelge sin Bygning maa disse Vedheng nermest betragtes som Lugtepapiller; medens de 3 betydelig lengere, og i en fin Spids udgaaende Vedheeng, som udspringer i nogen Afstand fra hine fra en afrundet Forhoining, utvivlsomt er at anse som egte Fole- berster. ; Andet Par Folere, der udspringer fra Hovedets nedre Flade umiddelbart nedenfor og lidt indenfor det iste Par, er meget forskjellige hos de 2 Kjon. Hos Hunnen er de (se Tab. VI, Fig. 9, a?; Tab. VII, Fig. 1, a*) forholdsvis smaa og simple, dannende et Par, som det synes fuldkommen ubevegelige fra Hovedet nedheengende pladeformige Flige. De er omtrent af samme Lengde som Qinene og nesten triangulere i Form, idet de udspringer med en tem- melig bred Basis og gradvis afsmalnes mod Enden, som er meget skraat afskaaret, med det bagre Hjorne uddraget i en skarp Spids. I sin forreste Kant har de nogle yderst smaa Foleborster, men er forovrigt ganske ubeveebnede. — Hos Hannen er disse Folere (se Tab. VI, Fig. 1, 2; Tab. VII, Fig. 2, a?) langt sterkere udviklede og omformede til kraftige Gribe- redskaber, hvormed Hunnen fastholdes under Copu- lationen. I Hviletilstand er de mere eller mindre steerkt ombsiede mod Bugsiden og rekker i denne Stilling omtrent til Midten af Forkroppen. Man kan paa dem adskille to skarpt begreendsede Afsnit: et tykt eylindriskt og sterkt muskulost Skaft, og en tynd kloformig Endedel. Skaftet viser ved Basis flere cireulere Indsnoringer, der antyder 3 til 4 ufuldsteendigt sondrede Led. Yderdelen af Skaftet har indad en noget tilskjerpet Kant, forsynet med en Rekke af smaa Tender, og ved Enden, indenfor Endedelens Insertion, findes en liden konisk tillobende Knude, eller rettere Bigren. Endedelen er noget kortere end Skaftet og meget smalere, men af ser- deles fast chitines Consistens. Den er bevegeligt articuleret med Skaftet og mere eller mindre sterkt indboiet, samt gradvis afsmalnende mod Spidsen, som er stumpt tilrundet. I Modsetning til hvad Til- felde er hos Hunnen, er disse Folere hos Hannen 45 The first pair of antenne (Pl. VI, fig. 9, at; Pl. VII, figs. 1, 2, a") are very small and simple in structure, each forming a very narrow cylindrical or almost filamentous stem, upon which no distinctly distinguished articulation can be shown. They are usually directed obliquely forwards and outwards (see Pl. VI, fig. 1—4), but may also, to‘a certain extent, be moved in other directions, while they are also, upon the whole, very flexible. At the tip, which is somewhat obliquely truncated, they carry (see Pl. VIII, fig. 2) a group of 8 extremely small and delicate sensory appendages, which on a power- ful magnification (fig. 3) exhibit a rod-like shape, with a short, double-contoured foot-piece, and a smallclear vesicle at the bluntly rounded point. From their structure those appendages must be chiefly considered as olfactory papillae, whilst the 3 considerably longer, and to a fine point issuing, appendages, which spring from a rounded prominence at some distance from the former, must indubitably be considered as ge- nuine sensory bristles. The scecond pair of antenne, which issue from the lower surface of the head immediately below and a little inside of the 1st pair, are very different in the 2 sexes. In the female they are (see Pl. VI, fig. 9, a®; Pl. VII, fig. 1, a*) relatively small and simple, forming a pair of apparently perfectly im- moveable plate-formed flaps hanging from the head. They are of about same length as the eyes, and almost triangular in shape, as they issue with a ’ pretty broad base and gradually diminish in breadth towards the extremity, which is very obliquely trun- cated, with the posterior corner drawn out to a sharp point. On the foremost edge they have a few extremely small sensory bristles, but are otherwise perfectly unarmed. In the male these antenne (see Pl. VI, fig. 1, 2, Pl. VII, fig. 2, a*) are far stronger developed, and are transformed into powerful prehen- sile organs by which the female is firmly held during copulation. In a condition of repose they are more or less greatly recurved towards the ventral side, and in that position extend to the middle of the anterior body. We are able to distinguish upon them two sharply defined divisions; a thick cylind- rical and strongly musculous shaft, and a thin claw-shaped terminal part. The shaft exhibits se- veral circular constrictions at the base, which indi- cate 3 to 4 imperfectly separated joints. The outer part of the shaft has, inwards, a somewhat sharp- ened edge, furnished with a series of small teeth; and at the extremity, to the inside of the insertion of the terminal part, there is found a small nodule, or more correctly speaking an accessory branch, which runs out conically. The terminal part is somewhat shorter than the shaft and much narrower, but of particularly firm chitinous consistency. It-is movably meget bevegelige og kan tilsammen virke som et meget kraftigt tangformigt Griberedskab, Af Munddelene er Overleben og de 2- Kind. bakker let ioinefaldende. Derimod er de 2 Par Kja- ver meget vanskeligere at opdage og lader sig egent- lig kun ngiere undersoge ved Dissection. Overleben (Tab. VI, Fig. 9, L; Tab. VII, Fig. 1, L; Fig. 3) har Formen af en aflang Lap, der fra Hovedets Ventralside strekker sig bagtil, og sedvan- ligvis fuldsteendig dekker over Kindbakkernes Tygge- dele (se Tab. VI, Fig. 9). Den viser paa Midten en svag Udvidning og ender med en stump Spids, hvis Kanter er fint cilierede. Dens ydre Flade er noget convex, medens den indadvendte Flade er plan eller concav og laadden af fine, tildels gruppevis ordnede Haar. “Ved Hjelp af flere sterke Muskler, som fra Hovedet passerer igjennem dens Indre, kan den snart loftes op fra Kindbakkerne, snart presses ind mod dem igjen. Ind under dens Basis ligger (se Tab. VII, Fig.3) Mundaabningen i Form af en tver- oval Spalte, der bagtil begreendses af en ubetydelig fremspringende, haaret Kant. Nogen egentlig Under- lebe er derimod ikke tilstede. Kindbakkerne (Tab. VI, Fig. 9, M; Tab. VII, Fig. 1, M; Fig. 4) er af meget kraftig Bygning og omslutter som et Par Boiler den nedre Del af Ho- vedet paa Greendsen mellem dets forreste og bagerste Parti. Det convexe baadformige Corpus, der saa- godtsom fuldstendig udfyldes af de kraftige, indad convergerende Tyggemuskler, ender oventil i en Spids, der er bevegeligt indleddet til Hovedets Inte- gument ved Enden af den dorsale Sutur, der be- grendser Nakkesegmentet fortil. Den ventrale Ende, eller den egentlige Tyggedel, er (se Tab. VIL, Fig. 4) sterkt indboiet og begreendset fra Corpus ved en svag Indknibning eller Hals. Den er stumpt afkuttet i Enden og har en oval Tyggeflade, der ved sterk Forstoerrelse (Fig. 5) viser, sig fint riflet paatveers, med den ydre Del af Riflerne noget grovere og besat med Rekker af tet sammentrengte tandformige Fremspring. Af nogen egentlig skjgwrende Del, er der imidlertid intetsomhelst Spor. De 2 Par Kjever kommer forst tilsyne, naar man betragter Dyret fra Bugsiden, efterat de for- reste Branchialfodder er fjernede eller lagte om til Siderne (se. Tab. VI, Fig. 9,m’—m*; Tab. VII, Fig. 1, m'-—m*). De er begge forholdsvis smaa og af enkel Bygning. — Forste Par (Tab. VII, Fig. 6) bestaar 46 articulated with the shaft and more or less strongly incurved, and gradually diminishes in breadth to- wards the point, which is bluntly rounded. In con- trast to what is the case in the female, these antenne are, in the male, very mobile, and can act together as a very powerful forceps-formed prehensile ap- paratus. Of the oral parts, the upper lip.and the 2 man- dibles are readily visible. On the other hand, the 2 pairs of maxilla are much more difficult to dis- cover and can, in reality, only be closely investigated upon dissection. ; The anterior lip (Pl. VI, fig. 9, L; PI. VII, figs. 1, L; fig. 3) has the shape of an oblong lobe, which extends backwards from the ventral side of the head, and usually completely covers over the masti- catory parts of the mandibles (see Pl. V1, fig. 9). It exhibits at the middle a faint dilation, and ter- minates in a blunt point whose edges are finely ciliated. Its outer surface is somewhat convex, while the inwards turned surface is plane or con- cave, and fluffy with fine hairs arranged partly in groups. With the aid of several strong muscles which from the head pass through its inside, it can easily be raised up from the mandibles, and be easily again pressed in towards them. In below its base lies the oral aperture, in the shape of a trans- verse-oval fissure, which is bordered behind by an inconsiderably projectant hirsute edge. Any real posterior lip is, on the contrary, not present. ' The mandibles (Pl. VI, fig. 9, M; Pl. VII, fig. 1, M, fig. 4) are of very powerful structure, and enclose, like a pair of bows, the lower part of the head at the limit between the anterior and posterior portions. The convex cymbiform corpus, which is almost completely occupied by the power- — ful, inwards-convergent masticatory muscles, ter- minates above in a point, which is movably arti- culated to the integument of the head, at the ex- tremity of the dorsal suture which limits the cer- vical segment in front. The ventral extremity, or the real masticatory part, is (see Pl. VII, fig. 4) strongly incurved and defined from the corpus by a faint constrietion or neck. It is bluntly truncated at the extremity, and has an oval masticatory sur- face which upon powerful magnification (fig. 5) shows itself to be finely fluted transversally, with the outer part of the flutings somewhat coarser, and beset with series of closely crowded dentiform, pro- jections. Of any real cutting part there is, how- ever, no trace.’ The 2 pairs of maxille appear first to view when we observe the animal from the ventral side after the foremost branchial feet have been removed or placed away to the sides (see Pl. VI, fig. 9 m.1W— m.?; Pl. VII, fig. 1 m.t—m.*). They are both rela- tively small and of simple structure. — The first e Am - af en tyk muskulos Basaldel og en med denne be- vegeligt forbunden og strkt indboiet Endedel. Denne sidste har Formen af et triangulert Blad, der paa sin frie, lige afskaarne Rand er besat med en Rekke af stive Borster, tiltagende i Lengde indad. Enhver Borste bestaar (Fig. 7) af en noget tykkere Basaldel besat i den ene Kant med grove Pigge, og en i en fin Spids udlobende, og i begge _ Kanter tet cilieret Endedel. — Andet Par Kje- 8) er langtfra saa kraftigt udviklede og ° _ synes heller ikke ifolge sin Stilling at kunne spille ver (Fig. nogen vesentlig Rolle ved Neringsoptagelsen. De udspringer (se Fig. 1, m’) lidt bag 1ste Par og er, ganske i Modsetning til hine, rettede udad. Basal- delen har paa den nedre Side 3 tykke Fjerborster. Endedelen synes kun at vere lidet bevegelig og viser en noget oval Form. Dens udadvendte Side er tet besat med’ stive, kort cilierede Borster, der staar i flere Reekker og divergerer til alle Sider. Den forreste Borste er noget grovere end de ovrige og festet i nogen Afstand fra disse til et kort Fremspring. _ Branchialfodderne (se Tab. VII, Fig. 9—13) er alle udpreget bladformige og af temmelig bred Form, med den forreste Flade noget hvelvet og den ba- gerste mere eller mindre concav. Man kan paa dem adskille de samme Hoveddele, som allerede ovenfor er beskrevne paa Branchialfodderne hos Nebalia. Basaldelen eller Stammen er af aflang Form og _neeten ens Brede overalt. I dens Indre sees for- skjellige hinanden delvis krydsende Muskelbundter, der dels tjener til at boie selve Stammen, dels vir- ker paa de forskjellige Vedheng. Stammens ydre Kant er noget fortykket og viser ved Basis nogle svage Ind- og Udbugtninger som en Antydning til en Slags ufuldsteendig Leddeling. Dens indre Kant er delt i 5 korte Lappe, de saakaldte Enditer, hvoraf den bagerste, eller overste, er meget bred og langs sin halymaaneformigt buede Rand besat med en tet Rad af kamformigt ordnede og sterkt .krummede Borster, alle fint cilierede og bestaaende af 2 tyde- lige Led (se Fig. 10). De ovrige Lappe er meget mindre, nesten af mammilledannet Form, og besat med lignende krummede Borster, samt desforuden foran dem med et Knippe betydelig grovere saa- danne. Endopoditen (end), der danner den umiddel- bare Fortsettelse af Stammen, er forholdsvis ganske kort og har Formen af en bred trianguler, noget indadrettet Plade, besat langs Yderkanten med stzrke Fjerborster, der ved Spidsen og langs den indre Kant efterhaanden antager Charaecteren af korte Torne, cilierede kun i den ene Kant. Exopoditen (ex), der er bevegeligt articuleret til en sa#regen Afsats af Stammen ved Ydersiden af Endopoditen, 47 ‘branchial feet of Nebalia. pair (Pl. VII, fig. 6) consist of a thick, musculous basal part, and a strongly incurved terminal part connected movably with it. The last-named has the form of a triangular lamella which, upon its free, straightly truncated margin, is beset with a series of stiff bristles, increasing in length inwards. Each bristle (fig. 7) consists of a somewhat thicker basal part, beset on the one edge with coarse spikes, and a terminal part which runs out in a fine point and is closely ciliated on both edges. — The second pair of maxille (fig. 8) are far from being so power- fully developed, and neither do they, from their position, appear to play any material part in the securing of nourishment. They issue (see fig. 1 m.®) a little behind the 1st pair, and are, quite in con- trast to them, directed outwards. The basal part has 3 thick plumose bristles on the lower side. The terminal part appears to be only little mobile, and exhibits a somewhat oval form. Its outwardly turned side is closely beset with stiff, short ciliated bristles placed in several series, and divergent to all sides. The foremost bristle is somewhat coarser than the others, and is attached at some distance from them to a short projection. The branchial feet (see Pl. VII, figs. 9—13) are all prominently foliaceous and of pretty broad form, with the foremost surface somewhat convex, and the backmost one more or less concave. We Scan distinguish in them the same chief parts, as have already been described above concerning the The basal part or stem is of an oblong shape, and almost uniform in breadth throughout. In its interior may be seen various bundles of muscles partly traversing each other, which serve partly to bend the stem itself, partly act on the various appendages. The outer edge of the stem is somewhat thickened, and at the base ex- hibits a few faint in- and out- curvatures, as an indication of a kind of imperfect articulation. Its inner edge is divided into 5 short lobes, the so-called endites, of which the backmost or uppermost one is very broad, and along its semi-lunary arcuate margin is beset with a close series of strongly curved bristles arranged like a comb, all finely cili- ated and consisting of 2 distinct joints (see fig. 10). The other lobes are much smaller, almost mammilli- form in shape, and beset with similar curved brist- les, and besides, in front of them, with a fascicle of considerably coarser sete. The endopodite (end) which forms the immediate continuation of the stem, is, comparatively, quite short, and has the form of a broad triangular, somewhat incurved plate, beset along the outer edge with strong plumose sete, which at the tip and along the inner edge succes- sively assume the character of short spines, ciliated only. on the one edge. The exopodite (ex) which is har Formen af et ovalt Blad, rundt om besat med en Rad af Fjerborster. I nogen Afstand fra Exo- poditen, omtrent ved Midten af Stammens Yder- kant, er Epipoditen (ep) festet. Den represente- res af et forholdsvis ikke meget stort, simpelt, aflangt, seekdannet Vedheng, der er rettet skraat nedad og bagud. I sin finere Structur skiller den sig noget fra de ovrige Vedheng, idet den er af mere spongios Beskaffenhed, og antager paa Spiri- tusexemplarer meget snart et temmelig opakt Ud- seende. Fornden de neynte Hoveddele, som alle ogsaa er tilstede hos Nebalia, kommer her endnu til et seregent Vedheng, der er specielt eiendomme- ligt for Gruppen Anostraca, og som jeg ovenfor har benzevnt «Dekpladen», for at antyde dets Bestemmelse, der nermest synes at vere den, til en vis Grad at erstatte det manglende Rygskjold ved at dekke over Roden af Branchialfodderne. Dette Vedheng (b) udgaar ligeledes fra Ydersiden af Stammen, men lige ved dennes Rod, og har For- men af en meget tynd og gjennemsigtig oval Plade, regelmessigt sagtakket i Kanterne. — Undersoger man ngiere de 11 Par Branchialfodder og sammen- ligner dem med hverandre, vil man finde enkelte mindre Differentser i deres Bygning. Hvad for det forste Storrelsen angaar, saa tiltager de gradvis noget i Lengde fra iste til omtrent 5te Par, for saa jevnt at aftage i Storrelse bagtil, saa at sidste Par neppe er halvt saa stort som 5te og noget min- dre end Iste. Det forreste Par (Fig. 9) skiller sig fra de folgeude ved en noget ringere Udvikling af Exopoditen, medens Endopoditen er forholdsvis ster- kere fremspringende, mindre indadrettet, og kun for- synet med en enkelt Torn i Inderkanten. Sidste Par (Fig. 12) udmerker sig fra de ovrige derved, at Epipoditen har antaget Characteren af en tynd Plade, besat i Kanterne med cilierede Borster, og derved at Dekpladen ganske mangler. Endopoditen er paa dette Par meget kort og af afrundet Form, medens Exopoditen er vel udviklet.— Hos Hannen skiller Branchialfodderne (Fig. 13) sig kjendeligt fra samme hos Hunnen ved Endopoditens betydelig ster- kere Udvikling. Den er navnlig paa de midterste Par sterkt fremspringende indad, nesten af le- dannet Form, og forsynet med et stort Antal af Randtorner. Rimeligvis har denne Modification af Endopoditen hos Hannen et vist Hensyn til Copula- tionen, idet Branchialfodderne derved delvis kan fun- gere som et Slags Griberedskaber og derved under- stotte 2det Par Antenner i deres Function at fast- holde Hunnen under Parringen. 48 o movably articulated to a separate ledge of the stem at the outer side of the’ endopodite, has the form of an oval lamella, beset all round with a row of plu- mose sete. At some distance from the exopodite, about in the middle of the outer edge of- the stem, the epipodite (ep) issecured. It is represented by a, comparatively, not very large, simple, oblong vesicu- lar appendage, which turns obliquely downwards and backwards. In its microscopical structure it differs somewhat from the other appendages, exhibiting a more spongious character, and in alcoholic specimens it very soon assumes a rather opaque appearance. Besides the above nained chief parts, which are all also present in Nebalia, another peculiar appendage is here added, which particularly distinguishes the group Anostraca, and which I have named above «the covering plate», in order to indicate its most probable purpose, viz, to replace to a certain extent the absent carapace in covering over the base of the branchial feet. This appendage (b) issues likewise from the outer side of the stem, but close to the base of the latter, and has the form of a very thin and pellucid plate, regularly serrated on the edges. — On a closer examination and comparison of the 11 pairs of branchial feet, some minor differences in their structure will be found to exist. Firstly, as . regards the size, they increase successively somewhat in length from the Ist to about the 5th pair, after which they again gradually decrease in size, in such a manner that the last pair are scarcely half as large as the Sth and also somewhat smaller than the Ist. The foremost pair (fig. 9) differ from the succeeding ones by a somewhat slighter development of the exopodite, whereas the endopodite is com- paratively more strongly produced, less incurvate, and only provided with a single spine on the inner edge. The last pair (fig. 12) distinguish themselves from the others by the epipodite having assumed the character of a thin plate edged with ciliated bristles, and by the complete want of any covering plate. The endopodite is, on this pair, very short and of rounded shape, whereas the exopodite is well developed. In the male the branchial feet (fig. 13) distinguish themselves very markedly from the same in the female, by the much stronger development of the endopodite. The latter is, especially on the middle pairs, strongly produced’ inwards, almost falciform in shape, and provided with a great num- ber of marginal spines. In all probability this mo- dification of the endopodite in the male has a cer- tain relation to the act of copulation, since the branchial feet thereby become, to a certain extent, enabled to act as a kind of prehensile organs, thus assisting the 2nd pair of antenne in their function to retain hold of the female during copulation. Indre Organer. Den indre Organisation er hos nerverende Form ikke saa serdeles vanskelig at studere, da Dyrets store Gjennemsigtighed gjor det muligt at observere saagodtsom alle indre Organer i sin Situs, uden at nogen Dissection er fornoden. Paa de her givne Habitusfigurer (Tab. VI, Fig. 1—4) er de vig- tigste indre Organer antydede, saaledes som de viser sig ved en svag Forstorrelse. Paa Tab. VII er af- bildet Detailler af Nervesystemet, Fordoielsessyste- met og Kjonssystemet i steerkere Forstorrelse. Fordgielsessystemet. — Tarmtractus bestaar af 3 tydeligt begreendsede Dele, nemlig Spiserer, Chy- lustarm og Endetarm. Spiseroret er meget kort, sterkt muskulost, og stiger lodret op fra Mund- aabningen til den forreste, i Hovedet beliggende Del af Tarmen. Denne sidste Del er noget udvidet og viser, overensstemmende med Legemets Konturer, en. svag Krumning, men gaar forevrigt umerkeligt over i den bagenfor liggende Del af Tarmen, uden at vere begrendset fra samme som nogen virkelig Mave. Fortil udsender denne Del til hver Side en afrundet blindsekformig Udvidning, som bedst sees, naar Legemet betragtes ovenfra (Tab. VI, Fig. 4). Ved nermere Undersogelser viser enhver af disse Udvidninger sig sterkt foldet (se Tab. VII, Fig. 10), eller ligesom bestaaende af et Antal uregelmessige secundere Udposninger, alle indvendigt bekledte med et kjertelagtigt Epithel, der delvis ogsaa fort- setter sig ind i selve Tarmen. Der er ingen Tviv] om, at disse 2 blindsekformige Udvidninger af Tar- men er homologe med det hos andre Phyllopoder i Hovedet beliggende complicerede kjertelagtige Organ, man ialmindelighed har kaldt Leveren, men som hos neerveerende Gruppe er steerkt reduceret og saa- ledes paa en Maade danner Overgangen til de simple blindseekformige Appendices, der forefindes paa samme Plads hos visse Cladocerer. Ligeledes maa de oven- for beskreyne saakaldte Leverseekke hos Nebalia an- tages at hore ind under samme Kategori, skjondt kun et Par af disse strekker sig ind i selve Hove- det. Tarmen danner forovrigt (se Tab. VI, Fig. 1—4) et simpelt cylindriskt, med steerke Ringmuskler forsynet Ror, der uden nogen Bugtninger strekker sig gjennem Dyrets Axe indtil Halens sidste Seg- ment, hvor den forbinder sig med Endetarmen. Denne sidste (se Fig. 10), der altsaa kun er ind- skrenket til sidste Halesegment, er, som det ovrige Tarmror, forsynet med steerke Ringmuskler og des- uden ved straaleformigt til dens Overflade gaaende Muskelfibre fixeret i sin Stilling. Ved Hjelp af alle disse Muskler bliver denne Del af Tarmtractus meget bevegelig og kan vexelvis sterkt indsnores og udvides, hvad der har sin Betydning ved Ud- tommelsen af Excrementerne. Medens Dyret lever, 49 Internal Organs. The internal organisation in the present form is not especially difficult to study, as the animal’s great transparency renders it possible to observe almost all the internal organs in situ, without the necessity of dissection. In the habitus figures here given (Pl. VI. figs. 1—4), the most important inter- nal organs are shown as they appear under a low power of the microscope. On Pl. VI, details of the nervous, the digestive and the sexual systems are given, more highly magnified. Digestive system. — The intestinal tract con- sists of 3 clearly-defined portions, viz, the «so- phagus, the chyle-intestine and the rectum. The gsophagus is very short and muscular, and ascends vertically from the oral orifice to the anterior por- tion of the intestine, which is situated in the head. This portion is somewhat expanded, and, in agree: ment with the contour of the body, exhibits a slight curve, passing then imperceptibly into that part of the intestine lying behind, without being defined from it as a true stomach. In front this portion sends out to each side a rounded, cecal dilatation, which is best seen on viewing the body from above (Pl. VI, fig. 4). On a closer examination, each of these dilatations proves to be very much folded (see Pl. VUI, fig. 10), or to consist, as it- were, of a number of irregular secondary lobules, all lined interiorly with a glandular epithelium which also partly extends into the intestine itself. There is no doubt that these two cecal dilatations of the intes- tine are homologous with the complicated glandular organ found in the head of other Phyllopoda, which has generally been called the liver, but which, in the present group, is very much reduced, thus form- ing, to some extent, the transition to the simple cecum-like appendages found in the same place in certain Cladocera. The previously-described biliary ceca in Nebalia may similarly be supposed to come under the same category, although only two of them extend as far as into the head itself. The rest of the intestine (see Pl. VI, figs. 1—4) is in the form of a simple cylindrical tube furnished with strong annular mus- cles, and extending, without any windings, through the animal’s axis as far as the last segment of the tail, where it unites with the rectum. This last (see fig. 10), which is thus confined to the last caudal segment, is, like the rest of the intestinal tube, furnished with strong annular muscles, and is also fixed in its position by muscle-fibres radiating towards the outer surface. By the aid of these muscles, this portion of the intestinal region becomes very mobile, and can be alternately contracted and expanded, thus assisting in the evacuation of the excrements. While the animal is alive, very vigor- observeres paa Tarmroret meget energiske peristal- | ous peristaltic movements of the intestinal tube may 7 —G. 0. Sars: Fauna Norvegix. tiske Bevegelser, der med stor Regelmessighed for- plantes langs ad dens hele Lengde, ialmindelighed i Retningen bagfra fortil. Circulationssystemet. — Hjertet danner (se Tab. VI, Fig. 2, 3, 11 ce) et overordentlig langstrakt, med bestemte Mellemrum indsnoret Ror, der strekker sig ovenfor Tarmen fra Nakkesegmentet og bagtil lige ind i Halens nestsidste Segment. Det er ved fine Muskeltraade festet til Indsiden af Ryggens Inte- gument, og viser for hvert Segment et Par venose Spaltaabninger, hvorigjennem Blodet optages i Hjer- tet. Den samlede Blodmasse, som paa denne Maade trenger ind i Hjertet, udstedes dels fra den forreste, dels fra den bageste Ende, og kommer derpaa ind i veglose Hulrum mellem de forskjellige Organer. Skjondt saaledes et egentligt Karsystem, bestaaende af Arterier og Vener, ganske mangler, circulerer dog Blodet med stor Regelmessighed omkring i Lege- met, idet det folger visse bestemte Baner. Blodet er, som sedvanligt, farvelost og indeholder en Mengde smaa, tildels amosboide Blodlegemer, * hvis Gang let lader sig forfolge hos det levende Dyr under Mikroskopet. Hjertets Pulsationer, hvorunder Spaltaabningerne afvexlende aabnes og Iukkes, er seerdeles livlige, saa det er meget vanskeligt at telle, hvormange der sker i Minuttet. Nervesystemet. — Centraldelene af Nervesyste- met bestaar; som hos andre Crustaceer, af et dorsalt Parti, det ovre Svelgganglion eller Hjernegangliet, og af en ventral Del, den saakaldte Bugganglie- kjede, begge forbundne ved en omkring Spiseroret lobende Commissur (se Tab. VIII, Fig. 1). Hjernegangliet (se Fig. 1, 4, 17), der. har sin Plads i den forreste Del af Hovedet, lige foran Be- gyndelsen af Tarmen, er af temmelig’ betydelig Stor- relse, og bestaar af 2, i Midten med hinanden for- bundne symetriske Halvdele. Oventil danner det flere Lappe, der delvis omfatter Basis af det enkle Mie (se Fig. 4), og til hver Side fortsetter det sig ji den megtigt udviklede Synsnerve (0), efterat have udsendt en tynd Nerve til lste Par Antenner (a’). Et andet Par Nerver sees at udgaa fra Hjernegang- liet leengere fortil, til hver Side af det enkle Gie. De ender hver med en liden ganglios Opsvulmning umiddelbart under en liden grubeformig Fordybning i Hovedets forreste Integument (a), rimeligvis sva- rende til de omtrent paa samme Sted hos Limnetis forekommende cilierede Gruber, der ialmindelighed ansees for et Slags Sandseorgan. Nerverne for 2det Par Folere (a*), der hos Hannerne er betydelig sterkere end hos Hunnerne, udspringer fra den for. reste Del af Svelgcommissurerne. Disse sidste for- bindes, inden de omfatter Spiseroret, ved en tynd Tvercommissur (se Fig. 1 og 4), der ligger ved Basis af Overleben. 50 \ be observed, these being transmitted with great regularity throughout its entire length, generally from behind forwards. Circulatory system. — The heart (see Pl. VI, figs..2, 3, 11¢) consists of an exceedingly elongated tube, constricted at regular intervals, and extending above the intestine from the cervical segment back- wards into the penultimate segment of the tail. It is attached by fine muscle-fibres to the inside of the dorsal integument, and exhibits, in each segment, a pair of venous ostia, through which the blood is received into the heart. The accumulated mass of blood, which thus forces itself into the heart, is expelled partly from the anterior, partly from the posterior end, and then enters the several cavities between the various organs. Although there is thus a total absence of a true vascular system consisting of arteries and veins, yet the blood circulates with great regularity through the body, following certain fixed courses. The blood is, as usual, colourless, and contains a number of small, partly amcbous blood-corpuscles, whose course may be easily traced under the microscope. The pulsations of the heart, during which the ostia alternately open and close, are exceedingly rapid, so that it is very difficult to count the number occurring in a minute. Nervous system. -- The central portion of the nervous system consists, as in other Crustaceans, of a dorsal part, the supracsophageal or cerebral ganglion, and of a ventral part, the so called ventral ganglion chain, connected with one another by a commissure round the cesophagus (see Pl. VIII, fig. 1). The cerebral ganglion (see figs. 1, 4 and 17), which is situated in the anterior part of the head, just in front of the commencement of the intestine, is of considerable size, and consists of 2 symmetri- cal halves connected with one another in the middle. Above, it forms several lobes which partially sur- round the base of the ocellus (see fig. 4), and, after sending out a fine nerve to each of the first pair of antennee (a), continues on each side in the form of the powerfully developed optic nerve (0). A second pair of nerves are seen to issue from the cerebral ganglion farther forward, on each side of the ocellus. They each end in a little ganglionic protuberance immediately below a small pit-like depression in the anterior integument of the head (a) probably ‘an- swering to the ciliated pits occurring in about the same place in Limmetis, and which are generally considered to be a kind of organ of sense. The nerves for the second pair of antenne (a*) which are considerably stronger in the males than in the females, originate from the anterior part of the cesophageal commissures. These, before they encircle . the esophagus, are connected by a thin transverse commissure (see figs. 1 and 4) lying near the base of the anterior lip. i ore Buggangliekjaden (se Fig. 1) er ikke vanskelig at observere saavel hos levende Exemplarer som hos Specimina opbevarede i fortyndet Spiritus. Man behover blot med Forsigtighed at udbrede Branchial- fodderne til hver Side og indstille Mikroskopet skarpt paa Bugfladen af Dyret, og denne Del af Nerve- systemet vil, ialfald delvis, klart og tydeligt sees, uden at nogen virkelig Dissection er fornoden. Dog er dens forreste Del altid temmelig vanskelig at ob- servere, da den fordetmeste skjules af de lidet. gijen- nemsigtige Kindbakker og af Kjzverne. Buggang- liekjeeden viser en meget udpreeget stigedannet Form, idet den bestaar af 2 vidt adskilte sterke Nerve- stammer, som i hvert Segment forbindes: med en dobbelt Tvercommissur. Paa dette Sted viser hver ‘Nervestamme en temmelig svag ganglios Opsvulm- ning (se Fig. 5), fra hvis ydre Side 2 sterke Nerver udspringer. Det ene Par af disse Nerver trenger ind i de respective Branchialfodder, medens det andet Par synes at inneryere de Muskler, der fra Kroppen passerer til Basis af disse Lemmer. En anden betydelig svagere Nerve udspringer omtrent fra Midten af enhyer af Langdecommissurerne og synes at ende i Legemets Sidemuskler. Antallet af de Nerveknuder, der sammen med Commissurerne danner Buggangliekjeden, er paa hver Side 15 (se Fig: 1). Heraf er de 3 forreste Par bestemte for Kindbakkerne og de 2 Par Kjever, det bageste Par for Genitalsegmentet, de 11 ovrige for de 11 Par Branchialfadder. Buggangliekjeden er saaledes ind- skrenket til Forkroppen alene. I Bagkroppen fort- settes rigtignok de 2 Nervestammer. lige til Enden af sidste Segment, men uden her at vere forbundne ved Tvercommissurer og uden at danne tydelige Ganglier. I hvert Halesegment udsender disse Nerve- stammer fine Nervegrene, hvoraf nogle synes at ud- brede sig i Halens Muskulatur, medens andre ender med en liden ganglios Opsvulmning lige under Huden (se Fig. 8). -Paa disse Steder sees altid en over- ordentlig fin Borste (Foleborste) at springe frem, til- dels omgiyen af smaa Hudpapiller (Fig. 9). 3 = _ Angaaende den Maade, hvorpaa de ovrige Ner- ver ender, skal her blot omtales Forholdet med de til Iste Par Folere gaaende Nerver og Synsnerverne. " Forste Par Foleres ee udspringer. (se Fig. 4) at ladende fra det basale Parti af Synsnerverne, let. begge Nerver ved sit Udspring er omgivet af e les Neryeskede. De trader derefter til hver ey som en tynd Stamme ind i Iste Par Foleres Basis og fortsetter sig igjennem deres Axe indtil henimod | Spidsen. Her deler Nerven sig (se Fig 2) i 2 Grene, der tilsammen danner en betydelig gang- Tos Masse ved Spidsen af Foleren. Fra denne 51 The. ventral. ganglion chain (see fig. 1) is not difficult to examine, either in living specimens or in those preserved in diluted spirit. It is only neces- sary to turn the branchial legs carefully to either side, and adjust the microscope close to the animal's ventral surface, when this part of the nervous sys- tem, will, at any rate to some extent, be seen clearly and distinctly, without the necessity of actual dissection. The front part, however, is always rather difficult of observation, as it is generally almost hidden. by the hut slightly transparent man- dibles: and by the maxille. The ventral ganglion chain. exhibits.a marked ladder-like form, in that it consists of 2, strong, widely-separated nerve-stems, which are connected in each segment by a double transverse commissure. Here each nerve-stem exhi- bits a rather slight ganglionic dilatation (see fig. 5), on the outer side of which, 2 strong nerves have their origin. One. of these pairs of nerves penetrates into the respective branchial legs, while the other pair appears to innerve the muscles passing from the body to the base of those appendages. Another much weaker nerve has its origin almost in the middle of each of the longitudinal commissures, and appears to end in the lateral muscles of the body. The number of ganglia that, together with the com- missures, form the ventral ganglion chain, is 15 on each side (see fig. 1). Of these the 3 foremost pairs are destined for the mandibles and the two pairs of maxille, the hindmost pair for the genital segment, and the remaining 11 for the 11 pairs of branchial legs. The ventral ganglion chain is thus confined to the anterior division of the body. It is true that the 2 nerve-stems are continued im the hinder part of the body as far. as the end of the last segment, but without being there connected by any transverse commissures, and without forming distinct ganglia. In every caudal segment these nerve-stems send out delicate rami, some of which appear to spread over the caudal musculature, while others end in a little ganglionic tuberosity just below the integument (see fig. 8.) At these places an exceedingly fine bristle (sensory bristle) is always seen to protrude, parti- ally surrounded by small cutaneous papille (fig. 9). With regard to the manner’in which the re- maining nerves end, only the circumstances relating to those of the 1st pair of antenne, and the optic nerves will be mentioned here. . The nerves of the Ist pair of antenne (see fig. 4) apparently originate from the basal, part of the optic nerves, both nerves being surrounded at their origin by a common neural-sheath: They then pass to either side. in the form of a thin stem into the base of the first pair of antennee, whence they con- tinue along the axis of the latter almost to the extremity. Here the nerve divides (see fig. 2) into 2 branches, which together form a considerable 52 gangliose Masse udgaar igjen overordentlig fine | Nervefibre til ethvert af de her feestede Vedheng. Synsnerverne (Fig. 4, 0) danner til hver Side en steerk, lige udad gaaende Stamme, der, efterat veere traadt ind i Mienstilkene, svulmer nd til et kolbe- formigt Synsganglion. Dette (se Fig. 6) er ved en transversal Indsnoring delt i 2 paa hinanden fol- gende Knuder eller Segmenter og udsender fra sin noget skjevt afrundede Ende talrige divergerende Nervetraade, der passerer til de enkelte Synselemen- ter. Ethvert af disse sidste er (se Fig. 7) isoleret ved en cylindrisk Skede, i hvis indre den saakaldte Synsstav sees som en fint tverstribet Axe (c), streek- kende sig mod Peripherien af Qiengloben, hvor den forbinder sig med en kegleformig fastere Del, den saakaldte Krystalkegle (b). Denne er omgivet af et morkeredt Pigment og ender med et sterkt lys- brydende, lindseformigt Legeme af ellipsoidisk Form (a). Den GWiengloben omgivende ydre Hud (cornea) er ganske glat, uden Spor af Facetter. . Kjonssystemet. — Han- og Hun-Organerne for- holder sig meget ulige, saavel hvad Bygning som Beliggenhed angaar, og maa derfor beskrives ser- skilt. Ovarierne (se Tab. VI, Fig. 3 og 4, Tab. VIII, Fig. 11) strekker sig i Form af 2 smale cylindriske Sekke igjennem Storsteparten af Truncus, til hver Side af og noget nedenunder Tarmen. Deres for- reste Ende er omtrent beliggende ved Grendsen af Ade og 5te fodberende Segment; den bagerste Ende strekker sig ind i selve Kjonsringen. Derimod fin- des ingen Del af Ovarierne i selve Bagkroppen, saa- ledes som Tilfeeldet er hos Slegten Branchipus. I nogen Afstand fra deres bagre Ende udgaar fra hvert Ovarium nedad en kort og tyk Agleder, der udmunder i Basis af Aggesekken. glederne er delvis omhyllede af en voluminos Kjertel, der af- sondrer Stoffet til Aiggeskallen. I Ovariernes Indre findes som oftest kun en enkelt Rekke af sig ud- viklende Ag (se Tab. VIII, fig. 11), med gronagtig Blommemasse og mere eller mindre tydelig Kim- blere. A ggene synes at udvikle sig fra den forre- ste Ende af Ovarierne, da her findes sammenhobede en hel Del smaa Celler. Fra Ovarierne passere Eggene, efterhvert som de modnes, ind i den sek- formige Matrix, hvor de omgives med sin Skal. Denne er temmelig fast og tyk, og viser sig i Tver- snit tydeligt dobbelt kontureret. gindholdet er i de fleste Tilfeelde uniformt, fintkornet, uden tydelig Kimblere (Fig. 14). I enkelte Tilfeelde (Fig. 13) syntes Klovningsprocessen allerede at vere begyndt, da Agindholdet var delt i 4 skarpt begrendsede Segmenter. ganglionic mass at the end of the antenna. From this ganglionic mass again, exceedingly delicate nerve-fibres run out to each of the appendages there attached. The optic nerves (fig. 4, 0) form, on each side, a strong stem going straight out, which, after having entered the eye-stalks swells out to a club-shaped optic ganglion. This (see fig. 6), by a transverse constriction, is divided into 2 successive dilatations or segments, and sends out, from its somewhat obli- quely rounded end, numerous divergent nerve-fila- ments, which pass to the several visual elements. Each\ of these is isolated by a cylindrical sheath (see fig. 7) in the interior of which the so-called optic rod is visible in the shape of a finely trans- versely striped axis (c) extending towards the peri- phery of the eye-ball, where it unites with a firmer, conical part, the so-called crystalline cone (b). The latter is surrounded by a dark-red pigment, and ends in a strongly refractive lentiform body, ellipsoid in shape (a). The skin (cornea) surrounding the eye- ball is quite smooth, without a trace of facets. Generative system. — The male and female organs are very dissimilar, both as regards struc-— ture and position, and must therefore be separately described. The ovaries (see Pl. VI, figs. 3 and 4, Pl. VIII, fig. 11) extend in the form of 2 narrow cylindrical bags through the greater part of the trunk, on each side of, and a little below the intestine. Their an- terior end lies almost at the boundary between the 4th and 5th pedigerous segments; the posterior end extends into the genital segment itself. On the other hand, no part of the ovaries is found in the posterior part of the body, as is the case in the genus Branchipus. At some distance from their posterior ends, a short, thick oviduct issues from each ovary, passing downwards, and opening into the base of the ovisac. The oviducts are partially enveloped by a voluminous gland which secretes the substance for the shell of the egg. In the inte- rior of the ovary there are found, as a rule, only a single row of ova in process of development (see Pl. VIII, fig. 11), with a greenish yolk-mass, and more or less distinct germ-vesicles. The ova appear to be developed from the anterior end of the ovaries, as a number of small cells are here found crowded together. Each egg, as it matures, passes from the ovary into the sac-like marsupium, where it is en- veloped in its shell. This is tolerably firm and thick, and in transverse sections shows a distinct double outline. The contents of the ova are, in most cases, uniform, finely granular and without distinct germ-vesicles (fig. 14). In one or two cases (fig. 14), the cleavage process seems to have already begun, the contents of the ovum being divided into 4 sharply-defined segments. ee ee ee Testes (Tab. VI, Fig. 11,t) har Formen af et Par forholdsvis smaa, sekformige Organer, der, uligt hvad Tilfeeldet er med Ovarierne, ikke streekker sig ind i Forkroppen, idet de fortil kun rekker til Be- gyndelsen af forreste Kjonsring, hvorimod deres bagre tilspidsede Ende strekker sig mere eller min- dre ind i 1ste Bagkropssegment. I nogen Afstand fra den forreste Ende udgaar nedad og bagtil Sed- lederen, der begynder med et noget blereformigt udvidet Parti, forestillende et Slags Sedbeholder. Ved Basis af de ydre Kjonsvedheng indsnevres dette Parti pludseligt til en trang Kanal, der gjor en sterk Bugtning inden den treder ind i selve Kjonsvedhenget (p), paa hvis Spids den udmunder. Sperma bestaar (se Fig. 12) af smaa klare Celler med tydelig Kjerne, imellem hvilke sees en Del endnu mindre og mere ugjennemsigtige Smaakugler. Udvikling. — Jeg har desverre ikke havt An- ledning til at forfolge den hele Udvikling af ner- verende Form, men har dog leilighedsvis paatruffet ‘en Del Udviklingsstadier, hvoraf jeg her kortelig skal omtale nogle. . Det tidligste Larvestadium, jeg har fundet, er afbildet Tab. VIL, Fig. 15, og maa nermest cha- racteriseres som et Metanauplius-Stadium, forsaavidt ‘som der allerede er tydelige Anleg til 7 Par Lem- mer bag de egentlige Munddele. Det egte Nauplius- Stadium er, som bekjendt, udmerket ved Tilstede- verelsen af kun 3 Par Lemmer, nemlig de 2 Par Folere og Mandibularfodderne, og i dette Stadium forlader nerverende Form, som de fleste ovrige Phyllopoder, igget. Legemet er i det her cmbandlede Stadium af- langt pereformigt, gradvis afsmalnende bagtil og stumpt afrundet fortil, uden tydelig Begreendsning af Hoved, Krop og Hale. De sammensatte Gine er .endnu ikke udviklede, og kun det enkle Vie tilstede i Midten helt fortil. iste Par Folere er endnu gan- ske korte, men rager tydeligt frem fortil og er paa Spidsen udrustede med lignende Vedheng som hos det voxne Dyr. 2det Par Folere er meget forskjel- lige fra samme hos det voxne Dyr, og udviklede til megtige Svommeorganer eller Aarer. De udsprin- ger, noget ventralt, til hver Side af den forreste Del af Legemet, lige bag 1ste Par, og er ialminde- lighed rettede lige udad. Man kan paa dem ad- skille en tyk og boielig, med-talrige Muskler fyldt Basaldel eller Skaft, og 2 ulige udviklede Grene. Skaftet er af cylindrisk Form og viser flere circu- lere Indsnoringer som en Antydning til Leddeling. Det udsender indad 2 mod Mundaabningen rettede Fortsatser, hvoraf den ydre, der udspringer ner Enden af Skaftet, har Formen af en grov, pigformig Borste, cilieret i sin ydre Del, medens den indre er klovet i Enden til 2 cilierede Borster. Under Aarer- nes Bevegelser bliver disse Fortsatser afvexlende The testes (Pl. VI, fig. 11,t) are in the form of a pair of comparatively small bag-like organs, which, unlike the ovaries, do not extend into the anteriot division of the body, but only as far for- ward as the beginning of the foremost genital segment. Their posterior pointed ends, on the other hand, extend more or less into the lst segment of the tail. At some distance from the anterior end issues, in a downward and backward direction, the spermatic duct, beginning with a bladder-like enlarged portion, representing a kind of seminal vesicle. At the base of the external sexual appendage, this part suddenly contracts to a narrow channel, which makes a sharp eurve before it actually enters the sexual appen- dage (p) at the point of which it discharges itself. The sperm (see fig. 12) consists of small, clear cells with distinct nuclei, among which there are a few still smaller and more opaque spherules. Development. — I have unfortunately had no opportunity of following the whole course of devel- opment of the present form, but have, however, occasionally come across certain stages of develop- ment, some of which I will now briefly mention. The earliest larval stage that I have found is represented on Pl. VIII, fig. 15, and may be best characterized as a metanauplius stadium, in as much as there are distinct indications of 7 pairs of limbs behind the oral region proper. The true nauplius stadium, as is well known, is distinguished by the presence of only 3 pairs of limbs, namely, the 2 pairs of antenne and the mandibular legs, and at this stage, the present form, like most other Phy Mopnda, leaves the egg. In the stage now under consideration, the body is oblong, pyriform, gradually narrowing posteriorly and bluntly rounded anteriorly, without any distinct division into head, body and tail. The compound eyes are not yet developed, and only the ocellus is present in the middle in front. The first pair of antenne are as yet quite short, but distinctly project in front, and are armed at the point with appendages similar to those in the full-grown animal. The second pair of antenne are very different from that pair in the full- grown animal, and have the character of powerful natatory organs, or oars. They have their origin a little ventrally at each side of the anterior part of the body, just behind the first pair, and generally point straight out. A thick, flexible basal part or scape, filled with numerous muscles may be distin- guished, and 2 unequally developed rami. The scape is cylindrical in form, and exhibits several circular constrictions as an indication of articulation. It sends out inwards, towards the oral aperture, 2 pro- jections of which the outer one, which springs from near the end of the scape, has the form of a coarse spike-like bristle, ciliated on the outer part; while the inner one is cloven at the end into 2 ciliated fjernet og nermet til Mundaabningen og bidrager , derved til Fodens Optagelse. Af de 2 Grene er den indre ganske kort, cylindrisk og forsynet paa Spid- sen med 4 cilierede Borster. Den ydre Gren-er der- imod af betydelig Storrelse, omtrent saa lang som Skaftet og temmelig tyk, dog gradvis afsmalnende mod Enden. Den er meget boielig og viser en An- tydning til en tet Leddeling, idet Kanterne er fint crenulerede, Langs ad dens indre Side findes en Rad af 15—16 sterke, cilierede Svommeborster, hvoraf 2 udgaar fra selve Spidsen. — Overleeben er meget stor og fremspringende, dannende en oval, i en stump Spids endende og i Flugt med Hovedets undre Flade gaaende Klap, der ganske dekker Mundaabningen nedad. — Kindbakkerne er synlige til: hver Side af Overleben som 2 convexe Frem- spring; men deres Tyggedele synes endnu ikke at vere udviklet. Derimod har enhver Kindbakke paa den ydre Side et temmelig stort fodformigt Vedheng af aflang oval Form og forsynet med ialt 8 cilierede Borster, hvoraf 3 udgaar fra Spidsen, 3 fra en bred Lap af den bagre Rand og 2 fra en noget mindre Lap mellem denne og Spidsen. To Par smaa knude- formige Fremspring umiddelbart bag Kindbakkerne antyder Anlegget til de 2 Par Kjever. Af Bran- chialfodder er der Anleg til 7 Par, successivt afta- gende i Storrelse bagtil. De har alle Formen af simple Tvervulster, uden Spor af Borster. Hale- enden gaar ud i 2 smaa tilspidsede Lappe, enhver endende med en enkelt liden simpel Borste. I det indre af Legemet sees tydeligt den med orangefarvet Ind- hold fyldte Tarmkanal, der fortil danner to simple tilrundede Blindsekke. Larven beveger sig meget raskt om i Vandet ved rythmiske Slag af 2det Par Folere, som i dette Stadium er dens eneste Loko- motionsorganer. Det Fig. 16 afbildede Larvestadium er allerede adskilligt videre udviklet. Legemet er sterkere forlenget og viser en begyndende Sondring i de 3 Kropsafsnit. Hovedet er dog endnu meget kort og nesten tvert afkuttet fortil. De sammensatte Oine har nu begyndt. at udvikle sig som to convexe Frem- spring ved Basis af Iste Par Folere; I deres indre er der afsat.en,ringe Mengde redt Pigment, og der er en syag Antydning til Synselementer. De 2 Par Folere og Munddelene forholder sig i alt vesentligt som hos det. foregaaende Stadium. Derimod er der indtraadt en kjendelig Udvikling af de bag Mund- delene folgende Lemmer, De i forrige Stadium fore- kommende 7 Par simple Tvervulster, der’ repreesen- terede Anlegget til Branchialfodderne, har nu for- detmeste sondret sig fra Kropssiderne og rager tyde- ligt. frem i Form af buede Plader, der er svagt ind- 54 bristles. During the movements of the oars, these projections are alternately brought near to and withdrawn from the oral aperture thereby assisting in the admission of food. The inner of the two rami is quite short, cylindrical, and furnished at the point with 4 ciliated bristles. The outer ramus, on the other hand, is of considerable size, about as long as the scape, and tolerably chick, though ta- pering towards the extremity. It is very flexible, and shows an indication of close articulation, the margins being finely crenulated. Along its inner side, there is a row of 15 or 16 strong, ciliated, natatory bristles, two of which issue from the very point. The labrum is very large and prominent, forming an oval, blunt-pointed flap extending back- wards as an immediate continuation of the inferior surface of the head, and quite covering the oral aperture below. The mandibles are visible on each side of the labrum.in the form of 2 convex projec- tions, but their masticatory part appears to be still undeveloped. Each mandible has, however, on the outer side, a rather large, oblong oval leg-like. appendage furnished with 8 ciliated bristles, 3 of which issue from the point, 3 from a broad lobe of the hind. margin, and 2 from a somewhat smaller lobe between the hind margin and the point. Two pairs of small knob-like projections immediately be-. hind the mandibles indicate the 2 incipient pairs of maxille. There are indications of 6 pairs of bran- chial legs, successively decreasing in size posteri- orly. They all have the form of simple transverse prominences without a trace of bristles. The end of the tail divides into 2 small pointed lobes, each terminating in a single, small, simple bristle. Within the body may be plainly seen the intestinal canal with its orange-coloured contents, forming in front 2 simple, rounded ceca. The larva moves about rapidly in the water with rythmical strokes of the _ second pair of antenne, which, in this stage, are its only organs of. locomotion. The larval stage represented i in fig. 16 is already considerably more. developed. The body is more elongated, and shows an. incipient, division into the 3 sections of the body. ‘The head is. still, however, very short and almost. abruptly cut off in front. The compound eyes have now begun to develop \in the form of 2 convex projections at;the base of. the first pair of antenne.- Inside them there is.a small quantity of red pigment, and there is a faint indi- cation of visual elements. The two pairs of antenne and the oral parts are essentially in the same con- dition as in thé foregoing stadium. On the other hand there is a perceptible development of the limbs behind the oral parts. The 7 pairs of simple trans- verse prominences in the previous stadium, which represented the incipient branchial legs, have now for the most part separated themselves from the ter. Bag disse 7 Par Lemmer sees endnu 2 Par smaa Tveervulster, hvorved disse Lemmers Antal er steget til 9 Par. Endnu mangler imidlertid ethvert Spor til de 2 sidste Par, som forst senere anlegges paa samme Maade som de ovrige. Bagkroppen er endnu gauske kort og uleddet. Dens Endelapper har sondret sig fra Haleenden og berer nu hver 3 borsteformige Vedheng, hvoraf det midterste er be- tydelig storre end de 2 ovrige. Fig. 17 fremstiller den forreste Del af Legemet hos et lidt senere Larvestadium, seet nedenfra og noget sterkere forstorret. De sammensatte Mine (0) har tiltaget betydelig i Storrelse og viser sig alle- rede kort stilkede, med @iengloben vel udviklet. iste Par Folere (a') er paa det nermeste uforan- drede. 2det Par Folere (a*) synes forholdsvis min- dre, idet de er bleven staaende paa samme Udvik- lingstrin, medens de fleste ovrige Dele er tiltaget i Storrelse. Det samme gjelder ogsaa Mandibular- fodderne (p), som i Forhold til selve Kindbakkernes Corpus (M) synes meget reducerede. Overleeben (L) er fremdeles meget stor og fremragende. De 2 Par Kjever er allerede tydeligt udviklede og forsynede med en Del Borster. Alle Branchialfodder er nu anlagte, men-de 2 bagerste Par endnu kun tilstede som ubetydelige Tvervulster. Under den videre Udvikling sondrer Anlegget til de 2 bagerste Par Branchialfodder sig fra Krops- siderne som tydeligt fremragende Lemmer, Halen strekker sig i Leengden og bliver, som det ovrige Legeme, tydeligt segmenteret, samtidigt med at Halepladerne mere tydeligt afgrendser sig og faar et storre Antal Borster. 2det Par Folere reduceres mere og mere, men beholder dog endnu en Tid lang sine Syommeborster og beveges som hos de yngre ‘Larver. Mandibularfodderne svinder mere og mere ind og er tilsidst kun tilstede som rudimentere Ved- heng. Larven, som paa dette Stadium har en Lengde _ af omtrent 5 mm, staar nu paa Overgangen til at antage den blivende Tilstand. Den er afbildet paa 2 dette Udviklingstrin Tab. VI, Fig. 5 og 6. Ved den — derpaa folgende Hudskiftning er Larvetilstanden - forbi, idet det sidste Spor af Mandibularfodderne er __ forsvundet og 2det Par Folere har tabt sin Betyd- ‘oe ‘ning af Lokomotionsorganer. Endnu er der dog paa de sidstneeynte Lemmer (se Fig. 7 og 8) en tydelig ; Adskillelse mellem Skaft og Grene. Den ydre Gren ender i en noget bugtet Spids, paa hvilken endnu de sidste svage Rester af de oprindelige Svomme- A borster sees (Fig. 8); Indergrenen ser ud som et -yderst: lidet: knudeformigt Fremspring, uden enhver peseenbels ‘Er- og bestemt. til at blive j La i Kanterne og delvis forsynede med korte | > s sides of the body, and project perceptibly in the form of curved lamellew, slightly. indented and with the edges partially furnished with bristles. Behind these 7 pairs of limbs, 2 more pairs of small transverse prominences are visible, raising their number to 9 pairs. All trace, however, of the last 2 pairs is still absent, and it is only later that they commence in the same way as the others. The hind part of the body is still quite short and inarticulated. Its terminal lobes have become separated from the caudal end, and now each carry 3 setiform appendages, the middle one of which is considerably larger than the other two. Fig. 17 represents the anterior part of the body in a somewhat more advanced larval stage, seen from below, and rather strongly magnified. The compound eyes (0) have increased considerably in size, and already have short peduncles, while the eye-ball is well-developed. The Ist pair of antenne (a*) are nearly unchanged. The 2nd pair of antenne (a?) seem to be comparatively smaller, having re- mained at the same developmental stage, while most of the other parts have increased in size. The same applies to the mandibular legs (p), which, in relation to the body of the mandible (M), seem very much reduced in size. The labrum (L) is still very large and projecting. The two pairs of maxille are al- ready perceptibly developed, and furnished with a few bristles. All the branchial legs have now ap- peared, but the hindmost 2 pairs still only as insig- nificant transverse prominences. During further development the rudiments of the hindmost .2 pairs of branchial legs separate themselves from the sides of the body as distinctly projecting limbs. The tail is elongated and becomes, like the rest of the body, perceptibly articulated, while, at the same time, the caudal lamelle are more distinctly defined, and havé acquired a larger number of bristles. The second pair of antenne be-* come more and more reduced, but still for some time retain their natatory bristles, and are -moved as in the younger larve. The mandibular legs dwindle more and more, and at last only appear as rudimentary appendages. The larva, which, at this stage, has a length of about 5 mm, is on the point of entering its permanent condition. It is thus re- presented on Pl. VI, figs. 5 and 6. With the en- suing exuviation, the larval period is past, the last trace of mandibular legs having vanished, and the 2nd pair of antenne having lost their importance as organs of locomotion. In the last-named limbs (see figs. 7 and 8) there is still, however, a distinct separation between the scape and the rami. The outer ramus ends in a somewhat curved point, upon which the last feeble remains of the original nata- tory bristles are visible (fig. 8). The inner ramus looks like an extremely small nodiform projection, af Hunkjon, sker der en end yderligere Reduktion af disse Folere, hvorved de antager det for Hunnen characteristiske Udseende af 2 simple triangulere Flige. Hos Hannen omformes Ydergrenen til Gribe- kloen, og Indergrenen persisterer som det lille knude- formige Fremspring ved Enden af Basaldelen, inden- denfor Kloens Udspring. Forekomst og Levevis. Nerverende Phyllopode synes at forekomme meget almindelig, i Ost-Finmarken, hvor jeg har taget den paa flere Steder i stor Mengde; saaledes i et lidet grundt Tjern ved Mehavn, hvor den fand- tes sammen med Polyartemia forcipata, i et lignende Tjern ved Vardo, og i flere Smaatjern og grunde Damme paa Fastlandet Ost af Vardo. Af Prof. Lilljeborg er den desuden taget ved Nordkap. I Vest-Finmarken har jeg derimod ikke observeret den, ligesaalidt som nogetsteds i Nordland. Merke- ligt nok optreeder den igjen langt sydligere i Lan- det, nemlig paa Dovres Hoeideplateau, hvor jeg har taget den meget almindelig i grunde Damme saavel ved Kongsvold som ved Jerkin. Denne isolerede Forekomst saa langt Syd paa kan kun forklares paa den Maade, at nerverende Phyllopode for i Tiden, da Klimatet var mere arktiskt, har veeret udbredt over hele vort Land, ogsaa i Lavlandet, men derpaa, efterhvert som Klimatet forandrede sig, har trukket sig tilbage nordpaa og tillige til Hoide- plateauerne, hvor de klimatiske Forhold mere lig- nede de oprindelige; med andre Ord: den er her Syd i Landet at betragte som en saakaldt «relict» Form, en Leyning fra den arktiske Fauna, der for i Tiden var udbredt over vort hele Land. | Da de Smaatjern og Damme, hvori den lever, regelmessigt udtorres mod Slutningen af Sommeren, og vesentlig kun skylder sin Tilbliven Snesmeltnin- gen paa Forsommeren, er denne Forms Levetid kun indskreuket til nogle faa Maaneder af Aaret. I Lobet af forholdsvis kort Tid har den imidlertid gjennemgaaet sin Udvikling, og derefter gaar For- plantningen hurtigt for sig. De i Agsekken inde- holdte Ag, bliver, som anfort, altid omgivne med en meget tyk Skal og er aabenbart alle beregnede paa at overvintre, for til den folgende Sommer at ud- vikle sig til en ny Generation. Arten er saaledes for hvert Aar kun representeret ved en enkelt Ge- neration. iggene afsettes i Mudret paa Bunden af Dammen, og da denne Afsetning af Ag foregaar gjentagne Gange af hvert Hunindivid, vil der snart ophobe sig en anseelig Mengde af Aig, der vil sikre Artens Tilverelse paa de Steder, der er gunstige for dens Trivsel. Det er forst ved Midsommertid, | with no bristles whatever. If the young one. is destined to be of the female sex, a still further re- duction of these antenne takes place, whereby they assume the appearance, characteristic of the females, of 2 simple triangular flaps. In the male the outer ramus is transformed into a prehensile claw, while the inner ramus becomes the small nodiform pro- jection at the end of the basal part, inside the root of the claw. Occurence and Habits. The present Phyllopod seems to occur very ge- nerally in East Finmark, where I have found it in many places in great numbers, for instance, in a little, shallow lake at Mehavn, where it was found together with Polyartemia forcipata; in a similar lake at Vardo, and in several small lakes and shallow ponds on the mainland east of Vardo. It has also been found by Prof. Lilljeborg at the North Cape. In West Finmark, on the other hand, I have not observed it, nor yet anywhere in Nordland. Curiously enough, it appears again much farther south, namely on the high plateau of the Dovre Mountains, where I found it very plentiful in shal- low ponds both at Kongsvold and Jerkin. This isolated occurrence so far south can only be ac- counted for by the supposition that formerly, when the climate was more arctic, this Phyllopod was distributed over the whole of our land (Norway), lowlands as well as highlands, but that, as the cli- mate changed, they have withdrawn to the north and the high plateaus, where the climatic conditions more resemble those originally prevailing; in other words, here in the south of the country, it must be regarded as a so-called «relict» form, a vestige of the arctic fauna which was formerly distributed over the whole country. As the small lakes and ponds in which it lives dry up periodically towards the end of the summer, and owe their existence chiefly to the melting of the snow in the spring, the life-time of this form is limited to only a few months of the year. In the course of a comparatively short time, however, it has passed through its developmental course, and propagation then proceeds rapidly. As already stated, the eggs in the ovisac always become surrounded by a very thick shell, and are evidently calculated to stand the winter, and in the ensuing summer to develop into a new generation. The species is thus represented every year only by a single generation. The eggs are deposited in the mud at the bottom of the pond, and as this deposition of eggs is re- peated several times by each female, a considerable number of eggs is soon amassed, which ensures the existence of the species in those places that are fayor- able to its well-being. It is not until Midsummer a ee eller i Juli Maaned, at man hos os ialmindelighed | finder denne Form fuldt udviklet. Jeg har paa denne Tid observeret den i store Mengder i Smaa- tjern paa Dovres Hoideplateau, Ost af Jerkin. Som -Tilfeeldet synes at vere med de fleste Phyllopoder, naar den temmelig tidligt, og lenge for den er fuldt udvoxet, Kjonsmodenhed. De storste Individer fin- der man derfor ialmindelighed lengere ud paa Ho- sten, medens Storrelsen forst paa Sommeren er be- tydelig ringere. Ofte er der ogsaa paa samme Tid adskillig Forskjel i Storrelsen i forskjellige ner liggende Tjern. I samme Tjern finder man derimod i Regelen alle Individer omtrent ens udviklede og af ens Farve. Det er et meget livligt Dyr, som er i uafbrudt Beveegelse, oftest mere eller mindre ner Overfladen af Vandet. Bevegelsen tilveiebringes hovedsageligt ved Branchialfoddernes Svingninger, der foregaar paa en meget regelmessig og elegant Maade, idet de ikke sker noiagtig samtidigt for alle Fodders Vedkommende men successivt, hvad der giver Ind- trykket af en eindommelig Undulation i Bevegelsen. Den herved frembragte Lokomotion er en ganske jevn i horizontal Retning, hvorunder Dyret altid vender Ryggen nedad. Dog kan det foretage mange ' forskjellige Volter i Vandet og dreie og sno sig i alle Retninger, hvorved Halens Bevegelser spiller en veesentlig Rolle. Hanner og Hunner sees ofte j Kopulation, idet Hannen med sine Gribeantenner fast omslutter Hunnens Genitalsegment fra Ryggen af, og saaledes kan begge Individer svomme om i lange Tider, begge vendende Bugsiden opad. Selve Kopulationsakten har jeg ikke faaet observeret. Rimeligvis afventer Hannen det Qieblik, da de modne AXg fra Ovarierne treder ind fi Basis af Rugesekken, hvor de, som ovenfor anfort, omgives af sin Skal. Dyrets Fode synes hovedsageligt at bestaa af mikroskopiske Alger og andre Plantedele, tildels vel ogsaa af Infusorier, der ved Branchialfoddernes Spil hvirvles ind mod Munden. Udbredning. — Nerverende Phyllopode er forst beskrevet fra Gronland, hvor den synes at vere meget almindelig, og er senere bleven gjenfunden paa flere andre Steder, saaledes det arktiske Ame- rika, paa Spitsbergen, Novaja Semlja, Kolahalvoen ogiSibirien. Idethele falder dens Udbredning, naar undtages det ovennevnte Findested i Norge paa Dovres Hoideplateau, udelukkende indenfor den ark- tiske Zone, og dens Forekomst her synes at stemple den som en egte arktisk og circumpolar Form. or July that this form is generally found fully developed here. At that season I have observed it in great numbers in small lakes on the high plateau of the Dovre Mountains, east of Jerkin. As seems to be the case with most Phyllopoda, it attains sexual maturity tolerably early, and long before it is fully grown. The largest specimens are therefore generally found later in the autumn, while the size in the beginning of the summer is very much smaller. There is also often considerable difference in their size in different lakes, while on the other hand, all the animals in one lake are, as a rule, uniformly developed, and uniform in colour. It is a very lively animal, and in constant motion, generally more or less near the surface of the water. The movement is chiefly brought about by the vibrations of the branchial legs, which take place in a very regular and graceful manner, not quite simultaneously with all the legs, but succes- sively, thereby imparting to the movement a peculi- arly undulatory effect. The motion thus produced is equable and in a horizontal direction, the back of the animal being always turned downwards. It may, however, make all kinds of springs in the water, turning and twisting in every direction, the movements of the tail playing an important part in these evolutions. Males and females are often seen in copulation, the male, with his prehensile antenne, firmly embracing the female’s genital segment from the back, and in this manner both animals may swim about for a long time with the ventral side uppermost. The act of copulation itself, I have not witnessed. The male probably awaits the moment when the mature ova enter from the ovary into the base of the marsupium, where, as previously stated, they are enveloped in their shell. The food of this animal seems to consist prin- cipally of microscopic alge and portions of other plants, partly also of infusoria, which are swept in towards the mouth by the movement of the bran- chial legs. Distribution. — The present Phyllopod was first described from Greenland, where it seems to be very common, and has since been found in several other places, e. g. arctic America, Spitzbergen, ‘Novaia Zemlia, the Kola Peninsula and in Siberia. Altogether its distribution, with the exception of the above-named place in Norway, on the high pla- teau of the Dovre Mountains, is exclusively within the aretic zone, and its occurrence .there seems to stamp it as a true arctic and circumpolar form. 8 —G. 0. Sars: Fauna Norvegix. Fam. 2. Polyartemiide. Legemet slankt, med Halen kort og ufuldkom- ment segmenteret hos Hunnen. Gribeantennerne hos Hannen uleddede, og delte i flere hageformigt krummede Grene; Frontalvedheng tilstede. 19 Par Branchialfodder, alle, undtagen sidste Par, med dob- delt Basalplade. Hunnens Agbeholder kort og tyk, ikke poseformigt fremragende bagtil. Hannens ydre Kjonsvedheng dobbelte. Halegrenene korte, blad- formige, kantede med cilierede Borster. Bemerkninger. — Af denne Familie kjendes hidtil kun en enkelt Slegt, Polyartemia, med en en- kelt Art. Hvad der hovedsageligt skiller denne Fa- milie fra den foregaaende, er det betydelig storre Antal Segmenter i Forkroppen og det deraf folgende foregede Antal Branchialfodder; fremdeles Halens Structur og Agbeholderens Form hos Hunnen; ende- lig Gribeantennernes eiendommelige Bygning hos Hannen. Gen. Polyartemia, Fischer, 1851. Slegtscharacter. — Legemet nesten cylindriskt og meget boieligt. Kjonsringene hos Hunnen sam- menvoxne med Halen; denne sidste hos Hunnen med kun et enkelt terminalt Segment, hos Hannen tydeligt 6-leddet Halegrenene forholdsvis korte. Hannens Gribeantenner 3-delte, den forreste Gren storst; Frontalvedhengene simpelt cylindriske. Branchial- fodderne forholdsvis brede og af samme Udseende hos de 2 Kjon, Exopoditen forholdsvis liden, oval, den ydre Lap af Endopoditen stumpt afrundet i Enden, begge Basalplader helrandede. Hunnens Egbeholder sterkt opblest fortil. Bemerkninger. — Nerverende Slegt er opstil-. let i Aaret 1851 af Fischer og vesentlig charac- teriseret ved det ualmindelig store Antal Branchial- fodder. Da denne Slegt i saa Henseende skiller sig fra alle andre Branchipodider, hos hvem Tallet 11 er fuldkommen constant, fortjener den utvivlsomt at opstilles som Typen for en egen Familie. Sleg- ten indeholder for Tiden kun en enkelt Art, som nedenfor nermere skal beskrives. 58 Fam. 2. Polyartemiide. Body slender, with a short and imperfectly segmented tail in the female. Prehensile antenne in male inarticulate and divided into several claw- like rami: frontal appendages present. Nineteen pairs of branchial legs, all, except the last pair, with double basal lamine. Marsupium of female short and thick, not projecting posteriorly like a bag. External sexual appendage of male double. Caudal rami short and laminar, edged with ciliated bristles. Remarks. — Only one genus of this family is known up to the present, Polyartemia, with a single species. What chiefly distinguishes this family from the preceding one is the much larger number of segments in the anterior part of the body, and the consequent augmented number of branchial legs; furthermore, the structure of the tail, and the shape of the marsupium in the female, and lastly, the peculiar formation of the prehensile antenne in- the male. Gen. Polyartemia, Fischer. 1851. Generic characters. — Body almost cylindrical and very flexible. Genital segments in female co- alesced with the tail; the latter, in the female, with a single terminal segment only, in the male distinctly 6-articulate. Caudal rami comparatively short. Prehensile antenne of male divided into three curved rami, the foremost being the lar- gest; frontal appendages of a simple cylindrical shape. Branchial legs comparatively broad, and of a similar appearance in the two sexes; exopodite oval and comparatively small; external lobe of the endopodite bluntly rounded at the end: both basal laminee plain. Marsupium of the female very much inflated in front. Remarks. — The present genus was established in 1851 by Fischer, and is chiefly characterized by the unusually large number of branchial legs. As it differs in this respect from all other Branchipo- did, where the number 11 is quite invariable, it without doubt merits being established as the type of a separate family. The genus contains at pre- sent only a single species, which will be more fully described below. —_.. 4 a iy Polyartemia forcipata, [ischer. (Pl. IX & X). Polyartemia forcipata, Vischer, Middendorff’s Sibirische Reise, Bd. 2. Zoologie, p. 154, Tab. VII, Fig. 24—28. Artscharacter. — Legemet smalt cylindriskt, nesten jeynt tykt hos Hunnen, noget afsmalnende bagtil hos Hannen. Hovedet hos Hunnen forholds- vis lidet og afrundet fortil, hos Hannen betydelig bredere og endende med 2 stumpt coniske, nedad- krummede Frontalfortsatser. Halen og Kjonsringene tilsammen neppe mere end halvt saa lang som den fodbwrende Del af Kroppen. Hunnens Agbeholder bredt afrundet fortil med et knudeformigt Frem. spring til hver Side. Hannens ydre Kjonsvedheng simpelt cylindriske og omtrent af Halens halve Lengde. Q@inene kolleformige, omtrent af Lengde som Hovedets halve Tverdiameter. Forste Par Fo- lere forholdsvis smaa, kortere end Minene. Andet Par Folere hos Hunnen betydelig kortere end Ho- vedet, endende i en trianguler Flig; samme Folere hos Hannen serdeles store, tregrenede, de 2 forreste Grene tangformigt krummede i Enden og fint cili- erede i den indre Kant, den bagerste Gren kort, lige nedad rettet og tet haaret i-Enden. Hale- pladerne bredt lancetformige, omtrent dobbelt saa lange som de ér brede ved Basis. Legemet gjennem- sigtigt med svagt gronligt, blaaligt eller rodligt Skjer. Hannen sedvanlig lys gulagtig. Hunnens _ Kjonsringe oventil med 2 ultramarinblaa kantede Pletter, mellem hvilke er 2 smale Striber af samme Farve, Mgbeholderen orangefarvet nedentil. Hun- nens Lengde indtil 16 mm, Hannens 10 mm. Bemerkninger. — Denne eiendommelige Phyllo- pode blev forst opdaget under Middendorffs Reise i Sibirien og er kortelig beskrevet under ovenstaaende - Navn af 8. Fischer, sammen med andre under Rei- sen indsamlede Entomostraceer. Den er senere _ ogsaa gjenfunden af andre Forskere, uden at dog - endnu nogen mere udforlig Beskrivelse er leveret. Beskrivelse af Hunnen. Lengden af Legemet, fra Panderanden til Enden af Halebladene, naar op til 16mm. Dog finder man den, saaledes som Tilfeldet er med andre Phyllo- poder, slegtsmoden lenge for den har naaet denne se. ‘ Legemet er (se Tab. IX, Fig. 1 og 2) slankt, eylindriskt, og nesten af ens Bredde, dog hos fuldt _ udviklede Individer kjendeligt opsvulmet. bagtil i _ Kjonsregionen. Man kan adskille de samme Krops- Polyartemia forcipata. Fischer. (Pl. IX & X). Polyartemia forcipata, Fischer, Middendorff's Siberische Reise, Bd. 2. Zoologie, p. 154, Tab. III, fig. 24—28. Specific characters. — Body narrow cylindrical, of almost uniform thickness in the female, tapering in the male. Head in female comparatively small and rounded in front, in male considerably broader, and ending in two bluntly conical, decurved fron- tal processes. Tail and genital segments together scarcely more than half as long as the pedigerous part of the body. Marsupium of female broadly rounded in front with a nodiform protuberance on each side. External sexual appendages of male simple cylindrical, and about half the length of the tail. Eyes club-shaped, about the length of half the transverse diameter of the head. First pair of antenne comparatively small, shorter than the eyes. Second pair of antenne in female considerably shorter than the head, and ending in a triangular lappet; in male very large, tripartite, the two fore- most rami being curved like a forceps at the end, and finely ciliated on the inner margin, the hind- most ramus short, pointing straight inwards, and densely hairy at the extremity. Caudal lamelle broadly lanceolate, about twice as long as they are broad at the base. Body transparent, with a faint . green, blue or red tinge: that of male generally pale yellow. Genital segments of female above with 2 angular ultramarine-blue patches, between which there are two narrow stripes of the same colour. Marsupium orange-coloured below. Length of female up to 16 mm, that of male, 10 mm. Remarks. — This peculiar Phyllopod was first discovered during Middendorff’s journey in Siberia, and is briefly described under the above name by 8. Fischer, together with other Entomostraca col- lected during that journey. It was subsequently also found by other naturalists, notwithstanding which, no more detailed description has as yet been furnished. Description of the Female. The length of the body, from the frontal mar- gin to the end of the caudal lamella, attains to 16 mm. It is found, however, as is also the case with other Phyllopoda, sexually mature long before it has attained this size. The body (see Pl. IX, figs. 1 and 2) is slender, cylindrical, and of almost uniform breadth through- out, though, in fully developed animals, perceptibly distended posteriorly in the sexual region. The afsnit som hos Branchinecta, skjondt deres indbyr- des Leengdeforhold er temmelig forskjelligt. Hovedet er forholdsvis af ringe Storrelse og stumpt afrundet fortil. Det afgrendser sig skarpt fra Nakkesegmentet, der til hver Side viser Skal- kjertelen meget tydeligt. Truncus er sterkt for- lenget, regelmessigt cylindrisk, og delt i ikke min- dre end 19 vel begrendsede Segmenter, hvert bee- rende et Par Branchialfodder. Bagkroppen udmerker sig i hoi Grad ved sin korte og plumpe Form, idet den neppe indtager mere end '/s af Kropslengden. Kjonsringene er fuldsteendig sammensmeltede saavel indbyrdes som med den bagenfor liggende Del af Halen, paa hvil- ken alene det bagerste Segment er tydeligt be- grendset. Hele dette Parti har, seet ovenfra (Fig. 2), en nesten peredannet Form, idet det fortil er sterkt fortykket og ligesom opblest, med en afrun- det knudeformig Protuberans til hver Side, medens det bagtil gradvis afsmalnes. Breden over den for- reste Del af dette Afsnit er mere end dobbelt saa stor som Breden over selve Truncus. Sees Dyret fra Siden (Fig. 1), viser sig Storsteparten af den ventrale Side af dette Parti optaget af den volumi- nose gbeholder, hvis forreste Del er serdeles steerkt hvelvet, medens den bagtil kun rager ube- tydeligt frem i Form af et kort koniskt Frem- spring. Paa Enden af dette Fremspring findes den ydre Aabning for Aigbeholderen, som hos Branchi- necta, begreendset af 2 vertikale mod hinanden be- vegelige Leber, hvoraf den overste er den storste og ender i en tilspidset Knude (se Tab. X, Fig. 12). Halepladerne (se Tab. IX, Fig. 6) er forholdsvis korte, neppe mere end dobbelt saa lange som de er brede ved Basis, og viser en bredt lancetdannet Form, med Spidsen smalt afrundet. De er hver kantede med omtrent 19 cilierede Borster der suc- cessivt tiltager i Lengde mod Spidsen. Minene (Tab. X, Fig. 1, 0) er forholdsvis korte og tykke, neppe lengere end Hovedets halve Brede, og af den seedvanlige peredannede Form, med @ie- globen jevnt afrundet. Qiepigmentet er morkt, dog hos det levende Dyr med et tydeligt purpurredt Skjer, og de enkelte Synselementer vel udviklede. Det enkle Gie sees som en tydelig mork Plet i Mid- ten af Hovedets Pandedel. Forste Par Folere (Fig. 1, a1, Fig. 3) er for- holdsvis betydelig kortere end hos Branchinecta, neppe halvt saa lange som Yinene, men viser for- ovrigt en meget lignende Bygning, og berer paa Spidsen de seedvanlige Lugtepapiller og Foleborster. Andet Par Folere (Fig. 1, a) er ligeledes min- dre end hos Branchinecta, og har Formen af 2, som det synes, fuldkommen ubeveegelige trekantede Flige, 60 same body-divisions can be distinguished as in Bran- chinecta, although their mutual relations as to length are rather different. The head is comparatively small and bluntly rounded in front. It is sharply defined from the cervical segment, which shows tlie shell-gland on each side very distinctly. The trunk is greatly elongated, regularly cylindrical, and divided into no less than 19 well-defined segments, each bearing a pair of branchial legs. The posterior part of the body is highly remar- kable for its short and stout form, constituting, as it does, scarcely 1/s of the length of the body. The genital segments are completely coalesced, both mutually and with that part of the tail posterior to them, in which only the hindmost segment is distinctly defined. The whole of this part, seen from above (fig. 2), is almost pyriform, being very much thickened in front, and as it were inflated, with a rounded, nodiform protuberance on each side, while posteriorly it tapers gradually. The breadth of the front part of this section is more than double as great as that of the trunk itself. When the animal is seen from the side (fig. 1), the greater part of the ventral side of this region appears to be occupied by the voluminous marsupium, the anterior part of which is boldly convex, while the posterior end projects only slightly in the form of a short, conical prominence. At the end of this prominence is seen the external opening of the marsupium, bounded, as in Branchinecta, by 2 movable lips, the upper of which is the larger, and ends in a pointed nodule (see Pl. X, fig. 12). The caudal lamelle (see Pl. IX, fig. 6) are comparatively short, being searcely more than double as long as they are broad at the base. They exhibit a broadly lanceolate shape with the point narrowly rounded, and are each fringed with about 19 ciliated bristles, which suc- cessively increase in length towards the point. The eyes (Pl. X, fig. 1, 0) are comparatively short and thick, scarcely longer than half the breadth of the head, and of the usual pyriform shape, with the eye-ball evenly rounded. The pig- ment is dark, though with a distinct tinge of crim- son in the living animal: the visual elements are well-developed. The ocellus is observable as a dis- tinct dark spot in the centre of the frontal part of the head. The first pair of antenne (figs. 1, a* and 3) are. comparatively much shorter than in Branchinecta, being scarcely half as long as the eyes, but in other ways exhibit a very similar structure, and carry at the extremity the usual olfactory papille and sensory bristles. ) The second pair of antenne (fig. 1, a*) are also smaller than in Branchinecta, and have the form of 2 apparently perfectly immovable triangular lappets der hver har en dyb Indbugtning fortil ner Spidsen. Langs Forkanten findes en Del meget smaa_ haar- formige Borster, der synes at vere Foleredskaber, da der til enhver af dem gaar en fin Nervetraad. Overleben (Fig. 1, L, Fig. 4 og 5) har Formen af en bred, nesten firkantet Lap, der nedad rager ud over Kindbakkernes Tyggedel. Paa Indsiden af denne Lap er der en langsgaaende, delvis haaret Forhgining, der ender bagtil i en frit fremragende, verticalt stillet Lob af smalt tungedannet Form (se Fig. 4 og 5). Kindbakkerne (Fig. 1, M, Fig. 6) har den for Branchipodiderne characteristiske Bygning, og ender med en fint riflet Tyggeflade, uden tydelige tand- formige Fremspring. Forste Par Kjever (Fig. 1, m', Fig. 7) har den bladformige Endedel af betydelig Storrelse og besat paa den tvert afkuttede Ende med en tet Rad af omkring 24 indadkrummede Borster af en lignende Beskaffenhed som de hos Branchinecta. Andet Par Kjever (Fig. 1, m*, Fig. 8) er for- holdsvis smaa og idethele af en simplere Bygning end hos Branchinecta, uden tydelig Adskillelse mel- lem Basal- og Endedel. De er i den ydre, noget udvidede Del tet haarede og har kun 2 cilierede Borster feestede til det indre Hjorne samt en bety- delig mindre simpel Borste i den indre Kant, om- trent i Midten. Branchialfodderne er 19 Par i Antal, svarende til de 19 Kropssegmenter. Naar undtages sidste Par, er de alle af ens Bygning og viser alle de Dele, som ovenfor er adskilte hos Branchinecta, hvortil endnu kommer en egen Plade ved Basis paa den ydre Side, hvoraf der intet Spor er at opdage hos hin Slegt. Det forreste Par (Fig. 9) er noget mindre end det 2det (Fig. 10), de folgende noget ner af ens Storrelse indtil omtrent det 12te Par, hvor- efter de successivt aftager i Storrelse bagtil. Paa dem alle er selve Stammen, eller Endopoditen, meget bred, pladeformig, med den forreste Flade noget hvelvet. Dens yderste Lap er meget stor og nesten _tvert afkuttet i Enden, samt kantet med sterke Borster, hvoraf dog ingen som hos Branchinecta, er kloformige. De 3 oventil folgende Lappe er ser- deles smaa og tet sammentrengte, af konisk Form, og hver besatte med 2—3 lengere og et Par kortere Borster. Den nestoverste Lap er kun utydeligt __skilt fra den overmaade brede, halvmaaneformige basale Lap, og begge kantede med en tet og regel- messig Rad af meget lange og leformigt krummede Borster, alle tydeligt leddede paa Midten. Exopo- _ diten er forholdsvis liden, og har Formen af et ovalt _ Blad, forbundet med den ydre Del af Endopoditen ved et tydeligt Led. Den er kantet med sterke, cilierede Borster, hvoraf de fra Enden udgaaede er lengst. Epipoditen er af et lignende Udseende som which each have a deep notch in front, near the point. Along the front edge there is a number of minute hair-like bristles, which appear to be sen- sory organs, as a fine nerve-fibre runs to each one. The labrum (figs. 1, L, 4 and 5) has the form of a broad, almost square lobe projecting down- wards over the masticatory part of the mandibles. On the inner side of this lobe, there is a longitudi- nal, rather hairy prominence, which ends posteriorly in a freely-projecting, vertically-placed lobe of a narrow, linguiform shape (see figs. 4 and 5). The mandibles (figs. 1, M and 6) are of the structure characteristic of the Branchipodide, and end in a finely-fluted masticatory surface without any distinct dentiform projections. The lamelliform terminal portion of the first pair of maxille (figs. 1,m?+and 7) is of considerable size, its abruptly truncated end being furnished with a close row of about 24 inward-curving bristles of the same structure as those in Branchinecta. ‘The second pair of maxille (figs. 1, m* and 8) are comparatively small and, on the whole, of a simpler structure than in Branchinecta, without any distinct separation between the basal and the ter- minal parts. In the outer, somewhat expanded part, they are densely hairy, and have only 2 cili- ated bristles attached to the inner corner, and one much smaller, simple bristle at about the middle of the inner margin. There are 19 pairs of branchial legs, correspon- ding to the 19 segments of the body. With the exception of the last pair, they are all of a uniform structure, and exhibit all those parts which have been already distinguished in Branchinecta, with the addition of a peculiar lamina at the base on the outer side, of which no trace is to be found in that genus. The foremost pair (fig. 9) is somewhat smaller than the second (fig. 10), the succeeding pairs being of almost uniform size until about the 12th pair, after which they successively decrease in size posteriorly. In all of them the stem, or endopodite, is very broad, lamellar, with the anterior surface somewhat convex. Its outermost lobe is very large and almost abruptly truncated, besides being edged with strong bristles, none of which, however. are claw-like as in Branchinecta. The 3 succeeding lobes above are exceedingly small and closely crowded, conical in shape, and each armed with 2 or 3 long, and a couple of shorter bristles. The upper- most lobe but one is only slightly separated from the exceedingly broad, crescent-shaped, basal lobe, and both are edged with a close, regular row of very long and falciform bristles, all distinctly jointed in the middle. The exopodite is comparatively small and of the shape of an oval leaf, united to the outer part of the endopodite by a distinct arti- culation. It. is edged with strong, ciliated bristles, 62 hos Branchinecta, dannende en aflang oval spongios | those at the end being the longest. The epipodite Plade, uden Spor af Borster. Ovenfor denne er til Ydersiden af Stammen festet 2 tildels hinanden dekkende tynde, afrundet ovale Plader, der begge maa opfattes som Dekplader. De er af noget ulige Storrelse, idet den overste er adskilligt mindre end den nederste, og begge har Kanterne ganske glatte, uden Spor af Sagtakker. Sidste Fodpar (Fig. 11) skiller sig fra de ovrige, foruden ved sin ringe Storrelse, ved den fuldsten- dige Mangel saavel af Epipodit som Basalplader. Exopoditen er serdeles liden og kun forsynet med 6 Randborster. Endopoditens yderste Lap er langt- fra saa fremragende som paa de ovrige Par og har et ringere Antal af Randborster, alle ganske korte. Ligeledes er Borsterne paa de 2 basale Lappe be- tydelig mindre udviklede end paa de ovrige Par, og kun ganske svagt boiede. Beskrivelse af Hannen. Uligt hvad Tilfeeldet er med Branchinecta og. som det synes ogsaa med andre Branchipodider, er Hannerne af nerverende Form gjennemgaaende noget mindre end Hunnerne og overskrider neppe en Lengde af 10 mm. Legemet er (se Tab. IX, Fig. 3 og 4) noget min- dre langstrakt, og baade Hovedet og Halen vesent- lig ulige samme hos Hunnen. MHovedet er af me- get betydelig Storrelse og viser oventil et sadel- formigt Indtryk. Fortil ender det med 2 finger- formige og noget divergerende Pandefortsatser, der er nedadkrummede og skilte i Midten ved et halv- maaneformigt Indsnit (se ogsaa Tab. X, Fig. 2). Til hver Side, tilsyneladende som en umiddelbar Fort- seettelse af Hovedet, udgaar med en bred Basis de eiendommeligt formede Gribeantenner (se Tab. IX, Fig. 3 og 4, Tab. X, Fig. 2). Enhver af disse er delt i 3 paa hinanden folgende indadkrummede fin- gerformige Grene, hvoraf den forreste er storst og synes at forestille den egentlige Stamme, medens de 2 ovrige nermest er at betragte som secundeere Sidegrene. Den bagerste Gren er betydelig mindre end de ovrige, stumpt tilrundet i Enden, og rundt om besat med fine Haar, medens de 2 ovrige kun er haarede langs ad den indre concave Kant (se Tab. IX, Fig. 5). Sammen med de 2 Pandefortsatser vil disse Lemmer,. naar de boies ind mod _ hinanden, kunne virke som et serdeles effektivt Gribe- og Fastholdningsapparat. Minene, Iste Par Folere, Munddelene og Bran- chialfodderne skiller sig i ingen Henseende fra samme hos Hunnen. _Derimod er Bagkroppen meget forskjellig og be- _ essentially unlike those parts in the female. resembles in appearance that in Branchinecta, and forms an oblong, oval, spongy lamella, without a trace of bristles. Above this, to the outer side of the stem, are fastened 2 thin rounded oval lamine, partly overlapping one another, which must be re- garded as cover-plates. They are somewhat unequal in size, the upper one being considerably smaller than the lower; and the edges of both are quite smooth, without a trace of serrations. The last pair of legs (fig. 11) are distinguished from the others not only by their small size, but also by the total absence of both epipodite and basal’ laminee. The exopodite is very small and fur- nished with only 6 marginal bristles. The outer- most lobe of the endopodite is not nearly so pro- jecting as in the other pairs, and has a smaller number of marginal bristles, all quite short. The bristles on the two basal lobes are also considerably less developed than in the other pairs, and only slightly curved. Description of the Male. Unlike the Branchinecta, and also, as it seems, the other Branchipodide, the males of the present species are generally rather smaller than the females, and scarcely exceed 10 mm. in length. The body (see Pl. IX, figs. 3 and 4) is somewhat less elongated, and both the head and the tail are The head is of very considerable size, and exhibits above » a saddle-like depression. It ends in front with two digitiform, and somewhat divergent frontal proces- ses, which are curved downwards and divided in the middle by a cresent-shaped notch (see also Pl. X, fig. 2). On each side, from a broad base, there issue, apparently as an immediate continuation of the head, the peculiarly formed prehensile antenne (see Pl. IX, figs. 3 and 4, Pl. X, fig. 2). Each of these is divided into 3 successive, incurved, digiti- form rami, of which the foremost is the largest, and seems to represent the stem proper, while the other two may be considered more properly as secondary lateral branches. The hindmost ramus is consider- ably smaller than the others, is bluntly rounded at the end, and fringed all round with fine hairs, while the other two are only hairy along the inner con- cave edge (se Pl. IX, fig. 5). In conjunction with the two frontal processes these two limbs, when ‘bent in towards one another, can act as a most effectual seizing and holding apparatus. The eyes, the first pair of antenne, the oral parts and the branchial legs do not differ in any respect from those organs in the female. The posterior division of the body, on the other 63 tydelig smekrere end hos Hunnen (se Tab. IX, Fig. | hand, is very different to, and much more slender 3 og 4, Tab. X, Fig. 6). De 2 Kjonsringe er tyde- | than that of the female (see Pl. IX, figs. 3 and 4; ligt adskilte i sit dorsale Parti og er, ovenfra seede, neppe. bredere end Truncus. Derimod danner de nedad en noget uregelmessig Udvidning, hvorfra de ydre Kjonsvedheng udgaar. Disse sidste er for- holdsvis storre end hos Branchinecta og af noget ner eylindrisk Form, eller kun ganske svagt afsmalnende mod Enden, og har det ydre Parti tet besat med fine Haar. Den bagenfor liggende Del, den egent- lige Hale, afsmalnes gradvis bagtil og er, uligt hvad Tilfeeldet er hos Hunnen, delt i 6 tydeligt begraend- sede Segmenter, foruden Halegrenene. Disse sidste er fuldkommen af samme Udseende som hos Hunnen. Farve. — Legemet er hos begge Kjon i levende Tilstand meget gjennemsigtigt, saa at de indre Or- ganer mere eller mindre tydeligt skinner igjennem de tynde Integumenter. Hos Hunnerne har det ial- mindelighed et svagt gronligt Anstrog, medens det hos Hannerne viser en lys gulagtig Tone. Dog va- rierer Farven betydeligt hos begge Kjon efter Lo- kaliteterne og spiller undertiden over i det blaalige eller rodlige. Hos fuldt udviklede Hunner findes meget constant (se Tab. IX, Fig. 1 og 2) paa Ryg- siden af Kjonsregionen 2 sidestillede rudeformige Pletter af en intensiv ultramarinblaa Farve og ind- fattede af en morkere Kant. Enhver af disse Plet- ter forlenger sig sedvanligvis fortil i en smal Stribe af samme Farve, og mellem begge disse sees ialmin- delighed 2 andre tet sammenstillede Lengdestriber af en lignende Couleur. Den forreste Del af Ag- beholderen er i Regelen orangefarvet, medens den bagerste Del viser nogle uregelmessige violette Shatteringer. De i Mghbeholderen indsluttede Hg er morkt gronfarvede. Hos Hannerne er ofte Spid- serne af Gribeantennernes Grene mere eller mindre tydeligt orangefarvede, og undertiden det bagerste Segment af Halen violet anstroget (se Tab. IX, Fig. 3 og 4). Indre Organer. Tarmen strekker sig, som hos Branchinecta, i Form af et simpelt cylindriskt Ror igjennem hele Legemet (se Tab. IX, Fig. 1—4), og er ialmindelig- hed fyldt med orangefarvet Indhold, der bagtil grad- vis antager en morkere brunagtig Farve. I Hovedet udgaar fra Forenden af Tarmroret 2 korte Blind- sekke af en lignende Structur som hos Branchinecta. _ Spiseroret (Tab. X, Fig. 4, 5, 0) viser ved sin For- bindelse med Tarmroret en eiendommelig klapformig Indretning, ligesom der paa dette Sted findes et Slags chitinagtigt Stotteapparat besat med et Antal af steerke, i Tarmens indre frit fremspringende borste- formige Fortsatser, cilierede i Kanterne. Endetar- | Pl. X, fig. 16). The two genital segments are dis- tinctly separated in their dorsal part, and, when seen from above, are scarcely broader than the trunk. Below, however, they form a somewhat irre- gular expansion, from which the external sexual appendages issue. The latter are relatively larger than in Branchinecta, and nearly cylindrical in form, being only very slightly tapered towards the end, and with the outer part covered with fine hairs. The posterior portion, or tail proper, tapers gradu- ally towards the end, and, unlike that of the female, is divided into 6 distinctly-defined segments, besides the caudal rami. The latter are of exactly the same appearance as those of the female. Colour. -~In the living state, the body in both sexes is very transparent, so that the internal or- gans are traced more or less distinctly through the thin integuments. In the females, it has generally a faint tinge of green, while in the males, it exhi- bits a light yellow shade. The colour varies, how- ever, considerably in both sexes, according to the localities, and sometimes has a blue or a red tint. In fully developed females, there is very generally found (see Pl. IX, figs. 1 and 2) on the dorsal side of the sexual region, 2 juxtaposed, diamond-shaped patches of an intense ultramarine-blue, surrounded by a darker rim. Each of these patches is generally prolonged anteriorly into a narrow stripe of the same colour, and between them are generally to be seen two other longitudinal stripes of the same colour, placed close together. The anterior portion of the marsupium is, as a rule, orange-coloured, while the posterior part exhibits some irregular purple markings. The eggs enclosed in the marsu- pium are of a dark green colour. In the males, the tips of the rami of the prehensile antenne are fre- quently more or less distinctly orange-coloured, and the hindmost. segment of the tail is often tinged with purple (see Pl. IX, figs. 3 and 4). Internal Organs. As in Branchinecta, the intestine runs in the shape of a simple cylindrical tube throughout the length of the body (see Pl. IX, figs. 1—4), its con- tents being generally of an orange-colour, gradually assuming a darker brown hue posteriorly. From the anterior end of the intestinal tube, in the head, there issue 2 short ceca of a structure similiar to that in Branchinecta. The esophagus (Pl. X, figs. 4, 5, 0) exhibits at its junction with the intestinal tube, a peculiar valve-like arrangement, and also at the same place a kind of chitinous support, clothed with a number of strong, setiform spikes with cili- ated edges, freely projecting inside the intestine. men er, som hos Branchinecta, kun indskrenket til sidste Halesegment, og viser en lignende Bygning som hos denne Slegt. Nervesystemet synes idethele at vere bygget paa samme Maade som hos Branchinecta, alene med den Forskjel, at Buggangliekjeden her er sammen- sat af et betydelig storre Antal Ganglier, overens- stemmende med det storre Antal Segmenter i For-. kroppen. Ovarierne (Tab. X, Fig. 12, 13, osv.) er her kun indskrenket til Kjonsregionen, idet de ligger til hver Side ved Basis af Aigbeholderen, uden at strekke sig ind, hverken i Forkroppen eller i den bagenfor AXgbeholderen liggende Del af Halen. De danner 2 korte cylindriske Sekke (Fig. 14), i hvis Indre ialmindelighed kun findes en enkelt Rekke af sig udviklende storre Hg fyldte med gron Blomme- masse, og desforuden, mere uregelmessigt fordelte, et Antal af meget smaa klare Celler med tydeligt fremtredende Kjerne.- Omtrent tra Midten af hvert Ovariums indre Kant udgaar Aglederen, der viser paa Midten en sterk, sekformig Udvidning og. mun- der i det indre af Agbeholderen. Mundingen er delvis omgivet af en meget voluminos Kjertelmasse (Fig. 12, 13, gl), der strekker sig igjennem hele Aig- beholderens Leengde, og som afgiver Stoffet til den sterke Skal, hvormed Aiggene her omgives. De modne af Ovarierne udkomne Aig ligger uregelmes- sigt ordnede i Agbeholderens Siderum (se Tab. IX, Fig. 1 og 2) og udtommes med visse Mellemrum gjennem dens klapformige Munding. De er da (se Tab. X, Fig. 15) omgivne af en temmelig tyk og meget fast chitinos Skal, der ved steerk Forstorrelse viser sig uregelmessig reticuleret. Aigindholdet er ensformigt kornet og af en meget mork gron, i det brunlige spillende Farve. Nogen Segmentering af Agget har jeg ikke kunnet paavise. Testes (Tab. X, Fig. 16, t) indtager omtrent samme Plads som Ovarierne, skjondt de strekker sig lidt ind i den bag Kjonsringene liggende Del af Halen. De har Formen af 2 smale Sekke, tilspid- sede i hver Ende, og noget tykkere fortil end bag- til. Noget bagenfor den forreste Ende udgaar fra den nedre Side Sedlederne, der, som hos Branchi- necta, danner en temmelig sterk, tvedelt Udvidning (vd), hvorpaa de hver antager Formen af en trang Kanal. Denne gjor en sterk slyngeformig Boining, inden den treder ind i de ydre Kjonsvedheng, paa hvis Spids den udmunder. Udvikling. Ogsaa af denne Form har jeg leilighedsvis havt Anledning til at undersoge flere Udviklingstrin, uden at det dog endnu har lykkets mig at faa stu- deret den hele Udvikling fra forst af. The rectum, as in Branchinectu, is limited to the last caudal segment, and exhibits a structure similar to that in the above-named genus. The nervous system seems, on the whole, to be constructed in the same manner as in Branchinecta, with the one difference that the ventral ganglion chain is composed of a considerably larger number of ganglia, corresponding to the greater number of segments in the anterior part of the body. The ovaries (Pl. X, figs. 12,13, ov) are confined to the genital region, and lie one on each side of the base of the marsupium, without extending either into the anterior part of the body, or into the caudal region behind the marsupium. They form two short cylindrical bags (fig. 14) within which there is generally only a single row of eggs under- going development, and filled with a green yolk-mass, and also, more irregularly dispersed, a number of minute clear cells with distinctly conspicuous nuclei. From about the middle of the inner edge of each ovary, issues the oviduct, with a large sac-like dila- tation in the middle, and opens into the inside of the marsupium. The mouth is partially surrounded by a very voluminous glandular mass (figs. 12, 13, gl), which extends through the entire length of the marsupium, and secretes the substance for the strong shell with which the egg becomes here sur- rounded. The mature ova that have come out of the ovary, are irregularly arranged in the lateral spaces of the marsupium (see Pl. IX, figs. 1, 2) and are evacuated at certain intervals through the valve-like mouth. They are then (see Pl. X, fig. 15) enveloped in a tolerably thick, and very firm chiti- nous shell, which on being highly magnified appears irregularly reticulated. The contents of the ovum are uniformly granulose and of a very dark green colour with a tinge of brown. I have been unable to discover any segmentation of the ovum. The testes (Pl. X, fig. 16, t) occupy about the same place as the ovaries, though they extend a little way into that part of the tail lying behind the genital segments. narrow bags, pointed at both ends and rather thicker in front than behind. From the inferior side, a little behind the anterior end, issue the efferent ducts forming, as in Branchinecta, a rather strong, bipartite expansion (vd), whereupon each assumes the form of a narrow channel. This makes a spiral curve before it enters the external sexual appendage, at the point of which it opens. Development. I have occasionally had the opportunity of exa- mining several developmental stages of this form also, although I have not yet succeeded in studying its whole development from the very beginning. They are in the form of 2 ae oe 65- Det tidligste Larvestadium, jeg har fundet, er | afbildet Tab. IX, Fig. 7. Det svarer, hvad Lem- mernes Udyikling angaar, noget ner til det Tab. VIII, Fig. 15 afbildede Stadium af Branchinecta, men skiller sig meerkeligt derved, at de sammen- satte Mine, der hos hint Stadium neppe endnu var anlagte, her er meget tydeligt og omtrent ligesaa vidt komne som paa det i andre Henseender meget videre udviklede Stadium af Branchinecta, som er fremstillet Fig. 17 paa samme Planche. Det synes altsaa som om disse Organer udvikles betydelig tid- ligere hos nerverende Phyllopode. De 2 Par Fo- lere og Kindbakkerne med sine Palper stemmer idet- hele meget noie med samme hos det tilsvarende Stadium af Branchinecta, alene med den Forskjel, at den inderste af de 2 fra 2det Par Foleres Skaft ud- gaaende, indadkrummede Fortsatser her er simpel, ikke tvekloftet. Af Branchialfodder er der kun til- Stede 7—8 svage Anleg i Form af simple Tver- vulster til hver Side af Kroppen, som allerede viser en tydelig Segmentering. Haleenden er noget ind- snoret yed Basis og ender med 2 meget korte Lappe, hver berende en enkelt Borste. Den videre Udvikling foregaar paa en fuldkom- men lignende Maade som hos Branchinecta, idet Branchialfodderne successivt udvikles forfra bagtil, medens 2det Par Folere 08 Mandibularfodderne grad- vis reduceres. Forekomst og Levevis. Nerverende eiendommelige Phyllopode er meget almindelig overalt i Finmarken. Jeg har truffet den paa folgende Lokaliteter: Bugo paa Sydsiden af Varangerfjorden, Vadso, Fastlandet indenfor Vardo paa mange Stedet, Vagge Tanafjord, Mehavn, Hasvig paa flere Steder, Hammerfest ligesaa. Leen- gere Syd paa Landet har jeg derimod aldrig stodt paa den, og den synes saaledes hos os udelukkende at vere indskrenket til den arktiske Zone. Den forekommer under lignende Forhold som Branchi- necla paludosa og ikke sjelden sammen med den. Det er iser i ganske grunde Smaatjern med mudret Bund og som ud paa Sommeren delvis eller fuld- ‘stendig udtorres, at den paatreeffes og her ofte i enorme Mengder. Dog har jeg ogsaa af og til truf- oa den i storre og dybere Vande, f. Ex. i et Tjern a Hoideplateanet ved Vagge i Bunden af Tana- en, hvor den viste en vakker blaalig Farve- - a Den svommer ialmindelighed om i Vandet _ mere eller mindre ner Overfladen og med en ganske _ jevn Fart, altid med Ryggen nedadvendt. Hanner Hunner treeffes meget ofte i Copulation, og Han- fastholder herunder Hunnen saa kraftigt med e Gribeantenner om Kjonsregionen, at det ikke 9 — G. 0. Sars: Fauna Norvegizx. The earliest larval stage that I have found is figured on Pl. IX, fig. 7. As regards the develop- ment of the limbs, it answers to the stage of Bran- chinecta represented on Pl. VIL, fig. 15, with the remarkable difference that the compound eyes, which, in that stadium, had scarcely commenced to appear, are here very distinctly developed, and are about as far advanced as in the, in other respects, much further developed stadium of Branchinecta shown on fig. 17 of the same plate. It therefore seems as if these organs were developed much earlier in the present Phyllopod. The two pairs of antenne and the mandibles with their palpi agree on the whole very exactly with those organs in the corresponding stage of Branchinecta, with the one difference, that the inner of the two incurved processes starting from the scape of the second pair of antenne are here simple, not bifid. There are only 7 or 8 slight rudiments of branchial legs in the form of simple transverse prominences on each side of the body, which already shows distinct articulation. The ex- tremity of the tail is somewhat constricted at the base, and ends in two very short lobes, each carrying a single bristle. Further development proceeds exactly as in Branchinecta, the branchial legs developing succes- sively from front to back, while the 2nd pair of antenne and the mandibular legs gradually di- minish. Occurrence and Habits. This peculiar Phyllopod is very common over the whole of Finmark. I have met with it in the following localities: Bugs, on the south side of the Varanger Fjord; Vadso; in many places on the mainland south of Varde; Vagge on Tana Fjord; Mehavn; Hasvig in many places; also Hammerfest. On the other hand, I have never come across it further south, and it thus seems, in this country (Norway) to be confined to the arctic zone. It is found under the same conditions as, and not infre- quently together with Branchinecta paludosa. It is especially in quite shallow, small lakes with muddy bottom, and which either partly or completely dry up towards the end of the summer, that it is met with, and there often in very great numbers. I have, however, now and then also found it in larger, deeper lakes, e. g. in a lake on the plateau at Vagge, at the head of Tana Fjord, where it was of a beautiful blue colour. It generally swims about more or less near the surface of the water at an even rate, and with its back always turned down- wards. Males and females are often found in copu- lation, during which the male clasps the female so firmly with its prehensile antenne about the genital 66 sjeldent lykkes at faa begge i Sammenheeng con- | region, that it is often possible to preserve both serveret paa Spiritus. Udbredning. — Arten blev forst opdaget af Middendorff i Smaatjern paa den sibiriske «Tundra» ved Floderne Taimyr og Boganida, ligesom ogsaa i Russisk Lapland ved Tri-Ostrowa, og er senere af Fries gjenfunden i Ostfinmarken. Derimod er den ikke kjendt hverken fra Gronland, det arktiske Amerika eller Spitsbergen. Sectio II. Notostraca. (Skjolddekte Phyllopoder). Syn: Phyllopoda cancriformia. Character. — Legemet mere eller mindre dek- ket oventil af et bredt hvelvet Rygskjold, -der for- til er sammenvoxet med Hovedet. Kroppen ensfor- migt segmenteret, jevnt afsmalnende bagtil, og en- dende med 2 forlengede Haletraade. Qinene ses- sile, ner sammen paa Oversiden af Hovedet. Andet Par Folere hos det voxne Dyr rudimentere eller ganske manglende. Munddelene tet sammentrengte bag Hovedets ventrale Duplicatur, og bestaaende af Over- og Underlebe, Mandibler og 2 Par Kjever. Fodderne overordentlig talrige og tet sammen- trengte bagtil, saa at flere Par er feestede til hvert enkelt Segment. Ingen ydre Aigbeholder. Udvik- lingen en compliceret Metamorphose begyndende med et Naupliusstudium. Bemerkninger. — Nerverende Gruppe adskiller sig meget skarpt fra de ovrige Phyllopoder ved en Rekke vel markerede Characterer, hvoraf den mest ioinefaldende er det fladt hvelvede Rygskjold, der fortil gaar i et med Hovedet og giver Dyret en umiskjendelig Lighed med Xiphoswrerne og derigjen- nem ogsaa med de forverdenske Trilobiter. Med disse sidste stemmer ogsaa nerverende Gruppe overens ved det overordentlig store Antal af uni- forme Segmenter, hvori Legemet er delt. Idethele synes flere Characterer, der udmerkede nogle af de eldste forverdenske Crustaceer, tydeligere at afspeile sig i neerveerende Gruppe end i nogen af de ovrige. Den indeholder for Tiden kun en enkelt Familie. together in spirit. Distribution. — This species was first disco- vered by Middendorff in small lakes on the Siberian «Tundra» at the rivers Taimur and Boganida, and also in Russian Lapland at Tri-Ostrowa; it was subsequently found again by Fries in East Finmark. It has not, however, been heard of either from Greenland, arctic America or Spitzbergen. Section I]. Notostraca. (Shield-bearing Phyllopods). Syn: Phyllopoda cancriformia, ‘ Characters. — Body more or less covered above by a broad, vaulted carapace, which is united ante- riorly with the head. Trunk uniformly segmented, - tapering evenly posteriorly, and ending in two elongated caudal filaments. Eyes sessile and close together on the upper surface of the head. Second pair of antenne in the full-grown animal either ru- dimentary or altogether wanting. Oral parts closely crowded behind the ventral duplicature of the head, and consisting of upper and lower lip, mandibles and 2 pairs of maxille. Legs extremely numerous and closely crowded together posteriorly, so that several pairs are attached to each segment. No external marsupium. Development, a complicated metamorphosis, commencing with a nauplius stadium. Remarks. — The present group is sharply de- fined from other Phyllopoda by a series of well-marked characters, of which the most conspicuous is the vaulted carapace which is united with the head, giving the animal an unmistakable likeness to the Xiphosure, and thereby also to the paleozoie Trilo- bites. With the latter the present group also agrees, in the extraordinarily large number of uniform seg- ments into which the body is divided. Taken as a whole, several of the characters that distinguished some of the oldest paleozoic Crustacea, seem to be reflected more clearly in the present group than in any of the others. single family. At present, it contains only a Fam. Apodide. Character: — Mbypesbiolaet bredt afrundet fortil, fladt hvelvet, og indskaaret bagtil, med en tydelig transversal Nakkefure, begrendsende Hovedet. bag- til; det sidste.skovlformet, visende en halvmaane- _ formig ventral Duplicatur, bag hvilken Folere og Munddele har sin Plads. Den bagre Del af Lege- met mere eller mindre fremragende bag Rygskjoldet og delt i talrige korte, med fine Torne omkrandsede _ Segmenter. Haletraadene sterkt forlengede. Over- leben bred, klapformig; Underleben tvekloftet. Wy Kindbakkerne med grovt tandet Eg. iste Par Kje- _ ver oxeformige; 2det Par med en membrangs lateral Fortsats. Alle Fodder med tydeligt begrendset Be isinap: Iste Par mere eller mindre ulige de _ ovrige, med Enditerne traadformige; de nest fol- gende Par prehensile, med Enditerne delvis klo- _ formige; 11te Par hos Hunnen med Epi- og Exopo- diten omformede til en kapselformig Mgbeholder. _ Hannerne meget sjeldne, betydelig mindre end Hun- __nerne, og uden specielle prehensile Organer. Bemerkninger. — Denne Familie indeholder kun 2 Slegter, Apus og Lepidurus, der staar hin- anden overmaade ner, og begge har en meget vid I aieiphick Udbredning, idet de er representerede _baade i den nye og gamle Verden, ligesom ogsaa i Australien. Kun den sidste af disse Slegter er repreesenteret i vor Fauna. Gen. Lepidurus, Leach, 1816. ___- Slagtscharacter. — Rygskjoldet ialmindelighed _ meget stort, dekkende den storste Del af Kroppen , forsynet bagti] med en mere eller mindre ud- langsgaaende dorsal Kjol. Sidste Haleseg- forlenget mellem Haletraadene til en plade- Udvidning. 1ste Fodpar med Enditerne for- -korte, kun lidet overragende Rygskjoldets . 63 Fodpar tilstede. Forovrigt overensstem- med. Een Apus. per. — Den her omhandlede Slegt ms af den bekjendte Naturforsker entlig characteriseret ved Tilstede- median Haleplade, der ganske mang- t ved de forholdsvis korte Enditer Da midlertid forovrigt de herhen , det noieste stemmer overens med bitus som i de anatomiske 67 Fam. Apodide. Characters. — Carapace broadly rounded in front, slightly vaulted and indented behind, with a distinct transverse cervical furrow defining the head posteriorly; the latter shovel-formed and exhibiting a crescent-shaped ventral duplicature, behind which the antenne and oral parts are situated. Hind part of the body projecting more or less behind the cara- pace, and divided into numerous segments, encircled by fine spikes. Caudal filaments very much elong- ated. Anterior lip broad and flap-like; posterior lip bifid. Mandibles with the cutting edge coarsely den- tated. First pair of maxille securiform, second pair with a membranous lateral expansion. All the legs with clearly defined coxal lobes; first pair more or less unlike the remainder, with the endites filiform; the next pairs prehensile, with the endites partially claw-like; 11th pair in the female, with the epipo- dite and exopodite transformed into a capsular ovi- sac. Males very rare, considerably smaller than the females, and without special prehensile organs. Remarks. — This family contains only two genera, Apus and Lepidurus, which are very nearly allied, and both have a very wide geographical dis- tribution, being represented both in the old and the new world, as also in Australia. Only the latter of these two genera is represented among the Nor- wegian fauna. Gen. Lepidurus, Leach, 1816. - Generic Characters. — Carapace usually- very large, covering the greater part of the body, and furnished posteriorly with a more or less marked longitudinal dorsal keel. Last caudal segment pro- longed between the caudal filaments to a lamellar expansion. First pair of legs with the endites com- paratively short and projecting only slightly be- yond the edge of the carapace. There are 63 pairs of legs. In other respects it agrees with the genus Apus. Remarks. — The genus here treated of was first established by the well-known English natu- ralist, Leach, and is characterised principally by the presence of a median caudal lamella, which is altogether absent in Apus, and by the comparatively short endites in the first pair of legs. As, however, the species belonging to this genus agree in other Detailler, kan det vere et Sporgsmaal, om disse 2 Slegter i Virkeligheden altid lader sig holde skarpt ud fra hinanden. Man vil nemlig finde, at Enditer- nes Lengde paa 1ste Fodpar er hos Arterne af Slegten Lepidurus ikke lidet varierende, og Hale- pladen er ialfald hos enkelte Arter saa betydelig reduceret i Storrelse, at den nesten maa kaldes rudimenter. Rygskjoldet er vistnok ialmindelighed storre hos Lepidurus end hos Apus, og dekker der- for hos den forste Slegt en storre Del af Kroppen end hos den sidste; men man vil dog finde, at der ogsaa i saa Henseende er adskillig Variation hos Arterne af begge Slegter. Hos Lepidurus glacialis er det saaledes neppe synderligt storre end hos Apus cancriformis, og hos den nordamerikanske Le- pidurus bilobatus er en fuldkommen ligesaa stor Del af Kroppen ubedekket af Rygskjoldet som hos Apus cancriformis. Man kjender 6 eller 7 forskjellige Arter af denne Slegt, hvoraf kun en tilhorer Nor- ges Fauna. Lepidurus glacialis (Kroyer). (Pl. XI; XII,. XI). Apus glacialis, Kroyer, Nat. Tidsskr. 2 R. Bd. 2, p, 481. Lepidurus glacialis, Packard, Monogr. Phyll. Crust. North Ame- rica. U. St. Geol. Surv. I, p. 316, Pl. XVI, Pl. XVII, figs. 1—5, Pl. XXI, figs. 1, 2. Artscharacter. — Rygskjoldet af middelmaadig Storrelse, bredt ovalt, jevnt afrundet fortil, med en tydeligt markeret dorsal Kjol; det bagre Indsnit temmelig dybt, vinkelformigt. 12—18 Segmenter ube- dekkede bag Rygskjoldet. Halepladen forholdsvis meget kort, i Regelen ikke leengere end sidste Hale- segment er bredt, tungeformig, neppe indsnoret ved Basis, undertiden svagt indskaaret i Spidsen, Kanterne med et begreendset Antal Sagtakker. 2det Par Fo- lere tilstede som smaa Rudimenter. iste Fodpar med Enditerne meget korte, kun ubetydeligt over- ragende Kanterne af Rygskjoldet. Farven hos le- vende Exemplarer mere eller mindre mork oliven- brun, paa Spiritusexemplarer ensformig gron. Leeng- den af Hunnen indtil 24 mm, af Hannen neppe mere end 12 mm. Bemerkninger. — Nerverende Art er forst kortelig beskreven paa ovenanforte Sted af Kroyer, og senere afbildet af samme Forfatter i Gaimard’s store Reiseveerk, dog her uden nogen Beskrivelse. Den adskiller sig fra de ovrige Arter af Slegten, og navnlig fra den i Mellemeuropa almindeligt fore- kommende Lepidurus productus, ved Rygskjoldets ringere Storrelse, de meget korte Enditer paa Lste Fodpar, og ved Halepladens Korthed. 68 | respects exactly with those of Apus, both in external habitus and in anatomical details, it may be questioned whether these two genera can in reality always be kept distinct from one another. For instance, it will be found that the length of the endites in the first pair of legs in the genus Lepidurus, varies not a little; and the caudal lamella, at any rate in cer- tain species, is so greatly reduced’ in size as to be almost rudimentary. The carapace is certainly ge- nerally larger in Lepidwrus than in Apus, and there- fore covers, in the former genus, a larger part of the body than in the latter; but it will still be found that even in this respect there is considerable variation in the species of both genera. For instance, in Lepidurus glacialis it is scarcely larger than in Apus cancriformis, and in the North American Lepidurus bilobatus, fully as large a part of the body is left uncovered by the carapace as in Apus cancriformis. Six or seven different species of this genus are known, only one of which belongs to the fauna of Norway. Lepidurus glacialis (Kroyer). (Pl. XI, XII, XII). Apus glacialis, Kroyer, Nat. Tidsskr. 2 R., Bd. 2, p. 481. Lepidurus glacialis, Packard, Monogr. Phyl]. Crust. North Ame- rica. U.St. Geol. Surv. I, p. 316, Pl. XVI, Pl. XVII, figs. 1—5, Pl. XXI, figs. 1, 2. Specific Characters. — Carapace of medium size, broadly oval, evenly rounded in front, with a dis- tinctly-marked dorsal keel; posterior emargination rather deep and angular. From 12 .to 18 of the posterior segments not covered by the carapace. Caudal lamella comparatively very short, generally not longer than the breadth of the last caudal seg- ment, linguiform, scarcely constricted at the base, and sometimes slightly notched at the extremity: edges with a limited number of denticles. Second pair of antenne present as small rudiments. First pair of legs with the endites very short, projecting only slightly beyond the edges of the carapace. Colour in living specimens more or less dark olive brown, in spirit specimens, uniform green. Length of the female up to 24 mm., of the male, scarcely more than 12 mm. Remarks. — The present species was first briefly described in the above-named paper, by Kroyer, and subsequently figured by the same author in Gai- mard’s great work, but without any description. It differs from the other species of the genus, and especially from Lepidurus productus, so common in Central Europe, by the smaller size of the carapace, the very short endites of the first pair of legs, and the shortness of the caudal Jamella. — ‘ \ d i 4 a j 7 : & | 4 ; , ss. - ~~ S so Beskrivelse af Hunnen. Lengden af de storste af mig undersogte Ex- emplarer er, maalt fra Panderanden til Enden af E Halepladen, 24 mm. Dog synes det at vere meget ___ sjeldent, at den naar en saa betydelig Storrelse, og 18—20 mm. maa ansees for Gjennemsnitsstorrelsen for fuldt udviklede Individer. Som hos de ovrige til denne Phyllopodegruppe -_ horende Former, er (se Tab, XI, Fig. 1) Storste- parten af Legemet dekket oventil af et bredt, kun svagt hvelvet Rygskjold, hvorved Legemsformen faar et noget fladtrykt Udseende. Dette Rygskjold er fortil fuldkommen sammenvoxet med Hovedet, hvorimod det bagtil kun lost dekker den underlig- gende Krop, som frit kan beveeges under samme (se Fig. 3). Sees Legemet ovenfra (Fig. 1), viser sig en ___ storre eller mindre Del af Kroppen at rage frem __ bagenfor Rygskjoldet i Form af en jevnt afsmal- nende, noget cylindrisk Hale, endende med 2 lange, _ divergerende Vedheeng, Haletraadene, mellem hvilke _ desuden rager frem en liden median Haleplade. Sees Legemet nedenfra (Fig. 2), ligger hele Dyrets _ Bugflade med sine forskjellige Vedheng frit for Be- _ skueren indenfor Rygskjoldets Concavitet. Helt for- til sees en fra Panderanden udgaaende halymaane- formig glat Flade, umiddelbart bag hvilken Folerne e og Munddelene har sin Plads. Derpaa folger den lange Reekke af Fodder, der viser et temmelig uens- artet Udseende. 1ste Par er ialmindelighed lige ud- strakt til hver Side, saa at det noget overrager Siderandene af Rygskjoldet, medens de derpaa fol- gende 10 Par er mere indadkrummede, dog saaledes, at der mellem dem i Regelen altid findes et aabent Rum, i Bunden af hvyilket Kroppens Bugside sees i Form af en smal rendeformig Fordybning, begreend- set til Siderne af de respective Fodders indadrettede Coxallapper. Lengere bagtil indsnevres dette Rum, og Fodderne ligger her tet sammen som Bladene i en Bog, aftagende gradvis i Storrelse. Den samlede -Fodmasse antager derved Formen af en bagtil ven- _ dende spids Kegle. Den bagerste Del af Legemet er uden Lemmer og af simpel cylindrisk Form. « a, (3 _ Rygskjoldet viser, ovenfra seet (Fig. 1), en bredt Form, med Sidekanterne jevnt buede og fortil de i et med den ligeledes buede Frontalrand edet. Bagtil er det noget indsnevret og har st, der antyder Mandibularsegmen- Nakkefuren liggende Del represen- i Midten viser en stumpt afrun- -hvilken de 2 sammensatte Gine 69 Description of the Female. The length of the largest specimen examined by me measured 24 mm. from the frontal margin to the end of the caudal lamella. It seems, however, very seldom that it attains so considerable a size, and from 18 to 20 mm. must’ be considered as the average size for fully-developed animals. As in the other forms belonging to this group of Phyllopoda, the greater part of the body (see Pl. XI, fig. 1) is covered abcve by a broad, only slightly vaulted carapace, whereby the body acquires a somewhat flattened appearance. This carapace is completely united in front with the head, whereas posteriorly it only loosely covers the underlying body, which can move freely beneath it (see fig. 3). When the animal is viewed from above (fig. 1), more or less of the body is seen projecting from behind the carapace in the form of an evenly tapering, somewhat cylindrical tail, ending in two long, di- vergent appendages, the caudal filaments, between which there also projects a small median caudal lamella. When viewed from below (fig. 2), the whole of the animal's ventral surface with its various ap- pendages lies exposed to view within the concavity of the carapace. Right in front, a crescent-shaped, smooth surface is visible, starting from the frontal margin, and immediately behind this are situated the antenne and the oral parts. Then follows the long row of legs which present a somewhat hetero- geneous appearance. The first pair is generally extended equally to both sides, so that it projects a little beyond the lateral edges of the carapace, while the following 10 pairs are more bent inwards, though in such a way, that, as a rule, there is an open space between them, at the bottom of which the ventral surface of the body is visible in the shape of a narrow groove bounded laterally by the inwardly inclined coxal lobes of the respective legs. Further back, this space is contracted, and the legs lie as close together as leaves in a book, diminishing gradually in size. The accumulated mass of legs then assumes the form of a posteriorly pointing cone. The hindmost part of the body is without limbs, and in the form of a simple cylinder. The carapace, seen from above (fig. 1), is of a broad oval shape with the lateral edges evenly curved, and continuous with the likewise curved fron- tal margin of the head. It is somewhat narrowed be- hind, and has, in the middle, a deep, angular inci- sion, the edges of which are armed with small, sharp denticles. In the anterior part above, may be seen a distinct transversal hollow, the cervical sulcus, at the bottom of which there is a rounded trans- verse prominence, indicating the mandibular segment. The region in front of the cervical furrow repre- sents the head, and exhibits, in the centre, a bluntly 70 har sin Plads. Bag Nakkefuren begynder den frie Del af Rygskjoldet, der som en Kappe lost bedek- ker den underliggende Krop. Denne Del har efter Midten en tydelig Kjol, der bliver mere fremtre- dende bagtil, hvor den ender med et spidst Frem- spring i Bunden af Rygskjoldets bagre Indsnit. Fortil er, som ovenfor anfort, Rygskjoldet fuldkom- men sammenvoxet med Hovedet og danner her ne- dentil {se Fig. 2) en halvmaaneformig horizontal Du- plicatur, hvorved Hovedet faar en udpreget, bredt skovldannet Form (se ogsaa Fig. 3). Hvad angaar Rygskjoldets finere Bygning, saa mangler det ethvert Spor af Kalkafleiringer og er derfor meget boieligt og idethele af en temmelig blod Consistens. Det er, som seedvanligt, sammensat af 2 Lameller, en ydre meget tynd, fuldkommen glat og glindsende Lamelle af chitinos Beskaffenhed, og en indre mem- branos og noget spongios Lamelle. Mellem begge findes et System af Hulrum, hvori Blodet cirkulerer, og desuden de 2 meget sterkt udviklede Skal- kjertler.. Disse er delvis udvendigt synlige som aflangt ovale, noget sabelformigt krummede Felter, der fra Nakkefuren strekker sig langs ad Siderne af den frie Del af Rygskjoldet (se Fig. 3). De be- staar hver (se Tab. XIII, Fig. 4) af en flere Gange slyngeformigt bugtet Kanal, der synes at udmunde ved Basis af Kindbakkerne. Borttager man den frie Del af Rygskjoldet, sees (Tab. XIU, Fig. 1 og 2) den underliggende Krop at vere delt i en Rekke meget ensformige Segmenter, der ikke. grupperer sig til tydeligt markerede Af- snit, om det end efter Forholdet af Lemmerne lader sig gjore med nogenlunde Sikkerhed at bestemme Grendserne for de 3 sedvanlige Kropsafsnit: Midt- krop, Bagkrop og Hale. Segmenternes Antal er ialt 28. Heraf tilhorer de 11 forste Midtkroppen og berer hvert et enkelt Par Fodder, hvorimod de 11 folgende, til Bagkroppen horende Segmenter beer hvert flere Par Fodder. De 6 bagerste Segmenter er fodlose og representerer derfor den egentlige Hale. De er meget skarpt begreendsede, med Bag- kanten noget hevet og rundt om bevebnet med korte Tagger, der ogsaa forefindes paa Rygsiden af de nermest tilgreendsende Segmenter af det fore- gaaende Afsnit. Sidste Halesegment (se Tab. XII, Fig. 23--27) er noget lengere end de foregaaende, og har oventil paa hver Side af Midtlinien en rund- agtig Knude besat med en Kreds af smaa Tagger, i hvis Midte en fin Sandseborste sees at rage frem (se Fig. 28). Ved Enden af Segmentet findes paa den ventrale Side Analaabningen, og umiddelbart over denne fortsetter Segmentet sig i en tynd ho- rizontal Plade, der skyder frem bagtil mellem Basis at de 2 Haletraade. rounded prominence, upon which the 2 compound eyes are situated. Behind the cervical furrow, the free portion of the carapace begins, covering loosely, like a mantle, the underlying body. Down the centre of this part, there is a distinct keel, which becomes more prominent posteriorly, and ends in a sharp projection at the bottom of the posterior emargination of thé carapace. As stated above, the carapace is completely coalesced in front with the head, and there forms, below (see fig. 2), a crescent-shaped horizontal duplicature, whereby the head: acquires a pronounced shovel- like shape (see also fig. 3). With regard to the finer structure of the carapace, no trace what- ever of calcareous deposit is found in it, and it is therefore very flexible and, on the whole, of a rather soft consistence. It is, as usual, composed of two lamella, one .external, very thin, perfectly smooth and shining, and of a chitinous nature, the other, an inner, membranous and somewhat spongy lamella. Between the two there is a system of cavities, through which the blood circulates, and also 2 very highly developed shell glands. These are partially visible externally in the form of long oval, rather ensiformly curved areas, extending from the cervical suleus along the sides of the free portion of the carapace (see fig. 3) They each consist (see Pl. XIII, fig. 4) of a tube with several windings, which seems to open at the base of the mandibles. If the free portion of the carapace be removed (Pl. XII, figs. 1, 2), the underlying body is found to be divided into a series of very uniform segments, which do not apportion themselves into distinctly marked sections, although it is possible, by the rela- tions of the limbs to one another to determine, with a measure of certainty, the limits of the 3 ordinary divisions of the body, — the mesosome, the meta- some and the tail. The number of the segments is 28 in all. Of these the first 11 belong to the meso- some, and each carry one pair of legs, whereas the following 11 segments, which belong to the meta- some, each carry several pairs of legs. The last 6 segments have no legs, and therefore represent the tail proper. They are very sharply defined, the posterior edge being somewhat raised, and armed all round with short denticles, which are also found on the dorsal side of the adjacent segments of the preceding section. The last caudal segment (see Pl. XII, figs. 23—27) is rather longer than the prece- ding ones, and has above, on each side of the me- dian line, a round prominence surrounded by a circle of small denticles, from the midst of which a fine sensory bristle is seen to project (see fig. 28). At the end of the segment, on the ventral side, is the anal orifice, and immediately above it, the segment is prolonged into a thin horizontal lamella, protru- ——_— —" - Denne Plade, der er eiendommelig for Slegten : Lepidurus, er hos nerveerende Art ialmindelighed af __ forholdsvis ringe Storrelse og som oftest ikke len- S. gere end sidste Halesegment er bredt. Formen er mere eller mindre udpreget tungedannet, uden nogen bemerkelig Indsnoring ved Basis. Den varierer for- ovrigt serdeles meget saavel i Storrelse som Form, a hvad der vil kunne sees af de her givne Figurer (Fig. 23—-27), og tiltager ialmindelighed i Lengde med Alderen. Fig. 25 fremstiller Halepladen hos et _ ganske useedvanlig stort Exemplar. Det er imidler- tid meget sjeldent, at den naar en saa betydelig ___ Storrelse som her angivet. Langs efter Midten har _ Halepladen hos alle Individer en stump Kjol besat med et noget varierende Antal af grove Tagger, _ sedvanligvis 2 eller 3. Kanterne er i sin ydre Del grovt og noget uregelmessigt sagtakkede. Hos de ____ fleste Exemplarer har Spidsen af Halepladen et lidet _ Indsnit i Midten, hvorved dannes 2 korte Ende- __ lapper, der ofte er asymetriske (se Fig. 27). De sammensatte Wine har, som ovenfor anfort, sin Plads paa den mest fremragende Del af Hovedets Dorsalside (se Tab. XI, Fig. 1 og 3, Tab. XIII, Fig. 1 og 2). De er, i Modsetning til hvad Tilfeeldet er hos Branchipodiderne, sessile, af nyredannet Form, og saaledes stillede, at deres Forende ligger ner _ sammen, medens der bagtil mellem dem er et storre Rum, der indtages af et ovalt, noget ophoiet og skarpt begrendset Felt, den saakaldte Postocular- -_ knude (Tab. XIII, Fig. 1, x, Fig. 8). Umiddelbart foran de sammensatte @ine ligger det enkle ie skinner igjennem Integumenterne. Hvad de sammen- satte Mines Bygning angaar, saa stemmer denne idethele naar afsees fra deres sessile Character, overens med samme hos Branchipodiderne, skjondt ogsaa visse Uoverensstemmelser kan paavises. det morkebrune Pigment sees talrige sterkt lysbry- dende Legemer at straale ud til alle Sider. Disse Legemer er den ydre Del af Krystalkeglerne, hvis indre spidst udtrukne Del er dybt indplantet i Pig- mentet. Enhver Krystalkegle viser sig ved neermere - Undersogelse (Fig. 6, 7) at vere sammensat af 4 — Lengdesegmenter og forbinder sig indad med den erstribede Synsstay, hvortil igjen slutter sig en af de mange Endefibre, hvori Synsnerven oploser Ethvert Synselement er-isoleret ved en mem- s Skede, i hvis Midte sees 2 tydelige, jevn- ende Kjerner (Fig. 7), » Par Folere (Tab. XII, Fig. 1, a', Fig. 2) paa Hovedets Ventralside til hyer Side ns Basis og umiddelbart bag den halv- Pandeduplicatur. De er meget smaa hed rettede skraat udad og fortil, idet om Bagkanten af den ovennevnte (Fig. 1, 5, oe), som dog ialmindeligled kun utydeligt Fra | ding posteriorly between the bases of the 2 candal filaments. This lamella, which is peculiar to the genus Lepidurus, is generally, in the present species, of comparatively small size, measuring as a rule no more in length than the last caudal segment does in breath. The shape is more or less decidedly lin- . guiform, without any noticeable constriction at the base. It also varies very mnch both in size and shape, as will be seen from the figures here given (figs. 23—27), and generally increases in length with age. Fig. 25 represents the candal lamella of an unusually large specimen; but it is very seldom that it attains to so considerable a size as that here shown. The caudal lamella in all specimens has medially a blunt keel armed with a rather variable number of coarse denticles, generally 2 or 3. The edges are coarsely and rather irregularly dentated in their outer portion. In most specimens there is a small indentation in the middle of the extremity of the caudal lamella, thus forming 2 short, termi- nal, often asymmetrical lobes (see fig. 27). The compound eyes, as above stated, are situ- ated on the most prominent part of the dorsal sur- face of the head (see Pl. XI, figs. 1, 3; Pl. XII, figs. 1,2). Unlike those in the Branchipodide, they are sessile, reniform in shape, and so placed that their anterior ends lie close together, while between them posteriorly there is a considerable space which is occupied by an oval, somewhat elevated and sharply-defined field, the so-called post-ocular tubercle (Pl. XIII, fig. 1 x, fig. 8). Immediately in front of the compound eyes lies the ocellus (figs. 1, 5, oc); which, however, is generally only indistinctly seen through the integuments. With regard to their structure, the compound eyes, ‘setting aside their sessile character, agree with those in Branchipodide, though a few points of difference can be found. Numerous strongly refractive bodies are seen radi- ating to all sides from the dark brown pigment. These bodies are the outer part of the crystalline cones, the inner pointed part being buried deeply in the pigment. Each crystalline cone proves, on a closer examination (figs. 6, 7), to be composed of 4 longitudinal segments, and to connect itself interi- orly with the transversely barred ocular rod to which, again, one of the numerous terminal fibres, into which the optic nerve resolves itself, is at- tached. Each visual element is isolated in a mem- branous sheath, in the middle of which are seen 2 distinet nuclei lying side by side (fig. 7). The first pair of antenne (Pl. XII, fig. 1, a}, fig. 2) spring from the ventral surface of the head on each side of the base of the upper lip, and imme- diately behind the crescent-shaped frontal duplica- ture. They are very small, and are generally di- rected obliquely outwards and forwards, bending Duplicatur. Man kan paa dem adskille et smalt, | round the posterior margin of the above-named du- af en Del utydeligt sondrede Led bestaaende Skaft og en noget opsvulmet, aflangt tenformig Endedel. Denne sidste ender med 3 korte Foleborster og har langs sin nedre Side talrige smaa Lugtepapiller, ordnede i flere Rekker (se Fig. 3). Enhver af disse Lugtepapiller (Fig. 4) viser sig ved sterk Forstor- relse at udspringe med en kort og tynd Stilk og har det ydre’ Parti skjevt udvidet, dannende en stump Vinkel med Stilken. De ender i en stump Spids, i hvis indre en liden sterkt lysbrydende Blere har sin Plads. Andet Par Folere (Tab. XII, Fig. 1 a*, Tab. XIII, Fig. 2, a*), der udspringer tet ved Iste Par, og lidt lengere udad, er blot tilstede som yderlig smaa Rudimenter, der er noget forskjelligt udviklede hos forskjellige Individer (se Tab. XII, Fig. 5, 6, 7). Talmindelighed danner de hver et smalt, i en tynd Spids udgaaende Appendix, paa hvilket undertiden: kan adskilles en noget tykkere Basaldel og en ten- takelformig Endedel. Hos et Exemplar var Spidsen ulige tvekloftet (Fig. 6). Af Munddelene er Overleeben og Kindbakkerne let bemerkelige, hvorimod de derpaa folgende Dele er mere eller mindre fuldstendig skjalte af Over- leben, saa at man kun ved Dissection kan faa Rede paa deres Bygning. Overleben (Tab. XII, Fig. 1, L, Tab. XII, Fig. 2, L) udspringer fra Midten af Pandeduplica- turen, med hvilken den er bevegeligt forbunden, saa at den til en vis Grad kan loftes op fra de evrige Munddele. lalmindelighed ligger den dog tet ind mod Kindbakkerne, dekkende en storre Del af samme (se Tab. XI, Fig. 2). Den er af forholdsvis betydelig Storrelse og viser en afrundet firkantet Form, med den nedre Flade svagt convex, den ovre noget concaveret. Enderanden er svagt udrandet i Midten og meget fint cilieret Kindbakkerne er meget kraftigt udviklede og hos det voxne Dyr uden ethvert Spor af nogen Palpe. Deres ydre Del er meget ioinefaldende, naar Dyret sees fra Bugsiden (Tab. XI, Fig. 2), og viser sig som en paatveers oval Forhoining til hver Side af Overleben. Derimod skjules deres indre Del, Tyggedelen, ganske af Overleeben og kommer forst tilsyne, naar denne bortfjernes eller loftes op (Tab. XU, Fig. 1, M). Det ovale, baadformige Corpus (se Fig. 8) er med sin ydre, i en Spids udgaaende Ende articuleret til Indsiden af Mandibularsegmentet og har den indre Hule fyldt med de kraftige Adductor- Muskler. Tyggedelen er sterkt, nesten oxeformigt udvidet, og delt i 8 kraftige, tvekloftede Tender, hvoraf den bagerste eller yderste er den storste og ved et storre Mellemrum skilt fra de ovrige, der successivt aftager i Storrelse. Den inderste Tand plicature. A narrow scape, consisting of some indis- tinctly articulated joints may be distinguished, and a rather swollen, oblong-fusiform terminal part. The latter ends in 3 short sensory bristles, and, along its lower side, has numerous small olfactory papille, arranged in several rows (see fig. 3). Each of these olfactory papille appears, when highly magnified, to stand on a thin, short stalk (fig. 4), while the distal part is obliquely expanded and forms an obtuse angle with the stalk. They end in a blunt point, inside which a small, strongly refrac- tive yesicle is found. The second pair of antenne (PI. XII, fig. 1, a?; Pl. XIII, fig. 2, a*), which spring out close to the first pair, and a little farther outwards, are only present as exceedingly small rudiments, which are developed differently in different specimens (see PI. XIU, figs. 5,6, 7). They generally each form a thin, finely-pointed appendage, in which may sometimes be distinguished a thickish basal part, and a ten- tacular terminal part. In one specimen, the point was unequally bifid (fig. 6). Of the oral parts, the labrum and the man- dibles are easily distinguished, whereas the succeed- ing parts are more or less concealed by the labrum, so that any knowledge of their structure is only to be obtained by dissection. “The labrum (PL XII, fig. 1, L; Pl. XIII, fig. 2, L) issues from the middle of the frontal duplicature, with which it is movably connected, so that it can, to a certain extent, be raised from the other parts. It generally, however, lies close in to the mandibles, covering the greater part of them (see Pl. XI, fig. 2). It is of comparatively large size, and presents a rounded quadrilateral shape, with the lower surface somewhat convex. The distal edge is slightly emar- ginated in the middle, and very finely ciliated. The mandibles are very powerfully developed, and, in the full-grown animal, possess no trace of palpi. Their outer part is very conspicuous in a ventral aspect of the animal (Pl. XI, fig. 2), and appears as a transverse oval prominence on each side of the labrum. Their inner, masticatory part, on the other hand, is quite hidden by the labrum, and is only visible when the latter is either removed or raised (Pl. XII, fig. 1, M). The oval, navicular body (see fig. 8) is articulated by its pointed distal end to the inside of the mandibular segment, its inner cavity being filled by the powerful adductor muscles. The masticatory part is greatly, almost securiformly expanded, and divided into 8 powerful, bifid teeth, the hindmost or outermost of which is the largest, and is separated by a greater space from the others, which successively decrease in size. or. ‘ ae eS ee ee tis i i, ees hed som Foddernes Epipoditer. er utydeligt tredelt og har i den indre Kant en fin Ciliering (Fig. 9). Bag Kindbakkerne folger nu t#t sammen de ovrige Munddele (se Tab, XII, Fig. 1), som det ikke er saa ganske let at isolere, da de delvis er for- bundne ved et System af sterke Chitinlister. Imid- lertid er det ikke saa vanskeligt at paavise, at de danner 3 paa hinanden folgende Rekker: forrest en vel udviklet Underlebe, derefter 2 Par normalt ud- viklede Kjever. - Underleben (Fig. 10, 1, Fig. 11) bestaar af 2 symetriske Halvdele eller Lappe, forbundne i Midten ved en tynd Membran. Enhver Sidelap er stottet af en noget bueformig Chitinplade, der ved Basis henger sammen med den tilsvarende forreste Kjave (se Fig. 10), og hvis Ende danner en smalt afrundet indbsiet Lob besat med tette Haar. Indad fort- setter Chitinpladen sig i en tyndere, halvt mem- branos Lamelle, der ligeledes er fint haaret i den indre Kant og lengere bagtil har et tet tveerstribet marginalt Parti. Af andre Forskere er Underlebens Sidelappe tydede som iste Kjevepar, hvad der aabenbart er urigtigt, da disse Lappe er fuldstendig ubeveegelige og desuden forbundne i Midten ved en tydelig Membran. Meerkelig er iethvertfald hos ner- verende Gruppe Tilstedeveerelsen af en vel udviklet Underlzbe, som hos de hoiere Crustaceer. Thi hos andre Phyllopoder, ligesom ogsaa hos den store Fler- hed af Entomostraceer, sees neppe en Antydning til denne Del. Iste Par Kjzever (Fig. 10 m', Fig. 12) danner hver en i Enden oxeformigt udvidet Chitinplade, der med sin tilspidsede Basis er forbunden med Under- lebens Chitinskelet, og derfor ved Dissection ial- mindelighed faaes i Sammenheng med Underleben. Paa Grund af Chitinsubstantsens Elasticitet kan de imidlertid til en vis Grad beveges imod hinanden, - og en Del tydelige Muskler, der lober skraat indad, besorger denne enkle Bevegelse. Paa den oxe- formigt udvidede indre Ende er de bevebnede med talrige korte Pigge og en hel Del stive Borster. Det forreste Hjorne danner en serskilt, noget paa- tvert stillet Lap, som er forsynet med en Del noget steerkere Pigge. 2det Par Kjever (Fig. 1, m*, Fig. 13), der af andre Forskere (Packard) feilagtigt er tydede som et Slags Kjevefodder, er af mere membranos Be- ‘skaffenhed og ender indad med en afrundet, tunge- formig Tyggelap, besat med-talrige grovt cilierede Borster. Paa den ydre Side findes en stumpt conisk af en noget. lignende spongios Beskaffen- Denne Udvidning maa nermest opfattes som et Slags rudimenter _ Fodderne er, som ovenfor neynt, overordentlig talrige, idet der paa den bagre Del af Truncus {Metasome) findes mange flere Fodpar end der er 10 — G. 0, Sars: Fawna Norvegiz. 73 The innermost tooth is faintly tripartite, and is finely ciliated on its inner edge (fig. 9). The remainder of the oral parts now follow closely behind the mandibles (see Pl. XII, fig. 1), and are not very easy to separate from one ano- ther, being partially connected by a system of strong chitinous fillets. It is not, however, difficult to see that they form 3 consecutive series: in front, a well-developed inferior lip, and then 2 pairs. of normally-deyeloped maxille. The inferior lip (figs. 10,1, 11) consists of 2 sym- metrical halves or lobes, connected in the middle by a thin membrane. Each lobe is supported by a somewhat arched chitinous lamella which is united at the base to the corresponding anterior maxilla (see fig. 10), and whose end forms a narrowly rounded, incurved, thickly ciliated lobe. The chiti- nous lamella is continued inwards in the form of a thinner, half-membranous lamina also finely ciliated on the inner edge, and whose marginal part, farther back, is thickly barred transversely. The lateral lobes of the lower lip are designated by other na- turalists as the first pair of maxilla, but this is clearly incorrect, as these lobes are quite immo- vable, and are connected in the middle by a distinct membrane. The presence, in this group, of a well- developed inferior lip, as in the higher Crustacea is, at all events, remarkable; for in other Phyllo- poda, as also in the majority of Entomostraca, there is scarcely an indication of this part. Each of the first pair of maxille (figs. 10 m’, fig. 12) has the form of a securiformly expanded chitinous lamella, which is connected by its pointed base with the chitine skeleton of the inferior lip, and is there- fore, when dissected, generally detached in conjunc- tion with that part. On account of the elasticity of the chitine however, they can, to a certain extent, be moved towards one another, and several distinct muscles, running obliquely inwards, effect this simple movement. On the securiformly expanded inner end, the maxille are armed with numerous short spines, and a number of stiff bristles. The foremost corner is in the form of a peculiar, somewhat obliquely- placed lobe, furnished with a few stronger spines. The second pair of maxille (fig. 1 m*, fig. 13) which have been incorrectly interpreted by other naturalists (Packard) as a sort of maxilliped, are of a more membranous nature, and terminate inside with a rounded linguiform masticatory lobe, clothed with numerous coarsely ciliated bristles. On the outer side, there is a bluntly conical expansion of a spongy nature, somewhat similar to that of the epipodites of the legs. This expansion should probably be regarded as a sort of rudimentary palp. The legs, as stated above, are remarkably numerous, there being on the posterior part of the trunk (the metasome), many more pairs of legs Segmenter. Paa Midtkroppen berer derimod hvert Segment kun et enkelt Par Fodder, og de er her ogsaa langt kraftigere udviklede (see Tab. XI, Fig 2), visende idethele, naar undtages iste Par, Charac- teren af wegte Griberedskaber, vel skikkede til at gribe og fastholde den Nering, hvoraf Dyret lever. Forovrigt er disse forreste Par, ligesaavel som de bagerste, forsynede med de 2 characteristiske ydre Vedheng, Exopodit og Epipodit, der begge synes at staa i Respirationens Tjeneste. Foddernes Antal er ialt ikke mindre end 63 Par. Iste Fodpar (Tab. XII, Fig. 1, p*, Fig. 14) skil- ler sig kjendeligt i sit Udseende fra de folgende Par, og er ogsaa ialmindelighed mere udadrettede, saa-at de delvis overrager Rygskjoldets Sidekanter. De bestaar imidlertid af de samme Hoveddele som de ovrige Fodder. Selve Stammen viser en mere eller mindre tydelig Segmentering. Navnlig er der paa Midten af samme en meget distinct Ledfoining, der deler Stammen i en indre og en ydre Del, dannende med hinanden en noget kneformig Boining. Den indre Del af Stammen har, som paa de ovrige Fod- der, ved Basis en vel udviklet og meget skarpt sondret. Coxallap, der er rettet lige indad og besat paa sin stumpt afrundede Ende med talrige korte Pigge og fine, indadkrummede Borster. Af de saa- kaldte Enditer er kun den inderste feestet til denne Del af Stammen, medens de 3 ovrige udgaar fra dens ydre Afsnit. De har alle Formen af forholds- vis smale, nesten traadformige Fortsatser, grovt sagtakkede i Kanterne og delvis visende en utyde- lig Leddeling. Den 4de eller yderste Endit er dob- belt saa lang som den Iste og omtrent af Stammens halve Lengde. Ved Basis af denne Endit er der et ubetydeligt lancetformigt Fremspring, der repreesen- terer Rudimentet af den paa de ovrige Fodpar me- get kraftigt udviklede 5te Endit. De 2 ydre Ved- heng er begge forholdsvis smaa. Epipoditen (ep) har Formen af en afrundet oval Lamelle, der ved en kort Stilk er festet til Stammens Yderside om- trent ved dennes kneformige Boining. Exopoditen (ex), der udspringer i kort Afstand fra Epipoditen lengere udad, er ligeledes pladeformig, men betyde- lig mindre og af uregelmessig trekantet Form, idet den er udtrukket i 2 Flige, hvoraf den yderste. er mest fremspringende og rundt om kantet med fine Borster. 2det Fodpar (Fig. 15) er adskilligt sterkere byg- get end Iste, og skiller sig desuden vesentlig ved Forholdet af Enditerne. Disse er nemlig kortere og .sterkere, nesten kloformige, og mangler ethvert Spor af Leddeling, skjondt de viser i begge Kanter et Antal af smaa, med fine Pigge besatte Afsatser. Den yderste eller 5te Endit, der paa 1ste Par kun 74 than there are segments. On the mesosome, on the= other hand, each segment carries only a single pair of legs, which are also much more powerfully developed. (see Pl. XI, fig. 2), exhibiting, on the whole, with the exception of the first pair, the character of true grasping organs, well fitted for seizing and retaining the food on which the animal lives. The anterior, as’ well as the pos- terior pairs, are furnished with the two charac- teristic external appendages, exopodite and epipo- dite, which both appear to serve as organs of respi- ration. The number of legs in all is no less than 63 pairs. The first pair of legs (Pl. XI, fig. 1, p', fig. 14) is conspicuously distinguished in appearance from the succeeding pairs, and is also generally directed more outwards, so as partially to project over the lateral edges of the carapace. These legs consist, however, of the same principal parts as the other legs. The stem itself shows a more or less distinct segmentation. In the middle of it, notably, there is a very distinct articulation, dividing it into a proximal and a distal part, which form with each other a somewhat geniculated flexure. As in the other legs, there is, at the base of the proximal portion of the stem, a well-developed and very sharply defined coxal lobe, directed straight inwards, and furnished at its bluntly rounded extremity with numerous short spines, and fine, incurved bristles. Of the so-called endites, only the innermost is attached to this part of the stem, while the other 3 issue from its distal section. They all have the form of comparatively narrow, almost filiform pro- cesses, coarsely serrated. at the edges, and partly showing an indistinct segmentation. The fourth, or outermost endite is twice as long as the first, and about half the length of the stem. At its base, there is a lanceolate projection, which represents the rudiment of the powerfully developed 5th endite on the other legs. The two outer appendages are both comparatively small. The epipodite (ep) is in -the shape of a rounded oval lamella, attached by a short peduncle to the outer side of the stem at about the geniculated bend. The exopodite (ex) which issues at a short distance from the epipodite, farther out, is also lamellar, but considerably smaller, and of an irregularly triangular shape, -being drawn out into two lobes, of which the outer is the more prominent, and is edged all round with fine bristles. : The 2nd pair of legs (fig. 15) is far more strongly built than the first, and is, in other respects, prin- cipally distinguished by the relations of the endites to one another. These are shorter and stronger, almost claw-like, and devoid of every trace of seg- mentation, although they exhibit at both edges a number of small serrations clothed with fine spinules. 75 var tilstede som et Rudiment, er her meget sterkt | The outermost, or 5th endite, which in the first udviklet, fuldkommen saa lang som den 4de, og ud- preget kloformig. Den er i Yderkanten besat med fine Borster og har Inderkanten fint og regelmessigt sagtakket. Coxallappen er noiagtig af samme Ud- seende som paa Iste Par. Derimod er de 2 ydre Vedheng, og navnlig Exopoditen (ex) forholdsvis storre. De folgende 7 Par gaar successivt over til at antage det Udseende, som 10de Fodpar viser. Dette sidste (Fig. 16) er idethele kortere og mere sammen- trengt, uden nogen tydelig Segmentering eller kne- formig Boining af Stammen. Coxallappen er for- holdsvis noget mindre end paa de 2 forreste Par og mere lige indadrettet. Enditerne er kortere og bre- dere, nesten pladeformige, og den yderste bredt lancetformig samt tet borstebesat i den ydre Kant. De ydre Vedheeng er begge af anselig Storrelse, og navnlig Exopoditen (ex) betydelig storre end paa de forreste Par; dens Form er ogsaa noget forskjellig, idet den er mere oval, med den nedre Flig bredt afrundet. llte Fodpar (Fig. 17) viser et fra de ovrige Fodder meget afvigende Udseende, idet de 2 ydre Vedheng her er omdannede paa en eiendommelig Maade, saa at de tilsammen danner en eskeformig Kapsel, hvori Aiggene midlertidigt optages, for at forsynes med sin Skal. Laaget af Kapselen, der vender fortil og er af regelmessig circuler Form, dannes af Epipoditen, medens Bunden af Kapselen udgjores af Exopoditen. Ogsaa denne er af tilrun- det Form, men noget bredere end Epipoditen, og udspringer med en bred Basis fra Stammen. Begge slutter temmelig noie sammen, dog saaledes, at der paa den ydre Side er en rendeformig Fordybning, der dannes af de omboiede Kanter af Exopoditen. Selve Stammen er kort og bred, pladeformig, og den yderste Endit ikke tydeligt begrendset, dannende en umiddelbar Fortsettelse af Stammen i Form af en triangular Lap. 12te Fodpar (Fig. 18) viser igjen et mere nor- malt Udseende og stemmer idethele i sin Bygning noie overens med 10de Par, naar undtages, at det er mindre og har den yderste Endit forholdsvis kor- tere og bredere. Det samme er ogsaa Tilfeeldet med Exopoditen, hvis nedre Del-er mindre fremsprin- gende. » _ De folgende Fodpar aftager successivt i Stor- relse og bliver tilsidst ganske rudimentere, skjondt alle de Dele, der findes paa de foregaaende Par, lader sig paavise. Fig. 19 fremstiller en Fod af et af de bagerste Par ved samme Forstorrelse som de foregaaende Par. Det vil sees, at Enditerne er betydeligt redu- pair was only found as a rudiment, is here very strongly developed, is fully as long as the 4th, and of a pronounced claw-like shape. The outer edge is clothed with fine bristles, and the inner edge finely and regularly serrated. The coxal lobe is of exactly the same appearance as in the first pair. The two outer appendages, on the other hand, and especially the exopodite (ex), are comparatively larger. Through the 7 succeeding pairs there is a gradual transition to the ‘appearance of the 10th pair of legs. This pair (fig. 16) is on the whole shorter and more compact, without any distinct seg- mentation or geniculation of the stem. The coxal lobe is relatively rather smaller than that in the foremost 2 pairs, and its direction is more directly inwards. The endites are shorter and broader, al- most lamellar, the outermost being broadly lanceolate in form, and densely setous on the distal edge. The outer appendages are both of considerable size, the exopodite (ex) especially being much larger than in the foremost pairs. Its shape is also somewhat dif- ferent, being more oval, and the lower lobe more broadly rounded. The 11th pair of legs (fig. 17) exhibits a very different appearance from the others, the 2 outer appendages being transformed in a peculiar manner, so as together to form a box-like capsule in which the ova are temporarily received in order to be fur- nished with their shell. The lid of the capsule, which turns to the front, and is of a regularly cir- cular shape, is formed by the epipodite, while the bottom of the capsule consists of the exopodite. This, too, is of a rounded form, but rather broader than the epipodite, and issues with a broad base from the stem. The two parts fit together tolerably exactly, yet in such a manner that on the outer side there is a channel-like hollow formed by the decurved edges of the exopodite. The stem itself is short, broad and lamellar: the outermost endite is not clearly defined, and forms a direct continuation of the stem in the shape of a triangular lobe. The 12th pair of legs (fig. 18) exhibits a more normal appearance, and, on the whole, agrees very nearly in its structure with the 10th pair, excepting that it is smaller, and that the outermost endite is relatively shorter and broader, This is also the case with the exopodite, the lower part of which is less projecting. The succeeding pairs of legs decrease succes- sively in size, and at last become quite rudimen- tary, although it is possible to distinguish all the parts that are found in the preceding’ pairs, Fig. 19 represents a leg of one of the hindmost pairs magnified with the same power as the pre- ceding pairs. It will be seen that the endites are 76 cerede og sterkere sammentrengte, og at ogsaa Epi-’| considerably reduced and more compressed, and that poditen har aftaget steerkt i Storrelse. Derimod er Exopoditen endnu forholdsvis af ikke ubetydelig Storrelse og noget afvigende i Form, med kun et be- greendset Antal af Randborster, hvoraf en udmerker sig ved betydelig Lengde. En Fod af sidste Par er fremstillet Fig. 21 ved samme Forstorrelse som Fig. 19, og Fig. 22 meget sterkere forstorret. Uagtet sin ringe Stor- relse, har Foden, som det vil sees, alle sine Dele i Behold, skjondt i hoieste Grad reducerede. Haletraadene (se Tab. XI, Fig. 1—3, Tab. XIU, Fig. 1, 2), der nermest maa opfattes som et Slags Lemmer, og aabenbart svarer til Halegrenene eller Furea hos Nebalia og hos Branchipodiderne, er af meget betydelig Lengde, adskilligt mere end halvt saa lange som hele Legemet, og synes til en vis Grad at vere bevegelige, da de snart er sterkt divergerende, snart mere lige bagudrettede. De ud- springer til hver Side af Halepladen, fra Enden af sidste Halesegment, og afsmalnes gradvis mod Enden, der gaar ud i en fin Spids. Af Consistens er de seerdeles elastiske, saa at de lader sig boie i alle Retninger, men nogen egentlig Leddeling synes ikke at vere tilstede. Derimod er de forsynede med tal- rige, noget skraatgaaende Tverrader af fine Pigge, som i den indre Kant antager Characteren af fine Borster (se Tab. XII, Fig. 23—24). Hannen (Tab. XI, Fig. 6, 6 a) er betydelig min- dre end Hunnen, idet den. kun opnaar en Leengde af 13 mm, og ligner ganske og aldeles unge Hunner af samme Storrelse, uden at der er nogen ioinefal- dende secundeere Kjonscharacterer at opdage. Det er derfor ikke saa let at kjende begge Kjon ud fra hinanden, og dette er vel for en Del Grunden ‘til, at Hanner inden denne Gruppe saa yderlig sjelden er blevne observerede. Ved en noget noiere Under- segelse, er det dog meget let at bestemme Kjonnet efter 11te Fodpars Bygning. Hos Hannen er nemlig dette Fodpar (Tab. XIII, Fig. 20) ganske bygget paa samme Maade som de umiddelbart foregaaende og efterfolgende Par, medens hos Hunner af samme Storrelse den characteristiske Mgkapsel allerede er tydeligt udviklet. Farven er hos levende Exemplarer af begge Kjon paa Oversiden mere eller mindre mork oliven- brun, med et temmelig svagt gronligt Skjer, og ofte fint spettet med gult og lysebrunt. Undersiden af Rygskjoldet og Foddernes ydre Vedheng viser seed- vanligvis et redbrunt Skjer, og Munddelene har en mere eller mindre hornbrun Farve. Efterat Dyret nogen Tid har ligget paa Spiritus, gaar Farven imidlertid over til et temmelig ensformigt morke- gront. the epipodite has also greatly diminished in size. The exopodite, on the other hand, is still relatively of a considerable size, and differs somewhat in shape, having only a limited number of marginal bristles, one of which is remarkable for its great length. One of the last pair of legs is represented in fig. 21 magnified with the same power as fig. 19, and in fig. 22, much more highly magnified. In spite of its insignificant size, the leg, as will be seen, has all its parts, though very greatly reduced. The caudal filaments (see Pl. XI, figs. 1—3; Pl. XII, figs. 1, 2) which must perhaps be . considered’ as a kind of limb, and evidently answer to the caudal rami or furca in Nebalia and in the Branchi- podide, are of very considerable length, much longer than half the length of the body, and seem to be movable to a certain extent, as at times they are widely divergent, at others directed more straight out behind. They issue, one on each side of the caudal lamella, from the end of the last caudal seg- ment, and taper gradually towards the finely-pointed extremity. Their consistence is exceedingly elastic, allowing of their being bent in all directions, but there seems to be no actual articulation. They are furnished with numerous rather oblique, transverse rows of fine spines, which, on the inner edge, as- sume the character of fine bristles (see Pl. XII, figs. 23, 24). The Male (Pl. XI, figs. 6, 6a) is considerably smaller than the female, and attains a length of only 13 mm. It exactly resembles young females of the same length, without there being any conspi- cuous secondary sexual characters. It is therefore not easy to distinguish one sex from the other, and this is probably partly the reason why the males in this group have so very seldom been observed. On a closer examination, it is, however, very easy to determine the sex by the structure of the 11th pair of legs. In the males, the structure of this pair of legs (Pl. XIII, fig. 20) is the same as that — of the pairs immediately preceding and following it; while in females of that size, the characteristic egg- capsule is already distinctly developed. The colour in living specimens of both sexes is of a more or less dark olive brown on the upper surface, with a slightly greenish tinge, and: is often finely speckled with yellow and light brown. The under surface of the carapace, and the outer appen- dages of the legs generally exhibit a reddish brown tinge, and the oral parts have a horny brown hue. After the animal has lain for some time in spirit, however, the colour changes to a tolerably uniform dark green. eM ee a ee — ee _* > a Indre Organer. Fordgielsessystemet. — Tarmen danner (se Tab. XIU, Fig. 1, 2) et simpelt og temmelig vidt, bagtil noget afsmalnende Ror, der strekker sig igjennem Axen af Legemet, og udmunder, efterat have dan- net en kort Endetarm, ved Enden af sidste Hale- segment, under Basis af Halepladen. Paa Under- siden af dens forreste stumpt afrundede Del munder Spiseroret, der er steerkt musculost og stiger lodret i Veiret fra Mundaabningen. Dets ovre'Ende sprin- ger frit frem i Tarmens Lumen, og viser her en eiendommelig klapformig Indretning (se Tab. XII, Fig. 10, 11, «), hvorved Tarmens Contenta hindres fra at passere tilbage ind i Spiseroret. Med den forreste Del af Tarmen forbinder sig et meget com- | pliceret leveragtigt Organ, der fylder en stor Del af * Hovedet (se Tab. XII, Fig. 1, 2,1). Det bestaar af 2 symetriske Halvdele, hver delt i talrige uregel- messigt forgrenede Blindsekke (Fig. 3), der er ud- kledt indvendig med et Lag af glandulose Celler. Alle disse Blindsekke samler sig tilsidst paa hver Side til en felles kort Stamme, der munder i den forreste Del af Tarmen. Det hele Apparat svarer _ utvivlsomt til de 2 forholdsvis simple blindsek- formige Udvidninger af Tarmen hos Branchipodi- derne. _. Karsystemet. — Hjertet (Fig. 1, 2, c) er af me- get langstrakt Form, og streekker sig igjennem hele Midtkroppen, fra Mandibularsegment og ind i 1l1te fodbeerende Segment. Som sedvanligt, ligger det umiddelbart ind under Kroppens dorsale Integument, og afsmalnes gradvis forfra bagtil, hvor det synes at ende blindt. Fortil har det derimod en vid Aab- A ning, hvorigjennem Blodet drives ud i Hovedet og ._ derfra i Rygskjoldet og den ovrige Krop. For hvert . Kropssegment har det et Par venose Spalter, for- synede med 2 klapformige, bevegelige Leber, der afvexlende Iukker og aabner sig, og hvorimellem Blodet optages i Hjertet fra de forskjellige Dele af Legemet. I Rygskjoldet finder en meget livlig Blod- circulation Sted, og Blodet gjennemstrommer her et meget compliceret System af Hulrum, beliggende mellem de 2 Lameller, hvoraf Rygskjoldet er sam- mensat. Nogen virkelige Blodkar existerer imidler- tid ligesaalidt her som hos andre Phyllopoder. oat i). es - Nervesystemet. — Som hos andre Krebsdyr, be- a staar Nervesystemets Centraldele af det ovre Svelg- na ganglion, eller Hjernegangliet, og en Bugganglie- kjede. Hjernegangliet er meget vanskeligt at un- dersoge, da det ligger tet omhyllet af andre Dele. Saavidt jeg har kunnet se ved omhyggelig Dissec- og af betydelig simplere Bygning end hos Branchi- podiderne, uden de hos disse forekommende dorsale tion, er det (Tab. XIII, Fig. 5, g) forholdsvis lidet » Internal Organs. Digestive system. — The intestine (see Pl. XIII, figs. 1, 2) is in the form of a simple, rather wide tube, slightly tapering posteriorly, and extending through the axis of the body; after having formed a short rectum, it opens at the end of the last caudal segment beneath the base of the caudal lamella. On the under side of its anterior, bluntly- rounded part, opens the esophagus, which is excee- dingly muscular, and rises perpendicularly from the oral aperture. Its upper end projects freely into the lumen of the intestine, exhibiting there a pecu- liar valve-like arrangement (see Pl. XII, figs. 10, 11, we), whereby the contents of the intestine are prevented from passing back into the csophagus. With the foremost part of the intestine is connected a very complicated hepaticous organ, which occupies a great part of the head (see Pl. XIII, figs. 1, 2, 1). It consists of 2 symmetrical halves, each divided into numerous irregularly ramified ceea (fig. 3), which are lined interiorly with a stratum of glan- dular cells. All these ceca unite at last, on each side, into a short common stem that opens into the anterior part of the intestine. The whole apparatus undoubtedly answers to the two comparatively simple cecum-like expansions of the intestine in the Branchipodide. Vascular system. — The heart (fig. 1, 2, c) is of a very elongated shape, and extends throughout the mesosome, from the mandibular segment into the 11th pedigerous segment. It lies, as usual, imme- diately below the dorsal integument of the body, and tapers gradually from the front to the back, where it seems to have no outlet. In front, on the contrary, it has a wide opening, through which the blood is driven out into the head, and thence into the carapace and the rest of the body. In each segment of the mesosome there are two venous ostia, each furnished with 2 valve-like movable lips, which alternately open and shut, and through which the blood is received into the heart from the diffe- rent parts of the body. A very active circulation takes place in the carapace, the blood flowing through a very complicated system of cavities lying between the 2 lamelle of which the carapace is composed. Actual blood-vessels, however, no more exist here than in other Phyllopoda. Nervous system. — As in other crustaceans, the central portion of the nervous system consists of an upper cesophageal ganglion, or cerebral ganglion, and a ventral ganglion chain. The cerebral ganglion is very difficult to examine, as it is closely enveloped by other parts. As far as I have been able to see by careful dissection, it is comparatively small (Pl. XIII, fig. 5, g), and of a much simpler structure than in the Branchipodide, without the dorsal lobes Lappe. Fra dets forreste Del udgaar til hver Side og noget opad en kort og tyk Nervestamme, som er Synsnerven. Efterat vere traadt hen mod den nedre Flade af Giet, oploser den sig i talrige diver- gerende Grene (se Fig. 7), hvoraf hver enkelt for- binder sig med et tilsvarende Synselement. Fra Midten af Hjernegangliets forreste Ende passerer en temmelig sterk Nervestamme lige fortil og omgiver med sin gangliost opsvulmede Ende det enkle ie bagtil (se Fig. 5). Hvor Nerverne-for Folerne ud- springer, har det ikke veret mig muligt at se, men der er Rimelighed for, at deres Udspring forholder sig som hos Branchipodiderne. Bagtil udgaar fra Hjernegangliet 2 lange Commissurer, der omgiver Spiseroret og nedentil forbinder sig med det Iste Ganglion i Buggangliekjezden. Denne sidste (se Fig. 9, 10, 11) bestaar af en stor Mengde Ganglier sva- rende til det store Antal Fodder, og er idethele be, tydelig sterkere udviklet end hos Branchipodiderne, ligesom den ogsaa viser et temmelig forskjelligt Ud- seende, noget nermende sig til det hos Phyllocari- derne. Som hos disse, ligger Ganglierne (se Fig. 9) meget tet sammen, om de end er tydeligt skilte baade ved Lengde- og Tvercommissurer. Af de sidste findes, som hos andre Phyllopoder, 2 for hvert Par Ganglier, og mellem dem er der en meget liden, tvert oval Aabning, medens der mellem Leengde- commissurerne er et storre, paa langs ovalt Mellem- rum. Fra hvert Ganglion udgaar til Siden 2 sterke Nervestammer, hvyoraf den forreste strax deler sig i 2 Grene; men angaaende disse Nervestammers videre Forlob har jeg ikke kunnet skaffe mig fuld Klarhed. Bagtil bliver Gangliekjeden (se Fig. 10, 11) gradvis smalere og de enkelte Ganglier tettere sammen- trengte, saaat Commissurerne mellem dem yanske- ligt adskilles. Den ender i en stump Spids paa det Sted, hvor de sidste Par rudimentzre Fodder findes. Fra denne bagerste Del af Buggangliekjeden udgaar Nerverne for Halen; men heller ikke om disses For- lob har jeg kunnet skaffe mig et klart Begreb. Ovarierne (Tab. XIII, Fig. 1, 2, ov) repreesen- teres af 2 temmelig volumingse og sterkt lappede Organer, der strekker sig langs Siderne af Tarmen igjennem Storsteparten af den fodberende Del af Kroppen. De munder hvert med en kort Adgleder ved Basis af 11te Fodpar, og indeholder et indre Hulrum, der staar i direkte Forbindelse med Ag- lederen. Undersoges et Stykke af de udpreparerede Ovarier under Mikroskopet, vil man finde, at ethvert sig udviklende Ag er indesluttet i en Follikel, der rager frem fra Ovariets Overflade i Form af en af- rundet, mere eller mindre fremspringende Blere. Man finder paa samme Stykke Ovarium Aig i alle Udviklingsstadier, fra overordentlig smaa, kun ved 78 found in the latter. From the anterior part there issues on each side, going a little upwards, a short, thick nerve-stem, which is the optic nerve. After advancing towards the lower surface of the eye, it is resolved into numerous divergent branches (see fig. 7), each one of which unites with a correspond- ing visual element. From the anterior end of the cerebral ganglion, a tolerably strong nerve-stem passes forwards and surrounds posteriorly, with its ganglionic swollen end, the ocellus (see fig. 5). It has not been possible for me to see where the nerves for the antenne originate, but it is probable that their origin is the same as in the Branchipo- dide. \From the cerebral ganglion, posteriorly, run two long commissures, which encircle the esophagus, and unite below with the first ganglion in the ven- tral ganglion chain. The latter (see figs. 9, 10, 11) consists of a considerable number of ganglia corres- ponding to the large number of legs, and is in the whole, much more highly developed than in the Branchipodide, exhibiting too, a rather different ap- pearance, somewhat approaching that of the Phyllo- caride. As in that group, the ganglia (see fig. 9) lie very close together, although distinctly separated both by longitudinal and transverse commissures. Of the latter there are, as in the other Phyllopoda, two to each pair of ganglia, and between them a very small, transversely oval opening, while be- tween the longitudinal commissures, there is a larger, longitudinally oval space. From each ganglion there issue laterally 2 strong nerve-stems, the anterior of which immediately divides into 2 rami; but concer- ning the farther course of these nerve-stems, I have been unable to ascertain anything clearly. Poste- riorly, the ganglionic chain (see figs. 10,11) becomes gradually narrower, and the several ganglia more crowded, so that the commissures between them are difficult to distinguish. It ends in a blunt point at the place where the last pair of rudimentary legs are found. From this posterior part of the ventral ganglion chain issue the nerves for the tail, but in their case also, I have been unable to obtain any clear idea as to the course they take. The ovaries (Pl. XIII, figs. 1, 2, ov) are repre- sented by 2 rather voluminous and much lobed or- gans, extending along the sides of the intestine throughout the greater part of the body. They each open by a short oviduct at the base of the 11th pair of legs, and contain an inner cavity, which is in direct communication with the oviduct. On exa- mining a portion of the dissected ovary under the microscope, it will be seen that each of the eggs undergoing development is enclosed in a follicle, which projects from the surface of the ovary in the form of a rounded, more or less projecting vesicle. On the same piece of ovary are found eggs in all stages of development, from exceedingly small rudi- meget sterk Forstorrelse synlige Anleg til temme- lig store, med et opakt Indhold fyldte Kapsler. I enhver Follikel findes altid 4 Celler combinerede. I de mindste Follikler (Fig. 13) er blot Kjernerne synlige, medens i de storre Follikler (Fig. 14, 15), de enkelte Celler skarpt afgrendser sig fra hver- andre. Af de 4 Celler er det alene den yderste, der repreesenterer den egentlige Ag-celle; de 3 ovrige er kun bestemte til dennes Ernering og absorberes derfor tilsidst ganske. Denne polare Celle skiller sig ogsaa kjendeligt fra de 3 ovrige derved, at Kjernen er mindre skarpt contureret. Paa den fuldt udviklede Aigcelle unddrager sig tilsidst Kjernen ganske for Observationen, og heller ikke Kjernerne i de 3 Neringsceller kan sees paa Grund af den opake, gulbrune Neringsblomme, som nu fylder det hele Aig (se Fig. 12). Er Aggene modne, treder de ind i Ovariernes indre Hule og udtommes derfra successivt gjennem Adglederen i 11te. Fodpars AKg- kapsel, hvor de omgives med en temmelig fast Skal (Fig. 16). Denne sidste viser sig ved sterk For- storrelse (Fig. 16') meget fint reticuleret, og dannes rimeligvis ved et af Kapselens Vegge afsondret Secret. I hver Hgkapsel finder man i Regelen kun et meget begrendset Antal Mg, fra 1 enkelt (se Tab. XII, Fig. 17, ov) til 4, og de forbliver her kun en ganske kort Tid, idet de successivt udtommes af Kapselen og falder tilbunds, hvor de indleires i Mudret, for til neste Sommer at udvikle sig til en ny Generation. / Testes har samme Beliggenhed som Ovarierne og ligner ogsaa ved forste Oiekast disse i Udseende. Ved nermere Undersogelse viser imidlertidjFollik- lerne sig forholdsvis mindre og af mere uregelmes- sig, noget affladet Form og ligesom slyngede ind i hinanden (se Tab. XII, Fig. 17). I enhver Follikel er der (se Fig. 18) en indre Hule, der staar i For- bindelse med det centrale Hulrum, og fra Follikler- nes Vegge udvikler Sedelementerne sig i Form af meget smaa simple Celler (Fig. 19). Hvor Testes udmunder, har det ikke lykkets mig at faa con- stateret, Udvikling. _ Jeg har heller ikke af denne Phyllopode kun- net forfolge den hele Udvikling, men har dog leilig- hedsvis faaet fat paa en Del Larvestadier, som jeg ee mane noiere skal omtale. di Det tidligste observerede Stadium er afbildet Tab. XI, Fig. 4, og Detailler af samme, Tab. XII, Fig. 21—27. Legemet har en Lengde (fraregnet Haletra- dene). af kun omtrent 2 mm., 6 er halvt gjennem- sigtigt, af gulrod Farve. 79 ments, only visible under a very high power of the microscope, to rather large capsules with opaque contents. In each follicle, 4 cells are always found combined. In the smaller follicles (fig. 13) only the nuclei are visible, while in the larger ones (figs. 14, 15) the cells are sharply divided from one another. Only the outermost of the 4 cells represents the egg-cell proper; the other 3 only serve to nourish that one, and are therefore at last completely ab- sorbed. This polar cell is also easily distinguishable from the other three by the less distinctly outlined nucleus. In the fully developed egg-cell, the nucleus at last entirely withdraws from sight, nor can the 3 alimentary cells be seen on account of the opaque, yellowish-brown food-yolk which now fills the entire ovum (see fig. 12). When the eggs are mature, they enter the inner cavities of the ovaries, and are thence evacuated successively through the oviduct into the egg-capsule of the 11th pair of legs, where they are enveloped in a rather firm shell (fig. 16). This, when highly magnified (fig. 16), appears to be very finely reticulated, and is probably formed by a secretion from the walls of the capsule. In each capsule there is found, as a rule, only a very limi- ted number of ova, from a single one (see Pl. XII. fig. 17, ov) to 4, and they remain there only a very short time, being discharged successively from the capsule, when they fall to the bottom, and are im- bedded in the mud, to develope in the following summer into a new generation. The testes occupy a similar position to the ovaries, and also, at first sight resemble them in appearance. Upon closer examination, however, the follicles prove to be relatively smaller, and of a more irregular, somewhat flattened shape, and are, as it were, twisted about one another (see Pl. XIII, fig. 17). In every follicle (see fig. 18) there is an inner cavity, in communication with the central ca- vity, and the sperm elements develope from the walls of the follicles in the form of very small simple cells (fig. 19). I have not succeeded im ascer- taining where the testes discharge themselves. Development. Of this Phyllopod too, I have been unable to follow the whole course of development, but have however occasionally succeeded in finding certain larval stages, which I will here describe more minutely. The earliest stage observed is figured on Pl. XI, fig. 4, and details of the same on Pl. XIII, figs. 21—27. The body has a length (not including the caudal filaments) of only about 2 mm. and is semi-trans- parent and of a yellowish-red colour. Rygskjoldet er vel udviklet, men forholdsvis mindre hvelvet end hos det voxne Dyr,,og har det bagre Indsnit bredere, nesten retvinklet. Den bag Rygskjoldet fremragende Del af Legemet er forholds- vis tykkere og mere sammentrengt end hos voxne Individer og rundtom saa tet besat med fine Pigge, at den faar et laaddent Udseende. Segmenteringen er endnu lidet tydelig og egentlig kun antydet ved de tet paa hinanden folgende Tverrader af Pigge (se Tab. XIII, Fig. 27). Sidste Segment er dog meget tydeligt begrendset og ved en kjendelig Ind- knibning sondret fra de foranliggende. Det er ogsaa af langt betydeligere Storrelse, og er aabenbart sondret lenge for disse. Af Form er det trapezoi- diskt, gradvis udvidet bagtil, og viser de 2 sidestil- lede dorsale Knuder meget tydeligt. De ydre Hjor- ner af Segmentet er bevebnede med en Tverrad af sterke Pigge. Halepladen er ufuldsteendigt udvik- let og kun repreesenteret ved en ubetydelig, i 2 sy- metriske Spidser udgaaende Udvidning af det dor- sale Integument. Haletraadene er endnu ganske korte, neppe mere end '/s saa lange som Legemet, og viser en noget tendannet Form. De er rundt om besatte med fine, tiltrykte Pigge, som dog ikke ordner sig i tydelige Tverrader, og har i Spidsen en seerdeles lang og 2 korte Pigge. De sammensatte Mine (se Fig. 21, 0) er for- holdsvis smaa og har endnu ikke Synselementerne tydeligt udviklede. Umiddelbart foran dem sees meget tydeligt det enkle Wie (oc), der nesten er af samme Storrelse som de sammensatte. Forste Par Folere (Fig. 21, a‘) ligner i Ud- seende dem hos det voxne Dyr, men er forholdsvis storre, saa at de rager kjendeligt ud over Pande- randen. De synes endnu ikke at have Lugtepapiller udviklede, hvorimod en af de apicale Foleborster er af betydelig Lengde. Andet Par Folere (Fig. 21, a*), hvoraf der hos det voxne Dyr kun er ubetydelige Rudimenter til- bage, er her megtigt udviklede, dannende et Par kraftige Aarer, ved Hjelp af hvilke Larven beve- ger sig raskt om i Vandet paa en eiendommelig stodvis Maade. De er hver sammensat af et stzerkt, cylindriskt, ved Basis i flere Led delt Skaft, der paa sin Ende berer 2 meget ulige udviklede Grene. Den ydre Gren er adskilligt lengere end Skaftet, smalt cylindriskt, og delt i 5 tydelige Led, hvoraf det iste er vel saa langt som de 4 ovrige tilsammen. Hvert Led berer ved Enden en lang, tet cilieret Svommeborste. Den indre Gren er meget. liden, neppe mere end '/s saa lang som Skaftet, 2-leddet, og forsynet i Spidsen med 3 ulige lange cilierede Borster. 80 The carapace is well developed, but compara- tively less vaulted than in the full-grown animal, and the posterior emargination is broader and almost rectangular. That part of the body projecting beyond. the’ carapace is comparatively shorter and thicker than in full-grown specimens, and so thickly covered all round with fine spines, as to present a hairy appearance. The’ segmentation is still very indistinct and really only indicated by the closely succeeding transverse rows of spines (see Pl. XIII, fig. 27). The last segment, however, is very distinctly defined, and is separated from those in front of it by a perceptible contraction; it is also far larger in size, and has evidently been formed long before they have. Its shape is trapezoidal, gradually widening posteriorly, and it exhibits very distinctly the 2 laterally-situated dorsal protube- rances. The external angles of the segment are armed with a transverse row of strong spines. The caudal lamella is imperfectly developed, and is only represented by a very slight expansion of the dorsal integument, projecting in two symmetrical points. The caudal filaments are still quite short, scarcely more than */s of the length of the body, and exhibit a somewhat fusiform shape. They are set all round with fine, adpressed spines, which, however, are not ‘arranged in distinct transverse rows; and at the extremity there is one particularly long spine and 2 short ones. The compound eyes (see fig. 21, 0) are compara- tively small, and the visual elements not yet dis- tinctly developed. Immediately in front of them, the ocellus (oc) is seen very clearly, almost of the same size as the compound eyes. The first pair of antenne (Fig. 21, a*) in appear- ance resemble those of the full-grown animal, but are comparatively larger, so that they project per- ceptibly over the frontal margin. They do not as yet seem to have developed olfactory papille, but on the other hand one of the apical sensory bristles is of considerable length. The second pair of antenne (fig. 21, a*) of which there are left only slight rudiments in the fullgrown animal, are here powerfully developed, constituting a pair of strong oars, by the aid of which, the larva moves rapidly through the water in a peculiar, jerky manner. Each antenna is com- posed of a strong cylindrical scape, divided at the base into several joints, and carrying at its extre- mity 2 very unequally developed rami. The outer ramus is considerably longer than the scape, narrow cylindrical and divided into 5 distinct joints, the first of which is rather longer than the other 4 together. Each joint bears at its extremity a long, densely-ciliated natatory bristle. The inner ramus is very small, scarcely more than '/s of the length of the scape, is bi-articulated, and furnished at the 81 Af Munddelene er (se Fig. 21) Overleben (L) og Kindbakkerne (M) let at observere, og synes i alt veesentligt at ligne samme hos det voxne Dyr. Af nogen Mandibularpalpe er der intetsomhelst Spor at se, skjondt den ganske sikkert har existeret paa et tidligere Stadium. Underleeben og Kjeverne har jeg ikke kunnet noiere undersoge. Af Fodderne er de til Midtkroppen horende Par allerede taalelig vel udviklede, med alle sine Hoved- dele tydelige, hvorimod de bagre Par bliver i hoi Grad rudimentere, forestillende tilsidst meget smaa, utydeligt indskaarne Skiver uden enhver Borste- beseetning (Fig. 26). Forste Fodpar (Fig. 22) viser i Henseende til Enditerne endnu ingensomhelst Forskjel fra de neer- mest folgende Par (Fig. 23), og den yderste eller 5te Endit, der hos det voxne Dyr er ganske rudi- menter, er her ligesaa vel udviklet som paa de fol- gende Fodder. Derimod er Exopoditen kjendelig mindre og kun forsynet med 8 Randborster, medens den paa 2det Par (Fig. 23) har ikke mindre end 14 saadanne. llte Fodpar (Fig. 24) er endnu kun lidet udviklet og viser intet Tegn til nogen Aigkapsel. Exopoditen er paatvers oval og forsynet med en Rad af 9 forholdsvis korte Randborster. Epipoditen er meget liden, knudeformig, og Enditerne afstum- pede i Enden. Paa de folgende Par (Fig. 25) bliver, som ovenfor neynt, alle disse Dele endmere rudi- mentere, og tilsidst (Fig. 26) er der neppe mere end ubetydelige Spor af dem tilbage. "Af indre Organer skinner Tarmen meget tyde- ligt igjennem Integumenterne (se Tab. XI, Fig. 4) og er ialmindelighed fyldt med orangefarvede Con- tenta. Fortil udsender den 2 korte Blindsekke (Tab. XII, Fig. 21, 1), der hver klover sig i 2 Grene, hvoraf igjen enhver er svagt tvelappet i Enden. Dette er Begyndelsen til den hos det voxne Dyr saa voluminose og complicerede Lever. Et noget senere Stadium er fremstillet Tab. XI, Fig. 5. Legemet har nu en Lengde af omtrent 4 mm. og er endnu halvt gjennemsigtigt, med et svagt gronagtigt Skjer og gulred gjennemskinnende Tarm. Rygskjoldet er nu forholdsvis noget storre, men endnu temmelig fladt, og Kroppen har strakt sig noget mere i Lengde. Forovrigt stemmer dette Stadium meget ner med det foregaaende, og 2det Par Folere fungerer fremdeles som Svommeredska- ber, skjondt de er noget reducerede i Storrelse, me- dens Fodderne synes mere udviklede. 11 — G. O. Sars: Fauna Norvegizx. extremity with 3 ciliated bristles of unequal length. Of the oral parts (see fig. 21), the labrum (L) and the mandibles (M) are easy to observe, and seem in every essential particular to resemble those parts in the full-grown animal. There is no trace what- ever of a mandibular palp, though it must certainly have existed at an earlier stage. The posterior lip and the maxille 1 have not been able to examine closely. The pairs of legs belonging to the mesosome are already tolerably well developed, all their prin- cipal parts being distinct, whereas the posterior pairs become extremely rudimentary, appearing at last like very small, indistinctly indented lamelle, entirely without bristles (fig. 26). As regards the endites, the first pair of legs (fig. 22) presents as yet no difference whatever from the pairs immediately following (fig. 23), and the outermost or dth endite, which in the full-grown animal is quite rudimentary, is here just as well developed as in the succeeding legs. On the other hand the exopodite is perceptibly smaller, and fur- nished with only 8 marginal bristles, while that of the 2nd pair (fig. 23) has no less than 14 such bristles. The 11th pair of legs (fig. 24) is as yet only slightly developed, and shows no sign of any egg-capsule. The exopodite is transversely oval, and furnished with a row of 9 comparatively short mar- ginal bristles. The epipodite is nodiform and very small, and the endites are truncated at the extre- mity. In the succeeding pairs (fig. 25), all these parts become, as stated above, more and more rudi- mentary, until at last (fig. 26) there is hardly more than a slight vestige of them left. Of the internal organs, the intestine shows very distinctly through the integuments (se Pl. XII, fig. 4), its contents generally being of an orange colour. It sends out in front 2 short ceca (Pl. XIII, fig. 21, 1), which each divide into 2 branches, each of which is in its turn slightly bi-lobed at the extre- mity. This is the commencement of the very volu- minous and complicated liver found in the full-grown animal. Pl. XI, fig. 5 represents a rather later stage. The body has now a length of about 4 mm. and is still semi-transparent, with a faint greenish tinge, and the yellowish-red intestine showing through. The carapace is now comparatively rather larger, though still somewhat flat, and the trunk has somewhat increased in length.- In other respects this stage agrees very closely with the preceding one, and the 2nd pair of antenne still officiate as swimming implements, though they are somewhat reduced in size, while the legs appear to be more developed. __ 82 I senere Stadier reduceres 2det Par Folere mere og mere og taber tilsidst sine Svommeborster fuld- steendigt, hvorved deres Betydning som Bevege- organer er ophort. Bevegelsen overtages nu ude- lukkende af de mere fuldkomment udviklede Fodder. Halepladen begynder saa smaat at forleenge sig og faar flere Randtorne, men er endnu hos temmelig store Unger meget liden (se Tab. XIII, Fig. 28). Levevis. — Nerverende Phyllopode synes ikke, som Tilfeeldet er med de fleste ovrige Former, at vere udelukkende indskrenket til mindre Vand- ansamlinger, som ud paa Sommeren torrer ganske eller delvis ud. Jeg har tvertimod hidtil kun fun- - det den i temmelig store og dybe Vande, og har seet den paa Dybder af mindst 3—4 Favne. Som Regel holder den sig lige ved Bunden og svommer langs denne, altid med Ryggen opad. Men ikke saa sjelden tager den sig ogsaa Udflugter hoiere op i Vandet og vender herunder snart Ryg, snart Bug opad, eller dreier sig rundt paa forskjellig Vis. Svomningen tilveiebringes hos det voxne Dyr ude- lukkende ved Hjelp af Fodderne og foregaar med en ganske jevn og ikke meget hurtig Fart. De grovt tandede Kindbakker og de sterke klo- formige Enditer paa de forreste Par Fodder tyder paa, at Dyret hovedsageligt lever af Rov, rimeligvis for en stor Del af andre Entomostraceer. Jeg har ogsaa ikke sjeldent mellem Fodderne paa dem fun- det Daphnier og forskjellige Copepoder (Cyclops, Heterocope). Efter Sigende skal den i visse Tilfelde ogsaa fortere Fiskerogn og derved blive skadelig for Fiskebestanden i de Vande, hvori den fore- kommer. De allerfleste Individer, man treffer, er af Hun- kjon, og det er forst efter et meget noie Eftersyn af talrige Exemplarer, at det er lykkets mig at finde frem nogle faa Hanner. Efter al Sandsynlig- hed er Hannernes Forekomst kun indskrenket. til en ganske kort Periode, rimeligvis til Slutten af Sommeren. Forekomst. — Selv har jeg her i Landet kun truffet den paa Filefjelds Hoideplateau, omkring Ny- stuen, dels i selve Nystuvandet eller i Udvidningen af den fra samme mod Vest udgaaende Ely, dels i et Fjeldvand, Vesleskartjernet kaldet, paa selve Nystufjeldets Ryg og i en Hoide af circa 4000 Fod over Havet. I det sidstnevnte Vand, der er tem- melig dybt, fandtes den i Slutningen af August 1887 i stor Mengde, og kunde fra Stranden af gjennem det krystalklare Vand sees overalt paa Bunden, Kun undtagelsesvis fandtes den saa ner Stranden og paa saa grundt Vand, at den kunde tages med en almindelig Haand-Haav, og min Fangst af den indskrenkede sig derfor ogsaa, forste Gang, jeg be- sogte dette Vand, kun til nogle faa Exemplarer. In later stages the 2nd pair of antennee become more and more reduced in size, and at last entirely lose their natatory bristles, whereby their impor- , tance as organs of motion ceases. The production of motion is now undertaken exclusively by the more fully developed legs. The caudal lamina com- mences slightly. to lengthen, and acquires several marginal spines, but is still, even’ in rather large young ones, very small (see Pl. XIII, fig. 28). Habits. — The present Phyllopod does not seem, as is the case with most of the other forms, to be exclusively confined to small pieces of water, which either quite or partially dry up towards the end of the summer. On the contrary, I have hitherto only found it in rather large and deep lakes, and have seen it at depths of at least 3 or 4 fathoms. As a rule, it keeps to the bottom, where it swims along, always with its back uppermost; but it not infrequently makes excursions higher up in the water, and during these, turns sometimes its back, sometimes its ventral surface uppermost, or twists about in various ways. The action of swimming in the full-grown animal is performed exclusively by the aid of the legs, and at a perfectly even, and not very rapid rate. The coarsely dentated mandibles, and the strong, claw-like endites of the foremost pairs of legs indi- cate that this animal lives principally by preying on others, probably to a large extent on other En- tomostraca, I have also not infrequently found between its legs Daphnie and various Copepods (Cyclops, Heterocope). According to report, it has also, in certain cases, been known to consume fish- spawn, and is thus detrimental to the stock of fish in the lakes where it occurs. - The greater number of specimens met with are of the female sex, and it is only after a very care- ful examination of numerous specimens that I have succeeded in finding a few males. In all probability, the occurrence of the males is limited to quite a short period, probably until the end of the summer. Occurrence. — In this country (Norway) I have personally only met with this form on the high plateau of the Filefjeld, about Nystuen, partly in Nystue Lake itself and the expansions of the river flowing out of it towards the west, and partly in a mountain tarn called Vesleskartjern, on the ridge of Nystue Mountain, and at a height of about 4000 feet above the sea, In the last-named lake which is rather deep, this species was found at the end of August, 1887, in great numbers, and could be seen from the shore, through the clear water, all over the bottom. Only in exceptional cases was it found so near the shore and in such shallow water, that it could be taken with an ordinary hand-net, so that my take of it, the first time I visited this lake, Forst efterat jeg havde forsynet mig med en meget lang, 4—5 Alens Stang, til hvis Ende Haaven fast- bandtes, kunde jeg fange den i storre Antal; men mange Exemplarer gik endnu saa dybt, at det var umuligt at naa i dem. Foruden paa Filefjeld er den af nu afdode Gartner Moe taget i Lom, og af Landskabsmaler Skari ved Kongsvold paa Dovrefjeld. I Finmarken er den derimod, saavidt mig bekjendt, aldrig bleven paatruffet, ligesaalidt som i Lavlandet Syd paa. Denne Phyllopode er saaledes hos os utvivlsomt en egte «relict» Form, der kun i vore Hoifjelde endnu har fundet de nodvendige Betingelser for sin Exi- stence. ! Udbredning. — Arten blev forst fundet i Gron- land, hvor den synes at vere meget almindelig. Senere er den ogsaa observeret i det arktiske Ame- rika, paa Spitsbergen, paa Novaja Semlja og i Sibirien. Den er saaledes en wgte arktisk Form, og i sin Udbredning circumpolar. RB was limited to a very few specimens. It was only when I[ had provided myself with a very long rod — 8 or 10 feet long — to the end of which the net was attached, that I was able to capture them in larger numbers; and many of them were still in such deep water, that it was impossible to get at them. Besides being found on the Filefjeld, it was found by the late florist, Moe, in the Lom, and by landscape-painter Skari at Kongsvold on the Dovre Mountains. On the other hand, it has never, to my knowledge, been met with in Finmark, nor yet in the south lowlands. This Phyllopod is thus in this country (Norway) a true «relict» form, which has found only on our mountains the conditions necessary for its existence. Distribution. — The species was first found in Greenland, where it seems to be very common. It has since been observed in arctic America, on Spitz- bergen, Novaia Zemlia, and in Siberia. It is thus a true arctic form, and circumpolar in its distribution. Sectio III. Conchostraea. Syn: Phyllopoda conchiformia, Characteristik. — Legemet omgivet af en stor, tveklappet Skal af chitinos Structur og festet til samme ved et smalt dorsalt Ligament. Valvlerne bevegelige ved Hjelp af en sterk Lukkemuskel og forbundne dorsalt med hinanden uden nogen egentlig Laas. Hovedet bevegeligt og vel sondret fra Krop- pen, gaaende ud i et mere eller mindre fremragende sammentrykt Rostrum. Kroppen ensformigt seg- menteret og endende med en kort, mere eller min- dre omboiet Haledel, sedvanligvis forsynet i Enden med 2 sterke bevegelige Klor og berende dorsalt 2 jevnsides stillede Borster. De sammensatte Mine ner sammen, undertiden sammensmeltede, og belig- gende i det indre af Hovedet. Det enkle ie vel udviklet. Begge Par Folere tilstede, Iste Par for- holdsvis smaa, enkle; 2det Par omdannede til kraf- tige, tvegrenede Svommeorganer. Munddelene ner- mest lignende dem hos Gruppen Anostraca. Fod- derne af uniform Bygning, pladeformige, fligede, med tydeligt udviklet Coxallap og med Exopoditen delt ien dorsal og en ventral Lap; det iste eller de Seetion IL. Conchostraca. Syn: Phyllopoda conchiformia. Characters. — Body surrounded by a large bi- valved shell of chitinous structure, to which it is attached by a narrow dorsal ligament. Valves movable by the aid of a strong adductor muscle, and connected dorsally with one another without having a true hinge. Head movable and well- defined from the trunk, terminating in a more or less prominent, compressed rostrum. Trunk uni- formly segmented, ending in a short, more or less deflexed caudal part, generally provided at the extre- mity with two strong, movable claws, and bearing dorsally 2 juxtaposed bristles. Compound eyes close together, sometimes merged into one another, and situated in the interior of the head. Ocellus well developed. Both pairs of antenne present, Ist pair comparatively small, simple; 2nd pair transformed into powerful, bi-ramous natatory organs. Oral parts most nearly resembling those in the Anostraca group. Legs of uniform structure, lamellar, lobate, with distinctly developed coxal lobe, and with the exopodite divided into a dorsal and a ventral lobe; 84 2 forreste Par hos Hannen omdannede til Gribe- redskaber. /Eggene meget smaa, beres sammen- hobede ind under den dorsale Del af Skallen. Ud- viklingen, naar undtages Slegten Cyclestheria, en compliceret Metamorphose, begyndende med et Nau- plius-Stadium. Bemerkninger. — Denne Gruppe af Phyllopoder adskiller sig fra de 2 foregaaende ved en Rekke af vel udpregede Characterer og danner paa en Maade Overgangen til Cladocererne. Som den mest ioine- faldende Character maa fremheves den store tve- klappede Skal, hvori Legemet fuldstendigt kan ind- drages, og som ofte viser en skuffende Lighed med Skallen hos visse bivalve Mollusker. Ogsaa 2det Par Foleres Bygning hos det voxne Dyr er vesent- lig forskjellig, idet de her, som hos Larverne af hine, danner et Par kraftige, tvegrenede Aarer, hvormed Dyret ror sig frem igjennem Vandet, Gruppen indeholder for Tiden 2 distincte Familier, nemlig Limnadiide og Limnetide, som begge er re- presenterede i Norges Fauna. | the 1st pair or the first 2 pairs in the male trans- formed into prehensile implements. Ova very small, carried crowded together beneath the dorsal part of the shell. Development, except in the case of the genus Cyclestheria, a complicated metamorphosis, commencing with a nauplius stadium. Remarks. — This group of Phyllopoda is dis- tinguished from the 2 preceding groups by a number of well-marked characters, and in a manner forms the transition to the Cladocera. As its most con- spicuous character must be noted the large bi-valved shell, into which the body can be completely with- drawn, and which often shows a striking resem- blance to the shell in certain bi-valve Mollusca. The structure of the second pair of antenne in the full-grown animal is also essentially different, forming here, as in the larvee of other Phyllopods, a pair of powerful, bi-ramous oars, with which the animal propels itself through the water. This group contains at present 2 distinct families, viz., Limna- diide and Limnetide, both of which are represented in the fauna of Norway. f Limnadiide. Fam. lI. Characteristik. — Skallen ialmindelighed sam- mentrykt og forsynet hos voxne Individer med et vexlende Antal af Veextstriber. Hovedet af middels Storrelse og kun lidet forskjelligt hos de 2 Kjon. Kroppen forlenget og meget bevegelig, Haledelen vel udviklet, ombgiet, dannende bagtil 2 jevnsides stillede tandede Plader, og endende med 2 bevege- lige Klor. Forste Par Folere mere eller mindre forlengede, og sedvanligvis lappede i den ene Kant; 2det Par med Grenene slanke og betydelig lengere end Skaftet. Kindbakkernes Tyggeflade uden tyde- lige Twender. Fodderne talrige, fra 16 til 28 Par, med forholdsvis korte Enditer; den dorsale Lap af Exopoditen forlenget hos Hunnen paa 2 eller 3 af de midterste Par til traadformige Vedheng, stot- tende Aigmassen. Bemerkninger. — Denne Familie er hovedsage- ligt characteriseret ved Skallens Form og Structur, det betydelige Antal Fodder og Haledelens tydelige Udvikling. Den indeholder for Tiden 4 Slegter, nemlig Limnadia Brogniart, ulimadia Packard, Estheria Riippel og Cyclestheria G.O. Sars. Hos os er blot den forste af disse Slegter representeret. Limnadiide. Fam. 1. Characters. — Shell generally compressed and furnished in the full-grown animal with a varying number of lines of growth. Head of medium size, and only slightly different in the 2 sexes. Trunk elongated and very moyable; caudal part well de- veloped, curved downwards, forming posteriorly 2 juxtaposed dentated lamelle, and terminating in 2 movable claws. First pair of antenne more or less elongated, and generally lobed in one margin; second pair with slender rami, considerably longer than the scape. Masticatory part of the mandibles without distinct teeth. Legs numerous — from 16 to 28 pairs — with comparatively short endites; dorsal lobe of exopodite in the female elongated, in 2 or 3 of the middle pairs, into filiform appendages, supporting the egg-mass. Remarks. — This family is principally charac- terised by the form ‘and structure of the shell, the large number of legs, and the conspicuous develop- ment of the caudal part. It contains at present 4 genera, viz. Limnadia, Brogniart, Eulimadia, Packard, Estheria, Riippel, and Cyclestheria, G.O. Sars. Only the first of these is represented in Norway. Gen. Limnadia, Brogniart, 1820. Slegtscharacteristik. —Skallen steerkt sammen- trykt, meget tynd, glat, uden tydelige Umboner, men hos det voxne Dyr med talrige Veextstriber. Hove- det forholdsvis lidet og forsynet med et stilket dor- salt Fastheftningsorgan, Pandedelen konisk frem- springende og sondret fra Rostrum ved en vinkel- formig Indbugtning. Foddernes Antal omkring 24 Par, den dorsale Lap af Exopoditen kun lidet frem- ragende; Epipoditen forholdsvis liden. Halepladerne udtrukne nedentil i et tilspidset, ikke kloformigt Hjorne og fint tandede bagtil. De sammensatte Mine tydeligt adskilte, skjondt tet sammenstillede; det enkle Mie triangulert. Forste Par Folere for- holdsvis korte, men tydeligt lappede i sin ydre Del; 2det Par med den indre Gren lengere end den ydre, begge delte i talrige skiveformige Led, besatte i den indre Kant med lange Syommeborster, i den ydre med korte Pigge. Aiggene meget smaa, om- givne af en turbinformet Skal. Forplantningen ude- lukkende parthenogenetisk. Udviklingen en complet Metamorphose. Bemerkninger. — Slegten Limnadia blev forst opstillet af Brogniart allerede i 1820, medens Sleg- ten Hstheria daterer sig fra en langt senere Tid, hvorfor ogsaa Familien bor beneevnes efter den for- ste og ikke, som det ofte er skeet, efter den sidste Slegt. Fra Slegten Hstheria er nerverende Slegt let kjendelig ved den sterkere sammentrykte og tyndere Skal, paa hvilken ingen tydelige Umboner findes, ved Hovedets meget forskjellige Form, tildels ogsaa ved iste Par Foleres, Foddernes og Hale- pladernes Structur. Meget nermere staar den Sleg- ten Hulimadia Packard, og den eneste mere vesent- lige Forskjel synes at vere, at Arterne af denne sidste Slegt er, ligesom de af Sl. Estheria, bisexuelle, medens Hanner af Sl. Limnadia endnu ikke, trods de omhyggeligste Efterforskninger, er forefundne og rimeligvis heller ikke existerer. Man kjender hidtil med Sikkerhed kun 2 Arter af denne Slegt, en euro- peisk og en amerikansk, LZ. americana Morse. De svrige til denne Slegt henregnede Arter synes alle at henhore til den neerstaaende Slegt, Hulimadia. Limnadia lentiecularis (Lin) (Pl. XIV—XVII). Monoculus lenticularis, Linné, Fauna Svecica, Edit. 2da, p. 499. Daphnia gigas, Herman, Mém. apterol. p. 134, Pl. V, fig. 4, 5, Pigs fig. 2. Limnadia Hermanni, Brogniart, Mém. du Mus. d’hist. nat., Tome VI, p- 84, PI. 18: Limnadia gigas, Grube, Archiv f. Naturgeschichte, 19 Jahrg., Bd. 1, p. 164. Artscharacteristik. — Skallen, seet fra Siden, bredt oval, med den storste Hoide foran Midten, 85 Gen. Limnadia, Brogniart, 1820. Generic Characters. — Shell greatly compressed, very thin, smooth, without distinct umbones, but with numerous lines of growth in the full-grown animal. Head comparatively small and furnished with a stalked dorsal affixing organ; frontal part conically projecting, and defined from the rostrum by an angular sinus. Number of feet, about 24 pairs; dorsal lobe of the exopodite only slightly projecting; epipodite comparatively small. Candal lamellae drawn out below to a sharp, not clawlike angle, and finely dentated posteriorly. Compound eyes quite distinct from one another, though placed close together: ocellus triangular. First pair of antenne comparatively short, but distinctly lobed in their distal portion; 2nd pair with the inner ramus longer than the outer, and both divided into numerous laminar joints, clothed on the inner edge with long natatory bristles, on the outer with short spines. Ova very small, surrounded by a turbinate shell. Propagation exclusively partheno- genetic. Development a complete metamorphosis. Remarks. — The genus Limnadia was first established by Brogniart as early as 1820, while the genus Hstheria dates from a much later time. The family ought therefore to be named after the first genus, and not, as is so often done, after the last. The present genus is easily distinguishable from Lstheria by the greater compression and thinness of its shell, on which no distinct umbones are to be found; by the very different form of the head; and to some extent by the structure of the 1st pair of antenne, the legs, and the caudal lamelle. The genus Eulimadia, Packard, is far more closely allied, and the only essential difference seems to be that the species of this last genus, like those of the ' genus Lstheria, are bi-sexual, while males of the genus Limnadia, in spite of the most careful investi- gations, haye not yet been found, and probably do not exist. Only two species of this genus are as yet known, one European and one American, L. americana, Morse. The other species referred to this genus would seem all to belong to the nearly- allied genus, Eulimadia. Limnadia lenticularis (Lin.) (Pl. XIV—XVID. ; Monoculus lenticularis, Linneus, Fauna Svecica, Edit. 2da, p. 499. Daphnia gigas, Herman, Mém. apterol. p. 134, Pl. V, figs. 4,5; Pl. IX, fig. a. Limnadia Hermanni, Brogniart, Mém. du Mus. d’hist. nat. Tome VI, p. 84, Pl. 13. Limnadia gigas, Grube, Archiv f. Naturgeschichte, 19de Jahrg. Bad. I, p. 154. Specific Characters. — Shell, seen from the side, broadly oval, with the greatest height in front acta Rygkanten hos fuldvoxne Individer sterkt buet i sin forreste Del, Bugkanten jevnt convex, Forenden meget kort, afstumpet, Bagenden noget uddraget og smalt tilrundet, med en tydelig Vinkel oventil —: seet ovenfra smalt tenformig, bredest foran Midten. Veextstriberne ikke meget skarpt markerede, og vex- lende efter Alderen indtil 15 paa hverSide. Hovedet nesten af trianguler Form, med Pandedelen smalt konisk og skilt fra det triangulere Rostrum ved et dybt vinklet Indsnit. Foddernes Antal hos fuld- voxne Individer 24 Par, 9—1lte Par med Exopo- ditens dorsale Lap traadformigt forlenget. Hale- pladerne hver med 10—16 smaa Tagger ovenfor det tornformigt udtrukne nedre Hjorne; Haleklorne fint tandede langs den concave Kant og besatte med fine Borster i den basale Del. Farven mere eller mindre tydelig olivengron, Fodderne ialmindelighed lyst gulrede. Leengden af Skallen indtil 17 mm. Bemerkninger. — Allerede Herman har ytret den Formodning, at det af ham som Daphnia gigas beskrevne Dyr maaske kunde vere identisk med Linné’s Monoculus lenticularis, og ogsaa Grube *) synes at vere af samme Mening. De senere af Prof. Lilljeborg*) anforte Data synes endmere at bekreefte Rigtigheden af denne Anskuelse, og det forekommer mig derfor nu at vere fuldt berettiget at optage igjen den Linnéiske Artsbetegnelse, lenti- cularis, saameget mere som den er noksaa beteg- nende. Det Navn, hvorunder nerverende Form af de fleste Forfattere, ogsaa af Prof. Lilljeborg, er op- fort, er Limnadia gigas. Beskrivelse. Hos de storste af mig observerede Exemplarer har Skallen en Lengde af 12 mm. og en Hoide af 9mm. Prof. Lilljeborg har fundet den at kunne naa en Lengde af indtil 17 mm. og en Hoide af ner 13 mm. Men en saadan Storrelse synes dog at maatte ansees som exceptionel. Skallen, der fuldsteendigt omslutter Dyret, saa at kun den forreste Del af Hovedet med Aarerne og Halen kan strekkes udenfor samme, er sterkt sammentrykt fra Siderne og temmelig tynd og gijen- nemsigtig, hvorfor Legemet sees meget tydeligt igjennem samme (se Tab. XI, Fig. 1). Den bestaar af 2 symetriske Halvdele eller Valvler, der langs Dorsalsiden steder sammen under en spids Vinkel og her er fast forbundne med hinanden, uden nogen virkelig Laas. Da imidlertid Skallen er meget elastisk, er Valvlerne til en vis Grad bevegelige 1) Ueber die Gattungen Estheria und Limnadia, p. 68. *) Ofversigt af Kgl. Vet. Akad. Forhandl. 1871, p. 824. of the middle; dorsal margin, in full-grown speci- mens, much arched in the foremost part; ventral margin evenly curved, anterior extremity very short and blunt, posterior end rather elongated and nar- rowly rounded, with a well-marked angle above —: seen from above narrowly fusiform, with the greatest breadth in front of the middle. Lines of growth not very clearly marked, varying according to age up to 15 on each side. Head almost triangular, with the frontal part narrowly conical and sepa- rated from the triangular rostrum by a deep an- gular notch. The number of legs in full-grown specimens 24 pairs, the 9th to the 11th pairs having the dorsal lobe of the exopodites elongated in the form of filaments. Caudal lamelle each with from 10 to 16 small denticles above the spine-like, elongated lower corner; caudal claws finely dentated along their concave edge, and the basal part clothed with fine bristles. Colour more or less distinctly olive- green, legs generally light yellowish red. Length of shell up to 17 mm. Remarks. — Herman has already surmised that the animal described by him as Daphnia gigas may © perhaps be identical with Linneeus’s Monoculus lenti- cularis, and Grube') seems to be of the same opi- nion. The data subsequently furnished by Prof. Lilljeborg*) seem still further to confirm the cor- rectness of this view, and I therefore feel fully justified in adopting again the Linnean specific de- signation, lenticularis, the more so as it is fairly characteristic. The name by which the present form is specified by most authors, Prof. Lilljeborg included, is Limnadia gigas. Description. In the largest specimens examined by me, the shell has a length of 12 mm. and a height of 9 mm. Prof. Lilljeborg has found it attaining a length of 17 mm., and a height of nearly 13 mm.; but such a size must probably be considered exceptional. The shell, which completely envelopes the ani- mal, so that only the anterior part of the head, with the oars and the tail can be extended from it, is greatly compressed, and rather thin and tran- sparent, so that the body is distinctly seen through it (see Pl. XIV, fig. 1). It consists of 2 symmetrical halves or valves which meet at an acute angle along the dorsal side, and are there firmly united to one another, without any true hinge. As, how- ever, the shell is very elastic, the valves are mov- able to a certain extent, and can be opened a little, 1) Ueber die Gattungen Estheria und Limnadia, p. 68. *) Ofversigt af Kgl. Vet. Akad. Forhandl. 1871, p. 824. eS ee re, eee ee Ae Dt ea 1¢* ua™ t i ace 87 og kan aabnes noget eller lukkes efter Dyrets Behag. I sidstnevnte Tilfeelde slutter deres frie Kanter tet mod hinanden, saa at Dyret er herme- tisk indesluttet i Skallens Cavitet. Skallen er fe- stet til Legemet oventil ved et temmelig smalt Ligament og noget nedenfor dette til hver Side ved den steerke Lukkemuskel, hvis Insertion til Inder- siden af hver Valvel viser sig som et vel begreend- set rundagtig Felt i dennes forreste Del. Umiddel- bart bag dette Felt sees Skalkjertelen straekkende sig paaskraat bagover hver Valvel. Seet fra Siden (Fig. 1) viser Skallen hos fuldt udvoxede Exempla- rer en noget uregelmessig, bredt oval Form, med den storste Hoide, der seedvanligvis overstiger °/4 af Leengden, beliggende foran Midten. Dorsalkanten er hos eldre Exemplarer meget sterkt buet i sin forreste Del og begreendset fortil ved en temmelig utydelig stumpvinklet Afsats, bagtil ved et noget sterkere fremtreedende Hjorne. Nedenfor disse Hjor- ner begynder Valvlernes frie Kanter, og disse dan- ner i hele sin Leengde en uafbrudt og fuldkommen jevn Bue. Forenden af Skallen er meget kort og afstumpet, medens Bagenden er noget uddraget og smalt tilrundet. Paa Siderne af Skallen sees et Antal meget fine concentriske Linier, de saakaldte Veextstriber. Deres Antal er varierende efter Al- deren. Hos de storste af mig observerede Individer har jeg talt 11 saadanne Striber paa hver Valvel; men Prof. Lilljeborg har paa ualmindelig store Exemplarer fundet indtil 15 Par Vextstriber. Alle disse Striber convergerer mod det forreste Hjorne af Skallen, og ligger folgelig her tet sammen, hvor- imod de bagtil ender i forskjellig Hoide langs Dorsal- kanten af Skallen. De yderste Linier, som ialmin- delighed er tettere, lober nogenlunde parallelt med Valvlernes frie Kanter; ved den inderste Linie be- grendses oventil et ovalt Felt, hvor Skallen har sin storste Brede, og indenfor hvilket Insertions- areaen for Skallens Lukkemuskel og Skalkjertelen har sin Plads. Seet ovenfra (Fig. 2) eller nedenfra (Fig. 3) viser Skallen en meget smal, noget ten- dannet Form, med den storste Brede, der er betyde- lig mindre end ‘/s af Lengden, foran Midten. * Hyvad Skallens finere Bygning angaar, saa viser den en fuldkommen glat og glindsende Overflade, uden Spor af nogen ydre Skulptur. Den er imidler- tid, ligesom Rygskjoldet hos Lepidurus, sammensat af 2 vesentlig forskjellige Dele, en ydre, tilsyne- ladende af flere Lag bestaaende chitinos Skikt, og en indre membranes Bekledning, der danner en Fortsettelse af Legemets Integument. Begge disse Skikter er forbundne med hinanden ved talrige Tverbjelker, der delvis sees udvendigt som uregel- messige opake Smaapletter, og mellem hyilke der or shut according to the pleasure of the animal. In the latter case, their free edges fit closely toge- ther, so that the animal is hermetically enclosed in the shell’s cavity. The shell is attached to the body above by a rather narrow ligament, and a little below this, to each side, by the strong ad- ductor muscle, whose insertion on the interior sur- face of each valve appears as a well-defined circular area in the foremost part of the valve. Imme- diately behind this area, the shell-gland is seen extending obliquely backwards over each valve. Seen from the side (fig. 1), the shell, in fully-grown specimens, exhibits a rather irregular, broadly oval form, with its greatest height, which generally ex- ceeds */s of its length, in front of the middle. The dorsal margin in older animals is very much curved in its foremost part, and bounded in front by a somewhat indistinct, obtuse angled projection, behind, by a rather more sharply projecting angle. Below these angles begin the free edges of the valves, and these form throughout their length an uninter- rupted and perfectly even curve. The anterior end of the shell is very short and blunt, while the other end is rather drawn out, and narrowly rounded. On the sides of the shell, a number of very fine concentric lines are visible, the so-called lines of growth. Their number varies according to age. In the largest specimens examined by me, I have counted 11 such lines on each valve; but Prof. . Lilljeborg has found as many as 15 pairs of lines of growth on unusually large specimens. All these lines converge towards the anterior corner of the shell, and consequently lie close together there; while at the back they end at different heights along the dorsal edge of the shell. The outermost lines, which are generally closer, run to a certain extent parallel with the free edges of the valves. The intermost line bounds, above, an oval field where the greatest breadth of the shell occurs, and within which the area of insertion of the shell’s adductor muscle, and the shell-gland are situated. Seen from above (fig. 2) or from below (fig. 3), the shell exhibits a very narrow, somewhat fusiform shape, with the greatest breadth, which is consider- ably less than */s of the length, in front of the middle. As regards its more delicate structure, the shell presents a perfectly smooth and shining surface, without a trace of any external sculpturing. It is, however, like the carapace in Lepidurus, composed of two essentially different parts, an exterior chiti- nous coating apparently consisting of several layers, and an internal membranous lining, forming a con- tinuation of the integument of the body. Both these strata are connected with one another by numerous crossbars, which are partially visible externally as small, irregular, opaque spots, and between which er et compliceret System af Hulrum, hvori Blodet cireulerer. Mellem disse Skikter af Skallen er ogsaa Skalkjertelen beliggende. Denne sidste viser sig ved nermere Undersogelse (se Tab. XV, Fig. 14) at bestaa af en flere Gange slyngeformigt bugtet Kanal, der fortil delvis omgiver Insertionsareaen for Skal- lens Lukkemuskel, men hvis Hoveddel ligger umid- delbart bag samme. Kanalens Udgangspunkt synes at ligge lige over den sidstneynte Area og omtrent paa samme Sted ogsaa dens Ende; men nogen skarp Begreendsning mellem begge har jeg dog ikke kun- net paavise, og det er muligt, at der her er en direkte Kommunikation, saa at Kanalen i Virkelig- heden danner et i sig selv tilbagegaaende Ror. Bag Muskelareaen danner Kanalen. 3 ind i hverandre liggende tungeformige Slynger, der, om man forfol- ger Kanalen fra dens tilsyneladende Udgangspunkt, folger paa hinanden i en saadan Orden, at den mid- terste Slynge er den forst dannede, den yderste den 2den, og den inderste den 3die. Den midterste og yderste Slynge er forbundet ved en smalt udlobende, tungeformig Omboining, der strekker sig dorsalt forover, og ender lige over Kanalens Udgangspunkt. Den yderste og inderste Slynge gaar over i hinan- den ved en lignende, men bredere Omboining, der ligger mere ventralt, lige nedenunder Muskelareaen, og her krydser den forreste Del af Kanalen. Over- alt viser Kanalens Konturer sig uregelmessigt tak- kede, og i dens Vegge sees spredte Cellekjerner, givende den et glandulost Udseende. Det i Skallen indesluttede Dyr (se Tab. XV, Fig. 1) indtager en forholdsvis liden Del af Skal- caviteten, hvori det er frit suspenderet, kun festet helt fortil ved det ovenomtalte dorsale Ligament og ved Skallens Lukkemuskel. Saavel den foran som bagenfor liggende Del af Legemet er derfor frit beveegelig, og flere Muskler sees ogsaa at pas- sere fra det dorsale Ligament saavel fortil som bagtil. Legemet lader sig naturligt dele i 2 Hoved- afsnit, der med hinanden danner en storre eller min- dre Vinkel, og hvis Begrendsning antydes ved det dorsale Ligament og Lukkemuskelen. Det foran disse Dele liggende Afsnit er meget mindre end det bagenfor liggende og kan igjen deles i 2 under- ordnede Afsnit, begreendsede fra hinanden oventil ved en dyb Indbugtning. Den forreste Del er det egentlige Hoved, den bagerste det saakaldte Nakke- segment. Det bagenfor det dorsale Ligament og Lukkemuskelen liggende, seerdeles bevegelige Afsnit lader sig ligeledes dele i 2, den egentlige Krop (truncus) og Haledelen, hvoraf den forste er af meget betydelig Storrelse, den anden ganske kort. Af ydre Vedheeng berer Hovedet de 2 Par Folere og fortsetter sig bagtil paa Undersiden i Overleben. 88 there is a complicated system of cavities in which the blood circulates. Between these strata of the shell, the shell-gland is also situated. This last proves, on a close examination (see Pl. XV, fig. 14) to con- sist of a twisted channel curled up in several windings, which in front partially surround the area of inser- tion of the shell’s adductor muscle, but of which the greater number lie immediately behind it. The point of issue of the channel appears to lie just over the above-mentioned area, and its end also at about the same place; but I have not been able to make out any sharp boundary between the two, and it is possible that there is here a direct commu- nication, so that the channel forms in reality a tube running back into itself. Behind the muscular area, the channel forms 3 linguiform coils lying within one another, which, if the course of the channel be traced from its apparent origin, so follow one an- other, that the middle coil is the first formed, the outermost one, the second, and the innermost, the third. The middle and outermost coils are con- nected by a narrowly projecting, lingular fold, which extends forwards dorsally, and ends just above the starting-point of the channel. The outer- most and. innermost coils run into one another with a similar, but broader fold, which is more ventral in position, just below the muscular area, and here crosses the front part of the channel. The outline of the channel is throughout irregularly jagged, and scattered cell-nuclei are visible in its walls, giving it a glandular appearance. The enclosed animal (see Pl. XV, fig. 1) oceu- pies a comparatively small portion of the cavity of the shell, within which it is freely suspended, being attached only at the very front by the before-men- tioned dorsal ligament and by the adductor muscle of the shell. Both the anteriorly and the posteri- orly situated part of the body can therefore be freely moved, and several muscles may be seen passing from the dorsal ligament both backwards and forwards. The body permits of being naturally divided into two principal sections, which form more or less of an angle with one another, and whose limits are indicated by the dorsal ligament and the adductor muscle. The section situated in front of these parts is much smaller than that lying behind, and can be again divided into 2 sub-sections, sepa- rated from one another above by a deep hollow. The fore part is the head proper, the back part, the so-called cervical segment. The extremely mobile section situated behind the dorsal ligament and the adductor muscle, is also capable of being divided into two, — the body proper (trunk) and the caudal part, the first of these being of very considerable size, the second, quite short. Of the external appendages, the head carries the 2 pairs of antenne, and is continued backwards Paa Grendsen mellem Hovedet og Nakkesegmentet ligger de 2 kraftige Kindbakker og tet bag dem paa Bugsiden de 2 Par Kjever. Truncus berer 22—24 Par Branchialfodder og er delt i et tilsva- rende Antal meget uniforme Segmenter. Haledelen er uden egentlige Lemmer, men berer paa Spidsen 2 sterke, beveegelige Klor og dorsalt 2 smaa jevn- sidesstillede Borster. Jeg gaar nu over til at beskrive ethvert af disse Afsnit noget ngiere. Hovedet (se Tab. XV, Fig. 2, 3, 4) er forholds- vis af ringe Storrelse og, seet fra Siden (Fig. 2), af uregelmessig triangular Form. Dets dorsale Flade er jevnt convex og beerer i Midten et eiendommeligt stilket, noget kolleformigt Appendix (af), som ial- mindelighed er tydet som et Fastheftningsredskab. Pandedelen er steerkt fremspringende, nesten koniskt udtrukket, og ender i en stump Spids, indenfor hvil- ken de sammensatte Gine har sin Plads. Nedenfor Pandedelen har Hovedet en dyb vinkelformig Ind- bugtning, hvorved Pandedelen meget skarpt sondres fra det triangulert fremspringende Rostrum. Dette sidste er noget trekantet i Gjennemsnit, idet det oventil har en tilskjerpet Kant, medens det nedentil er svagt indhulet langs ad Midten. Bunden af Ind- hulingen viser sig, naar Hovedet sees fra Siden, som en buet Linie, der strekker sig fra Spidsen af Ro- strum bagover mod Basis af Overleben. Seet oven- fra (Fig. 3) eller nedenfra (Fig. 4), viser Hovedet sig temmelig bredt bagtil, men afsmalnes hurtigt fortil mod den smalt tilrundede Pandedel. Nakkesegmentet er oventil sondret fra Hovedet ved en meget distinct og temmelig dyb Indbugtning, i hvis Bund der lader sig paavise en tydelig tver- gaaende Sutur (se Fig. 3), der ender til hver Side med et lidet sterkt chitiniseret Fremspring, hvortil Kindbakkernes ovre Ende er articuleret. Den dor- sale Del af Segmentet er sterkt hvelvet og nesten af samme Leengde som Hovedet, hvorimod den ven- trale Del er meget kort og kun indskrenket til Mellemrummet. mellem Kindbakkerne og Skallens Tmkkemuskel. Den egentlige Krop (truncus) (se Fig. 1) er over dobbelt saa lang som de 2 foregaaende Afsnit til- sammen og nesten cylindrisk af Form, eller kun ganske syagt afsmalnende bagtil. Den er delt i en Rekke meget uniforme Segmenter, hvert berende et Par Branchialfodder. Antallet af Segmenter er hos fuldvoxne Individer, i Overensstemmelse med Bran- chialfoddernes Tal, 22—24, hvoraf dog det bagerste sedvanligvis er ufuldkomment sondret. Alle Seg- menter, med Undtagelse af de allerforreste, har oventil et Knippe af bagudkrummede Borster, mest udviklede paa de bagerste Segmenter. Nogen tyde- 12 — G. 0. Sars: Fauna Norvegiz. 89 on the under side in the form of the labrum. On the boundary between the head and the cervical segment lie the 2 powerful mandibles, and immediately behind them on the ventral side, the 2 pairs of maxille. The trunk carries from 22 to 24 pairs of branchial legs, and is divided into a corresponding number of very uniform segments. The caudal sec- tion is without any true limbs, but carries at the extremity 2 strong, movable claws, and dorsally 2 small, juxtaposed bristles. I will now pass on to describe each of these sections more fully. The head (see Pl. XV, figs. 2, 3, 4) is of com- paratively small size, and, seen from the side (fig. 2), of an irregular, triangular shape. Its dorsal surface is evenly convex, and carries in the middle a pecu- liar, stalked, somewhat club-shaped appendage (af) which is usually interpreted as an organ of attach- ment. The frontal part is very prominent, almost conically drawn out, and ending in a blunt point, within which the compound eyes are situated. Below the frontal part, the head has a deep angular inden- tation, whereby the frontal part is very sharply divided from the triangularly projecting rostrum. The latter is somewhat triangular in section, having above a sharp edge, while below it is slightly hol- lowed out along the middle. The bottom of the groove appears, when the head is seen from the side, like a curved line extending from the point of the rostrum backwards towards the base of the labrum. Seen from above (fig. 3) or from below (fig. 4), the head looks rather broad at the back, but tapers rapidly in front towards the narrowly rounded frontal part. The cervical segment is separated above from the head by a very distinct and rather deep hollow, at the bottom of which may be traced a dis- tinct transverse suture (see fig. 3) ending at each side in a highly chitinised process, to which the upper ends of the mandibles are articulated. The dorsal part of the segment is considerably vaulted, and of almost the same length as the head, the ventral part, on the other hand, being very short, and confined only to the space between the man- dibles and the adductor muscle of the shell. The body proper (trunk) (see fig. 1) is more than twice as long as the 2 preceding sections together, and almost cylindrical in shape, or only very slightly tapering behind. It is divided into a series of very uniform segments, each bearing a pair of branchial legs. The number of segments in full-grown individuals corresponds with the number of branchial legs, viz from 22 to 24, of which, however, the hindmost is generally imperfectly defined. All the segments, with the exception of the very foremost ones, have a bunch of backward- curved bristles above, those on the hindmost seg- lig udpreget Sondring af Midtkrop og Bagkrop fin- des ikke. Men, i Lighed med hvad vi har gjort med Lepidurus, lader sig maaske Greendsen mellem begge sette ved det 1lte Segment, der berer det bagerste af de 3 Par Branchialfodder, hvis Exopoditer er om- formede til Feste for Agmassen, og hvor ogsaa Kjonsaabningerne har sin Plads. Haledelen (se Tab. XVI, Fig. 7) er ganske kort, usegmenteret, og omboiet mod Bugsiden. Den er i sin forreste Del temmelig tyk, men udvides bagtil mod Enden til 2 tynde, jevnsidesliggende Plader, der hver nedad springer frem i Form af en tornformig Fortsats. Ovenfor denne Fortsats er Randen af hver Plade delt i et noget vekslende Antal (fra 8 til 15) smaa tandformige Fremspring cilierede i Kan- terne. Hvor Pladerne ophorer oventil, er der i Mid- ten en liden Knude, hvorpaa er festet 2 fint cili- erede 2-leddede Borster (Haleborsterne), og ovenfor dem igjen er den sterkt convexe, neesten helformigt fremspringende Rygflade af Halen bevebnet med omkring 6 sterke bagudboiede Torne, fint tandede i Kanterne, og ordnede i 2 uregelmessige Rader (se ogsaa Fig. 7, bis). Til den afstumpede Ende af Haledelen er bevegeligt indleddede 2 serdeles lange og sterke, men kun ganske svagt boiede Klor (Hale- klorne), der morphologiskt synes at svare til Hale- traadene hos Apodiderne og den saakaldte Furca hos Branchipodider og Phyllocarider. De afsmalnes grad- vis mcd Enden, som gaar ud i en fin Spids, og har langs den bagre, noget concave Side talrige smaa Tagger samt desuden i sin basale Del et Antal af fine Borster. De sammensatte Mine (se Tab. XV, Fig. 2, 3, 4, 0) har, som ovenfor nevnt, sin Plads i det indre af den koniskt fremspringende Pandedel, hvis stumpt til- rundede Ende de nesten fuldsteendigt udfylder. De ligger meget ner sammen og stoder endog hos fuld- voxne Individer umiddelbart til hinanden i Midt- linien (se Fig. 3, 4). Seet fra Siden (Fig. 2) har hvert Gie en fuldsteendig cirkelrund Form, hvorimod de, ovenfra eller nedenfra seet, viser sig paatveers ovale. Begge Mine er (se Tab. XVI, Fig. 10, 0) om- givne af en felles tynd og gjennemsigtig Membran og bestaar af et meget betydeligt Antal af Syns- elementer, hvis ydre Del, som sedvanlig, har For- men af sterkt lysbrydende korte Kegler indplantede med sin Spids i det morke Giepigment. Dette sidste har en noget lysere overfladisk Skikt, hvorfor Kry- stalkeglerne indenfor Kanterne af Oiet tager sig ved paafaldende Lys ud som tet sammen liggende regel- meessige morke Pletter, medens de i Peripherien danner en klar Brem, eller Indfatning om Wiet. Minene er til en vis Grad bevegelige, idet de dels kan trekkes noget tilbage i Hovedet, dels noget 90 ments being the most highly developed. There is no distinctly-marked division of the mesosome and me- tasome; but as in Lepidurus, we may perhaps place the boundary between the two, at the 11th seg- ment, which carries the hindmost of the 3 pairs of branchial legs whose exopodites are transformed to support the egg-mass, and where, too, the genital openings are situated. The caudal part (see Pl. XVI, fig. 7) is quite short, unsegmented and curved towards the ventral surface. In its anterior part it is rather thick, but expands posteriorly towards the extremity into 2 thin, juxtaposed lamella, each of which projects below in the form of a spiniform prominence. Above this prominence, the margin is divided into a somewhat varying number (from 8 to 15) of small dentiform projections with ciliated margins. Where the lamelle end above, there is, in the middle, a little tubercle, to which are attached 2 finely-ciliated, 2-jointed bristles (caudal bristles), and above them again is the highly convex, almost heel-like, projecting dorsal surface of the tail, armed with about 6 strong, backward-curved spines, finely dentated at the edges, and arranged in 2 irregular rows (see also fig. 7, bis). To the blunt end of the caudal part, 2 particularly long and strong, but only very slightly curved claws (caudal claws) are movably articulated; they seem, morphologically, to correspond to the caudal filaments in the Apodide, and the so-called furea in the Branchipodide and Phyllocaride. They taper gradually towards the extremity, which is very finely pointed, and along their posterior, somewhat concave side they are clothed with numerous small teeth, and moreover in their basal part with a number of fine bristles. The compound eyes (see Pl. XV, figs. 2, 3, 4, 0) are situated, as already mentioned, inside the coni- cally projecting frontal part, almost filling its bluntly rounded end. They le very close together, and even touch one another in the median line in full- grown animals (see figs. 3, 4). Seen from the side (fig. 2), each eye has a perfectly circular shape, whereas seen from above or below, they appear transversely oval. Both eyes (se Pl. XVI, fig. 10, 0) are surrounded by a thin and transparent common membrane, and consist of a very considerable num- ber of visual elements, whose outer part has, as usual, the shape of short, highly-refractive cones, with their point planted in the dark ocular pigment. This pigment has a rather lighter superficial coating causing the crystalline cones within the margin of the eye to appear, when the light falls upon them, like closely-adjacent, regular, dark spots, while those in the periphery form a clear rim or setting round the eye. The eyes are movable to a certain extent, being partly capable of slight retraction into the head, partly of being slightly turned on their axis. — i = = a dreies om sin Axe. Dette sker ved Hjelp af 3 tynde Muskler, der fra Hovedets Integument passerer bag- fra fortil til hvert Gie (Fig. 10, m). Det enkle Gie (Tab. XV, Fig. 2, 4, oc) ligger i en temmelig betydelig Afstand fra de sammensatte Mine, lige ved Basis af Rostrum, og har, seet fra Siden (Fig. 2) en trekantet Form, med den ovre Ende spidst udtrukket. Ved noiere Undersogelse (se Tab. XVI, Fig. 11, 12, 13) viser det et noget prismatiskt Udseende, idet man paa det kan adskille 4 Flader, begreendsede ved skarpe Kanter og hver indfattet af en smal Stribe af morkerodt Pigment: 2 fortil sammenstodende Sideflader, en bagre Flade og en nedre Flade. Den sidste er den mindste, de 3 ovrige omtrent af ens Storrelse. Alle Flader viser i visse Belysninger en sterkt iriscerende Glands, men tager sig ialmindelighed ved direkte paafaldende Lys opakt hvide ud. Det enkle Mie er holdt i Situs ved 2 tynde strengformige Ligamenter, hvoraf det ene passerer fra den spidst udtrukne ovre Ende af Organet skraat opad ind i Hovedets Pandedel, og fester sig her til en liden grubeformig Fortykkelse af Integumentet lige under de sammen- satte Oine. Det andet Ligament udgaar fra For- kanten af den nedre Flade og begiver sig direkte ind i Rostrum, hvor det oploser sig i flere korte Smaagrene, hver endende med en liden knapformig Fortykkelse (se Tab. XV, Fig. 2, Tab. XVI, Fig. 9). Forste Par Folere (Tab. XV, Fig. 2, 3, 4, a}, Fig. 5), der udspringer til hver Side ved den nedre Del af Hovedet, bag Rostrum, er mindre rudimen- tere end hos de i det foregaaende beskrevne Phyl- lopoder, og neesten af Hovedets Lengde. De be- staar hver (se Fig. 5) af en kort Basaldel og en smalt kolleformig Endedel, der i Forkanten viser et noget vexlende Antal (fra 5—8) afrundede Lappe, hvoraf de 2 yderste indtager Spidsen af Foleren. Alle disse Lappe er tet besatte med smaa Lugte- papiller, som ved sterk Forstorrelse (Fig. 6) viser sig at bestaa af en kort, skarpt kontureret Stilk og en serdeles delikat cylindrisk Endedel, forsynet strax indenfor Spidsen med en liden gjennemsigtig Blere. Prof. Lilljeborg har troet at finde paa Ende- delen af Foleren et Antal af fine Tveersuturer, saa- ledes ordnede, at egentlig enhver af de laterale Lappe skulde tilhore et serskilt Led. Jeg har dog ikke paa de af mig undersogte Exemplarer kunnet med Sikkerhed paavise en saadan Leddeling, som derimod hos visse Arter af Estheria er meget tydeligt udpreget. Ved Hjelp af nogle tynde Muskler, der fra Hovedet passerer ind i Basaldelen kan disse Folere til en vis Grad beveges frem og tilbage. Andet. Par Folere (Tab. XVI, Fig. 1) er megtigt udviklede og forestiller Dyrets vesentligste Bevege- organer. De udspringer med en bred Basis fra 91 These movements are accomplished by the aid of 3 thin muscles, which pass from the back of the integument of the head, forwards to each eye (fig. 10, m.). The ocellus (Pl. XV, figs. 2, 4, oc) is situated at rather a considerable distance from the compound eyes, close to the base of the rostrum, and, when seen from the side (fig. 2), exhibits a triangular shape, with the upper end drawn out acutely. On closer observation (see Pl. XVI, figs. 11, 12, 13), it presents somewhat of a prismatic appearance, 4 sur- faces, bounded by sharp edges, and each bordered by a narrow band of dark-red pigment, being dis- tinguishable, viz, 2 lateral surfaces meeting in front, 1 posterior surface, and 1 inferior. The last is the smallest, the other 3 of almost uniform size. In certain lights, all the surfaces. have an iridescent lustre, but generally appear opaquely white under directly falling light. The ocellus is kept in posi- tion by 2 thin cord-like ligaments, one of which passes from the acutely drawn-out end of the organ, obliquely upwards into the frontal part of the head, there attaching itself to a small pit-like thickening of the integument, just below the compound eyes. The other ligament issues from the anterior edge of the inferior surface, and proceeds directly into the rostrum where it is resolved into several short ramuli, each terminating in a small bud-like expan- sion (see Pl. XV, fig. 2; Pl. XVI, fig. 9). The first pair of antenne (PI. XV, figs. 2, 3,4, a‘, fig. 5), which spring out to each side from the lower part of the head, behind the rostrum, are less rudi- mentary than in the previously-described Phyllo- pods, and are almost as long as the head. They each consist (see fig. 5) of a short basal part and a narrow club-like terminal part, on whose front margin is a somewhat varying number (from 5 to 8) of rounded lobes, of which the two outermost occupy the point of the antenna. All these lobes are thickly set with small olfactory papille, which, when highly magnified (fig.6) prove to consist of a short, sharply- defined stalk, and an exceedingly delicate cylindrical terminal part, provided, just within the point, with a small, transparent vesicle. Prof. Lilljeborg states having found a number of fine transverse sutures, so arranged that each of the lateral lobes belongs to a separate joint. I have not, however, in the specimens I have examined, been able to make out with certainty such an articulation, which, on the other hand, is very distinct in certain species of Estheria. By the aid of some fine muscles, which run from the head into the basal part, these an- tenne can to a certain extent be moved backwards and forwards. The 2nd pair of antenne (Pl. XVI, fig. 1) are powerfully developed, and they. constitute the ani- mal's principal organs of locomotion. They issue Sidefladerne af Hovedet (se Tab. XV, Fig. 1), og bestaar hver af et cylindriskt, muskulost Skaft og 2 sterkt forlengede Grene. Skaftet viser ved Basis en noget albuformig Boining og er her i Bagkanten forsynet med et lidet borstebesat Fremspring (se ogsaa Fig. 3, a*). Dets ydre Del er meget boielig og delt i omtrent 8 korte Segmenter tet besatte fortil med sterke, pigformige Borster. Grenene er meget smale og af meget betydelig Lengde, navnlig den indre eller bagre, der er over dobbelt saa lang som Skaftet. Begge Grene er delte i talrige (fra 1U til 14), meget skarpt afsatte og noget skivefor- mige Led, hvoraf hvert i Bagkanten har flere lange, 2-leddede og fint cilierede Svommeborster, i Forkan- ten ligeledes et storre Antal af sterke, i Enden noget hageformigt krummede Pigge. Saavel Grene- nes indbyrdes Leengde som Antallet af Led paa hver Gren er forovrigt noget varierende hos forskjellige Individer. Overleben (Tab. XV, Fig. 2, 4, £, Fig. 7) ud- gaar bagtil som den umiddelbare Fortsettelse af Hovedets ventrale Del, og hvelver sig paa Under- siden ud over Kindbakkernes Tyggedel, samt naar med Spidsen ind mellem Basis af Iste Fodpar (se Fig. 1). Den er imidlertid til en vis Grad bevege- lig, idet den ved to tynde til dens Basis lobende Muskler kan loftes noget af fra Munddelen og igjen ved andre Muskler presses tet ind mod samme. Af Form er den nesten halveylindrisk, med den nedad- vendte Flade sterkt convex, den ovre noget concav. Ved Enden indsneevres den pludselig, dannende til hver Side et vinkelformigt Hjorne, og forlenger sig til en meget boielig og i Enden fint cilieret Spids. Ovenover denne tentakelformige Fortsats har den en skiveformig, lodret stillet Endelamelle, der leg- ger sig ind mellem de 2 Par Kjever, naar Over- leben presses ind mod Legemet. I Overlebens indre sees flere celleagtige Legemer, der synes at vere af kjertelagtig Natur, og ligeledes et storre Antal tveergaaende Muskler, der virker paa den blode ovre Flade og rimeligvis har Betydning ved Svelgnings- processen. Kindbakkerne (Tab. XV, Fig. 2, 3,4, 1, Fig. 8), der som 2 Boiler omfatter Siderne af Legemet paa Grendsen mellem Hovedet og Nakkesegmentet, er meget kraftigt udviklede og hos det voxne Dyr uden ethvert Spor af Palpe. Den spidst udlobende ovre Ende af det baadformige Corpus er beveegeligt arti- culeret med en liden knopformig Fortykkelse af Integumentet ved hver Ende af den Tversutur, som findes i Bunden af den dorsale Indbugtning mellem Hovedet og Nakkesegmentet. Tyggedelen er steerkt indbgiet og sondret fra Corpus ved en tydelig Ind- knibning eller Hals. Den ender, som hos Branchi- podiderne med en bred, fint riflet Tyggeflade uden 92 from the lateral surfaces of the head, with a broad base (see Pl. XV, fig. 1), and each consist of a cylindrical, muscular scape, and two greatly elon- gated rami. The scape exhibits at the base a some- what elbow-like bend, and on the hind margin at this point, is furnished with a little setous projec- tion (see also fig. 3, a’). Its distal part is very flexible, and divided into about 8 short segments, thickly clothed in front with strong spiniform brist- les. The rami are very narrow, and of considerable length, notably the inner or hinder one, which is more than twice as long as the scape. Both rami are divided into numerous (from 10 to 14) very clearly defined and somewhat lamellar joints, each of which has several long, bi-articulated and finely ciliated natatory bristles in the hind margin, and a large number of strong, rather hamous spines in the front margin. Both the mutual length of the rami, and the number of joints in each ramus, varies somewhat in different specimens. The labrum (Pl. XV, figs. 2,4, Z, fig. 7) projects backwards as the immediate continuation of the ventral part of the head, and on its inferior side arches over the masticatory part of the mandibles, its point extending in between the base of the first pair of legs (see fig. 1). To a certain extent, how- ever, it is movable, for it can be raised a little from the oral parts by two thin muscles running to its base, and again, by other muscles, can be pressed close in against those parts. In shape, it is almost semi-cylindrical, with the down-turned surface very convex. At the extremity it is suddenly contracted, forming on each side a sharp corner, and being produced to a very flexible point, finely ciliated at the extremity. Above this tentacular projection there is a discoid, vertically-situated, terminal lamella, which is interposed between the 2 pairs of maxille, when the labrum is pressed in towards the body. In the interior of the labrum are visible several cell-like bodies, which appear to be of a glandulous nature, and also a large number of transverse muscles, which act upon the soft upper surface, and probably perform a part in the process of swallowing. The mandibles (Pl. XV, figs. 2, 3, 4, M, fig. 8) which embrace the sides of the body like 2 bows, on the boundary-line between the head and the cer- vical segment, are very powerfully developed, and, in the full-grown animal, without a trace of palpi. The pointed upper end of the boat-like body is movably articulated with a small bud-like thickening of the integument at each end of the transverse suture found at the bottom of the dorsal hollow between the head and the cervical segment. The masticatory part is very much incurved, and sepa- rated from the corpus by a distinct constriction or neck. It ends, as in the Branchipodide with a Spor af tandformige Fremspring. Foruden de kraf- tige Adductormuskler, der fylder Storsteparten af den indre Hulhed af Corpus, sees ogsaa en Del andre Muskler at passere til Kindbakkerne, ved Hjelp af hvilke disse kan dreies om sin Axe inden visse Grendser. De sterkeste af disse Rotations- muskler udspringer fra den dorsale Flade af Nakke- segmentet og convergerer mod Kindbakkernes bagre Side (se Fig. 2). Nogle betydelig mindre Muskler passerer fra Hovedets dorsale Integument til For- siden af Kindbakkerne. Nogen Underlebe har det ikke lykkets mig at paavise. Prof. Lilljeborg tror dog at have fundet den i Form af 2 meget smaa tilspidsede og tet haa- rede Lappe. Forste Par Kjever (Fig. 2, 4, 9, m', Fig. 10) bestaar af en kort og tyk Basaldel og en meget beveegelig indadboiet, skiveformig Endedel, der paa sin frie Rand er besat med en tet Rad af tynde, leformigt krummede Borster, alle tydeligt 2-leddede og fint cilierede. Foruden dem findes der endnu en Rad af betydelig kortere Borster eller Pigge, der er grovt tandede i Kanterne og ender i en serdeles fin og delicat Spids (se Fig. 11). Disse Borster er dog kun indskrenkede til den bagre Halvdel af Randen. Endelig bemerkes fortil, i Vinkelen mellem Basal- ~ delen og Endelamellen en meget liden, men tydeligt begreendset, secunder Lamelle af smal tungedannet Form og kantet med nogle ganske korte Borster. Andet Par Kjever (Fig. 2, 4,9, m?, Fig. 12, 13) er betydelig mindre end 1ste Par og, som det synes, kun lidet bevegelige. De bestaar ligeledes af en kort Basaldel og en indadrettet Endelamelle af elliptisk Form, med det indre afrundede Hjorne be- tydelig mere fremspringende end det ydre. Lamellen er kantet med omkring 24 tet cilierede Borster, som dog er utydeligt leddede og kun mod det indre Hjorne naar nogen betydelig Lengde. Af Fodder har jeg hos fuldt udviklede Individer talt 22—23 Par. Prof. Lilljeborg har hos ualmin- delig store Exemplarer endnu fundet et Par bag disse, saa at deres Tal kan stige til 24 Par ialt; ja Grube paastaar endog hos et Individ at have talt 26 Par. De er idethele af en meget uniform Byg- uing og viser alle Characteren af egte Branchial- fodder. Foruden til Respiration, har de imidlertid ogsaa en veesentlig Betydning ved Neringsoptagel- sen, idet de i Vandet verende organiske Smaadele, hvoraf Dyret nerer sig, ved Foddernes rhytmiske Bevegelser bliver hvirvlet ind mod Munddelene. De 10 eller 11 forreste Par er nogenlunde af samme Lengde, men fra det 11te Par begynder de steerkt at aftage i Storrelse, og de allerbagerste Par er overmaade smaa og vanskelig at telle. De har alle 93 broad, finely-fluted molar surface without a trace of dentate projections. Besides the powerful adductor muscles, which fill the greater part of the inner cavity of the body, a few other muscles are also seen passing to the mandibles, which, by their aid, ean turn upon their axis within certain limits. The strongest of these rotatory muscles issue from the dorsal surface of the cervical segment, and converge towards the posterior side of the mandibles (see fig. 2). Some much smaller muscles pass from the dorsal integument of the head to the anterior side of the mandibles. I have not succeeded in proving the presence of any posterior lip. Prof. Lilljeborg, however, be- lieves that he has found it in the shape of two very small, pointed, and densely hairy lobes. The first pair of maxille (figs. 2, 4, 9, m', fig. 10) consist of a short and thick basal part, and a very movable, incurved, lamellar, terminal part, which is clothed on its free margin with a close row of thin, falciformly curved bristles, all distinctly 2-jointed and finely ciliated. In addition to these, there is yet another row of much shorter bristles or spines, which are coarsely dentated at the edges, and end in a particularly fine and delicate point (see fig. 11). These bristles, however, are only con- fined to the posterior half of the margin. Lastly, there is visible in front, in the angle between the basal part and the terminal lamella, a very small, but distinctly defined lamella, of a narrow lingular form, and edged with a few very short bristles. The 2nd pair of maxille (figs. 2, 4, 9, m?, figs. 12, 13) are considerably smaller than the first pair, and apparently only slightly movable. They also consist of a short basal part, and an inward-direc- ted terminal lamella of elliptical shape, with the inner rounded corner considerably more prominent than the outer one. The lamella is bordered with about 24 thickly ciliated bristles, which are how- ever, indistinctly articulated, and only at the inner corner attain any considerable length. In fully developed animals, I have ented from 22 to 23 pairs of legs. Prof. Lilljeborg has even found a pair behind these in unusually large speci- mens, so that their number can rise to 24 pairs in all; indeed, Grube asserts that in one specimen he has counted as many as 26 pairs. They are, on the whole, of a very uniform structure, and exhibit all the characters of true branchial legs. They are, however, of essential importance, not only in respi- ration, but also in the admission of nourishment, as the organic particles in the water, on which the animal feeds, are whirled in towards the oral parts by the rhythmical movements of the legs. The 10 or 11 foremost pairs are of about equal length, but after the 11th pair they begin to diminish rapidly, the hindmost pairs being exceedingly small and (se Tab. XVI, Fig. 3) Formen af nedadrettede aflange, noget buede og uregelmessigt fligede Plader, hvis convexe Side vender fortil, den concave bagtil, og som i Kanterne er rigeligt borstebesatte. Man kan paa dem adskille de samme 3 Hoveddele som hos andre Branchiopoder, nemlig Endopodit, Exopodit og ' Epipodit. Endopoditen, eller den egentlige Stamme, har ved Basis indad en meget tydeligt. sondret Coxallap (mx) af temmelig compliceret Bygning (se Fig.4). Den er noget skraat indadrettet, af stumpt konisk Form og meget rigeligt forsynet med Bor- ster. Ved Spidsen har den 2 korte Pigge, og en lig- nende Pig findes ogsaa paa den indre Side. denne sidste Pig strekker sig en noget skraat lobende Rad af lange, leformigt indad krummede Borster, der alle er tydeligt 2-leddede og fint cili- erede. En anden Rad af cilierede Borster strekker sig langs den ydre Kant af Coxallappen, men disse Borster er ikke leformigt krummede og aftager hur- tigt i Lengde mod Spidsen. Umiddelbart ovenfor dem udgaar fra Yderkanten en noget stzrkere, skraat indadrettet Borste. Den indre Kant af En- dopoditen er ved smaa Indsnit delt i 4 korte og brede Lappe (Enditer), der berer en dobbelt Rad af fint cilierede Borster, hvoraf de i den ene er ser- deles lange, tydeligt 2-leddede og bagudboiede. Den yderste af disse Lappe er noget mere fremspringende end de ovrige, og til dens ydre Side er articuleret en smal tungeformig Lamelle, rundt om besat med cilierede Borster. Denne Lamelle forestiller den yderste (Ste) Endit, eller Endopoditens Endeled, det eneste tydeligt begreendsede Led paa Foden. Epi- poditen (ep) har Formen af et aflangt ovalt, noget sekformigt Appendix, uden ethvert Spor af Borster. Den er festet til Ydersiden af Endopoditen i en kort Afstand fra dennes Basis og rettet lige opad over Siderne af Kroppen (se Tab, XV, Fig. 1). Exopoditen (ex), der udspringer med en bred Basis ligeledes fra Ydersiden af Endopoditen og umiddel- bart nedenfor Epipoditen, er af betydelig Storrelse og delt i 2 smale i forskjellig Retning udgaaende Lappe, en ventral og en dorsal. Den ventrale Lap rekker omtrent til Spidsen af Endopoditens Ende- lamelle, og er ligesom denne rundtom kantet med cilierede Borster. Den dorsale Lap (ex!) er betyde- lig mindre end den ventrale, neppe overragende Epipoditen, og er berstebesat alene i den ydre Kant. Paa 9de til 11te Fodpar er imidlertid hos fuldt ud- viklede Individer (se Tab. XV, Fig. 1) denne Lap udtrukket til en meget lang traadformig Fortsats, der rager op i Skallens dorsale Cavitet, hvor den tjener til Feste for den her sig ansamlende Aig- masse. 23de eller sidste Fodpar (Fig. 5, 6) skiller sig i visse Henseender kjendeligt fra de ovrige. Det er serdeles lidet og har Endopoditen ganske kort, med kun 3 Lappe indad, foruden Coxallappen. Bor- sterne paa disse Lappe, saavelsom paa det korte, Fra | 94 difficult to count.. They all (see Pl. XVI, fig. 3) have the shape of down-pointing, oblong, somewhat curved, and irregularly lobed lamin, whose convex side turns to the front, the concave to the back, and whose edges are thickly clothed with bristles. The same 3 principal parts can be distinguished in them as in other Branchiopods, namely, endopodite, exopodite and epipodite, The endopodite, or stem proper, has on the inner side of the base a very distinctly-defined coxal lobe of rather complicated — structure (see fig. 4). It is directed rather obliquely inwards, is of a bluntly conical shape, and abun- dantly provided with bristles. At the point it has two short spines, and a similar spine is also found on the inner side. From this last-mentioned spine, runs a rather oblique row of long, falciformly incurved bristles, all distinctly 2-jointed and finely ciliated. Another row of ciliated bristles runs along the outer edge of the coxal lobe, but these are not falciformly curved, and they rapidly decrease in length towards the point. Immediately above them, there issues from the outer edge a somewhat stronger bristle, directed obliquely inwards. The inner edge of the endopodite is divided by small indentations into 4 short, broad lobes (endites) carrying a double row of finely ciliated bristles, which in one row are particularly long, distinctly 2-jointed, and bent back- wards. The outermost of these lobes is rather more projecting than the others, and to its outer side is articulated a narrow lingular lamella, edged all round with ciliated bristles. This lamella represents the outermost (5th) endite, or the terminal joint of the endopodite, the only distinctly defined joint in the leg. The epipodite (ep) is in the shape of an oblong oval, somewhat sac-like appendage, with no trace of bristles. It is attached to the outer side of the endopodite at a short distance from its base, and is directed straight upwards over the sides of the body (see Pl. XV, fig. 1). The exopodite (ex), which issues with a broad base also from the outer side of the endopodite, and immediately below the epipodite, is of considerable size, and is divided into 2 narrow lobes, one ventral and one dorsal, pro- jecting in opposite directions. The ventral lobe reaches almost to the point of the terminal lamella of the endopodite, and is likewise edged all round with ciliated bristles. The dorsal lobe (ex') is con- siderably smaller than the ventral, scarcely reaching beyond the epipodite, and is edged with bristles only on the outer margin. On the 9th, 10th and 11th pairs of legs in fully-developed specimens, how- ever (see Pl. XV, fig. 1), this lobe is drawn out to a very long filiform projection, which extends up into the dorsal cavity of the shell, where it serves as an attachment for the accumulated egg-mass there. The 23rd or last pair of legs (figs. 5 and 6) is conspicuously distinguished in certain respects ae afrundede Endeled er meget reducerede i Antal. Epi- poditen er overmaade liden og rudimenteer, hvorimod Exopoditen er forholdsvis vel udviklet, naaende med sin ventrale Lap langt ud over Endopoditen. Den er kantet med omtrent 23 Borster af noget ulige Lengde. Meget lignende, skjondt endnu noget sim- plere, er Bygningen af det 24de Par hos meget store Exemplarer, saaledes som dette er beskrevet og af- bildet af Prof. Lilljeborg. Legemets Farve er hos fuldvoxne Exemplarer mere eller mindre tydelig olivengron, gaaende paa Bugsiden og paa Fodderne over til gulrodt. Selve Skallen er lyst hornfarvet og temmelig gjennem- sigtig, dog meget constant med Dorsalkanten af en ret ioinefaldende mork graasort Farve. Indre Organer. Paa Grund af denne Forms store Gjennemsigtig- hed, vil den indre Organisation ret vel kunne stu- deres, navnlig paa levende Exemplarer, tildels ogsaa paa vel preserverede Spiritusexemplarer, uden at nogen Dissection strengt taget er fornoden. Kun hvor det gjelder en mere detailleret (histologisk) Undersogelse af Organerne, vil det vere nyttigt at skride til en Sonderlemmelse af Dyret. Med den seedvanlige Indleirings- og Snitmethode kommer man ikke synderlig vidt, og denne i vor Tid i saa stor Udstrekning anvendte Undersogelses- methode synes idethele at vere lidet anvendelig, hvor det gjelder Krebsdyr. Fordgielsesapparat. — Tarmen strekker sig som et nogenlunde jevnt tykt Ror gjennem hele Dyrets Legeme, og skinner meget tydeligt igjennem Inte- gumenterne ved dens sedvanligvis morke Contenta (se Tab. XV, Fig. 1). Den ender i Halen med en kort, sterkt muskulos Endetarm, som udmunder paa Halens Spids, mellem Haleklorne. I Nakkesegmentet gjor Tarmen en pludselig, nesten vinkelformig Boi- ning nedad, i Overensstemmelse med Legemets steerke Krumning paa dette Sted. Tarmens Indhold er i denne forreste Del seedvanligvis lysere, orangefarvet eller blegt gulagtigt. Spiseroret er ganske kort og passerer fra Mundaabningen lige fortil, hvor det munder i Tarmens forreste Ende med en i dens Lumen fremspringende noget udvidet Del (se Fig. 9, oes). I Forbindelse med Tarmen staar et temmelig voluminost og compliceret kjertelagtigt Organ (Fig. 2, 3, 2), der udfylder en stor Del af Hovedets indre Hule, og aabenbart svarer til den hos Lepidurus ligeledes i Hovedet beliggende Lever. Ligesom hos Lepidurus, bestaar Organet af 2 symetriske Haly- from the others. It is very small, and its endopo- dite is quite short, with only 3 lobes inside in addi- tion to the coxal lobe. The bristles on these lobes, as also on the short rounded terminal joint, are greatly reduced in number. The epipodite is excee- dingly small and rudimentary, whereas the exopo- dite is comparatively well developed, reaching far out over the endopodite with its ventral lobe. It is edged with about 23 bristles of somewhat unequal length. The structure of the 24th pair found in very large specimens, though rather more simple, ‘is very similar, as described and figured by Prof. Lilljeborg. The colour of the body in full-grown specimens is more or less distinctly olive-green, merging into yellowish red on the ventral side and on the legs. The shell itself is of a light horn-colour, and toler- ably transparent, though the dorsal margin is almost invariably of a very conspicuously dark grey colour. Internal Organs. On account of the great transparency of this form, its internal organisation may be very easily studied, especially in living specimens, to a certain extent too, in well-preserved spirit specimens, with- out the necessity of dissection. Only when a more minute (histological) investigation of the organs is to be made, will it be useful to resort to a dismem- bering of the animal. By the ordinary imbedding and section method, not much information is to be gained, and this mode of investigation, now so widely employed, seems, on the whole, to be of very little use as regards Crustaceans. Digestive System.— The intestine runs, in the form of a tube of fairly even thickness, through the whole body of the animal, and is very distinctly seen through the integuments by reason of its gene- rally dark contents (see Pl. XV, fig. 1). It -termi- nates in the tail in a short, very muscular rectum, which opens out at the point of the tail, between the caudal claws. In the cervical segment, the inte- stine makes a sudden, almost angular bend down- wards, following the sharp curve of the body at that place.. The contents of the intestine in this foremost part. are generally lighter, of an orange or pale yellow hue. The csophagus is quite short and passes from the oral aperture straight for- wards, where it opens into the anterior end of the intestine by a somewhat expanded part projecting into its lumen (see fig. 9, oes). In connection with the intestine, there is a rather voluminous and eomplicated glandular organ (figs. 2, 3, 2) occupying a great part of the inner cavity of the head, and evidently answering to the liver in Lepidurus, which dele som hver udmunder med en kort Udforselsgang noget lateralt i Tarmens forreste Del, og i sin Peri- pheri er delt i talrige bugtede Blindsekke, ialminde- lighed fyldte med et intenst gultfarvet Stof. Hvert Organ udsender nedad en Sidegren, der i Hovedets ventrale Del, umiddelbart foran Basis af Overleben, oploser sig i flere uregelmessige Lappe. Hoved- massen af Organet ligger dog dorsalt, hvor det sammen med det tilsvarende Organ paa den anden Side danner en tilsyneladende sammenhengende Kalot over Tarmens forreste Del (se Fig. 2 og 3). Circulationsapparatet. — Hjertet (se Tab. XV, Fig. 1) er beliggende ovenover Tarmen i den forre- ste Del af Truncus, strekkende sig fortil ind i Nakkesegmentet, bagtil ind i det 4de fodberende Segment. Det har Formen af et fortil noget videre cylindriskt Ror, aabent i begge Ender, og desuden forsynet til hver Side med 4 tydelige Spaltaabninger, 1 Par for Nakkesegmentet, de 3 ovrige Par for de 3 forreste Segmenter af Truncus. Af nogen virke- lige Blodkar har jeg ikke kunnet finde noget Spor; men Blodet folger dog under sin Circulation i Lege- met visse meget bestemte Baner. Da Blodlegemerne er meget tydelige, er det ikke saa vanskeligt paa tilstrekkelig gjennemsigtige levende Exemplarer at studere de vesentligste Trek af Circeulationen, og jeg skal i det folgende i Korthed beskrive samme, saaledes som jeg har troet at finde den ved gjen- tagne omhyggelige Undersegelser. Fra den bagre Del af Legemet kommer en sterk Strom af Blod, der folger Rygsiden af Truncus og passerer direkte ind i Hjertet gjennem dettes bagre Aabning. Ved Hjertets Systole lukkes denne Aabning, saavelsom de laterale Spaltaabninger, og Blodet stedes med stor Kraft ud af Hjertets forreste Ende. En Del af den saaledes af Hjertet udkomne Blodmasse pas- serer direkte ind i den forreste Del af Legemet og forsyner Hovedet med dets forskjellige Vedheng med Blod. En anden Blodstrom boier pludselig om under Hjertet og lober bagover, umiddelbart neden- for den tilforende dorsale Blodstrom, lige til Hale- delen, hvor den synes at boie om paa Bugsiden af Dyret for at forsyne Branchialfodderne med Blod. En 3die betydelig Del af den fra Hjertet udstedte Blodmasse passerer til hver Side mod Skallens Lukke- muskel, hvor den i Omkredsen af Muskelareaen trenger ind i selve Skallen. Herfra fordeles Blodet rundt om i de to Valvler, idet det i forskjellige Baner gjennemstrommer det complicerede System af Hul- rum, der, som ovenfor anfort, findes mellem disses 2 Lameller. Efrerat have circuleret i Skallen sam- ler Blodet sig lidt efter lidt i 2 dorsale Hoved- stromme, der lober langs Rygkanten af Skallen, en ganske kort forreste, og en betydelig lengere 96 is there also situated in the head. As in Lepidurus. this organ consists of two symmetrical halves each opening by a short excretory duct somewhat later- ally in the anterior part of the intestine, and divided in its periphery into numerous cea, gene- rally filled with a substance of an intense yellow colour. Each organ sends down a lateral branch which is resolved into several irregular lobes in the ventral part of the head immediately in front of the base of the labrum. The great bulk of the organ, however, is situated dorsally, where, together with the corresponding organ on the other side, it forms an apparently continuous cap over the anterior part of the intestine (see figs. 2 and 3). Circulatory System. — The heart (see Pl. XV, fig. 1) is situated above the intestine in the anterior part of the trunk, extending forwards into the cer- vical segment, and backwards into the 4th pediger- ous segment. It has the shape of a cylindrical tube, rather wider in front, and open at both ends, and also furnished at each side with 4 distinct ostia, one pair for the cervical segment, the other 3 for the 3 foremost segments of the trunk. I have been unable to find any trace of actual blood-vessels, but during its circulation through the body, the blood follows certain fixed courses. As the corpuscles are very distinct, it is not difficult in sufficiently tran- sparent living specimens to study the principal fea- tures of the circulation, and I will here briefly describe them as I have found them by repeated careful investigations to be. From the hind part of the body comes a strong stream of blood, keeping to the dorsal side of the trunk, and passing directly into the heart through its posterior aperture. This aperture, as well as the lateral ostia, is closed by the heart’s systole, and the blood is ejected with great force from the anterior end of the heart. A portion of the quantity of blood thus issuing from the heart, passes directly into the anterior part of the body, and supplies the head and its various appendages with blood. Another stream of blood turns suddenly below the heart and flows back- wards immediately below the afferent dorsal stream right up to the caudal part, where it appears to turn to the ventral side of the animal, in order to supply the branchial legs with blood. A third con- siderable part of the quantity of blood ejected from the heart, passes on both sides towards the adductor muscle of the shell, where, within the circumference of the muscular area, it forces its way into the shell itself. From this the blood is distributed over the two valves, flowing by various courses through the complicated system of cavities which, as stated above, is found between their 2 lamelle. After having circulated in the shell, the blood gradually collects in two principal, dorsal streams which run along the dorsal edge of the shell, one quite short ‘Branchialfodder. 97 bagerste Strom. Begge modes ved det dorsale Liga- | anterior stream, and one considerably longer pos- ment, hvor de boier om indad og udtommer sit Blod, sammen med det fra Hovedet tilbagevendende, i den forreste Del af Hjertet gjennem dettes Iste Par Spaltaabninger. De ovrige 3 Far Spaltaabninger synes at optage det Blod, der, efterat have circuleret i Fodderne, vender tilbage til Hjertet. Respirationsapparat.-— Rent morphologiskt maa vistnok Foddernes Epipoditer ansees som de egent- lige Respirationsorganer, da de aabenbart svarer til Gjellerne hos hoiere Krebsdyr. Men da ogsaa de ovrige Dele af Fodderne viser en lignende over- maade delikat Struktur, har man Grund til at an- tage, at Respirationen ikke er udelukkende ind- skrenket til hine Vedheng, men foregaar overalt paa Foddernes Overflade, hvad der ogsaa har givet Anledning til den almindelig benyttede Benzvynelse Som det physiologiskt vigtigste Respirationsorgan maa vi dog utvivlsomt anse selve Skallen, i hvilken der, som ovenfor anfort, finder en meget livlig Blodcirculation Sted. Ved Foddernes rhytmiske Bevegelser sker der nemlig en stadig For- nyelse af Vandet indenfor Skallen, og da dette Vand umiddelbart beskyller den serdeles delikate Mem- bran, der bekleder Valvlerne indvendigt, synes alle Betingelser at veere tilstede for at en hurtig Gas- udvexling her kan ske med det indenfor Membranen strommende Blod. Nervesystemet. — Den i Hovedet beliggende Del af Nervesystemet er ikke vanskelig at obser- vere paa tilstrekkelig gjennemsigtige Exemplarer. Den bestaar af det saakaldte ovre Svelgganglion, eller Hjernegangliet, med de fra samme udgaaende Nerver. Selve Hjernegangliet er ikke af serdeles betydelig Storrelse, og ligger (se Tab. XV, Fig. 2) ‘temmelig langt tilbage i Hovedet, umiddelbart bag det enkle Wie, hvormed det forbinder sig med en temmelig bred Fortsats (se ogsaa Tab. XVI, Fig. 9, 10). Det bestaar, som sedvanlig, af 2 symetriske, med hinanden i Midtlinien forbundne Halvdele, hvoraf enhver er udtrukket i 2 divergerende, koni- ske Fortsatser. Fra de forreste Fortsatser udgaar de overordentlig lange og sterke Synsnerver og desuden en ganske liden Nerve for Giemusklerne. Selve Synsnerverne passerer fortil ind i Hovedets Pandedel, hvor enhver af dem svulmer ud til et kolleformigt Synsganglion. Begge Ganglier ligger tet sammen, uden dog at smelte sammen, og deres Ender er kun ubetydeligt fjernet fra de sammen- satte Wine (se Fig. 10). Fra dem udgaar talrige fine Nervefibre, der trenger ind i Minene og for- binder sig med disses enkelte Synselementer. De bagre Fortsatser af Hjernegangliet (a') er noget kortere end de forreste og mere udadrettede (se Fig. 10), men af en lignende konisk Form. De giver 13 — G. 0, Sars: Fauna Norvegizx. terior one. They meet at the dorsal ligament, where they turn inwards, and empty their blood, together with that running back from the head, into the an- terior part of the heart through that organ’s first pair of ostia. The 3 other pairs of ostia appear to receive the blood which, after having circulated in the legs, returns to the heart. Respiratory Organs. — From a purely morpho- logical point of view, the epipodites of the legs must be considered as the true respiratory organs, as they evidently answer to the gills in higher Crustaceans. But as the other parts of the legs also show a similar exceedingly delicate structure, there is reason to suppose that the function of respiration is not confined exclusively to these appendages, but is carried on over the entire sur- face of the leg, a circumstance which has given rise to the generally used term — branchial legs. As the physiologically most important organ of respi- ration however, we must undoubtedly regard the shell itself, in which, as stated above, a very active circulation of the blood goes on. By the rhythmical movements of the feet, a constant renewal of the water inside the shell takes place, and as this water is in immediate contact with the peculiarly delicate membrane lining the interior of the valves, all the conditions requisite for a rapid exchange of gas with the blood flowing within the membrane, appear to be present. Nervous System. — That part of the nervous system lying in the head is not difficult to observe in sufficiently transparent specimens. It consists of the so-called supra-cesophageal ganglion or cere- bral ganglion, with the nerves proceeding from it. The cerebral ganglion itself is of no very consider- able size, and is situated (see Pl. XV, fig. 2) rather far back in the head, immediately behind the ocel- lus, with which it is connected by a_ tolerably broad projection (see also Pl. XVI, figs. 9, 10). It consists as usual of 2 symmetrical halves connected with one another in the median line, each half being drawn out into 2 divergent conical protuber- ances. From the foremost of these issue the excee- dingly long and strong optic nerves, as also a very small nerve for the ocular muscles. The optic nerves themselves pass forwards into the frontal part of the head, where they each swell out into a club-like optic ganglion. These ganglia lie close together without however coalescing, and their extremities are at only a slight distance from the compound eyes (see fig. 10). Numerous delicate nerve-fibres issue from them, entering the eyes, and connecting themselves with the several visual ele- ments of those organs. The hind protuberances of the cerebral ganglion (a') are rather shorter than ‘the front ones, and directed more outwards (see Udspringet for Nerverne til 1ste Par Folere, nemlig en meget tynd Nerve for de i Basaldelen af disse Folere indtreedende Muskler, og en betydelig steerkere Nervestamme, der passerer ind i den kolleformige Endedel og til enhver af de laterale Lappe udsen- der talrige Fibrer (se Tab. XV, Fig. 5). Nerverne for 2det Par Folere (a*) udgaar ikke fra Hjerne- gangliet selv, men fra de fra samme bagtil udgaaende steerke Commissurer, der omgiver Spiseroret for at forbinde sig med Buggangliekjaden. Man kan tyde- ligt adskille 2 saadanne Nerver af omtrent ens Tykkelse og udspringende tet sammen, noget foran Midten af Commissurerne, som paa dette Sted viser en ganske svag ganglios Opsvulmning. Angaaende disse Nervers videre Forlob ind i selve Folerne, har det dog ikke veret mig muligt at skaffe mig noget tilfredsstillende Begreb. Den ovrige Del af Centralnervesystemet er meget vanskelig at observere og lader sig neppe hverken ved Dissection eller ved andre Methoder fremstille i sin Helhed. Jeg har imidlertid stykke- vis kunnet ngiere undersoge samme og fundet, at den, som hos Branchipodiderne, dannes af 2 vidt adskilte sterke Nervestammer, der passerer bagtil langs Bugsiden af Truncus og i hvert Segment er forbundne med 2 tynde Tvercommissurer. Nerve- stammerne viser paa dette Sted en ganske svag ganglios Opsvulmning og udsender udad, i adskillig Afstand fra hinanden, 2 sterke Nerver, hvoraf den ene treder ind i den respective Fod, medens den anden synes at udbrede sig i Kroppens Side- muskulatur. Forplantningsapparat. — Da alle hidtil obser- verede Exemplarer af denne Phyllopode har vist sig at vere af Hunkjon, har vi her kun at omtale Hunorganerne eller Ovarierne. Disse (se Tab. XV, Fig. 1) har Formen af 2 noget skrueformigt dreiede Ror, der strekker sig igjennem Storsteparten af Truncus, til hver Side af Tarmen, og ender bagtil med en ‘smalere spidst udlobende Del. Bagenfor Midten udgaar fra hvert Ovarium nedad en kort Agleder, der udmunder i Basis af den tilsvarende Fod af 1lte Par. Fra Overfladen af Ovarialrorene udgaar talrige smaa blindsekformige Udvidninger, som hos ganske unge Individer (se Tab. XVI, Fig. 15) viser et temmelig uniformt Udseende, medens de hos zldre Individer antager en meget forskjellig Udvik- ling og delvis grupperer sig paa en drueklaseformig Maade (se Fig. 16, 17). Disse Udvidninger er Ag- folliklerne, hvori AAggenes forste Dannelse foregaar. Undersoges disse Follikler noiere (se Fig. 18), vil man i deres Indre altid finde, som hos Lepidurus, 4 Celler combinerede, hvoraf blot den yderste bliver til det virkelige Mg, medens de 3 ovrige forestiller Neringsceller. Paa de mindste Follikler, der er nogenlunde cylindriske af Form, er alene de 4 Celle- 98 fig. 10), but are of a similar conical shape. From them originate the nerves for the 1st pair of an- tenn, viz., a very fine nerve for the muscles in the basal part of these antenne, and a much stronger nerve-stem which passes into the club-like terminal part, and sends off numerous fibres to each of the lateral lobes (see Pl. XV, fig. 5). The nerves for the 2nd pair of antenne (a?) do not issue from the cerebral ganglion itself, but from the strong com- missures running backwards from it, which surround the esophagus in order to join the ventral ganglion chain. Two such nerves can be clearly distinguished, of about equal thickness, and issuing close together a little in front of the middle of the commissures which here exhibit a very slight ganglionic swelling. ’ As regards the further course of the nerves in the. antenne themselves, it has not been possible for me to obtain any very satisfactory idea. The remainder of the central nervous system is very difficult to observe, and scarcely allows of being represented in its entirety, either by dissec- tion or by any other method. I have, however, been able to examine parts of it in detail, and have found that, as in the Branchipodide, it is formed of 2 widely-separated, strong neryve-stems, passing back- wards along the ventral side of the trunk, and connected in each segment with 2 thin transverse commissures. The nerve-stems here exhibit a very slight ganglionic swelling, and send out outwards, at a considerable distance from one another, 2 strong nerves, one of which enters the corresponding leg, ‘while the other seems to spread over the lateral musculature of the body. Sexual Organs. — As all the specimens of this Phyllopod hitherto observed have proved to be of the female sex, we have here only to describe the female organs or ovaries. These (see Pl. XV, fig. 1) are in the shape of 2 tubes, twisted somewhat after the manner of a screw, which extend through the greater part of the trunk on each side of the intes- tine, ending behind in a narrower, pointed part. Beyond the middle, a short oviduct issues in a downward direction from each ovary, opening one on each side at the base of the 11th leg. From the surface of the ovarial tubes, there issue numerous small cecal expansions, which in quite young speci- mens (see Pl. XVI, fig. 15) present a fairly uniform appearance, while in older animals they assume a very varied development, and are to a certain extent grouped in a botryoidal manner (see figs. 16, 17). These expansions are the egg-follicles, in which the earliest formation of the ova takes place. On a close examination of these follicles (see fig. 18) there will always be found inside them, as in Le- pidurus, 4 cells combined, of which only the outer one turns into a true ovum, while the other 3 represent alimentary cells. In the smallest follicles, 99 kjerner synbare; men meget snart sondres dog det | which are somewhat cylindrical in shape, only the til enhver Kjerne horende Plasma og afgrendser sig ved skarpt markerede Linier. Samtidigt begyn- der den terminale Celle hurtigt at voxe og fylder sig med et opakt kornet Indhold, medens de 3 ovrige Celler forbliver gjennemsigtige og omvendt reduceres i Storrelse, saa at de tilsidst kun er tilstede som ubetydelige Rudimenter ved den indre Side af den egentlige Aigcelle. Denne sidste naar tilsidst (se Fig. 17) en temmelig anselig Storrelse og fylder den hele Follikel, som nu springer frem fra Ovarialroret som en kugleformig, kort stilket Blere. Er Mggene ferdige, losnes de fra Folliklernes Vegge og treeder ind i Ovariernes Hule. I denne har der imidlertid ansamlet sig et opakt hvidagtigt Indhold (se Tab. XIV, Fig. 6), der paa friske Exemplarer viser sig overordentlig fint kornet, men paa Spiritusexemplarer hurtigt coagulerer til en compakt gulbrun Masse, der indtager Axen af Ovarialrorernes indre Hule og delvis ogsaa fortseetter sig ind i Auglederen. Dette Indhold synes at vere et Secretionsprodukt af Ovarialrorernes Veegge, bestemt til at afgive Mate- rialet til den eiendommelige Skal eller Kapsel, der senere omgiver hvert enkelt Mg. I Begyndelsen, efterat vere indkomne i Ovariernes indre Hule, er dog ggene endnu nogne, og antager derfor for- skjellige Former ved gjensidigt Tryk eller derved, at de passerer igjennem trangere Steder af Ovari- erne (se Tab. XVI, Fig. 16). De synes at opholde sig i Ovarialhulen i lengere Tid, og bliver herunder ved peristaltiske Bevegelser af Ovarierne skyvet frem og tilbage, hvorved deres Overflade kommer i intim Contact med det ovenomtalte Secret. Snart observeres ogsaa paa dem den forste Antydning til Skallen (se Fig. 19), og denne er ialmindelighed fuldt feerdig, skjondt endnu bled og boielig, forend Eggene gjennem Aglederen udfores af Legemet. De samler sig derefter umiddelbart over Truncus til en compact Masse, der holdes i Situs ved Hjelp af den traadformigt forlengede dorsale Lap af 9de til llte Fodpars Exopoditer (se Tab. XIV, Fig. 1, 2). Aigmassen, der ligger noget foran Midten af Skal- lens dorsale Hule, viser en temmelig uregelmessig Form, med den ovre Flade sterkt hvelvet, den nedre concav, og Kanterne uregelmessigt indskaarne. Den beres her af Dyret i lengere Tid, indtil Ag- kapslerne har naaet den fornodne Fasthed, og dens Farve forandres herunder gradvis fra en meget lys, hvidagtig til en mork hornbrun Couleur. De i den indeholdte Aig, der er holdte sammen ved et kleb- rigt Stof, er meget smaa og derfor i Regelen over- ordentlig talrige. De er hvert omgivet af en hoist eiendommeligt udseende og meget fast Kapsel af nesten turbinJignende Form (se Tab. XVI, Fig. 20, 21, 22), med 2 lodret paa hinanden stillede vinge- formige Udvidninger. Langs ad den ene af disse Udvidninger lober en tydelig fortykket Ribbe, hvor- 4 cell-nuclei are visible; but very soon the plasma belonging to each nucleus is separated and defined by clearly-marked lines. At the same time the ter- minal cell begins to grow quickly, and to be filled with contents of an opaque, granular character, while the 3 other cells remain transparent, and are inversely reduced in size, until at last they are only present as indistinct vestiges on the inner side of the egg-cell proper. The latter at last (see fig. 17) attains a very considerable size, and fills the whole follicle, which now projects from the ovarial tube like a spherical, short-stalked vesicle. When the ova are ready, they become detached from the walls of the follicles, and enter the cavities of the ovaries. Here an opaque, whitish matter has meanwhile collected (see Pl. XIV, fig. 6), which in fresh specimens appears to be very finely granular, but in spirit specimens rapidly coagulates into a compact yellowish-brown mass occupying the axis of the inner cavities of the ovarial tubes, and is also to some extent continued into the oviduct. This substance seems to be a secretive product of the walls of the ovarial tubes, designed to furnish the material for the peculiar shell or capsule which subsequently envelopes each ovum. At first, after having entered the inner cavities of the ovaries, the ova are still naked, and therefore assume various shapes resulting from reciprocal pressure, or from their passage through narrow parts of the ovaries (see Pl. XVI, fig. 16). They appear to remain for some time in the ovarial cavity, and, by peristaltic movements of the ovaries, are pushed backwards and forwards, their surfaces thus being brought into close contact with the above-mentioned secretion. The first indication of a shell is soon observable wpon them (see fig. 19), and, though soft and pli- able, it is quite perfect before the ovum is evacu- ated from the body through the oviduct. The ova then collect immediately above the trunk, into a compact mass, which is retained in position by the aid of the filiformly elongated dorsal lappet of the exopodite of the 9th, 10th and 11th pairs of legs (see Pl. XIV, figs. 1, 2). The egg-mass, which lies a little in front of the middle of the dorsal cavity of the shell, is of a rather irregular shape, with the upper surface highly convex, the lower concave, and the edges irregularly indented. It is carried here by the animal for some time, until the egg-capsules have acquired the necessary firmness, and during that time its colour gradually changes from a very light, whitish hue to a dark horny brown colour. The ova composing it are held together by a glu- tinous substance, and are very small and therefore generally exceedingly numerous. They are each enveloped in a very firm capsule of most peculiar appearance, and almost turbinate shape (see Pl. XVI, fra buede Sideribber udgaar til den modstaaende Udvidning, hvilken sidste ender med en tilskjerpet Kant og viser en fint cellulos Structur (se Fig. 23). Ved hvilke mekaniske Midler denne eiendommelige Form af Xgkapselen, der er noiagtig ligedan hos alle Ag, tilveiebringes, er ikke saa godt at sige. Rimeligvis spiller herved den skrueformige Dreining af Ovarialtuberne en vesentlig Rolle. AZgmassen bliver med visse Mellemrum, rimeligvis i Forbindelse med Hnudskiftningsakten, udstodt af Skallen, og fal- der derpaa tilbunds, hvor den indleires i Mudret. Imidlertid har Ovarierne produceret et nyt Set Mg, som snart samler sig til en ny Augmasse under den dorsale Del af Skallen. Paa denne Maade kan et og samme Individ i Lobet af nogle Uger producere et enormt Antal af Mg. Disse udklekkes dog i Regelen aldrig samme Aar, som de er lagte, men er alle bestemte til at overvintre; ja der er Grund til at antage, at de i mange Tilfelde kan henligge i en hvilende Tilstand gjennem meget lange Tids- rum, tildels fuldstendig indtorrede, for de ud- klekkes. Udvikling. — Om Udviklingen af denne Phyllo- pode har den franske Naturforsker Lereboullet i Aaret 18661) leveret en meget udforlig, af Afbild-. ninger ledsaget Fremstilling, hvortil senere Forskere altid har henholdt sig, uden at der, saavidt mig bekjendt, er anstillet fornyede Undersogelser over denne Side af nerverende Forms Biologi. Ogsaa Kjonsorganernes Bygning er af samme Forsker meget udforligt omtalt i samme Afhandling, men hans Fremstilling er her i flere vesentlige Punkter urigtig og misvisende. Da jeg har havt en sjelden god Anledning til at studere denne Forms Udvik- ling og tror i flere vesentlige Punkter at kunne supplere og berigtige den af Lereboullet givne Frem- stilling, skal jeg i det folgende forsoge noget ud- forligere at beskrive samme. Udviklingen kan passende inddeles i 2 Perioder, den larvale og postlarvale, begge vel markerede fra hinanden. Den forste Periode er tilendebragt i meget kort Tid, ialmindelighed i Lobet af nogle faa Dage, hvorimod der til den anden Periode udkreves mindst en hel Maaned. Larveudviklingen. — Larven kommer til Ver- den i en yderst ufuldkommen Tilstand, som en saa- kaldt Nauplius, uden at vise nogensomhelst Lighed med det voxne Dyr. Legemet har i dette Iste Sta- dium (Tab. XVII, Fig. 1) kun en Lengde af 0,25 mm. og bestaar af 2 ved en svag median Indknib- ning sondrede Afsnit af omtrent lige Storrelse. Det forreste Afsnit repreesenterer Hovedet, det bagerste *) Annales des Sciences naturelles, Zoologie, 5me Série, T. V, 100 figs. 20, 21, 22) with 2 wing-like expansions placed perpendicular to one another. Along one of these expansions runs a distinctly thickened rib, from which curved lateral ribs run to the opposite expan- sion, this last ending in a sharp edge, and exhibiting a finely cellular structure (see fig. 23). By what mechanical means this peculiar form of egg-capsule, which is exactly similar in all the ova, is brought about, it is not easy to say. Probably the screw- like twist of the ovarial tubes has much to do with it. The egg-mass, at certain intervals, probably connected with the process of exuviation, is thrust out, of the shell, and thereupon sinks to the bottom, where it is imbedded in the mud. In the meantime the ovaries have produced a new set of ova, which soon collect into a new egg-mass beneath the dorsal part of the shell. In this way, one animal, in the course of a few weeks, can produce an enormous number of eggs. These, however, as a rule, are never hatched in the same year that they are laid, but are all designed to stand a winter; indeed, there is reason to suppose that in many cases they may lie in a state of quiescence for very long periods of time, sometimes completely dried up, before they are hatched. Development. — The French naturalist Lere- boullet, in the year 1866+), published a very detailed account of the development of this Phyllopod, accompanied by illustrations; and more recent na- turalists have always referred to this, without, as far as I am aware, any fresh investigations on this point in the biology of the present form having been instituted. The structure of the sexual organs is also very fully described in the above treatise, but here his description, in many essential points is incorrect and misleading. As I have had an unu- sually good opportunity of studying the develop- ment of this form, and believe that in several important points I can supplement and correct the account given by Lereboullet, I will here endeavour to describe it somewhat more fully. The development may be suitably divided into 2 periods, the larval and the post-larval, both well- marked. The first period is brought to a conclusion in a very short time, generally in a few days, whereas at least a month is required for the second. . Larval Development. — The larva is brought into the world in an exceedingly imperfect condition, as a so-called nauplius, without exhibiting any resemblance whatever to the adult animal. The body in this 1st stage (Pl. XVII, fig. 1) has a length of only 0.25 mm., and consists of 2 sections of about equal size, defined by a slight median contraction. The front section represents the head, the hind one, the 1) Annales des Sciences naturelles, Zoologie, 5me Série, T. V. den ovrige Krop. Hovedet er temmelig tykt, lige- som opsvulmet i sit dorsale Parti, og stumpt afkuttet fortil, uden Spor af noget Rostrum. Det forlenger sig bagtil paa Undersiden i en meget voluminos Plade, der hvelver sig ud over Bugsiden af Dyret og ender i en smal, konisk tillobende Fort- sats. Denne Plade er den enormt udviklede Over- lebe (labrum). I det indre af Hovedet helt fortil bemerkes i Midten en meget ioinefaldende blodred Pigmentmasse af noget uregelmessig Form: det enkle Mie. Af de sammensatte Gine er der derimod intetsomhelst Spor at se. Af Lemmer findes kun 3 Par, de saakaldte Nauplius-Lemmer, alle tilhorende det forreste Afsnit af Legemet og representerende de 2 Par Folere og Mandibularfodderne. Det for- reste Par (a') (Iste Par Folere) er dog saa smaa og rudimentere, at de let kan oversees, og er heller ikke bemerkede af Lereboullet. De har Formen af 2 ubetydelige knudeformige Fremspring til hver Side af den forreste Ende af Hovedet og noget ventralt, hver forsynet med en enkelt delicat Foleborste (se ogsaa Fig. 5a). Det 2det Par Lemmer (a’), der re- presenterer 2det Par Folere, er derimod af serdeles betydelig Storrelse, forestillende et Par kraftigt ud- viklede, til Siderne udstrakte Aarer nesten af hele Legemets Lengde. Enhver af disse Lemmer bestaar af et tykt cylindriskt Skaft og 2 noget ulige ud- viklede Endegrene. Skaftet har ved Basis i Bag- kanten en konisk Fortsats, der ender med en kort borsteformig Spids, og ved dets Ende findes, lige- ledes i Bagkanten, en lignende, med en noget len- gere bagudkrummet Borste endende Fortsats. Af Grenene er den ovre eller forreste noget storre end den anden og omtrent af Skaftets halve Lengde. Den er noget opsvulmet paa Midten, nesten ten- formig, og viser en meget utydelig Leddeling, samt berer 5 leddede, men endnu ucilierede Svomme- berster, hvoraf de 3 udgaar fra tilsvarende Afsatser i den bagre eller ydre Kant, de 2 ovrige fra Spidsen. Den bagre Gren er simpelt cylindrisk og delt i 2 utydeligt sondrede Led, hvoraf det yderste har ved Spidsen 3 Borster af et lignende Udseende som de paa den forreste Gren. Det 3die Par Lemmer (Mp), de saakaldte Mandibularfodder, hvoraf intet Spor findes hos det voxne Dyr, udgaar omtrent fra Midten af Legemet, paa Greendsen mellem Hoved og Krop, og er ligesom 2det Par udstrakte til hver Side, skjondt sedvanlig noget mere bagudboiede. De udspringer hver fra en noget fortykket, knude- formigt fremspringende Basis, som forestiller det endnu uudviklede Corpus af Kindbakkerne. Hver Mandibularfod bestaar af 3 utydeligt sondrede Led, hvoraf det Iste er storst og forsynet i Bagkanten med 2 pigformige Borster. 2det Led berer en enkelt lignende Borste, og sidste Led i Spidsen 3 saadanne. Den bagenfor liggende Del af Legemet er uden Spor af Lemmer og af aflang oval Form, 101 remainder of the body. The head is rather thick and as it were swollen in its dorsal region, and is bluntly truncated in front, without any trace of a rostrum. It is produced posteriorly on the inferior side to a very voluminous plate, which arches over the ventral side of the animal and ends in a narrow, conical projection. This plate is the enormously developed upper lip (labrum). Inside the head, in the middle right in front, a rather irregularly- shaped, very conspicuous mass of blood-red pigment is visible, — the ocellus. On the other hand, there is no trace whatever of the compound eyes. There are only 3 pairs of limbs, the so-called nauplius limbs, all belonging to the anterior section of the body, and representing the 2 pairs of antenne, and the mandibular legs. The foremost pair (a) (the 1st pair of antenne) are, however, so small and rudimentary, that they can easily be overlooked, and have not, indeed, been noticed by Lereboullet. They are in the shape of 2 small, nodiform protu- berances one on each side of the front end of the head, and somewhat ventral, each furnished with a single delicate sensory bristle (see also fig. 5 a). The 2nd pair of limbs (a*), which represent the 2nd pair of antenne, are, on the other hand, of very considerable size, forming a pair of powerfully developed oars, extended laterally, and almost as long as the body. Each of these limbs consists of a thick cylindrical scape, and 2 rather unequally developed, terminal rami. At its base, in the hind margin, the scape has a conical projection, ending in a short, bristle-like point, and at its end, also in the hind margin, a similar projection ending in a rather longer bristle bending backwards. Of the two rami the upper or foremost one is rather larger than the other, being about half the length of the scape. It is somewhat swollen in the middle, almost fusiform, and exhibits a very indistinct arti- culation; it also carries 5 jointed, but not as yet ciliated natatory bristles, 3 of which issue from corresponding ledges in the hinder or outer margin, the other 2 from the point. The hind ramus is of a simple cylindrical shape, and is divided into 2 indistinctly defined joints, the outer of which has at its point 3 bristles similar in appearance to those on the front ramus. The 3rd pair of limbs (Mp), the so-called mandibular legs, of which no trace is to be found in the adult animal, issue from about the middle of the body, at the dividing line between the head and the trunk, and, like the second pair, extend one to each side, though gene- rally bent rather more backwards. They each issue from a somewhat thickened, nodiformly projecting base, which represents the still undeveloped body of the mandibles. Each mandibular leg consists of _ 8 indistinctly defined joints, of which the Ist is the largest, and is furnished, on the hind margin, with 102 med et lidet Indsnit i Enden (f). Af de ovenfor beskrevne Lemmer, der alle horer til Hovedet, er det forreste Par udelukkende Foleredskaber, medens de 2 ovrige Par, og navnlig det 2det, er Svomme- apparater, ved hvis Slag forfra bagtil Legemet stod- vis drives frem gjennem Vandet. Bevegelserne er dog i dette 1ste Stadium endnu temmelig afbrudte og ubehjelpelige. Forst efterat Larven har under- gaaet sin Iste Hudskiftning, og Svommeborsterne har faaet sin Ciliering, bliver Bevegelserne mere regelmessige og energiske. Angaaende den indre Organisation, saa lader sig herom lidet eller intet anfore, da der endnu kun synes at vere indtraadt en yderst ufuldkommen Differentiation af de for- skjellige Vev. Hele Legemet ligesaavelsom Lem- merne er fyldt med en amorph ensformig kornet Ma- terie, der giver Dyret en temmelig opak graalig Farve, uden at nogen indre Organer med Sikkerhed lader sig paavise. Vistnok bemerkes ofte i Axen af Legemet en svag gulagtig Tone, der kunde synes at antyde Tilstedeverelsen af Tarmroret; men dette er i ethvert Fald endnu ikke tydeligt afgreendset fra de omliggende Dele. Umiddelbart efter den iste Hudskiftning ser Larven saaledes ud som fremstillet Fig. 2 (fra Ryg- siden). Det bagre Afsnit af Legemet har nu for- lenget sig adskilligt og antaget en mere cylindrisk, eller noget konisk Form, og viser i nogen Afstand fra Enden en svag Indsnoring, ligesom antydende et terminalt Segment, svarende til Haledelen hos det udviklede Dyr. Bagtil har dette Segment en liden Indbugtning og gaar til hver Side af denne ud i en kort indadkrummet Fortsats. Hovedets Form er paa det nermeste uforandret, og ogsaa Lemmerne af en lignende Bygning som hos Iste Stadium, dog med den Forskjel, at alle Svomme- berster paa 2det Par nu er fint cilierede, og at de 2 fra Skaftet udgaaende Fortsatser begge har an- taget Formen af sterke, bagudkrummede Borster, hvoraf navnlig den inderste er kraftigt udviklet og tet cilieret i sit ydre Parti. Ogsaa de 3 laterale Borster paa Mandibularfodderne er nu grovt cilierede, medens de 3 Endeborster synes at mangle Ciliering. Overlebens terminale Fortsats har forlenget sig adskilligt, saa at den rekker noget ud over Lege- mets bagre Ende. Legemet er endnu fyldt med en lignende amorph kornet Materie som i 1ste Stadium, men Tarmroret er dog nu tydligere sondret og viser sig betydelig tykkere fortil end bagtil. Larven, der nu har en Leengde af 0,36 mm, svommer temmelig raskt om i Vandet ved rhytmiske Slag af 2det Par 2 spiniform bristles. The 2nd joint carries one such bristle, and the last joint, at its extremity, 3. The part of the body lying behind has no trace of limbs, and is of an oblong oval shape, with a small emargination at the extremity (f). The foremost pair of the above-described limbs, all of which belong to the head, are exclusively sensory organs, while the other 2 pairs, and the 2nd in particular, are swimming implements, by whose strokes from front to back, the body is driven forward by jerks through the water. The movements in this 1st stage, however, are still rather intermittent and awkward. Only when the larva has undergone its first exuviation, and the natatory bristles have become ciliated, do its movements become more regular and energetic. Concerning the internal organisation there is little or nothing to be said as only an exceedingly imperfect differentiation of the various tissues appears as yet to have taken place. The whole of the body, as well as the limbs, is full of an amorphous, uniform, granular matter, which gives the animal a rather opaque, grayish colour, without allowing any of the internal organs to be made out with certainty. It is true that in the axis of the body a faint yellow tinge may often be observed, which might seem to indicate the presence of the intestinal tube; but this is at any rate not distinctly marked off from the surrounding parts. Immediately after the Ist exuviation, the appea- rance of the larva is as represented in fig. 2 (from the dorsal surface). The hind section of the body has now lengthened considerably, and has assumed a more cylindrical, or somewhat conical shape, and at some distance from the end it exhibits a slight constriction, as though indicating a terminal seg- ment, answering to the caudal part of the fully- developed animal. At the tip, this segment has a small sinus, and goes out on each side into a little incurved projection. The shape of the head is as nearly as possible unchanged, and the structure of the limbs is very similar to that in the Ist stage, yet with the difference that all the natatory bristles on the 2nd pair are now finely ciliated, and that the 2 projections issuing from the scape have both assumed the shape of strong, backward-curving bristles, of which the inner one is more powerfully developed and thickly ciliated in its outer part. The 3 lateral bristles on the mandibular legs are also now coarsely ciliated, while the 3 terminal bristles seem to be destitute of cilia. The terminal protu- berance of the labrum has lengthened considerably, so that it extends somewhat beyond the hind end of the body. The body is still full of an amorphous, granular matter like that in the first stage, but the intestinal tube is now more distinctly defined, and appears considerably thicker in front 103, Folere og delvis ogsaa Mandibularfodderne, hvorved snart Ryg- snart Bugside vendes opad. Et noget senere Stadium er fremstillet Fig. 3 fra Bugsiden. Larven har nu naaet en Lengde af 0,47 mm og har Legemets bagre Afsnit end mere forlenget, skjondt fremdeles uden Spor af Lemmer. De terminale Fortsatser, som aabenbart svarer til Haleklorne hos det voxne Dyr, har strakt sig be- tydeligt i Lengde og er skilt ved et dybt Indsnit, i hvis Bund Analaabningen er beliggende. I det indre af Overleben sees flere meget tydelige celle- agtige Legemer, aabenbart af kjertelagtig Natur, og dens terminale Fortsats er nu fuldkommen saa lang som den proximale Del af Overleben og skraat nedadrettet. Mandibularfoddernes Rodstykke har sondret sig skarpere fra Legemet og forlenget sig indad mod Mundaabningen, hvorved det nu meget tydeligt viser sig at representere Kindbakkernes Corpus. Selve Lemmerne synes dog ikke at have undergaaet nogen vesentlige Forandringer i sin Structur. Legemet er i dette Stadium betydelig mere gjennemsigtigt end i de 2 foregaaende Stadier og neesten vandklart, saa at den med gulfarvet Indhold fyldte Tarmkanal med stor Tydelighed skinner igjennem de tynde Integumenter. Fig. 4 fremstiller (fra Rygsiden) et betydelig senere Stadium, som er nerved at skifte Hud. Lar- ven har nu en Lengde af 0,65 mm. og har under- gaaet flere vesentlige Forandringer. Legemet er idethele temmelig langstrakt, og det bagre Afsnit, uden at regne de terminale Fortsatser, dobbelt saa langt som det forreste, fra hvilket det er sondret ved en meget tydelig Indknibning. I det indre af Hovedet viser sig nu det forste Spor af de sammen- satte Gine i Form af 2 smaa, endnu vidt adskilte Pigmentpletter, der ligger til hver Side og noget ovenfor det enkle Mie. Lereboullet har ment, at de sammensatte Mine dannedes ved en Afspaltning fra det enkle @ie, hvad der er aldeles urigtigt. De dannes ganske uafhengigt af det enkle Mie, der baade hvad Storrelse og Form angaar, er fuldkom- men uforandret. Af Lemmerne er Iste Par fuld- kommen af samme Udseende som hos de tidligere Stadier, men synes at vere rykkede noget lengere ned paa Bugsiden. Paa 2det Par har den basale Fortsats klovet sig i Enden i 2 borsteformige, tet cilierede Spidser, og den bagre Gren har faaet en Svommeborste flere paa Spidsen. Mandibularfodderne viser nu alle sine 3 Led meget tydeligt begraendsede, og den fra nestsidste Led udgaaende Borste har than behind. The larva, which is now 0.36 mm. in length, swims ahout with tolerable rapidity in the water, with rhythmical strokes of the 2nd pair of antenne, and partly of the mandibular legs, whereby now the dorsal, now the ventral surface is turned uppermost. A somewhat later stage is represented in fig. 3, from the ventral surface. The larva has now attained a length of 0.47 mm. and has the posterior section of the body even more elongated, though still without a trace of limbs. The terminal pro- jections, which evidently answer to the candal claws in the adult animal, have increased considerably in length, and are separated from each other by a deep emargination, at the bottom of which the anal aperture is situated. Inside the labrum are visible several very distinct cellular bodies, evidently of a glandular nature; and its terminal projection is now fully as long as the proximal part of the labrum, and directed obliquely downwards. The basal part of the mandibular legs has become more sharply divided from the body, and is produced inwards towards the oral aperture, thereby showing very clearly that it represents the body of the mandibles. The limbs themselves, however, do not seem to have undergone any essential change in their structure. The body in this stage is consider- ably more transparent than in the two preceding stages, being almost as clear as water, so that the intestinal canal, with its yellow-coloured contents, shows with great distinctness through the thin integuments. Fig. 4 represents (from the ventral surface) a very much later stage, when the animal is about to cast its skin. The larva now has a length of 0.65 mm., and has undergone several important changes. The body is on the whole rather elon. gated, and the posterior section, not including the terminal projections, is twice as long as the ante- rior, from which it is separated by a very distinct contraction. Inside the head, the earliest traces of the compound eyes now appear in the shape of two small, and as yet widely-separated spots of pigment, lying one on each side, and somewhat above the ocellus. Lereboullet thought that the compound eyes were formed by a splitting off from the ocellus, a theory which is altogether incorrect. They are formed quite independently of the ocellus, which, both as regards size and shape, is altogether unchanged. The Ist pair of limbs is of exactly the same appearance as in the earlier stages, but they seem to have moved a little farther down on the ventral surface. In the 2nd pair, the basal projec- tion has divided at the end into 2 bristle-like, thickly ciliated points, and the posterior ramus has acquired another natatory bristle at the point. The man- dibular legs now show all their 3 joints very antaget en pigformig Character, dannende den umid- delbare Fortsettelse af Leddet. Den terminale Fort- sats af Overleben, ligesom de nu steerkt forleengede Halefortsatser viser sig rundtom tet besatte med korte Pigge. Paa det bagre Afsnit af Legemet be- meerkes de forste Anleg til Rygskjoldet og til de 6 forreste Par Fodder. Alle disse Dele er dog endnu dekkede af Larvehuden, som uden nogensomhelst Afbrydelse strekker sig over dem. Rygskjoldet (den senere Skal) har Formen af 2 smaa, endnu ikke med hinanden dorsalt forbundne afrundede Folde helt fortil, i hvis Indre den forste Antydning til Skalkjertelen lader sig paavise. Fodderne har endnu kun Udseende af en Rekke af 6 ubetydelige knop- formige Fremspring langs Siderne af Kroppen umid- delbart bag Anlegget til Rygskjoldet. De aftager successivt i Storrelse bagtil, og de 2 sidste Par er kun meget svagt antydede. I det indre af det ser- deles gjennemsigtige Legeme sees nu Tarmkanalen med stor Tydelighed. Den har bagtil sondret en vel begreendset, sterkt muskulos Endetarm, og gaar fortil ud i 2 korte blindsekformige Udvidninger: den forste Begyndelse til den senere saa complicerede Lever. De forskjellige Muskler, der tjener til Aarernes og Mandibularfoddernes Bevegelse kan nu med stor Tydelighed adskilles, og Larven beveger sig ogsaa i dette Stadium adskilligt mere energiskt end i de tidligere. I det neste her afbildede Stadium (Fig. 5) har Larven en Lengde af 0,87 mm, og viser en videre Udvikling af det bagre Afsnit af Legemet, som nu, inclusive de terminale Forsatser, er over 3 Gange saa langt som det forreste. De Dele, der paa fore- gaaende Stadium, viste sig umiddelbart indenfor Larvehuden, nemlig Rygskjoldet og de 6 Par Fod- knuder, treder nu alle frit frem fra Legemets Over- flade og har tiltaget noget iStorrelse. De sammen- satte ine er ligeledes betydelig sterre og er ryk- kede noget nermere sammen, skjondt de endnu er skilte i Midten ved et tydeligt Mellemrum. Ethvert af dem er nu omgivet af en klar Bram, hvori senere de enkelte Synselementer udvikler sig. I Bygningen af de 3 Par oprindelige Nauplius-Lemmer viser ikke Larven nogen vesentlige Forskjelligheder fra samme hos det sidst beskrevne Stadium. En Foler af Iste Par er afbildet meget sterkt forstorret Fig. 5a; den viser, som det vil sees, fuldkommen det samme rudimentere Udseende som hos de yngste Larver. Fig. 6 fremstiller en Larve i et senere Stadium, seet fra venstre Side, med den tilsvarende Aare udeladt, for at vise de af denne dekkede Dele af Hovedet tydeligere. Larvens Lengde er lidt over 1mm. De 2 Afsnit af Legemet viser sig meget 104 | distinctly defined, and the bristle projecting from the last joint but one has acquired a spiniform character, forming the immediate continuation of the joint. The terminal protuberance of the labrum, as also the now greatly elongated caudal projections, appear thickly covered all round with short spines. On the posterior section of the body, the earliest rudiments of the carapace and of the 6 foremost pairs of legs are observable. All these parts, how- ever, are still covered by the larval skin, which is stretched over them without any interruption what- ever. The carapace (the future shell) is in the shape of 2 small, rounded folds right in front, and not connected dorsally with one another, inside which the earliest indication of the shell-gland may be made out. The legs have still only the appea- rance of a row of 6 small, bud-like projections along the sides of the body, immediately behind the rudiment of the carapace. They diminish in size successively behind, and the last 2 pairs are only very faintly indicated. In the interior of the exceedingly transparent body, the intestinal canal is now seen with great distinctness. Posteriorly, a well-defined, very muscular rectum has been di- vided off, and in front, it forms 2 short ceecal expan- sions, — the earliest commencement of the subse- quently so complicated liver. The different muscles employed in the motion of the oars and the mandi- bular legs, can now be very clearly distinguished, and the larva moves much more energetically in this stage than in the earlier ones. In the next stage represented here (fig. 5) the larva has a length of 0.87 mm. and exhibits a further development of the posterior section of the body, which now, including the terminal projections, is more than 3 times as long as the anterior sec- tion. Those parts which in the preceding stage appeared immediately within the larval skin, viz. the carapace and the 6 pairs of pedal buds, now all project freely from the surface of the body, and have somewhat increased in size. The compound eyes are also considerably larger, and have moved a little nearer together, though they are still sepa- rated in the middle by a distinct space. They are both surrounded by a clear rim, in which the visual elements are subsequently developed. In the struc- ture of the 3 pairs of original nauplius limbs the larva presents no essential difference from those in the last-described stage. One antenna of the Ist pair is shown, very highly magnified, in fig. 5 a; as will be seen, it presents exactly the same rudi- mentary appearance as in the youngest larva. Fig. 6 represents a larva in a later stage, seen from the left side, with the left oar omitted in order to show more distinctly those parts of the head which it covers. The length of the larva is a little over 1 mm. The 2 sections of the body appear r ————— ee 105 tydeligt sondrede, idet der mellem dem ogsaa dor- salt er en temmelig dyb Indbugtning. Hovedet er jevnt hvelvet oventil og afrundet fortil, med et stumpt Fremspring nedenfor det enkle @ie, forestil- lende Anlegget til Rostrum. Umiddelbart bag dette Fremspring sees de endnu knudeformige 1ste Par Folere at udgaa. Bag disse igjen rager den enormt udviklede Overlebe frem, med sin skraat nedad- rettede pigformige Endefortsats. Ved dennes Basis er der indad en liden cilieret Lap, der seedvanligvis er boiet ind mod Mundaabningen og som svarer til den verticalt stillede Endelamelle hos det voxne Dyr. Til hver Side af Mundaabningen sees de nu vel udviklede Kindbakker, fra hvis ydre Side Man- dibularfodderne udgaar, og umiddelbart bag dem igjen viser sig Anlegget til de 2 Par Kjever. Ryg- skjoldet har nu udviklet sig til en kappeformig Hudduplicatur, bestaaende af 2 symetriske Halvdele skilte bagtil i Midten ved en dyb Indbugtning. Det har nu tydeligt sondret sig ogsaa fortil; men de 2 Halvdele gaar ganske umerkeligt over i hin- anden dorsalt, uden at der endnu er nogen tydelig Sondring af 2 Valvler. De sig udviklende Fodder, der nu fuldstendig dekkes oventil af Rygskjoldet, har forlenget sig til noget polseformige Fortsatser, der er rettede skraat bagtil og ligger tet sammen. Den bagerste Del af Kroppen er ganske svagt om- beiet mod Bugsiden og begynder at sondre sig som en tydelig Haledel. De terminale Fortsatser viser sig nu klarlig at vere identiske med de senere be- vegeligt til Enden af Haledelen indleddede Hale- klor. I nogen Afstand fra dem paa Dorsalsiden har allerede Haleborsterne udviklet sig; derimod er der endnu ikke noget Spor af de for det voxne Dyr characteristiske tandede Haleplader. Af de For- andringer, der er foregaaet med den indre Organi- sation kan nevynes, at de i tidligere Stadier simple _blindsekformige Udvidninger af Tarmens forreste Del har hver sondret sig i en dorsal og en ventral Lap, og at Hjertet har dannet sig i den forreste Del af Truncus. Sidste Larvestadium er fremstillet Fig. 7, fra Rygsiden. Legemet har nu en Lengde af 1,14 mm. og ligner idethele samme hos de 2 foregaaende Sta- dier, dog med den Forskjel, at Hovedets Pandedel er noget mere fremspringende, og at Rygskjoldet er betydelig storre. Dette sidste dekker nu som en bred Kappe Storsteparten af Truncus tilligemed de til samme horende Lemmer oventil og har bagtil et dybt Indsnit. Fodderne, hvis Antal fremdeles -kun er 6 Par, er endnu fuldstendig ubevegelige, men har nu sondret sig i sine respective Hoved- -afsnit, hvoraf navnlig Epipoditerne er meget tyde- lige i Dyrets dorsale Stilling. Fra Enderne af Fod- derne er allerede korte Borster begyndt at spire 14 — G. 0. Sars: Fauna Norvegiz. very distinctly defined, as there is, dorsally too, a rather deep hollow between them. The head is evenly arched above and rounded in front, with a blunt projection below the ocellus, representing the rudiment of the rostrum. Immediately behind this projection, the still nodiform 1st pair of antenne are seen to issue. Behind them again, projects the enormously developed labrum, with its spiniform terminal protuberance directed obliquely downwards. At its base inside, there is a little ciliated lobe, which is usually bent in towards the oral aperture, and which corresponds to the vertically-placed ter- minal lamella in the full-grown animal. On each side of the oral aperture are seen the now well- developed mandibles, from the outer side of which issue the mandibular legs, and immediately behind them again, appear the rudiments of the 2 pairs of maxille. The carapace has now developed into a hood-shaped cuticular duplicature, consisting of 2 sym- metrical halves, separated behind in the middle by a deep depression. It has also become well defined in front, but dorsally the two halves run quite imperceptibly into one another, without as yet any distinct division into 2 valves. The developing legs, which are now completely covered above by the carapace, have lengthened into somewhat sausage- shaped protuberances, directed obliquely backwards, and lying close together. The hinder part of the body is very slightly bent down towards the ventral surface, and begins to be marked off as a distinct caudal part. The terminal projections now show themselves clearly to be identical with the caudal claws subsequently movably articulated to the end of the caudal section. At some distance from them on the dorsal side, the caudal bristles have already developed, whereas there is as yet no trace of the dentated caudal lamelle characteristic of the adult animal. Among the changes that have occurred in the internal organisation, it may be mentioned that the simple cecal expansions of the front part of the intestine in earlier stages, have become marked off into a dorsal and a ventral lobe, and that the heart has been formed in the anterior part of the trunk. In fig. 7, the last larval stage is represented, seen from the ventral surface. The body now has a length of 1,14 mm., and on the whole resembles that in the 2 preceding stages, though with these differences, viz., that the frontal part of the head is rather more prominent, and that the carapace is considerably larger. The latter now covers like a broad mantle the upper portion of the greater part of the trunk and limbs, and has a deep emargina- tion behind. The legs, which still only number 6 pairs, are as yet quite immovable, but are now divided into their respective principal parts, of which no- tably the epipodites are very distinct in the ani- mal’s dorsal position. From the extremities of the frem, og, sees Dyret fra Bugsiden, lader ogsaa Coxallappene sig tydeligt adskille. De sammensatte Qine er nu rykkede ner sammen, og i den periphere Area har allerede Synselementerne begyndt at danne sig. Larven beveger sig om i. Vandet paa fuld- kommen samme Maade som i tidligere Stadier. Be- vegelsen tilveiebringes hovedsageligt ved 2det Par Folere eller Aarerne, ved hvis rhytmiske Slag for- fra bagtil Legemet drives frem gjennem Vandet paa en eiendommelig stodvis Maade. Ved hvert Slag af Aarerne fores deres basale indadkrummede Fortsats ind mellem Overleben og Kroppen, saa at de 2 borsteformige Spidser kommer i Contact med Mund- regionen, og det synes derfor som om denne Fort- sats har en vesentlig Betydning ved Neringsopta- gelsen. lLarvetilstanden er nu endt, og med den umiddelbart folgende Hudskiftning begynder den 2den Periode i Dyrets Udvikling, den postlarvale Tilstand. Postlarval Udvikling. — Fig. 8, 9 fremstiller Iste postlarvale Stadium, hvilket folger umiddelbart paa det ovenfor beskrevne sidste Larvestadium, idet kun en enkelt Hudskiftning betegner Grendsen mellem begge. Og dog viser Dyret nu et totalt forskjelligt Udseende, ligesom dets Maade at bevege sig paa er meget afvigende. Man har nu ikke syn- derlig Vanskelighed ved i det at erkjende en ung Limnadia, skjondt der endnu er tilbage nogle Spor fra Larvetilstanden.- Hyad der vesentlig charac- teriserer dette Stadium ligeoverfor Larvestadierne, er den betydelige Udvikling af Rygskjoldet, som nu har omformet sig til en tydeligt tveklappet Skal, der bedekker Storsteparten af Legemet, ikke blot oventil, men ogsaa til Siderne. Skallen er dog endnu ikke saa stor, at Legemet kan fuldstendig inddrages i samme, saaledes som Tilfeeldet er med fuldt udviklede Exemplarer, og Hovedet, ligesom ogsaa Halen er derfor altid ubedekkede. En anden veesentlig Forandring bestaar i Reductionen af Man- dibularfodderne og den fuldsteendige Mangel af de 2 fra Aarernes Skaft udgaaende bagudboiede Fort- satser. Endelig maa anfores som en veesentlig Cha- racter, at de hos Larven fuldkommen ubevegelige Branchialfodder nu er traadt i Virksomhed, ud- forende sine rhytmiske svingende Bevegelser. Leeng- den af Legemet, maalt fra Panden til Enden af Haleklorne er 1,14 mm, eller noiagtig den samme som hos Larven i sidste Stadium. Men medens Skal- len hos dette sidste Stadium kun var 0,40 mm. lang og neppe mere end halvt saa hoi, har den nu en Lengde af 0,70 mm. og en Hoide af 0,60 mm. Den er ganske klar og. gjennemsigtig, uden Spor af de hos voxne Exemplarer forekommende concentriske Linier, ligesom Formen er noget afvigende. Seet fra Siden (se Fig. 9) viser den en-uregelmessig af-_ 106 | | ‘ner as in the earlier stages. legs, short bristles have already begun to shoot forth, and when the animal is seen from the ventral surface, the coxal lobes may also be distinguished clearly. The compound eyes have now moved close together, and in the peripheral area the visual ele- ments have already begun to form. The larva moves about in the water in exactly the same man- The movement is brought about chiefly by the 2nd pair of antenne or the oars, by whose rhythmical strokes from front to back the body is propelled through the water in a peculiar, jerky manner. At each stroke of the oars, their basal, incurved projection is carried in between the labrum and the body, so that the 2 bristle-like points are brought into contact with the oral region. It therefore seems as though this projection was of essential importance in the admis- sion of food. The larval condition is now termi- nated, and with the immediately succeeding exuvia- tion begins the 2nd period in the animal’s develop- ment, the post-larval condition. Post-larval Development. — Figs. 8 and 9 repre- sent the first post-larval stage, which follows imme- diately after the above-described last larval stage, only a single exuviation marking the boundary be- tween the two. And yet the animal now presents a totally different appearance, its manner of moving being also very different. There is very little diffi- culty now in recognising in it a young Limnadia, although there are still some traces left of its larval -condition. What principally characterises this stage as compared with the larval stages is the consider- ‘able development of the carapace which is now ‘transformed into a distinctly bi-valved shell, cover- -ing the greater part of the body, not only above, but also at the sides. The shell, however, is not yet so large as to allow of the body being completely withdrawn into it, as is the case with fully deve- loped animals; the head therefore, and the tail are always uncovered. Another essential change con- sists in the reduction of the mandibular legs and the total absence of the 2 backward-curved projec- tions from the scape of the oars. Lastly, it must be mentioned as an essential character that the quite immovable branchial legs in the larva have now begun to act by performing their rhythmical, swinging movements. The length of the body, mea- sured from the frontal part to the end of the caudal claws is 1.14 mm., or exactly the same as that of the larva in the last stage. But while the shell in that stage was only 0.40 mm. long, and scarcely more than half as high, it now has a length of 0.70 mm. and a height of 0.60 mm. It is quite clear and transpa- rent, without a trace of the concentric lines occurring in fullgrown animals, and the shape is somewhat diffe- rent. Seen from the side (see fig. 9), it shows an irre- gular, rounded shape, with the upper margin where the rundet Form, med den ovre Kant, hvor Valvlerne stoder sammen, neesten ret og endende saavel fortil som bagtil med et tydeligt fremspringende Hjorne. Ovenfra seet (se Fig. 8) viser den sig temmelig buget, idet Breden nesten er lig Hoiden. Til hver Side sees Skalkjertelen med den umiddelbart foran samme liggende Muskelarea med stor Tydelighed, og paa Grund af Skallens store Gjennemsigtighed treeder ogsaa den af samme bedekkede Del af Lege- met klart og tydeligt frem. Man kan nu paa Lege- met adskille alle de Afsnit, som ovenfor er beskrevet hos det voxne Dyr. Dog er Nakkesegmentet endnu temmelig kort, og Truncus kun lidet lengere end det forreste Afsnit af Legemet. Hovedet har en fra samme hos det voxne Dyr temmelig afvigende Form. Dets ovre Flade er noget uregelmessigt hvelvet og endnu uden Spor af det characteristiske stilkede Fastheftningsorgan, som forst senere dan- nes ved en gradvis Afsnoring af en Del af Hovedets Dorsalparti. Pandedelen er endnu kun lidet frem- springende, og mellem den og det stumpt tilrundede Rostrum er der neppe engang den svageste Indbugt- ning at se. Af Hovedets Vedheng er iste Par Fo- lere lidt mere forlengede end hos Larverne, men endnu forholdsvis smaa og uden laterale Lappe. 2det Par Folere, eller Aarerne, har, som ovenfor anfort, tabt baade den bagudbgiede Borste ved Enden af Skaftet og den tvedelte basale Fortsats. For- ovrigt stemmer de, saavel hvad Skaftets som Gre- nenes Bygning angaar, temmelig ner overens med samme hos Larverne, alene med den Forskjel, at der i Yderkanten af den ovre Gren har udviklet sig en kort Pig, hvoraf intet Spor var at se hos hine. Overleben er nu betydelig reduceret i Storrelse og har antaget det for det voxne Dyr characteristiske Udseende, idet den lange, dolkformige Endedel er svundet ind til en forholdsvis liden tentakelformig Fortsats. Paa Kindbakkerne er der endnu igjen et Rudiment af Mandibularfodderne i Form af et til deres Yderside festet ubetydeligt koniskt Appendix uden Spor af Leddeling eller Borstebesetning. Bag Kindbakkerne sees de 2 Par Kjever, som nu, lige- som Kindbakkerne, er i fuld Virksomhed med at bearbeide den optagne Nering. De hos Larven an- lagte 6 Par Branchialfodder er nu functionsmessigt udviklede, udforende sine characteristiske svingende Bevegelser for Respirationens og Neringsoptagel- sens Formaal, og bag dem er der endnu Anleg til 3 eller 4 Par nye Fodder. -Haledelen er endnu kun svagt omboiet og Haleklorne ufuldstendigt son- drede fra Haleenden. De har hver ner Basis en enkelt kort Sidetand, og umiddelbart ovenfor dem udgaar fra Halens Dorsalside 2 meget smaa jevn- sides stillede Fremspring, som forestiller det forste Anleg til de tandede Haleplader. Ovenfor Hale- borsterne har der endvidere udviklet sig et enkelt Par af de hos det voxne Dyr her forekommende 107 _ to be seen. valves meet, almost straight, and ending both in front and behind in a distinctly projecting corners Seen from above (see fig. 8), it appears rather bulging, its breadth being almost equal to its height. On each side is seen the shell-gland very distinctly, with the muscular area lying immediately in front of it; and on account of the great trans- parency of the shell, that part of the body which it covers is seen very clearly and distinctly. All the sections of the body described above in the adult animal, can now be distinguished. The cervi- cal segment, however, is still rather short, and the trunk only a little longer than the foremost section of the body. The head has a rather different shape to that in the adult animal. Its upper surface is somewhat irregularly arched, and still without a trace of the characteristic stalked organ of attach- ment, which is formed, but not until later, by a gradual constriction of a part of the dorsal region of the head. The frontal region still projects only slightly, and between it and the bluntly rounded rostrum, there is scarcely even the slightest hollow Among the appendages of the head, the first pair of antenne is a little more elongated than in the. larva, but still comparatively small and without lateral lobes. The 2nd pair of antenne, or the oars, have, as stated above, lost both the backward-curved bristle at the end of the scape and the bifid basal projection. In other respects they agree very closely, as regards the structure of both the scape and the rami, with those limbs in the larva, with the one difference that in the outer margin of the upper ramus a short spike has deve- loped, of which there was no trace in the larva. The labrum is now considerably reduced in size, and has assumed the appearance characteristic of the adult animal, the long, ensiform terminal part having shrunk into a comparatively small, tenta- cular projection. There is still a rudiment of the mandibular legs left on the mandibles in the form of an indistinctly conical appendage, — without a trace of articulation or bristles, — attached to their outer side. Behind the mandibles are seen the 2 pairs of maxille, which now, like the mandibles, are in full activity, manipulating the food admitted. The 6 pairs of branchial legs commenced in the larval stage are now able to perform their function, executing their characteristic swinging movements for the purpose of respiration and the admission of food; and there are the rudiments of 3 or 4 pairs of new legs. The caudal part is still only slightly bent down, and the caudal claws imperfectly marked off from the end of the tail. They each have near the base a single, short, lateral tooth, and imme- diately above them, there issue from the dorsal side of the tail 2 very small juxtaposed projections, _ representing the earliest rudiment of the dentated steerke, bagudrettede dorsale Torne. De sammen- satte Oine har tiltaget i Storrelse, og deres Syns- elementer er nu noksaa tydelige. Umiddelbart neden- for dem ligger det enkle Wie, som har bibeholdt sit Udseende temmelig uforandret, Af de 2 Lappe, hvori hos sidste Larvestadium enhver af de blind- sekformige Udvidninger af Tarmen var delt, viser den dorsale allerede en Antydning til en yderligere Klovning. Ungen svommer om i Vandet paa en fra samme hos Larverne meget forskjellig Maade, idet Beveegelsen nu ikke lengere er stodvis, men mere har Characteren af et ganske jevnt Lob, be- virket ved hastigt paa hinanden folgende Slag af Aarernes ydre Parti. Dyret vender herunder snart Ryg- snart Bugside opad og gjor ofte kredsformige Volter i Vandet. Paa Tab. XIV er afbildet fra venste Side 2 umiddelbart folgende Stadier (Fig. 4 og 5), hvoraf vil sees, at Skallen hurtigt voxer i Storrelse, saa at den tilsidst er tilstrekkelig rummelig til at Le- gemet fuldstendigt kan trekkes ind isamme. Skal- lens Form er imidlertid temmelig uforandret, skjondt maaske noget mere oval end i Iste Stadium, og der er fremdeles ingen concentriske Linier at se paa Valvlerne. Hovedet er nu ved en tydelig dorsal Indbugtning sondret fra Nakkesegmentet, og den umiddelbart foran Indbugtningen liggende Del af dets dorsale Flade begynder at heve sig i Veiret for at danne det for det voxne Dyr saa characteri- stiske Fastheftningsorgan, hvilket dog endnu lenge udgaar fra Hovedet med en forholdsvis bred Basis. Pandedelen begynder lidt efter lidt at antage den for det voxne Dyr characteristiske koniske Form, og under den sees allerede en temmelig dyb Ind- bugtning, hvorved den sondres fra det nu triangu- lert fremspringende Rostrum. iste Par Folere be- gynder at forlenge sig og antage en smalt kolle- dannet Form, men er endnu hos det sidste af de her omhandlede 2 Stadier (Fig. 5) simple, uden late- rale Lappe. Aarerne, hvis basale Del nu altid er fortilstrakt, forandrer sig ligeledes gradvis, an- tagende mere og mere den for det voxne Dyr cha- racteristiske Bygning, idet Grenene forlenger sig og afsnores i et storre Antal Led. Antallet af de paa dem festede Svommeborster og Pigge er dog endnu meget ringe sammenlignet med samme hos det voxne Dyr. Kindbakkerne har tabt den sidste Rest af Mandibularfodderne og er nu, saavel hvad Form som Bevebning angaar, fuldkommen overens- stemmende med samme hos fuldt udviklede Individer. Branchialfoddernes Tal tiltager gradvis, idet der successivt bagtil danner sig nye Anleg, efterat de foranliggende er bleven functionsmessigt udviklede. Deres Tal er paa det Fig. 4 afbildede Stadium 9, 108 caudal lamine. Above the caudal sete moreover, there have developed a single pair of the strong, backward-pointing, dorsal spines occurring here in the full-grown animal. The compound eyes have increased in size, and their visual elements are now fairly distinct. Immediately below them lies the ocellus, which has maintained its appearance almost unchanged. Of the 2 lobes into which each of the cecal expansions of. the intestine was divided in the last larval stage, the dorsal one already shows signs of further cleavage. The young animal swims about in the water in a manner very different to that of the larva, the motion being no longer jerky, but having more the character of an even dart, brought about by the rapidly succeeding strokes of the distal part of the oars, during which the ani- mal turns now its dorsal, now its ventral side uppermost, and often makes circular turns in the water. On Pl. XIV, 2 immediately following stages (figs. 4 and 5) are illustrated from the left side. It will be seen from these that the shell is rapidly increasing in size, until at last it is sufficiently capacious to allow of the body being completely withdrawn into it. The form of the shell, however, is almost unchanged, though perhaps somewhat more oval than in the first stage, and there are still no concentric lines to be seen on the valves. The head is now divided from the cervical segment by a distinct dorsal depression, and that part of- its dorsal surface immediately in front of the de- pression, begins to be raised up in order to form the organ of attachment so characteristic of the adult animal, which still for some time issues from the head with a comparatively broad base. The frontal region begins little by little to assume the conical form characteristic of the full-grown animal, and beneath it may be already seen a rather deep depression, by which it is divided from the now triangularly projecting rostrum. The Ist pair of antenne begin to lengthen and assume a narrow clavate shape, but are still, in the latter of the 2 stages now in question (fig. 5), simple and without lateral lobes. The oars, whose basal part is now always extended forwards, are also changing gra- dually, and assuming more and more the structure characteristic of the adult animal, the rami being elongated and divided into a greater number of joints. The number of natatory bristles and spines attached to them is still very small compared with that in the adult animal. The mandibles have lost the last remnants of mandibular legs, and are now, both as to form and equipment, exactly like those of the fully-developed animal. The number of branchial legs increases gradually, new rudiments being successively formed behind, as soon as those in front are developed sufficiently to perform their paa det Fig. 5 fremstillede 14 Par ialt. sondrer sig tydeligere fra Truncus og bliver mere omboiet. Haleklorne er nu bevegeligt articulerede paa Spidsen, og Halepladerne begynder at springe steerkere frem. I deres Bagkant viser sig nogle faa tandformige Fremspring, ligesom de ovenfor Hale- borsterne udgaaende dorsale Torne begynder at til- tage i Antal. Hvad den indre Organisation angaar, skal her blot henledes Opmerksomheden paa den ganske gradvise Udvikling af det i Hovedet liggende leveragtige Organ, der allerede i det sidste af de 2 her omhandlede Stadier (Fig. 5) har opnaaet en temmelig compliceret Bygning. Leengden af Skallen hos disse 2 Stadier er henholdsvis 1,10 mm. og 2,30 mm. Endnu foregaar der en lignende gradvis Ud- vikling af alle Dele af Legemet indtil Skallen har naaet en Lengde af 6—7 mm. Da indtreder den Iste Hudskiftning inden den postlarvale Tilstand, og meget kort Tid efter denne er allerede Individet kjonsmodent, skjont det endnu neppe har opnaaet synderlig mere end Halvparten af dets definitive Storrelse. Fig. 6 paa samme Planche fremstiller et Individ nogen Tid efterat denne Hudskiftning er foregaaet. Som man ser, har Valvlerne nu faaet sin forste Veextstribe, der lober nogenlunde parallel med og i forholdsvis kort Afstand fra Valvlernes frie Rand. Dannelsen af denne Veextstribe er ikke vanskelig at forstaa. Ved Hudskiftningen bliver nemlig kun den indre Membran af Skallen afkastet, medens den ydre chitinose Lamelle bliver siddende igjen og sup- pleres nu med en nydannet peripher Del. Denne lste Veextstribe er altsaa intet andet end Kanterne af de primere Valvler, der skarpt afgrendser sig fra den efter Hudskiftningen optreedende nydannede Del af Valvlerne. Skallen, der nu har en Lengde af 8 mm. og en Hoide af 6 mm., har den dorsale Kant jevnt bueformig boiet, dog langtfra saa sterkt som hos fuldt udvoxede Individer, og det forreste Hjorne er, i Modsetning til hvad Tilfeeldet er hos disse, fuldkommen ligesaa sterkt fremtreedende som det bagre. Det i Skallen indesluttede Dyr er i alle Henseender normalt udviklet, alene med den For- skjel, at Branchialfoddernes Antal er noget ringere end hos fuldvoxne Exemplarer, nemlig kun 20 tyde- ligt udviklede Par, hvoraf allerede 9de til 11te Par har den ovre Lap af Exopoditen traadformigt for- lenget. Til Siderne af Tarmen sees nu tydeligt Ovarierne med sine talrige Agfollikler, og i deres indre har allerede afsat sig det opakt hvide Secret, der skal tjene til Dannelsen af Mgkapslerne. Efter nogen Tids Forlob har Individet faaet sin charac- teristiske Aigmasse under den dorsale Del af Skal- len. Denne beres i Regelen af Dyret til neste Hudskiftning, da den sammen med den afkastede Hud bliver udstodt af Skallen bagtil. Efter Hud- 109 Haledelen | functions. In the stage shown in fig. 4, their number is 9 pairs, in that in fig. 5, there are in all 14 pairs. The caudal part is more distinctly divided from the trunk, and becomes more bent downwards. The caudal claws are now movably articulated at the point, and the caudal lamelle begin to project more. On their hind margin a few denticular pro- minences appear, while the dorsal spines issuing from above the caudal sete, begin to augment in number. With regard to the internal organisation, attention is here only drawn to the very gradual development of the hepatic organ in the head, which, in the latter of the 2 stages here under dis- cussion (fig. 5), has already attained a tolerably complicated structure. The length of the shell in these 2 stages is respectively 1.10 mm. and 2.30 mm. A gradual development of this kind still goes on of all the parts of the body, until the shell has attained a length of 6 or 7 mm. Then occurs the 1st exuviation in the post-larval condition, and very shortly after this, the animal is sexually mature, although it kas scarcely attained more than half its eventual size. Fig. 6 on the same plate, represents an animal some time after this exuviation has taken place. It will be seen that the valves have now acquired their first line of growth, which runs almost parallel with, and at a comparatively short distance from the free edge of the valves. The formation of this line of growth is not difficult to understand, for in the exuviation, only the inner membrane of the shell is cast, while the outer chitinous lamella remains, and receives the addition of a newly-formed peripheral part. This Ist line of growth is thus nothing more than the edges of the primary valves, which are sharply defined against the newly-formed portion of the valves appearing after the exuviation. The shell, which now has a length of 8 mm. and a height of 6 mm., has its dorsal edge evenly curved, though not nearly so much as in fully developed specimens; and the foremost corner, unlike that in ‘adult animals, is fully as prominent as the hind one. The animal enclosed in the shell is in every respect normally developed, with the one exception that the branchial legs are rather fewer in number than in adult specimens, there being only 20 dis- tinctly developed pairs, the 9th, 10th and 11th of which already have the filiform elongation of the exopodite. The ovaries with their numerous egg- follicles are now distinctly visible at the sides of the intestine, and the opaque white secretion to be employed in the formation of the egg-capsules has already been deposited inside them. After some time has elapsed, the animal has its characteristic mass of eggs under the dorsal part of the shell. This is generally carried by the animal until the next exuviation, when it is cast, together with the skiftningen er Valvlerne forsynede med nok en Vextstribe udenom den Iste, en ny Aigmasse dan- nes og saaledes fremdeles. Antallet af paa hinan- den folgende Hudskiftninger er derfor, iberegnet den, der er gaaet umiddelbart forud for 1ste postlarvale Stadium, noiagtig det samme som Antallet af Vext- striber paa hver Valvel, og omtrent ligemange Gange har i Regelen Individet afsat en Aigmasse. Efterhvert som Skallen paa denne Maade ved ny- dannede periphere Lag tiltager i Storrelse, foran- dres lidt efter lidt dens Form, idet Rygkanten bli- ver mere og mere buet isin forreste Del. Samtidigt bliver de primere Valvler ligesom skudt fortil og indtager tilsidst en forholdsvis liden Del af Skallen ved dennes overste forreste Hjorne, hvilket sidste i samme Forhold bliver utydeligere og mere afstumpet (se Fig. 1). Hos meget gamle Individer antager Skallen tilsidst, seet fra Siden, en nesten trianguler Form, med den primere Area skudt helt fortil og neesten umboformigt fremragende, saaledes som an- tydet paa den af Prof. Lilljeborg givne Figur (Skallen i naturlig Storrelse). Forekomst og Levevis. Allerede Grube har opgivet, at der i Berliner- Museet findes opbevaret Exemplarer af denne Form, indsamlede af H. Rathke i Norge. Men da dette Fund ikke med et eneste Ord er omtalt i den sidst- neevnte Forskers bekjendte Verk: «Beitrage zur Fauna Norwegens», og jeg sely under mine mange- aarige Undersogelser af vor Ferskvandsfauna aldrig havde paatruffet den, fandt jeg Paalideligheden af denne Opgift af Grube meget tvivlsom og udtalte mig ogsaa derhen i en i Vid. Selsk. Forhandlinger meddelt forelobig Meddelelse om Norges Phyllopoder. Forst i Aaret 1885 lykkedes det mig med fuld Sik- kerhed at faa constateret denne eiendommelige Phyl- lopodes Forekomst her i Landet. Under en Reise, jeg dette Aar foretog langs Sydkysten af Landet, tog jeg d. 22de Juli Station paa en ikke meget stor - og temmelig flad 0, «Merdo», udenfor Arendal, og fandt her allerede den forste Dag efter min Ankomst store Mengder af Limnadia-Larver i et grundt med Gresbund forsynet Tjern, «Storekjer» kaldet, be- liggende omtrent midt paa Men. Paa denne Tid var kun meget faa Exemplarer naaet ud over Larve- tilstanden, men i Lobet af de folgende Dage op- traadte postlarvale Stadier i stor Mengde, og ved Slutten af Maaneden var ingen Larve lengere at finde. Flere Exemplarer var da allerede egbe- rende og havde Valvlerne forsynede med de forste Vextstriber. Ved min Afreise, d. 10de August, var Skallen hos de storste Individer omtrent 10 mm. lang og hayde 5 Par Vextstriber. For om muligt at finde fuldvoxne Individer, besogte jeg igjen Wen 110 skin, out of the shell behind. After the exuviation the valves acquire another line of growth outside the first, a new mass of eggs is formed, and so on. The number of successive exuviations, including that which immediately preceded the 1st post-larval stage, is therefore exactly the same as the number of lines of growth on each valve, and the animal has, as a rule, deposited a mass of eggs about the same number of times. While the shell in this manner increases in size by the addition of new peripheral layers, it gradually changes its shape, the dorsal edge becoming more and more curved in its front part. At the same time the original valves are as it were pressed forward, and at last occupy a comparatively small part of the shell at its upper front angle, which also, in the same proportion, be- comes more indistinct and blunter (see fig. 1). In very old specimens the shell, seen from the side, at last assumes an almost triangular shape, with the original area pushed right to the front, and pro- jecting almost umbonately, as indicated in the figure given by Prof. Lilljeborg (the shell in its natural size). Occurrence and Habits. Grube has already stated that in the Berlin Museum there are preserved specimens of this form, collected by A. Rathke in Norway. But as this discovery is not so much as named in the latter naturalist’s well-known work «Beitriige zur Fauna Norwegens», and I myself, during my many years’ investigations of our (Norwegian) fresh-water fauna, had never met with the form, I considered the trustworthiness of Grube’s statement to be very doubtful, and expressed myself to that effect in a preliminary account of the Phyllopoda of Norway in the Viden. Selsk. Forhandlinger (Proceedings of the Scientific Society). Not. until the year 1885 did I succeed in substantiating with certainty the occurrence of this peculiar Phyllopod in this country (Norway). During a journey I made that year along the south coast, I stopped, on the 22nd July, at a rather flat, and not very large island off Aren- dal, called «Meerdo», and there found, on the very day after my arrival, large numbers of Limnadia larve in a shallow lake called «Storekjer», situated in about the middle of the island, and with a grassy bottom. At that time only a very few specimens were advanced beyond the larval condition, but in the course of the few following days, post-larval stages made their appearance in great numbers, and by the end of the month there was not a larva to be found. Several specimens were then already carrying eggs, and had their valves furnished with the first lines of growth. At the time of my departure, the 10th August, the shells on the i September samme Aar og opholdt mig her fra den 9de til den 15de. Limnadierne var nu meget sjeldne, men adskilligt storre end de tidligere fundne, skjondt ingen oversteg en Lengde af 12 mm. Foruden i det omtalte Tjern fandt jeg den ogsaa paa nogle andre Steder af Yen, tildels i yderlig smaa Vand- ansamlinger, dog her af mindre Storrelse. Derimod fandtes den ikke paa en eneste af de mange omlig- gende Wer. Ogsaa det folgende Aar gjenfandt jeg denne Form i Begyndelsen af August paa de samme Steder, men ingen storre end de tidligere indsam- lede. Sommeren 1888 fandt Prof. Collett denne Phyllopode paa en ganske anden Lokalitet, nemlig i en liden Vandkulp i Nerheden af Hamar. For at undersoge denne nye Lokalitet noiere, reiste jeg derop den folgende Sommer i August, og jeg havde ikke synderlig Vanskelighed ved, efter Prof. Colletts nermere Angivelser, at finde den omhandlede Kulp. Den var imidlertid nu fuldstendig udtorret paa Grund af lengere Tids forudgaaende tort Veir, saa jeg alene kunde forsyne mig med noget af det ind- torrede Mudder for senere kunstige Udkleknings- forsog. To Gange senere har jeg besogt den samme Lokalitet, nemlig i Begyndelsen af September 1894 og i Midten af Juli 1895. Begge Gange fandtes tilstrekkeligt Vand i Kulpen og store Mengder af forskjellige Entomostraceer, men af Limnadier var der intetsomhelst Spor at opdage, hverken Larver eller voxne, saa det nesten ser ud til, at den nu her er fuldsteendig uddeet, for kanske efter en lang Aarrekke paany at optrede ligesaa pludselig som den er forsvunden. Heller ikke af det Mudder, der paa disse 2 Udflugter medtoges fra Kulpen har jeg -kunnet udklekke en eneste Limnadia, medens mine mange Gange gjentagne Udklekningsforsog med det i 1889 samlede Mudder aldrig har slaaet feil. Idet- hele synes, ogsaa efter andre Forskeres Beretninger, denne Phyllopodes Optreden at vere yderst lune- fuld. Et Aar kan den treffes i storste Mengde paa et begreendset Omraade, for saa igjen sporlost ‘at forsvinde, og forst efter lange Aarrekker kan den saa optrede igjen enten paa samme Lokalitet eller paa Steder, hvor man tidligere aldrig har fun- det den. Angaaende denne Forms Levevis forovrigt, saa synes overalt kun et enkelt Kuld Individer at ud- vikle sig for hver Sommer. Man har ialfald hidtil ingen sikre Data for, at flere Generationer har fulgt paa hinanden samme Aar. Individernes Livsperiode synes i Regelen kun at vere indskrenket til et Par Maaneder, ofte kanske ikke engang saa lenge. Men i Lobet af denne korte Tid vil ialfald en Del | af Individerne naa til Kjonsmodenhed og kunne af- largest specimens were about 10 mm. long, and had 5 pairs of lines of growth, In order to find, if pos- sible, full-grown specimens, I again visited the island in September of the same year, and stayed there from the 9th to the 15th. The Limnadix were then very rare, but considerably larger than those pre- viously found, although none exceeded a length of 12 mm. I also found it in other places on the island besides the above-mentioned lake, sometimes in exceedingly small accumulations of water, though then of a smaller size. On the other hand it was not to be found on a single one of the ‘many sur- rounding islands. In the following year also, I found this form again in the beginning of August -in the same places, but none larger than those pre- viously taken. In the summer of 1888, Prof. Collett found this Phyllopod in quite another locality, namely in a little pool in the neighbourhood of Hamar. In order to examine this new locality more minutely, I went up there the following sum- mer in August, and, from Prof. Collett’s exact des- cription, had not much difficulty in finding the pool in question, It was however completely dried up, owing to the preceding long period of dry weather, so that all I could do was to take away with me some of the dried mud, in order to attempt arti- ficial hatching at a future time. Twice subse- quently have I revisited the same locality, namely, in the beginning of September, 1894 and in the middle of July, 1895. Both times I found sufficient water in the pool, and large numbers of various Entomostraca, but no trace of Limnadia was to be discovered, whether larva or adult, so that it almost ‘appears as if it were now completely extinct, per- haps to appear again after a number of years as suddenly as it has disappeared. Nor yet have I succeeded in hatching one single Limnadia out of the mud brought away from the pool on these two excursions, while my oft-repeated hatching attempts with the mud collected in 1889 have never failed. It seems, on the whole, as also from the accounts of other naturalists, that the appearance of this Phyllopod is extremely capricious. One year it may be met with in large numbers over a limited area, then vanish utterly, and only after many years may appear again, either in the same loca- lity, or in places where it has never been found previously. With regard to the habits of this form in other respects, it always appears that only a single brood of animals is developed each summer. We have not, at any rate up to the present, any cer- tain data to prove that several generations have succeeded one another in the same year. The living -period of the individual animals seems as a rule to be limited to a couple of months, frequently perhaps even less. But in the course of this short time a sette sine Aig, hvad der sikrer Artens fortsatte Existens, om Forholdene et andet Aar skulde vise sig gunstige for en ny Generations Udvikling. Som Regel synes det dog at vere et meget lidet Procent- tal af de utallige Larver, som i Begyndelsen ud- klekkes, der virkelig kommer til fuld Udvikling. Larver og Unger finder man uden Forskjel overalt i de Vandansamlinger, hvori de treffes, lige saa hyppigt tet inde ved Bredden som ude paa dybere Vand. Anderledes er det med fuldvoxne Exempla- rer. Disse holder i Regelen kun til paa de dybeste Steder af“ Dammen og her gjerne ner Bunden. Da Dyrene i Regelen er meget gjennemsigtige, er det ikke saa godt at faa Die paa dem fra Stranden af. Dog vil ialmindelighed den opake gulbrune Ag- masse forraade dem, navnlig naar Bunden, henover hvilken de beveger sig, bestaar af morkt Mudder. Bevegelsen er ikke synderlig hurtig og har Cha- racteren af et forholdsvis sagte og noget ujevnt Lob, hvorunder i Regelen Ryggen vender opad. Holdte i Aquarier kan man noiere studere deres Bevegelser og ovrige Levevis. Der kan ikke vere nogen Tvivl om, at Dyrets hovedsageligste Be- veegelsesorganer er Aarerne. Det er ved hurtigt gjentagne Slag til Siderne af disse Lemmers ydre Parti, at Legemet bliver drevet igjennem Vandet, skjondt ogsaa Branchialfoddernes Svingninger tor til en vis Grad understette Bevegelsen. Stoder Dyret under sine Bevegelser paa tette Conferve- masser, formaar det med stor Behendighed at ar- beide sig igjennem dem, hvorved den meget beveege- lige Bagkrop spiller en vigtig Rolle. Idethele sees Dyret meget ofte at foretage energiske Boininger og Strekninger af denne Del af Legemet, dels for at overvinde Hindringer for dets Passage gjennem Vandet, dels for at befri det indre af Skallen for fremmede indkomne Partikler. Meget ofte faar man se, at Dyret med Forenden hefter sig fast til de i Vandet verende Gjenstande, navnlig til Undersiden af Blade eller Conferver i Overfladen af Aqvarierne, og forbliver i denne Stilling sedvanligvis i lengere Tid. Fastheftningen synes hovedsageligst at tilveie- bringes ved de sterke hageformige Pigge langs For- siden af Aarernes Grene, tildels ogsaa ved det eien- dommelige fra Hovedets Dorsalside udgaaende kolle- formige Appendix, som man ved noiere Undersogelse altid vil finde er i umiddelbar Contact med den Gjenstand, hvortil Dyret er fastklamret. Dyret er herunder ikke i absolut Ro, men der foregaar en svag rhytmisk Svingning af hele Legemet frem og tilbage, aabenbart foraarsaget ved de heftigt beve- gede Branchialfodder. Disse Svingninger sker paa fuldkommen samme Maade som hos Branchipodiderne, idet de ikke er simultane men successive, hvad der giver Indtrykket af en eiendommelig grazios Undu- lation i Bevegelsen. Idethele er det meget sjelden at denne svingende Bevegelse af Branchialfodderne | some, at any rate, of the animals attain to sexual maturity, and are able to deposit their eggs, thereby ensuring the continued existence of the species, should conditions another year be favorable for the development of a new generation. As a rule, it appears to be a very small percentage of the innu- merable larve at first hatched, that really become fully developed. Larve and young ones are found without distinction all over the pieces of water in which they are met with, quite as frequently close to the bank as out in deeper water. It is otherwise with fullgrown animals. They generally keep to the deeper parts of the pond and near the bottom. As the animals are generally very transparent, it is not very easy to see them from the shore. The opaque, yellowish brown mass of eggs, however, will generally betray them, especially if the bottom, over which they move, consists of dark mud. The motion is not remarkably quick, but has the cha- racter of a comparatively slow and somewhat uneven dart, during which the back is generally uppermost. When kept in an aquarium, its move- ments and other habits may be more carefully stu- died. There can be no doubt that the animal's most important organs. of locomotion are the oars. It is by quickly repeated side-strokes of the distal part of these limbs that the body is driven through the water, although the swinging of the branchial legs may also, to a certain extent, assist the movement. Should the animal, as it moves, come in contact with thick masses of conferve, it manages with great dexterity to work its way through them, the very mobile hind part of the body playing an important part in that proceeding. The animal may often be observed to make ener- getic bends and extensions of this part of the body, partly to overcome obstacles to its passage through the water, partly to rid the shell of foreign par- ticles that have entered. The animal may very often be seen to attach itself by its anterior end to objects in the water, especially to the under surface of leaves or confervee on the surface of the aquarium, and generally remain in this position for some time. The attachment appears principally to be effected by means of the strong, hook-like spines along the front of the rami of the oars, and partly by the peculiar clavate appendage issuing from the dorsal surface of the head, and which, on close examination, will always be found in immediate contact with the object to which the animal is clinging. The animal meanwhile is not absolutely at rest, for there is a slight rhythmical swinging to and fro of the whole body, occasioned by the violent agitation of the branchial legs. These pul- sations take place in exactly the same manner as in the Branchipodide, not being simultaneous but suc- cessive, thus producing the impression of a peculiar, EO — ganske stopper op. Det sker kun, naar Dyret plud- selig foruroliges, i hvilket Tilfeelde alle Dele af Legemet hurtigt trekkes ind i Skallen, hvorpaa denne hermetisk lukker sig og Dyret synker til- bunds. Meget snart aabner imidlertid Valvlerne sig igjen, den forreste Del af Hovedet tilligemed Aarerne strekker sig forsigtigt frem fortil, og Halen bagtil, hvorpaa igjen Branchialfodderne begynder sine rhythmiske svingende Beveegelser. Dyret synes hovedsageligt at nere sig af op- smuldrede Plantedele, encellede Alger, maaske ogsaa Infusorier. Disse Dele bliver ved Branchialfoddernes Bevegelser hvirvlet ind i Skallen og passerer der- efter bagfra fortil mellem Fodderne imod Munden. Kindbakkerne sees at vere i stadig Aktivitet med at bearbeide den af Munden optagne Nering, som derefter ved Hjelp af de talrige fra Overleben til Spiseroret gaaende Musklers Virkning bliver svelgt og indfort i Tarmens forreste Del. Her undergaar Foden en forelobig Oplosningsproces ved det intenst gule Secret, der udsondres af Leveren. Fordgielsen synes idethele at gaa meget hurtigt for sig, idet Tarmens Contenta hurtigt forandrer sin Farve, efter- som de passerer bagtil, fra lyst gult eller orange til et meget morkt brunt eller nesten sort. Med visse Mellemrum bliver Excrementerne ved Ende- tarmens Contractioner udstedte, ofte’i temmelig lange sammenheengende Masser. I Lighed med hvad Til- feeldet er hos Branchipodiderne, observeres ofte i Tarmrorets Vegge energiske peristaltiske Beve- gelser. Som ovenfor anfort, har alle hidtil observerede Individer af denne Form vist sig, ifolge sit hele Udseende, at vere Hunner, og alle Exemplarer bli- ver ogsaa uden Undtagelse, naar de har opnaaet en vis Grad af Udvikling, forsynede med de characteri- stiske AZgpaketter under Skallens dorsale Del. Da jeg har observeret denne Form gjennem en Rekke af Aar til forskjellige Tider af Sommeren, og tillige gjentagne Gange har opdrettet den i mine Aqvarier og havt den gaaende her maanedsvis, tror jeg med fuld Sikkerhed at kunne constatere, at Hanner over- | hovedet ikke existerer, og at altsaa nerveerende Phyllopodes Forplantning er exclusiv parthenogene- tisk. Dette er saameget mere merkeligt som For- holdet er et helt andet med Arterne af den meget neerstaaende Slegt Eulimadia; hvor Forplantningen er udpreeget bisexuel eller gamogenetisk, idet Han- ner og Hunner til alle Tider synes at forekomme i omtrent lige Antal. En Tid har jeg rigtignok staaet i den Formening, at alle Individer af den her om- handlede Phyllopode maaske kunde vere hermaphro- ditiske eller rettere protandriske, idet visse Forhold ved Kjonsorganernes Bygning syntes mig at pege i denne Retning; men Resultaterne af de af mig 15 — G. 0, Sars: Fauna Norvegiz. 113 parthenogenetic. gracious, undulatory motion. It is, on the whole, very seldom that this swinging motion of the branchial legs entirely ceases; for it happens only when the animal is suddenly alarmed, in which case all the parts of the body are withdrawn into the shell, which then closes hermetically, and the animal sinks to the bottom. The valves, however, very soon reopen, and the fore part of the head, together with the oars, is cautiously extended in front, and the tail behind, whereupon the branchial legs recom- mence their rhythmical swinging movements. The animal appears to feed principally on broken portions of plants, unicellular alge, and possibly infusoria. These are whirled into the shell by the movements of the branchial legs, and then pass from back to front between the legs towards the mouth. The mandibles are seen to be con- stantly oceupied in manipulating the food taken in by the mouth, which then, by the aid of the nu merous muscles running from the labrum to the jesophagus, is swallowed and introduced into the anterior part of the intestine. Here the food under- goes a preliminary process of dissolution by the intensely yellow secretion deposited by the liver. Digestion seems on the whole to take place very rapidly, the contents of the intestine quickly changing colour as they pass backwards, from light yellow or orange to a very dark brown or almost black. At certain intervals the excrements are ejected by the contractions of the rectum, often in rather long, connected masses. As in the Branchi- podide, energetic peristaltic movements may often be observed in the walls of the intestinal tube. As. stated above, all the specimens of this form hitherto observed, have proved, from their whole appearance, to be females; and all specimens, without exception, when they have attained to a certain degree of development, are provided with the characteristic cluster of eggs beneath the dorsal part of the shell. Having observed this form at different periods of the summer through a series of years, and haying also reared it repeatedly in my aquaria, where it has existed for months toge- ther, I think I may declare with perfect certainty that. males in reality do not exist, and that the propagation of this Phyllopod is thus exclusively This is.so much the more remark- able, as the circumstance is altogether different in the species of the very nearly-allied genus Euli- madia, where propagation is very markedly bi-sexual or gamogenetic, males and females seeming at all seasons to occur in about equal numbers. At one time indeed, I was under the impression that all the specimens of the Phyllopod in question might perhaps be hermaphroditic, or rather protandric, as certain circumstances in the structure of the sexual organs seemed to me to point in. that direction; senere i den Anledning anstillede noiere Under- sogelser har dog ikke forekommet mig overbevi- sende nok til at jeg tor fastholde denne Opfatning. Hoist merkverdig er Aiggenes lange Leve- dygtighed, der endog synes at hamle op med den vel bekjendte seige Spireevne hos lenge opbevarede Plantefro. Som ovenfor anfort, forsynede jeg mig Sommeren 1889 med et storre Qvantum af torret Mudder fra den Aaret iforveien af Prof. Collett undersogte Kulp ved Hamar. Af dette Mudder, som jeg har staaende i en liden Kasse paa mit Laboratorium i den Tilstand, hvori det blev taget, har jeg senere hver Sommer udtaget Smaaportioner og dermed. an- stillet Udklekningsforseg i mine Aqvarier. Disse Ud- klekningsforsog har endnu ikke nogen Gang slaaet feil. Altid har store Mengder af Larver inden meget kort Tid vist sig i Aqvarierne, og af disse Larver har i Regelen ialfald en Del gjennemgaaet sin hele Udvikling. De paa denne Maade kunstigt opdret- tede Individer har jeg havt gaaende i mine Aqva- rier mere eller mindre langt ud overSommeren. De har tilsyneladende trivets udmerket, har paa sed- vanlig Vis produceret sine Aigpaketter og har ial- mindelighed naaet den samme Maximumsstorrelse som de af mig frit indsamlede Exemplarer. Ved de forste Forsog udklekkedes sammen med Limnadierne ogsaa forskjellige andre Entomostraceer; men i de senere Aar er det alene Limnadier, der lader sig udklekke af Mudret. Ganske nylig har jeg i et opvarmet Rum gjort et nyt Forsog med det samme Mudder, og ogsaa denne Gang, altsaa fulde 6 Aar efterat Mudret blev taget, ser jeg, at Larver ud- klekkes i temmelig betydeligt Antal, trods den uheldige Aarstid (vi skriver idag, da dette ned- skrives, den 18de Februar). Det er min Agt at fortseette Experimenterne fremdeles med den tilovers- blevne Rest af Muddret, da det forekommer mig at have adskillig Interesse at faa paa denne Maade sikkert constateret Udstrekningen af Auggenes Leve- dygtighed. En ganske besynderlig Omstendighed maa jeg her neyne, og det er, at det endnu ikke har lykkets mig at faa de i mine Aqvarier afsatte Mg af denne Form udklekkede, skjondt Residuet er behandlet paa samme Maade som ved andre Ud- klekningsforsog, idet jeg har ladet det ligge i ind- torret Tilstand Vinteren over. Det synes herefter nesten som om Aggene af Limnadia trenger, for at kunne udvikle sig, at ligge torre ikke blot et, men flere Aar itrek. At jeg paa Merdo har paa- truffet denne Phyllopode i 2 paafolgende Aar paa de samme Lokaliteter, kan ikke egentlig siges at modbevise en saadan Hypothese, da det jo aldeles ikke er afgjort, at de paatrufne Individer netop er udklekkede af de den foregaaende Sommer af- satte Ag. De eiendommelige vingeformige Udvidninger, 114 but the results of more careful observations made by me subsequently, have not appeared to me to be sufficiently convincing to permit of my main- taining that view. The great vitality of the eggs is most remar- kable, and seems to be on a par with the well-known tenacious germinating power in long preserved plant seeds. As already stated, I provided myself, in the summer of 1889, with a considerable quantity of dried mud from the pool near Hamar, examined by Prof. Collett the year before. Of this mud, which stands’ in a little box in my laboratory, in the condition in which it was taken, I have since then, every sum- mer, taken out small quantities, and made hatching- experiments in my aquaria. These experiments have never yet been unsuccessful. Always, within a very short period of time, large numbers of larvee have made their appearance in the aquaria, and, as a rule, a proportion, at any rate, of these larve have gone through their whole development. The specimens artificially reared in this way have lived in my aquaria more or less far on towards the end of the summer. They have apparently thriven well, have produced their egg-masses, and have generally attained the same maximum size as the naturally- reared specimens collected by me. At the first attempts, various other Entomostraca were hatched with the Limnadie; but in the later years, Limnadie only have been hatched from the mud. I have quite recently made a fresh trial with the same mud in a heated room; and this time too, fully six years after the mud was taken, I see that the larve are being hatched in considerable numbers, in spite of the disadvantageous time of year (it is the 18th February when I write this). It is my intention to continue the experiments with the remainder of the mud, as it appears of conside- rable interest to me to prove with certainty in this way the extent of the period of the eggs’ vitality. One very peculiar circumstance I must mention here, namely, that I have not yet succeeded in hatching out any of the eggs deposited in my aquaria by this form, although the residuum has been treated in exactly the same way as in other hatching experiments, as I have left it in a dried-up condition throughout the winter. It seems from this as if the eggs of Limnadia, in order to be able to develope, require to lie dry, not one year only, but several years in succession. The fact that on Merdo I have met with this Phyllopod in the same loca- lities 2 years in succession, cannot really be said to disprove such a hypothesis, as it is not at all cer- tain that the specimens found were hatched from eggs deposited the previous summer. ’ The peculiar wing-like expansions with which the hvormed Aiggenes Skal er forsynet, har rimeligvis sin Betydning for Aggenes Spredning. Naar Dam- mene torrer ud, vil nemlig Aiggene derved sammen med det opsmuldrede Mudder let kunne hvirvles op af Vinden og fores afsted i storre Afstande. En saadan Spredning af Aggene ved Vindens Hjelp har jeg ogsaa troet at kunne constatere paa Merdo. Foruden i «Storekjer», som synes at vere det Sted, hvortil denne Form oprindelig har veret indskren- ket, paatraf jeg den paa flere andre Punkter af Gen, tildels i en meget betydelig Afstand fra det nevnte Tjern, og undertiden i saa smaa og grunde Regnpytter, at det var umuligt andet end antage, at Mg rent tilfeeldigvis med Vinden er overfort hertil fra «Storekjer». Det synes imidlertid som om der skal ganske seregne Betingelser til, for at denne Phyllopode skal kunne trives. Thi der var adskillige Smaadamme paa Gen, tildels lige i Ner- heden af «Storekjer», hvor intetsomhelst Spor af den kunde opdages, skjondt disse Damme for andre Entomostraceers Trivsel syntes at vere meget gun- stige. Dette synes ogsaa for en Del at kunne for- klare denne Phyllopodes merkverdig sporadiske Forekomst. Udbredning. — Arten blev forst opdaget af Herman i grunde Grofter ved Strassburg, hvor den ogsaa senere er fundet af vy. Siebold. Brogniart fandt den i Smaatjern ved Fontaineblau, og Grube anforer den ogsaa fra Omegnen af Breslau og Berlin. Ligeledes er den af Dr. Spangenberg fundet ved Neustadt i Mecklenburg. I Sverige blev den Som- meren 1871 fundet af Prof. Lilljeborg ved Ronneby i Blekinge og, ifolge samme Forsker, opbevares i Stockholms Museum Exemplarer fra Stockholms Om- egn og fra Hallands Vaders. Endelig har Dr. Hans- son taget den i Bohuslin. Dens Udbredning strek- ker sig altsaa til folgende europeiske Lande: Norge, Sverige, Tyskland og Frankrig. Andetsteds er den, saavidt mig bekjendt, ikke paatruffet, medmindre, som jeg er tilboielig til at tro, den amerikanske Form, Limnadia americana Morse, skulde vise sig at vere identisk med vor Art. 115 shell of the egg is provided have probably their signi- ficance in the distribution of the eggs. When the ponds dry up, the eggs, together with the pulverised mud, may be easily caught up by the wind, and carried away to some distance. Such a distribution of the eggs by the help of the wind, I think, too, may be demonstrated at Merdo. Besides in «Store- kjer», which seems to be the place to which this form has originally been confined, I met with it at several other points of the island, sometimes at a very considerable distance from the above-named little lake, and sometimes in such small and shallow rain-pools, that it was impossible to assume other- wise than that eggs have been quite accidentally earried thither from «Storekjer», by the wind. It appears, however, that very special conditions are requisite if this Phyllopod is to thrive; for there were numerous small ponds on the island, some in the immediate neighbourhood of «Storekjer» where no trace of it whatever could be discovered, although these same ponds seemed to be very favorable to the well-being of other Entomostraca. This also seems partly to account for the remarkably sporadic occurrence of this Phyllopod. Distribution.— This species was first discovered by Herman in shallow ditches at Strassburg, where it has since been found again by v. Siebold. Brog- niart found it in small lakes at Fontainebleau, and Grube reports it also from the neighbourhood of Breslau and Berlin. It has also been found by Dr. Spangenberg at Neustadt, in Mecklenburg. In Swe- den, it was found in the summer of 1871, by Prof. Lilljeborg, at Ronneby in Blekinge, and, according to the same naturalist, there are in the Stockholm Museum specimens from the neighbourhood of Stock- holm and from Halland’s Vaderé. Finally, Dr. Hansson has, taken it in Bohuslin. Its distribution thus extends over the following European countries: Norway, Sweden, Germany and France. Elsewhere it has not, as far as I am aware, been met with, unless, as I am inclined to think, the American form,. Limnadia americana, Morse, should prove to be iden- tical with our species. 8 Fam. Limnetide. Character. — Skallen sterkt buget, Valvlerne uden Veextstriber og forbundne dorsalt med en ufuldkommen Laas. Hovedet af enorm Storrelse, gaaende ud i et nedadkrummet Rostrum af for- skjellig Form hos de to Kjon. Truncus forholdsvis kort og massiv; Halen rudimenter. iste Par Folere smaa og simple; 2det. Par forholdsvis korte, men kraftige. Kindbakkernes Tyggedel stumpt tandet. 2det Par Kjever rudimentere. Foddernes Antal ikke overstigende 12 Par; de ydre Enditer. finger- formigt forlengede; kun iste Par hos Hannen prehensile. Forplantningen udpreget bisexuel. Ud- viklingen en compliceret Metamorphose, begyndende med et eiendommeligt Naupliusstadium. Bemerkninger. — Denne Familie er kun ba- seret paa en enkelt Slegt, Limnetis, som dog synes mig i saa mange vesentlige Punkter at afvige fra de til foregaaende Familie henregnede Slegter, at den fortjener at udskilles fra samme. Af Packard er den ogsaa opstillet som 'Typen for den ene af de 2 Underfamilier, hvori hans Familie Limnadiade deles. Det fortjener dog her at nevnes, at den til foregaaende Familie horende Slegt Cyclestheria i visse Forhold synes at vise en Tilnermelse til neer- verende Familie, uden at den dog kan henregnes til samme. Gen. Limnetis, Lovén, 1846. Syn. Hedessa Liévin. Slegtscharacter. — Skallen mere eller mindre kugleformig, glat, uden tydelige Umboner. ‘Hovedet kjolet efter Midten og forleenget til et hos Hunnen mere eller mindre tilspidset, hos Hannen tveert af- kuttet Rostrum; til Siderne af Hovedet en vel ud- viklet bueformig Fornix. Haledelen meget liden, ikke omboiet og uden tandede Plader, men dekket nedenunder af en operkelformig Lamelle. Umiddel- bart foran den hos Hunnen 2 fra den dorsale Flade af Truncus udgaaende bladformige Plader. De sam- mensatte Mie sammensmeltede i Midten. Det enkle Mie vel udviklet, beliggende ner. de sammensatte Mine. Foran dem 2 tet sammenstillede cilierede Feldter. iste Par Folere kolleformige; 2det Par med Grenene neppe lengere end Skaftet og delte i talrige korte Led, hvert kun berende en enkelt Sveommeberste i Bagkanten. Overleben simpel, uden nogen tentakelformig Fortsats. 2det Par Kjever Fam. Limnetide. Characters. — Shell very tumid; the valves without lines of growth, and connected dorsally by an imperfect hinge. Head of enormous size, ending in a downward-curved rostrum of a different form in the two sexes. Trunk comparatively short and massive; tail, rudimentary. First pair of antenne small and simple; 2nd pair comparatively short, but powerful. The ‘masticatory part of the mandibles bluntly den- tated. Second pair of maxille rudimentary. Num- ber of legs not exceeding 12 pairs; the outer endites digitiformly produced; only the 1st pair in the male prehensile. Propagation markedly bi-sexual. Deve- lopment a complicated metamorphosis, beginning with a peculiar nauplius stage. Remarks. — This family is based upon only a single genus, Limnetis, which yet seems to me to differ in so many essential points from the genera be- longing to the foregoing family, that it merits being separated from them. It has also been established by Packard as the type of one of the 2 sub-families, into which his family Limnadiade is divided. It is, however, deserving of mention here that the genus Cyclestheria, belonging to the foregoing family, seems, in certain points, to approach the present family, though it cannot be classed under it. Gen. Limnetis, Lovén, 1846. Syn. Hedessa Liévin. Generic Characters. — Shell more or less sphe- rical, smooth, and without distinct umbones. Head carinated medially, and produced in the female to a more or less pointed rostrum, in the male to one abruptly truncated; at the sides of the head a well- developed arcuate fornix. Caudal part very small, not bent downwards, and without dentated lamelle, but covered beneath by an opercular lamella. Imme- diately in front of it in the female, there are two foliate lamelle issuing from the dorsal surface of the trunk. The compound eyes merged together in the middle. Ocellus well-developed, situated near the compound eyes. In front of them two juxta- posed, ciliated fields. First pair of antenne cla- vate; 2nd pair with the rami scarcely longer than the scape, the former composed of numerous short joints, each carrying only a single natatory bristle on the hind margin. Labrum simple, without kun bestaaende af to simple Lameller, uden enhver Bevebning. Fodderne hos Hunnen 12 Par, hos Hannen 10 Par; den dorsale Lap af Exopoditen paa de 7 forreste Par enormt udviklet, paa 9de og 10de Par hos Hunnen omformet til cylindriske omboiede Strenge. Aiggene omgivne af en simpel Skal og sammenhobede under den bagre Del af Hunnens Skal til 2 kageformige Masser. Larven ved sin Udklekning forsynet med et stort, fladt Rygskjold. Bemerkninger. — Denne Slegt er opstillet i Aaret 1846 af Lovén for en sydafrikansk Art, L. Wahlbergi. Den kort Tid efter af Liévin opstillede Slegt Hedessa er identisk med Lovén’s Slegt. Man kjender ialt 8 eller 9 forskjellige Arter, som dog ikke alle er tilstreekkeligt characteriserede. Sleg- ten synes at have en meget vid geographisk Ud- bredning, idet Representanter er fundne i samtlige Verdensdele. Hos os forekommer kun én Art. Limnetis brachyurus, (Miill.) (Pl. XVUI—XxX). Lynceus brachyurus, O. F. Miller, Entomostraca, p. 69, Tab. VIII, figs. 1—12. Hedessa Sieboldi, Litvin, Schriften des naturf. Gesellsch. in Danzig, Bd. IV, Heft II, p. 4, Tab. I, IL. Hedessa brachywra, Siebold, Preuss. Provincialbl. 1849, Bd. VII, Heft 3, p. 198. Limnetis branchyurus, Grube, Archiy f. Naturgeschichte, Bd. - XIX, p. 71, Tab. V—VII. Artscharacter. — Skallen, seet fra Siden, rund- agtig, neesten ligesaa hoi som lang, den storste Hoide fortil, Rygkanten noget skraa og kun svagt buet, de frie Kanter af Valvlerne dannende en uaf- brudt Bue, Forenden meget bredere en Bagenden: — seet ovenfra bredt #gformig, den storste Bredde bag Midten. Langs Dorsalsiden en dyb Fure, i hvis Bund Valvlerne er forbundne med_hinanden. Hovedet hos Hunnen nesten saa langt som Truncus, Dorsalkanten jevnt buet, Rostrum endende i en skarpt tilspidset Fortsats, ved Basis af hvilken der er to korte laterale Fremspring. Hovedet hos Han- nen kortere, Rostrum tvert afkuttet, uden nogen terminal Spids. Haledelens Endeflige hos Hannen betydelig mere forlengede end ~hos Hunnen. Iste Par Fodder hos Hannen med Haanden nesten qva- dratisk og beveebnet langs Inderkanten med en Rad af 9 sterke, pladeformige Tender, Kloen leformigt krummet og tilspidset i Enden, den subapicale Lap temmelig smal, kloformigt indadkrummet, og borste- besat alene i Spidsen. Farven mork olivengron. Lengden af Skallen indtil 41/2 mm, 117 any tentacular projection. Second pair of maxilla consisting of only two simple lamelle, quite unarmed. Twelve pairs of legs in the female, in the male 10; dorsal lobe of the exopodite in the 7 foremost pairs enormously developed, in the 9th and 10th pairs, in the female, transformed into cylindrical cords bent at the tip. Eggs surrounded by a simple shell, and accumulated beneath the hinder part of the female’s shell, into 2 cake-like masses. The larva, when hatched, furnished with a large, flat carapace. Remarks. — This genus was established in the year 1846, by Lovén, for a South African species, L. Wahlbergi. The genus Hedessa, established a short time after by Liévin is identical with Lovén’s genus. Eight or nine different species are already known, not all, however, sufficiently characterised. The genus seems to have a very wide geographical distribution, representatives being found in all quar- ters of the globe. Only one species occurs in this country (Norway). Limnetis brachyurus, (Miill.) (Pl. XVUI—XX). Lynceus brachyurns, O. F. Miiller, Entomostraca, p. 69, Tab. VIII, figs. 1—12. Hedessa Sieboldi, Lievin, Schriften des naturf. Gesellsch. in Danzig, Bd. IV, Heft II, p. 4, Tab. I, Il. Hedessa brachyura, Siebold, Preuss. Provincialbl. 1849, Bd. VII, - Heft 3, p. 198. Limnetis branchyurus, Grube, Archiv f. Naturgeschichte, Bd. XIX, p. 71, Tab. V—VIL. Specific Characters. — Shell, seen from the side spheroidal, almost as high as it is long, the greatest height being in front; dorsal margin rather oblique and only slightly arched, the free edges of the valves forming an uninterrupted curve: the anterior end much broader than the posterior. Seen from above, the shell is broadly ovate, with the greatest breadth behind the middle. Along the dorsal surface, runs a deep furrow, at the bottom of which the valves are connected with each other. Head in the female almost as long as the trunk, dorsal margin evenly curved, rostrum ending in a sharply pointed projection, at the base of which there are two short lateral prominences. Head in the male shorter, rostrum abruptly truncated with- out any terminal point. Terminal lobes of the caudal part im the male considerably more produced than in the female. First pair of legs in the male with the hand almost square, and armed along the inner margin with a row of 9 strong, lamellar den- ticles; claw falciformly curved, and pointed at the extremity; sub-apical lobe rather narrow, bent inwards like a claw, and clothed with bristles only Bemerkninger. — Nerverende Phyllopode er allerede i Aaret 1785 beskrevet af O. Fr. Miiller som Lynceus brachyurus. At den senere som Hedessa Sieboldi af Liévin opforte Form er identisk med Miiller’s Art, er forst sikkert bleven constateret af Grube. Af de fra andre Verdensdele opforte Arter synes de 2 nordamerikanske, L. Gouldii Baird og L. mucronata Packard at komme vor Art meget ner. Derimod afviger de 2 australiske Arter, L. macleayana King og ZL. Tatei Brady, som jeg begge har havt Anledning til at undersoge noiere, meget bestemt i Henseende til Formen af Rostrum. Af den euro- pewiske Art har Grube givet en meget udforlig og indgaaende Beskrivelse, ligesom han ogsaa forst har givet nermere Oplysninger om dens eiendommelige Larveudvikling. Beskrivelse af Hunnen. Skallen har hos de storste af mig indsamlede Exemplarer en Lengde af 41/2 mm. og en Heide af 3,80 mm. Den bestaar, som hos Limmnadia, af 2 tydeligt begrendsede Valvler, forbundne med _hin- anden langs Dorsalsiden. Forbindelsen er temmelig ulig den hos Limnadia og gjor mere Indtryk af at vere en virkelig Laas, i Lighed med hvad man finder hos Ostracoderne. Medens nemlig hos den ‘sidstneevnte Slegt de 2 Valvler stoder sammen oven- til under en spids Vinkel, danner de her, for de for- binder sig med hinanden, en pludselig Omboining eller Fold, hvorved Forbindelsen mellem begge kom- mer til at ligge i Bunden af en dyb Fure, der strekker sig langs Rygsiden af Skallen (se Tab. XVII, Fig. 7 og 8). Seet fra Siden (Fig. 6), har Skallen en noget uregelmessig rundagtig Form, med den storste Hoide, der falder over den forreste Del, nesten ligesaa stor som Leengden. Dorsalkanten er kun meget svagt buet og skraat heldende bagtil, forbindende sig med den bagre Kant uden nogen tydelig Vinkel. Fortil er der en noget fremsprin- gende, men afrundet Forhoining, hvor Dorsalkanten forbinder sig med Forkanten. De frie Kanter af Valvlerne danner en fuldkommen jevn og uafbrudt Bue, som dog er noget fladere fortil, hvorfor ogsaa Skallen viser sig fortil ligesom stumpt afkuttet, medens den bagtil er mere jevnt afrundet. Seet ovenfra (Fig. 8), viser Skallen sig overordentlig steerkt buget, bredt «gformig, med den storste Brede bag Midten, og noget mere afsmalnende fortil end bag- til, hvor den pludselig indsnevres til en kort stump Fremragning. Naar, som sedvanlig er Tilfeeldet, Valvlerne er halvt aabne (se Fig. 2), synes Skallen, ovenfra eller nedenfra seet, end bredere og nesten fuldstendig kugleformig. Dreies Skallen saaledes, 118 at the point. Colour, a dark olive-green. of the shell, up to 4’/2 mm. Remarks. — This Phyllopod was described by O. Fr. Miller as early as the year 1785, under the name of Lynceus brachyurus. That the form subse- quently described by Liévin as Hedessa Sieboldi is identical with Miiller’s species, was first proved with certainty by Grube. Of the species described from other quarters of the globe, the 2 North Ame- rican species, L. Gouldii, Baird, and L. mucronata, Packard, seem very much to resemble our species. On the other hand, the two Australian species, L. macleayana, King, and ZL. Tatei, Brady, both of which I have had the opportunity of examining minutely, differ very decidedly in regard to the form of the rostrum. Grube has given a very detailed description of the European species, and was also the first to give any exact information about its peculiar larval development. Length Description of the Female. In the largest of the specimens collected by me the shell has a length of 41/2 mm. and a height of 3.80 mm. It consists, as in Limnadia, of 2 dis- tinctly defined valves, connected with one another along the dorsal side. The connection is rather unlike that in Limnadia, and gives more the impres- sion of an actual hinge, such as is found in the Ostracods; for while in the latter genus the 2 valves meet above in an acute angle, they here, before joining one another, form a sudden bend or fold, ~ thereby causing the connection between them to lie at the bottom of a deep furrow, which extends along the dorsal side of the shell (see Pl. XVIII, figs. 7 and 8). Seen from the side (fig. 6), the shell has a somewhat irregular, rounded form, with the greatest height, which falls over the foremost part, almost equal to the length. The dorsal margin is only very slightly curved, and inclines obliquely back- wards, uniting with the hind margin without any distinct angle. In front there is a very projecting but rounded prominence, where the dorsal margin unites with the anterior. The free edges of the valves form a perfectly even and uninterrupted curve, which, however, is rather flatter in front, thus causing the shell to appear anteriorly as if bluntly truncated, while at the back it is more evenly rounded. When seen from above (fig. 8), the shell appears to bulge very much, and is broadly ovate, with the greatest breadth behind the middle, and rather more tapering in front than behind, where it suddenly contracts into a short, blunt pro- jection. When, as is usually the case, the valves are half open (see fig. 2), the shell, when seen from above or below, appears still broader and almost spherical. When the shell is turned in such a way — oe a - der ogsaa er bemerket af Grube. 119 at man faar se den lige forfra (Fig. 7), viser den sig at have sin storste Brede nermere Dorsalsiden, medens Valvlerne nedad stoder sammen under en temmelig spids Vinkel. Den dorsale Fure viser sig i denne Stilling af Skallen som en dyb Indbugtning oventil. I den forreste Del af hver Valvel sees mere eller mindre tydeligt den rundagtige Inser- tionsarea for Skallens Lukkemuskel og umiddelbart bag denne Skalkjertelen. Denne sidste (se Tab. XIX, Fig. 16) viser i alt veesentlig samme Bygning som hos Limnadia, men er forholdsvis kortere og bredere. Skallens Overflade er ganske glat, uden Spor af Vextstriber. Rigtignok sees under visse Belys- ninger, i nogen Afstand fra Valvlernes frie Kanter, ligesom en svag buet Linie (se Tab. XVIII, Fig. 6), men jeg har overbeyist mig om, at dette ikke er nogen virkelig Vextstribe, men skriver sig fra den Omstendighed, at Valvlernes Randparti viser en noget anden Structur end den ovrige Del, noget Skallen bestaar forovrigt, som hos Limnadia, af 2 Lameller, en ydre temmelig sterk, men meget elastisk chitinos La- melle, og en seerdeles delikat indre Membran, der danner en Fortsettelse af Legemets Integument. Ved meget sterk Forstorrelse viser Skallens ydre Lamelle regelmessige rundagtige Masker eller For- dybninger. Kanterne af Valvlerne er noget fortyk- kede og fuldkommen glatte. Selve Legemet er (se Tab. XIX, Fig. 1) feestet til Skallen paa en fuldkommen lignende Maade som hos Limnadia, nemlig ved et smalt dorsalt Ligament, der udgaar indad fra Skallens mest fremspringende Del, og i nogen Afstand under dette ved Adductor- muskelen. Legemet er paa denne Maade ophengt paa en lignende Maade som hos hin Slegt i Skal- lens Hule, saaledes at baade den forreste og bager- ste Del er frit bevegelige. I Forhold til Skallen er imidlertid Legemet hos neerverende Form meget mere volumingst end hos Limnadia, hvorfor ogsaa i Regelen, saavel hos levende som Spiritus-Exemplarer, en storre Del af Hovedet rager frem af samme for- til (se ogsaa Tab. XVIII, Fig. 1 og 2). Ved en meget sterk Boining af Hovedet, hvorved dette legges ind mod Bugfladen af Kroppen, kan dog dette, ligesom det ovrige Legeme, helt inddrages indenfor Valvlerne, som da slutter tet sammen overalt. Som hos Limnadia, falder Legemet natur- ligt i 2 Hovedafsnit, et forreste og et bagerste, begreendsede fra hinanden ved det dorsale Ligament og Skallens Lukkemuskel; men Forholdet mellem disse 2 Afsnit er her et helt andet, idet det forre- ste er fuldkommen ligesaa stort som det bagerste. Begge Afsnit lader sig igjen dele i 2, det forreste i Hovedet og Nakkesegmentet, det hegeravas i Trun- cus og Halen. as to be seen from straight in front (fig. 7), its greatest breadth appears to be nearer the dorsal side, while the valves meet below in a rather sharp angle. The dorsal furrow, in this position of the shell, is like a deep hollow above. In the front part of each valve is seen, more or less distinctly, the round area of insertion of the adductor muscle of the shell, and immediately behind this, the shell- gland. The latter (see Pl. XIX, fig. 16) exhibits, in all essential particulars, the same structure as in Limnadia, but is comparatively shorter and broader. The surface of the shell is quite smooth, with- out a trace of lines of growth. It is true that in certain lights, what appears to be a faint, curved line is visible at some distance from the free edges of the valves (see Pl. XVIII, fig. 6); but I am con- vinced that this is no true line of growth, but is due to the circumstance that the marginal portion of the valves is of a somewhat different structure to the other part, a fact which has also been observed by Grube. In other respects the shell consists, as in Limnadia, of 2 lamelle, an external, fairly strong, but very elastic, chitinous lamella, and an internal extremely delicate membrane, which forms a continuation of the integument of the body. Under a very high magnifying power, the external lamella of the shell exhibits regularly rounded meshes or hollows. The edges of the valves are somewhat thickened, and perfectly smooth. The body itself (see Pl. XIX, fig. 1) is attached to the shell in exactly the same way as in Limnadia, namely, by a narrow dorsal ligament which runs inwards from the shell’s most prominent part, and at some distance below this, by the adductor muscle. The body is thus suspended in the cavity of the shell in the same way as in Limnadia, so that both the fore and the hind parts can be moved freely. In proportion to the shell, however, the body in the present form is much more voluminous than in Lim- nadia, and consequently, as a rule, a large portion of the head, both in living and in spirit specimens, projects from the shell in front (see also Pl. XVII, figs. 1 and 2). By a very great flexure of the head, however, whereby it is bent in against the ventral surface of the body, it can, like the rest of the body, be completely drawn into the shell, when the valves fit closely together all round. As in Lim- nadia, the body falls naturally into two principal sections, one anterior and one posterior, separated from one another by the dorsal ligament and the adductor muscle of the shell; but the proportion of these 2 sections is here quite different, the anterior one being fully as large as the posterior. Both sec- tions admit of sub-division into 2, the anterior into head and cervical segment, the posterior into trunk and tail. 120 Hovedet (se Tab. XIX, Fig. 1 og 11) er af enorm Storrelse, og viser, seet fra Siden, en neesten halvymaanedannet Form. Det fortsetter sig nedad umiddelbart i et serdeles stort, leformigt krummet Rostrum, der er rettet skraat nedad og bagud. Dets dorsale Kant er kjolformigt tilskjerpet og danner en fuldkommen jevn og uafbrudt Bue lige til Spid- sen af Rostrum. ‘Til hverSide sees en anden meget tydelig og noget uregelmessig bugtet Kjol, hvorved Hovedets Sideflader deles i en dorsal og en ventral Area. Denne Kjol, der aabenbart svarer til den saakaldte Fornix hos Cladocererne og navnlig viser en umiskjendelig Lighed med samme hos Lynceiderne, begynder ved Kindbakkernes Feste og strekker sig herfra med en ganske svag Krumning skraat fortil, henimod Midten af Hovedets Lengde, hvorpaa den gjor en meget sterk, nesten vinkelformig Boining og lober skraat bagtil langs Siderne af Rostrum, endende med et kort tandformigt Fremspring i nogen Afstand fra Spidsen. Sees Hovedet lige for- fra (Tab. XVIII, Fig. 4), viser denne laterale Kjol sig sterkt fremspringende i sin proximale Del, idet den her som et Hvelv dekker over Basis af Aarerne. Lengere nedad nermer de 2 Kjole sig til hinanden og gjor derved Indtrykket af en tydelig Indknibning at Hovedet ved Basis af Rostrum. Dette sidste viser sig i denne Stilling af Hovedet ligesom tredelt i Enden, gaaende i Midten ud i en sterk dolk- formigt tilspidset Fortsats, og til hver Side af denne i et betydelig kortere tandformigt Fremspring, der danner Enden af de laterale Kjole. Nakkesegmentet (se Tab. XIX, Fig. 1 og 11) er ganske kort og begrendset fra Hovedet ved en vel markeret Tversutur, ved hvis Ender Kindbak- kernes ovre Del er festet. Det er ganske svagt hvelvet oventil og viser til hver Side en kort, skraat opadgaaende Ribbe, der paa en Maade er en Fortseettelse af Hovedets laterale Kjole. Truncus er omtrent af Hovedets Lengde og temmelig tyk fortil, men afsmalnes hurtigt og jevnt bagtil. Den er delt i 12 uniforme Segmenter, hvert berende et Par Branchialfodder. Dorsalsiden af Segmenterne er ganske glat, uden Borster. Der- imod udgaar fra Siderne af de 2 bagerste Segmenter et Par eiendommelige, lateralt udbredte Plader, hvor- til intet tilsvarende findes hos andre Phyllopoder. Disse Plader (Fig. 9, 1), som alene forefindes hos Hunnen, er af ikke ubetydelig Storrelse, bladformige, og gaar ud i 3 triangulert tilspidsede Flige, hvoraf den forreste er storst. Ifolge sin Stilling synes de nermest at vere bestemte til at stotte de 2 kage- formige AZgmasser, som beeres under Skallen. The head (see Pl. XIX, figs. 1 and 11) is of enormous size, and when seen from the side, ex- hibits an almost semi-lunar shape. It is continued downwards into an exceedingly large, falciformly curved rostrum, which points obliquely downwards and backwards. Its dorsal margin is sharpened in the form of a keel, and forms a perfectly even and uninterrupted curve right to the point of the rostrum. On each side is visible another very dis- tinct, and somewhat irregularly wavy keel, by which the lateral surfaces of the head are divided into a dorsal and a ventral area. This keel, which evi- dently answers to the so-called fornix in Cladocera, and notably exhibits an unmistakable resemblance to that in the Lynceide, commences at the place of attachment of the mandibles, and runs thence with a very gentle curve obliquely forwards to about the middle of the length of the head, where it makes a very sharp, almost angular bend, and runs backwards along the sides of the rostrum, ending in a short, dentate projection at some distance from the point. When the head is seen from the front (Pl. XVIII, fig. 4), this lateral keel appears very prominent in its proximal part, where it covers the base of the oars like an arch. Farther down, the 2 keels approach one another, thereby giving the impression of a distinct contraction of the head at the base of the rostrum. The latter appears, in this position of the head, as if tripartite at the extremity, being produced in the middle to a strong, mucronate projection, on each side of which is a considerably shorter, dentiform prominence, forming the end of the lateral keel. The cervical segment (see Pl. XTX, figs. 1 and 11) is quite short and separated from the head by a well-marked transverse suture, to the ends of which the upper portion of the mandibles is attached. It is very slightly arched above, and shows, on each side, a short, obliquely-ascending bar, which in one way is a continuation of the lateral keel of the head. The trunk is of about the same length as the head, and rather thick in front, but tapering rapidly and evenly behind. It is divided into 12 uniform segments, each carrying a pair of branchial legs. The dorsal surface of the segments is quite smooth, and without bristles. On the other hand, from the sides of the two hindmost segments, there issues a pair of peculiar, laterally-extended lamine, to which there is nothing corresponding to be found in other Phyllopoda. These lamine (fig. 9,1) which are only found in the female, are of no inconside- rable size, are foliate and project into 3 triangularly- pointed lobes, of which the foremost is the largest. Judging from their position, they appear to be intended to support the 2 cake-like masses of eggs that are carried beneath the shell. Halen (Fig. 7, 8) er meget liden og rudimenter, ikke omboiet, og kan heller ikke i Regelen strekkes synderlig langt ud fra Skallen. Den ender i 2 skraat nedadrettede og jevnsides liggende Flige af triangu- ler Form og tet cilierede i Kanterne, hver berende i Spidsen en liden, som det synes, fuldsteendig ube- vegelig Torn, der aabenbart svarer til Haleklorne hos andre bivalve Phyllopoder. Dorsalt findes om- trent paa Midten af Halen et stumpt Fremspring, hvyortil de 2 Haleborster er festede. Disse er vel udviklede, tydeligt 2leddede og tet cilierede. Ha- lens ventrale Side er delvis dekket af en eiendom- melig, operkelformig Plade (op), der udgaar fra dens Basis, og hvortil intet tilsvarende kjendes hos andre Phyllopoder. De sammensatte Oine (Fig. 11, 0) er beliggende ner Forkanten af Hovedet, omtrent ved Enden af den iste Trediedel af dets Lengde. De er forholds- vis smaa og stoder umiddelbart sammen i Midten, saa at de egentlig tilsammen danner et enkelt Organ, paa hvilket dog de 2 oprindelige Halvdele let lader sig paavise, naar Organet sees forfra (Tab. XVIII, Fig. 4) eller nedenfra (Tab. XIX, Fig. 13, 0). De er omgivne af en felles Kapsel og viser et stort Antal af smaa Krystalkegler udstraalende til alle Sider fra det morke Pigment. Som hos Limnadia, er de til en vis Grad bevegelige ved Hjelp af 3 fra Hovedets Integument til hver Halvdel udgaaende Muskler (se Fig. 11). I ganske kort Afstand nedenfor de sammensatte Mine ligger det enkle Mie (Fig. 11, 13, 14, oc, Fig. 15). Det er af en noget uregelmessig afrundet eller ret- tere kubisk Form og viser ved noiere Undersogelse, -ligesom hos Limnadia, 4 Flader indrammede af et morkt Pigment. Fladerne er temmelig sterkt ud- buede og viser under visse Belysninger en lignende iriserende Glands som hos hin Slegt. Det er holdt i Situs ved fine til Hovedets Integument gaaende Ligamenter,:hvoraf et fester sig til Forkanten af Hovedet ved Basis af Rostrum (Fig. 11, p). Umiddelbart foran det enkle Gie bemerkes i Hovedets Integument 2 jevnsides stillede aflangt ovale Felter (Fig. 11, ol), der er meget skarpt con- turerede og har til Underlag en blod Masse af til- syneladende ganglios Natur. Ethvert af disse Feld- ter (se Fig. 12) er dekket af en’ meget delicat Mem- bran, hvorfra et Antal af fine Haar eller Cilier springer frem, hvert udgaaende fra en liden knop- formig Fortykkelse i Membranen. Der kan neppe vere nogen Tvivl om, at disse eiendommelige Dan- nelser, der ogsaa er omtalte af Grube, repreesenterer et Slags Sandseredskaber, men af hvilken Art er vanskeligt at sige. Endnu en eiendommelig Dan- nelse maa her omtales. Folger man Dorsalkanten 16—G. 0. Sars Fauna Norvegiz. 121 The tail (figs. 7 and 8) is very small and rudi- mentary, is not bent down, and cannot as a rule be extended very far from the shell. It ends in 2 obli- quely-pointing, juxtaposed lobes of a triangular shape, and thickly ciliated at the edges, each car- rying at the point a small, apparently quite immov- able spine, which evidently answers to the caudal claws in other bi-valved Phyllopoda. At about the middle of the tail dorsally there is a blunt projec: tion, to which the 2 caudal sete are attached. The latter are well-developed, distinctly 2-jointed and thickly ciliated. The ventral surface of the tail is partly covered by a peculiar opercular lamella (op), issuing from its base, and to which there is nothing corresponding in other Phyllopoda. The compound eyes (fig. 11,0) are situated near the front margin of the head, at about the end of the first third of its length. They are compara- tively small, and meet in the middle, thus forming in reality a single organ, in which, however, the 2 original halves may be easily distinguished, when the organ is seen from the front (Pl. XVII, fig. 4) or from below (Pl. XIX, fig. 13, 0). They are sur- rounded by a common capsule, and exhibit a large number of small crystalline cones radiating to all sides from the dark pigment. As in Limnadia, they are movable to a certain extent by the help of 3 muscles issuing from the integument of the head to each half (see fig. 11). At a very short distance below the compound eyes, is the ocellus (figs. 11, 13, 14 oe, fig. 15). It is of a somewhat irregular, rounded or rather cubi- cal shape, and presents, on a closer examination, just as in Limnadia, 4 surfaces encircled by a dark pigment. The surfaces are not a little convex, and in certain lights, like the above-mentioned genus, have an iridescent lustre. It is held in position by fine ligaments running to the integument of the head, one of which is fastened to the anterior margin of the head at the base of the rostrum (fig. 11, p). Immediately in front of the ocellus, may be observed, in the integument of the head, 2 juxtaposed oblong oval fields (fig. 11, ol) very sharply outlined, and with a soft mass of an ap- parently ganglionic nature as sub-stratum. Each of these fields (see fig. 12) is covered by a very delicate membrane, from which spring a number of fine hairs or cilia, each issuing from a little nodiform thickening of the membrane. There can hardly be any doubt that these peculiar for- mations, which are also mentioned by Grube, re- present a kind of sensory apparatus, but of what kind, it is difficult to say. Yet another peculiar formation must be mentioned here. In following 122 af Hovyedet opover, vil man helt bagtil, i nogen Afstand fra den tvergaaende Sutur, der skiller Ho- vedet fra Nakkesegmentet, bemerke en liden grube- formig Fordybning (Fig. 11, x), der constant fore- kommer her hos alle Individer, baade Hanner og Hunner. Ifolge sin Plads maa denne Grube ner- mest ansees for homolog med Fastheftningsorganet hos Limnadia, skjondt det er lidet troligt, at denne ubetydelige Grube kan her fungere som et saadant Organ. Forste Par Folere (Fig. 11, a1, Fig. 2), .som er feestede til hver Side af Hovedets ventrale Del, umiddelbart foran Basis af Overleben, er meget smaa og af noget kelledannet Form. De bestaar hver af et kort Skaft og en noget buet, i sit ydre Parti fortykket Endedel, der fortil er tet besat med delicate Lugtepapiller (Fig. 2a); af et lignende Ud- seende som hos Limnadia. Disse Folere er til en vis Grad bevegelige ved Hjelp af en Del smaa Muskler, som passerer til dem fra Hovedets Inte- gument. Andet Par Folere, eller Aarerne (Fig. 3), ud- springer, som hos Limnadia, med en bred Basis fra Hovedets Sider, umiddelbart under den bagre, mest fremspringende Del af Fornix. De bestaar af de samme Dele som hos. Limnadia, nemlig et tykt, eylindriskt Skaft, og 2 Grene; men disse sidste er her paa langt ner ikke saa steerkt forleengede som hos hin Slegt. Skaftet, hvis basale Del synes at vere fuldstendig ubeveegelig, er derimod paa Midten meget boieligt og her delt i flere korte, tildels ufuld- steendigt sondrede Led, medens dets ydre Trediedel danner et enkelt Led for sig. Fra Basaldelen ud- gaar bagtil et Antal af omkring 5 sterke nedad- rettede Fjzrborster, og i Forkanten af det yderste af de mediane Led er der en Del grove Pigge, ord- nede i en Tverrad. En lignende Tverrad af Pigge findes ogsaa ved Enden af Skaftet fortil. Grenene er neppe lengere end Skaftet og omtrent af ens Storrelse, eller den bagre ubetydeligt lengere end den forreste. De er begge delte i et stort Antal (fra 15 til 18) korte Led, der dog ved Basis af Gre- nene er meget utydeligt sondrede. Ethvert Led har i Bagkanten en enkelt lang Svommeborste, og paa den forreste Gren har de fleste Led endnu hvert en enkelt steerk Pig i den modsatte Kant. Sidste Led har paa den bagre Gren 2 Svommeborster, paa den forreste desforuden en Pig. Naar Aarerne er i Hvile, legges de almindeligvis. langs ad Siderne af Hovedet, umiddelbart bag. dettes laterale Kjole. De fra Hovedets Integument til Aarerne gaaende Musk- ler er meget kraftige og fester sig alle ved det midterste boielige Parti af Skaftet. I dettes ydre Del sees andre Muskler, der virker paa enhyer af Grenene. ; | the dorsal margin of the head upwards, there is observable, at the very back, at some distance from the transverse suture, which separates the head from the ceryical segment, a small pit-like depression (fig. 11, z), which occurs invariably in all specimens, both males and females. From its place, this pit must probably be regarded as homologous to the organ of attachment in Limnadia, although it is almost incredible that this insignificant hollow can here act as such an organ: The Ist pair of antenne (fig. 11, a’, fig, 2) which are attached to the sides of the ventral portion of the head, immediately in front of the base of the labrum, are very small, and of a somewhat clavate form. They each consist of a short scape, and a somewhat curved terminal part, thickened in its outer portion, and thickly set in front with delicate olfactory papille (fig. 2a), of an appearance similar to those in Limnadia. These antenne are movable to a certain extent by the aid of several small muscles passing to them from the integument of the head. The second pair of antenne, or the oars (fig. 3) issue, as in Limnadia, with a broad base from the sides of the head, immediately below the hinder, most projecting part of the fornix. They consist of the same parts as in Limnadia, namely a_ thick, cylindrical scape, ‘and 2 rami; but the latter are here not nearly so much elongated as in the before- mentioned genus. The scape, of which the basal part appears to be quite immoyable, is, on the other hand, very flexible.in the middle, and is here divided into seyeral short, to some extent imper- fectly defined joints, while its distal third . part forms a single joint by itself. From the basal part there issue at the back about 5 strong, downward- pointing plumose sete, and on the anterior margin of the most distal of the median joints, there are-a number of coarse spines arranged in a transverse row. A similar transverse row of spines is also found at the end of the scape in-front. The rami are scarcely longer than the scape, and are of almost equal size, the hind one being very slightly longer than the front one. They are both divided into a great number (from 15 to 18) of short joints, which, however, are very. indistinctly defined at. the base. On the hind margin: of. each joint, there is a single long natatory bristle, and on the front ramus, most of the joints have, yet another single, strong spine on the opposite margin. On the hind ramus there are 2 natatory bristles on the last joint, and. on the front..ramus, a spine as _ well. When. the oars are at rest, they generally. lie along, the sides of the head, immediately behind its lateral keel, - The muscles running from. the integu- ment of the head to the oars are very powerful, and are all attached to the middle,, flexible: iis of. - ; : 123 Overleben (Fig. 11, Z), som danner den umiddel- bare Fortsettelse af Hovedets ventrale Flade, er af betydelig Storrelse og rekker ind mellem Basis af Iste, tildels endogsaa 2det Fodpar. Den har For- men af en aflang, noget sammentrykt Lap, der i sit ydre Parti danner en noget nedadboiet, rundtom fint cilieret oval Lamelle, uden nogen saadan ten- takelformig Fortsats som hos Limnadia. Overleben kan loftes af fra Munddelene ved et Par tynde Muskler, der fra Hovedets Integument passerer til dens Basis. I dens Indre sees, som hos Limnadia, flere celleagtige Legemer og et Antal af tvergaaende Muskler, som virker paa dens ovre blode og rende- formigt fordybede Flade. Kindbakkerne (Fig. 4, Fig. 11, M) ligger, som hos Limnadia, i Form af 2 boileformige Legemer til hver Side paa Grendsen mellem Hovedet og Nakke- segmentet. Deres ovre tilspidsede Ende er articu- leret til et fortykket Parti af Integumentet ved Enderne af den mellem begge de ovenneevnte Dele gaaende T'veersutur, medens deres nedre, steerkt ind- boiede Ender modes paa Undersiden ved Mundaab- ningen. Tyggedelen er stwrkt, nesten oxeformigt udvidet, og viser en noget tilskjerpet Kant delt i en Rekke stumpe Tender, hvoraf den yderste er storst. I sin Bevebning skiller altsaa Kindbakkerne hos nerverende Form sig meget vesentligt fra samme hos de ovrige bivalve Phyllopoder og viser en Tilnermelse til den for Apodiderne characteristiske Bygning. Forste Par Kjever (Fig. 4, 11, m*, Fig. 5), be- staar, som hos Limnadia, af en tykkere Basaldel og en beveegelig Endeplade; men denne sidste er her betydelig smalere, leformigt indadkrummet, og kun forsynet med et begrendset Antal af sterke, uled- dede Borster. Langs den indre Kant af Pladen tel- ler man 8 saadanne Borster, noget tiltagende i Lengde udad og fint cilierede i den ene Kant (se Fig. 5a). Ved Spidsen af Pladen er festet 3 be- tydelig kortere Borster, der er pigformige og grovt tandede i begge Kanter (se Fig. 5b). I den ydre Kant har Pladen ved Basis en meget fin Ciliering. Andet Par Kjever (Fig. 4, 11, m*, Fig. 6), der ikke er bemerkede af Grube, er meget rudimentere, kun forestillende et Par simple, noget hjertefcrmige Lameller af en delikat membranos Beskaffenhed, i hvilken Henseende de nermest synes at svare til den ydre Udvidning (Palpe) af disse Kjever hos Lepidurus. Deres Beliggenhed, temmelig langt fijer- nede fra Midtlinien (se Fig. 4), taler ogsaa for en saadan Tydning, hvorved altsaa den egentlige Tygge- del maa antages at vere ganske oblitereret. Lamel- the scape. In the outer part of the latter, other muscles are visible, which act upon each of the rami. The labrum (fig. 11, Z), which forms an imme- diate continuation of the ventral surface of the head, is of considerable size, and extends between the bases of the 1st, and partly also of the 2nd pair of legs. It has the form of an oblong, ra- ther compressed lobe, whose outer part forms a somewhat downward-curved, oval lamella, finely ciliated all round, and without any such tentacular projection as in Limnadia. The labrum can be raised from the oral parts by a pair of thin muscles passing to its base from the integument of the head. In its interior may be seen, as in Limnadia, several cellular bodies, and a number of transverse mus- cles, acting upon its upper soft and grooved surface. The mandibles (fig. 4, fig. 11, JZ) lie, as in Lim- nadia, in the shape of 2 bow-shaped bodies, one on each side, at the boundary between the head and the cervical segment. Their upper pointed end is articulated to a thickened part of the integument, at the ends of the transverse suture which runs between the two parts just named; while their lower, much incurved ends meet on the under sur- face at the oral aperture. The masticatory part is strong, and almost securiformly expanded, and exhibits a somewhat sharpened edge, divided into a series of blunt teeth, the outermost of which is the largest. Thus, in the matter of equipment, the man- dibles in this form are very essentially distinct from those in the other bi-valve Phyllopoda, and show an approach to the structure characteristic of the Apodide. The ist pair of maxille (figs. 4, 11, m'*, fig. 5) consist, as in Limnadia, of a thicker basal part and a movable terminal lamella; but the latter is here considerably narrower, is curved falciformly inwards, and furnished with only a limited number of strong, unarticulated bristles. Along the inner edge of the lamella, 8 such bristles may be counted, somewhat increasing in length outwards, and finely ciliated on one edge (see fig. 5a). To the point of the lamella are attached 3 considerably shorter bristles, which are spiniform and coarsely dentated on both edges (see fig. 5b), At its base the lamella is very finely ciliated on the outer margin. The second pair of maxille (figs. 4, 11, m’, fig. 6), which have not been observed by Grube, are very rudimentary, representing only a pair of simple, somewhat cordate lamelle of a delicate, membranous consistency, in which respect they seem almost to correspond to the outer expansion (palp) of these maxille in Lepidurus. Their position, at some distance from the median line (see fig. 4), also favours such an interpretation, whereby the true masticatory part must be assumed to be quite lerne synes til en vis Grad at vere beyegelige, idet 2 tynde Muskler passerer til hver af dem ovenfra. Branchialfoddernes Antal er, som ovenfor an- fort, 12 Par. Af disse er de 3 forreste Par omtrent af ens Lengde, medens de ovrige hurtigt aftager i Storrelse bagtil. Tab. XX, Fig. 1 fremstiller en Fod af 3die Par seet fra den forreste Flade. Som det vil sees, er Formen temmelig afvigende fra samme hos Limnadia, skjondt man kan adskille de samme Hoveddele. Endopoditen er idethele bredere og mere pladeformig, og af Enditerne har kun de 2 inderste et lignende Udseende som dem hos Lim- nadia, medens de 3 derpaa folgende er forlengede til fingerformig indadrettede Fortsatser besatte i den ene Kant med en dobbelt Rad af sterke Borster. Den yderste (Ste) Endit er, som hos Limnadia, be- vegeligt articuleret til Endopoditen og forestiller egentlig dennes Endeled. Coxallappen (mx) er vel udviklet og skraat indadrettet, visende adskillig Lighed i Form med Endepladen af 1ste Par Kjzver. Den er imidlertid (se Fig. 1 b) forsynet med et sterre Antal Borster i den indre Kant, tildels ord- nede i 2 Rekker. Yderkanten har kun en enkelt indadrettet Borste ner Spidsen og er forevrigt meget fint cilieret. Epipoditen (ep) er af middels Storrelse og viser en lignende Form og Structur som hos Limnadia. Derimod har Exopoditen et temmelig afvigende Udseende. Den er rigtignok ogsaa her deit i en ventral og en dorsal Lap; men den ven- trale Lap (ex), som hos Limnadia er den storste, er her kun tilstede som en forholdsvis ubetydelig, smalt tilspidset Fortsats, kantet med lange, cilierede Borster, medens den dorsale Lap (ex') er enormt udviklet, dannende en bred, halvmaaneformigt krum- met Plade, der rager hoit op over Kropsiderne (se Tab. XIX, Fig. 1). Denne Plade har langs Yder- kanten en tet Rad af forholdsvis korte, men tet cilierede Borster og er ogsaa tildels borstebesat i Inderkanten. Fra dens stumpt afrundede Ende ud- gaar desuden en meget lang og tynd, ucilieret Borste. Af vesentlig samme Udseende som det ovenfor beskrevne 3die Fodpar er ogsaa de 2 forreste og de 4 folgende Par, hvilke sidste dog gradvis aftager i Storrelse. 8de Fodpar (Fig. 2) skiller sig imidlertid, for- uden ved ringere Storrelse, meget vesentligt ved den fuldsteendige Mangel af Epipodit. Ligeledes er Enditerne mere sammentrengte og mindre ulige, idet de 2 bagerste er mere fremspringende, de 3 yderste kortere end paa de foregaaende Par. Exopoditens dorsale Lap er forsynet i Enden med flere lange, divergerende Borster af samme Beskaffenhed som den enkle apicale Borste paa 3die Par. 124 obliterated. The lamelle appear, to a certain extent to be movable, as 2 thin muscles pass to each of them from above. As stated above, the number of branchial legs is 12 pairs. The 3 foremost of these are of about uniform length, while the remainder rapidly diminish in size towards the back. Pl. XX, fig. 1, represents a leg of the 3rd pair seen from the front. As will be seen, the shape differs not a little from that in Limnadia, although the same principal parts are distinguishable. The endopodite is on the whole broader and more lamellar; and only the innermost endites have a similar appearance to those in Lim- nadia, while the next 3 are elongated into digiti- form, inward-pointing projections, clothed on one edge with a double row of strong bristles. The outermost (5th) endite, as in Limnadia, is movably articulated, to the endopodite, really representing the latter’s terminal joint. The coxal lobe (mx) is well developed, and directed obliquely inwards, and exhibits a considerable resemblance in form to the terminal lamella of the lst pair of maxille. It is, however (see fig. 1 6), furnished with a larger number of bristles on the inner margin, arranged to some extent in 2 rows. The outer margin has only a single inward-directed bristle near the point, and, in addition, is very finely ciliated. The epipo- dite is of medium size, and exhibits a similarity in form and structure to that of Limnadia. The exo- podite, on the other hand, is rather different in appearance, It is, indeed, here too, divided into a ventral and a dorsal lobe; but the ventral lobe (ex), which in Limnadia is the larger, here appears only as a comparatively insignificant, narrowly-pointed projection, edged with long ciliated bristles, while the dorsal lobe (ex +) is enormously developed, for- ming a broad, crescent-shaped curved lamella, which extends far up over the sides of the hody (see Pl. XIX, fig. 1), Along its outer margin this lamella has a close row of comparatively short, but thickly ciliated bristles, and is also setous to some extent.on the inner margin. There also projects from its bluntly rounded end a very long, thin, unciliated bristle. The 2 foremost pairs of legs, and the 4 sueceed- ing pairs are essentially of the same appearance as the above-described 3rd pair, the 4 succeeding pairs, however, diminishing gradually in size. The 8th pair of legs, however (fig. 2), besides being distinguished by their smaller size, differ very essentially in the total absence of an epipodite. The endites too are more crowded together and less dissi- milar, the 2 hind ones being more projecting, and the 3 outer ones shorter than in the preceding pair. The dorsal lobe of the exopodite is furnished at the extremity with several long, divergent bristles of the same appearance as. the single apical bristle: on the 3rd pair. sins gant OE ————————<«—— — = De 2 folgende (9de og 10de) Par (se Fig. 3) mangler, ligesom det 8de, ganske Epipodit, og ud- meerker sig desuden ved det eiendommelige Udseende af Exopoditens dorsale Lap. Denne er nemlig paa begge disse Par omformet til en cylindrisk Streng, der er hageformigt omboiet i Enden og her forsynet med en tet Ciliering. Det er aabenbart, at disse 4 Appendices (se ogsaa Tab. XTX, Fig. 1, Fig. 9, fb) er bestemt til, i Forening med de ovenfor omtalte, fra Rygsiden af de 2 bagerste Truncus-Segmenter udgaaende, bladformige Plader (1), at stotte de 2 kageformige Aigmasser, der beres under Skallens bagre Del. De 2 sidste Fodpar (Tab. XX, Fig. 4, 5) er meget smaa, navnlig det bagerste (12te) Par, og mangler baade Epipodit og den dorsale Lap af Exopoditen., Forovrigt ligner de i Structur de 2 foregaaende Par, og har, som disse, alle Enditer, ligesom ogsaa Coxal- lappen, tydeligt udviklede, skjondt meget tet sam- mentrengte. Den ventrale Lap af Exopoditen er paa sidste Par (Fig. 5) reduceret til et fra den ydre Side af Endopoditen udgaaende meget lidet, med 5 Borster forsynet Appendix. Beskrivelse af Hannen. Hannerne er gjennemgaaende noget mindre end Hunnerne, idet Skallen neppe opnaar en Lengde af 4 mm. Den er ogsaa (se Tab. XVIII, Fig. 3) noget mere uregelmessig af Form, med Forenden mere tvert afkuttet, og de nedre Kanter dannende fortil en meget sterk, nesten vinkelformig Krumning. Forovrigt ligner Skallen samme hos Hunnen og er fuldkommen ligesaa sterkt buget som hos denne. Det i Skallen indesluttede Dyr (se Tab. XX, Fig. 6) viser flere characteristiske Eiendommelig- heder, hvorved det strax skiller sig fra samme hos Hunnen. Hovedet er saaledes betydelig kortere og Rostrum af en meget afvigende Form. Seet fra Siden (se Tab. X VIL, Fig. 3, Tab. XX, Fig. 6) er det neesten jevnt bredt og har Enden, ikke som hos Hunnen udtrukket til en skarp Spids, men stumpt afrundet. Forfra seet (Tab. XVIII, Fig. 5) viser det sig tvert afkuttet i Enden, idet den mediane Spids ganske mangler, medens de laterale Fortsatser, hvori Hovedets Sidekjole gaar ud, er betydelig mere ud- staaende end hos Hunnen og nesten retvinklede. Af de eiendommelige trefligede Blade, der hos Hun- nen udgaar fra Rygsiden af Truncus bagtil, er der intetsomhelst Spor at opdage (se Tab. XX, Fig. 6). Haledelen (Fig. 10) har ogsaa en noget forskjel- lig Form, idet de 2 Endeflige er betydelig sterkere forlengede end hos Hunnen og tettere cilierede. The 2 succeeding (9th and 10th) pairs (see fig. 3) are, like the 8th, marked by a total absence of an epipodite, and are also distinguished by the peculiar appearance of the dorsal lobe of the exopodite. In both these pairs, this lobe is converted into a eylindrical cord, which is bent down at the end like a hook, and thickly ciliated. It is evident that these 4 appendages (see also Pl. XIX, fig. 1, fig. 9, fb) are intended, in conjunction with the above-men- tioned leaf-like lamelle (1) issuing from the dorsal side of the 2 hindmost segments of the trunk, to support the 2 cake-like masses of eggs, which are borne beneath the posterior part of the shell. The last 2 pairs of legs (Pl. XX, figs. 4, 5) are very small, especially the hindmost (12th) pair, and are without both epipodite and dorsal lobe of the exopodite. In other respects they resemble the 2 preceding pairs in structure, and have, like them, all the endites, as well as the coxal lobe, distinctly developed, although very closely crowded together. The ventral lobe of the exopodite in the last pair (fig. 5) is reduced (to a very small appendage pro- jecting from the outer side of the endopodite, and furnished with 5 bristles. Description of the Male. The males, on an average, are rather smaller than the females, as the shell scarcely attains a length of 4 mm. It is also (see Pl. XVIII, fig. 3) rather more irregular in shape, with the anterior end more abruptly truncated, and the lower edges forming in front a very sharp, almost angular curve. In other respects the shell resembles that of the female, and is quite as much vaulted. The animal enclosed in the shell (see Pl. XX, fig. 6) exhibits several characteristic peculiarities, thereby being immediately distinguished from the female. The head is considerably shorter, and the rostrum of a very different shape. Seen from the side (see Pl. XVIII, fig. 3; Pl. XX, fig. 6), if is of almost even breadth, the end not. being drawn out, as in the female, to a sharp point, but being bluntly rounded, Seen from the front (Pl. XVIII, fig. 5), it appears abruptly truncated at the end, the median point being altogether absent, while the lateral pro- jections into which the side keels of the head are produced are considerably more prominent than in the female, and almost rectangular. There is no trace whatever to be discovered of the peculiar tri- lobed lamelle, which, in the female, issue from the dorsal surface of the trunk behind (see Pl. XX, fig. 6). The caudal part (fig. 10) is also of a somewhat different shape, the 2 terminal lobes being consider- ably more elongated than in the female, and more thickly ciliated. 126 Hvad de forskjellige Lemmer angaar, saa viser de til det forreste Afsnit af Legemet horende neppe nogen vesentlig Forskjel fra samme hos Hunnen, skjondt maaske Iste Par Folere er noget storre og rigeligere forsynede med Lugtepapiller. Derimod bemerkes flere characteristiske Eiendommeligheder ved de til det bagerste Afsnit horende Lemmer eller Branchialfodderne. For det forste er deres Tal her constant et ringere, nemlig kun 10 Par ialt, og der- nest er iste Par meget uligt samme hos Hunnen, idet det er omdannet til et Par serdeles kraftige Griberedskaber, hvormed Hannen under Parringen fastholder Hunnens Skal (se Tab. XX, Fig. 6). Fig. 7 fremstiller en Fod af dette Par, seet fra den forreste Flade, og Fig. 8 det ydre Parti af samme noget sterkere forstorret. Som det vil sees, er Exopoditen og Epipoditen, ligesom ogsaa Coxal- lappen, noget neer af samme Udseende som hos Hun- nen. Derimod er det terminale Afsnit af Endopo- diten meget sterkt modificeret og omdannet til en med den proximale Del bevegeligt forbunden Haand, ligesom de til dette Afsnit horende Enditer er eien- dommeligt omformede. Selve Haanden er nesten qvadratisk af Form, med den indre Kant, eller Pal- men, sterkt buet og bevebnet med en Rad af 9 meget sterke, noget pladeformige Pigge, mellem hvilke rager frem stive Borster. Den yderste Endit er omformet til en kraftig, leformigt indadkrummet Klo, der udgaar med en noget udvidet Basis fra Enden af Haanden og kan ved Hjelp af en Del Muskler boies ind mod de ovenomtalte Pigge. Ved Roden af denne Klo udgaar et andet Appendix, der sedvanligvis ogsaa er indadkrummet, men ender i en stump, med lange Borster besat Spids og som synes at forestille den nestsidste omformede Endit. Lengere indad, mellem Kloen og de ovenomtalte Pigge er endelig feestet nok et Appendix, der er lige nedadrettet og har Formen af et ovalt Blad, tet besat med Borster. Dette Blad synes at repraesen- tere den 3die sidste Endit. Fra den proximale Del af Endopoditen udgaar indad en enkelt bred plade- formig Udvidning kantet med en dobbelt Rad af lange Borster, og rimeligvis fremkommen ved en Sammensmeltning af de 2 inderste Enditer. 2det Fodpar (Fig. 9) er fuldkommen normalt bygget, men skiller sig dog ved en noiere Under- segelse fra samme hos Hunnen ved den nestsidste Endits Beveebning (se Fig. 9 a). Foruden de seed- vanlige Borster findes der nemlig langs den indre Kant af denne Endit en Rekke af eiendommelige, i Enden tvedelte Torne, der successivt tiltager i Lengde mod Spidsen. Den yderste af disse Torne (Fig. 9,b) har foruden de 2 Endespidser i den indre Kant 4 korte Smaateender. De folgende 6 Par stemmer i alt viéeondiiligt The limbs belonging to the anterior section of the body exhibit scarcely any essential difference to those in the female, although the first pair of antenne are perhaps rather larger and more abun- dantly provided with olfactory papille. On the other hand, several characteristic peculiarities may be noticed in the jimbs belonging to the posterior section, or the branchial legs. In the first place their number is invariably smaller, namely, only 10 pairs in all; and in the second place, the 1st pair is very unlike that in the female, being converted into a pair of exceedingly powerful prehensile organs, by. means of which the male, during copulation, grasps the shell of the female (see Pl. XX, fig. 6). Fig. 7 represents one leg of this pair seen from the front, and fig. 8, the outer part of the same, mag- nified rather more highly. As will be seen, the exopodite, the epipodite, and the coxal lobes are nearly of the same appearance as in the female. The terminal section of the endopodite, on the other hand, is very greatly modified and converted into — a hand, movably connected with the proximal part, the endites belonging to this section also being peculiarly transformed. The hand itself is almost quadratic in shape, with the inner edge, or palm, much arched and armed with a row of 9 very strong, somewhat lamellar spines, between which project stiff bristles. The outermost endite is trans- formed into a powerful, falciform, inward-curving claw, which issues with a somewhat expanded base from the end of the hand, and can, by the aid of certain muscles, be bent in towards the above- mentioned spines. At the root of this claw, issues another appendage, which is also usually bent in- wards, but ends in a blunt point clothed with long bristles, and seems to represent the penultimate transformed endite. Farther in between the claw and the above-mentioned spines, there is attached yet another appendage, which points straight down- wards, and is in the shape of an oval lamina, closely set with bristles. This lamina seems to — represent the antepenultimate endite. From the proximal part of the endopodite there runs inwards a single, broad, lamellar expansion edged with a double row of long bristles, and probably produced by a coalescence of the two innermost endites. The 2nd pair of legs (fig. 9) is quite normal in structure, but on a closer examination, is distin- guished from that of the female by the equipment of the penultimate endite (see fig. 9a). In addition to the usual bristles, there is also, along the inner edge of this endite, a row of peculiar bifid spines, which successively increase in length towards the point. The outermost of these spines (fig. 9, b) has, in addition to the two terminal points, 4 short den- ticles on the inner margin. The succeeding 6 pairs agree in all essential overens med samme hos Hunnen, de og 10de Par mangler derimod ganske den paa disse Par hos Hunnen forekommende strengformige dorsale Lap af Exopoditen, hvorimod de ganske synes at stemme overens i Bygning med 1l1te og 12te Par hos Hunnen, Farven er hos begge Kjon i levende Tilstand meget mork, olivengron. Dette skyldes imidlertid veesentligt det i Skallen indesluttede Dyr. Skallen selv er derimod temmelig gjennemsigtig og af lys horngul Couleur, med kun et svagt gronligt Skjer. Indre Organer. Den indre Organisation stemmer i sine vesent- ligste Trek overens med samme hos Limnadia. Dog vil man ved en noiere Sammenligning finde visse characteristiske Eiendommeligheder. Tarmen (se Tab. XIX, Fig. 1, Tab. XX, Fig. 6) strekker sig som et temmelig jevnt tykt Ror igjen- nem Axen af Legemet og ender bagtil med en kort, muskulos Endetarm, der udmunder mellem Halens Endeflige. Fortil er Tarmen noget nedadkrummet i Overensstemmelse med Legemets Boining paa dette Sted og forbinder sig ventralt med det temmelig korte, fortil fra Mundaabningen lobende Spiseror. Dette sidste viser ved sin Forbindelse med Tarmen en lignende klapformig Indretning som hos Limnadia (se Tab. XIX, Fig. 4, oes). I Forbindelse med Tar- mens forreste Del staar, som hos Limnadia, et af 2 symetriske Halvdele bestaaende compliceret lever- agtigt Organ (Fig..11, Ww); men dette Organ er her kun indskrenket til den ventrale Del af Hovedet og udfylder Storsteparten af Rostrums Hule. Hver Halvdel bestaar af talrige bugtede Blindsekke, der samler sig oventil til en enkel forholdsvis meget rum- melig Udforselsgang (co), udmundende i Tarmen med en vid Aabning (se ogsaa Tab. XVIII, Fig. 4 og 5). _ Hjertet (Tab. XIX, Fig. 1, h, Fig. 10) har en lignende Beliggenhed som hos Limnadia og viser ogsaa en lignende Structur. Det er imidlertid for- holdsvis kortere, idet det kun strekker sig lidt ind i 3die fodbeerende Segment, og har kun 3 Par late- vale Spaltaabninger, medens 4 saadanne er tilstede hos Limnadia. _ Nervesystemet. — Hjernegangliet (see Tab. XIX, Fig. 11,13, 14) ligger delvis skjult mellem Leverens ‘Udforselsgange, og viser idethele en lignende Byg- ning som hos Limnadia. Dog er Synsnerverne (opt) her betydelig kortere og deres kolbeformigt opsvul-— mede Ender er adskilte ved et tydeligt Mellemrum (se Fig. 13). De Fortsatser, hvorfra Nerverne for | iste Par Folere udgaar (a’) er sterkt forlengede — 127 points with the corresponding legs in the female. The 9th and 10th pairs, on the other hand, are altogether without the cord-like dorsal lobe of the exopodite found in those pairs in the female, while they appear to agree in structure with the 11th and 12th pairs in the female. The colour in both sexes in the living condi- tion, is a very dark olive-green. This, however, is principally due to the animal enclosed in the shell. The shell itself is fairly transparent, and of a light, horny yellow colour, with only a faint greenish tinge. Internal Organs. The internal organisation agrees in its essential features with that in Limnadia, although certain characteristic peculiarities are to be found on closer comparison. ' The intestine (see Pl. XIX, fig. 1; Pl. XX, fig. 6) extends, in the shape of a tolerably even, thick tube, through the axis of the body, ending posteri- orly in a short, muscular rectum, which opens out between the terminal lobes of the tail. Anteriorly, the intestine is somewhat downward-curved in accor- dance with the curve of the body at that place, and is connected ventrally with the rather short esophagus running forwards from the oral aperture. The cesophagus, in its connection with the intestine, exhibits a valve-like contrivance similar to that in Timnadia (se Pl. XIX, fig. 4, oes). Communicating with the foremost part of the intestine, as in Lim- nadia, there is a complicated, liver-like organ, con- sisting of 2 symmetrical halves (fig. 11, lv); but this organ is here confined to the ventral part of the head, and occupies the greater part of the cavity of the rostrum. Each half consists of numerous curved ceca, which meet above in a single, com- paratively very capacious excretory duct (co), open- ing by a wide mouth into the intestine (see also Pl. X VIL, figs. 4 and 5). The heart (Pl. XIX, fig. 1, h, fig. 10) has a situation similar to that in Limnadia, and also exhibits a similar structure. It is however compa- ratively shorter, as it only extends a little way into the 3rd pedigerous segment, and has only 3 pairs of lateral ostia, whereas in Limnadia there are 4. The Nervous System. — The cerebral ganglion (see Pl. XIX, figs. 11, 13, 14) lies partly hidden. be- tween the excretory ducts of the liver, and exhibits on the whole,a similar structure to that. in’ Lim- nadia, The optic nerves (opt), however, are consi- erably. shorter here, and. their club-like swollen -ends-are separated by a distinct space (see fig. 13). The projections from which issue the nerves for the og skraat bagudrettede. Nerverne for Aarerne (a *) udspringer ogsaa her fra de fra Hjernegangliet bagud gaaende Commissurer. Buggangliekjeden (Tab. XX, Fig. 19) ligner samme hos Limnadia, dog med den Forskjel, at Nervestammerne er forholdsvis sterkere og ligger noget nermere sammen. Antallet af gangliose Opsvulmninger er selvfolgelig, i Overens- stemmelse med det langt ringere Antal Fodpar, mindre end hos Limnadia. Ovarierne (se Tab. XIX, Fig. 1) er af betydelig Storrelse, strekkende sig til hver Side af Tarmen gjennem hele Truncus. De viser et sterkt lappet Udseende, idet Hgfolliklerne grupperer sig drueklase- formigt omkring Ovarialrorene (se Tab. XX, Fig. 13). Mglederen udgaar fra den bagerste Del af hvert Ovarium og synes at udmunde umiddelbart under de ovenomtalte trefligede dorsale Blade. Paa dette Sted ser man nemlig ofte storre Masser af modne JEg samlede. Som hos Limnadia, indeholder hver Mgfollikel 4 Celler, hvoraf alene den terminale bli- ver til det egentlige Ag, medens de 3 svrige fore- stiller Neringsceller og derfor tilsidst ganske absor- beres (se Fig. 14—17). De af Ovarierne udkomne Hg grupperer sig sammen til 2 rundagtige kage- formige Masser, der beres under Skallen helt bagtil (se Tab. XVIIT, Fig. 1 og 2). Hver igmasse inde- holder et stort Antal af Mg; der ved et klebrigt Stof er heftede sammen. Xggene er omgivne af en simpel, ikke meget fast Kapsel, uden nogen ioine- faldende Skulptur. Testes (se Tab. XX, Fig. 6) har samme Belig- genhed som Ovarierne og ligner disse ganske hvad Anordningen af Folliklerne angaar (se Fig. 12). Disse sidste er imidlertid her alle af nogenlunde ens Storrelse og af noget uregelmessig Form, samt indeholder hver en med den centrale Kanal i For- bindelse staaende Hule, i hvis Vegge de meget smaa celleagtige Sedelementer udvikle sig. Mundingen for vasa deferentia synes at ligge omtrent paa samme Sted som Mundingen for Mglederne hos Hunnen. Udvikling. — Jeg har desverre ikke selv havt Anledning til at studere denne Phyllopodes Udvik- ling. Men ifolge Grubes Undersogelser synes den i flere veesentlige Punkter at skille sig fra den hos andre Phyllopoder. Larven har et meget eiendom- meligt Udseende, som noget minder om samme hos Cirripedierne. Selv i det tidligste af Grube obser- verede Stadium, som ifolge Lemmernes Beskaffenhed ubetinget er et Nauplius-Stadium, er nemlig Lege- — met dekket oventil af. et meget stort fladt Ryg- skjold, og har nedentil et lignende men mindre Skjold, | der forestiller Overleben. Hovedet har en meget eiendommelig Form, idet det gaar ud i3 korsformigt RD Ist pair of antenne (a’), are very much elongated, and directed obliquely backwards. The nerves for the oars (a*) also originate hére, starting from the commissures which run backwards from the cerebral ganglion. The ventral ganglion chain (Pl. XX, fig. 19) resembles that in Limmadia, though with the difference that the nerve stems are comparatively stronger, and lie rather nearer together. The num- ber of ganglionic dilatations is, of course, in accor- dance with the far smaller number of legs, less than in Limnadia. The ovaries (see Pl. XIX, fig. 1) are of consi- derable size, extending through the whole trunk on each side of the intestine. They present a very much lobed appearance, from the fact that the egg- follicles are grouped botryoidally about the ovarial tubes (se Pl. XX, fig. 13). The oviduct issues from the hind part of each ovary, and seems to open immediately below the before-mentioned tri-lobed dorsal lamella; for at that place large masses of mature eggs are often seen accumulated. As in Lim- nadia, each egg-follicle contains 4 cells, of which the terminal one only becomes the true egg, the other 3 representing alimentary cells, and being therefore at last quite absorbed (see figs. 14—17). The eggs that have issued from the ovaries congre- gate into 2 round, cakelike masses, which are borne beneath the shell at the very back (see Pl. XVIII, figs. 1 and 2). Each eggmass contains a large number of eggs, which are fastened together by a glutinous substance. The eggs are surrounded by a simple, not very firm capsule, without any conspi- cuous seulpturing. The testes (see Pl. XX, fig. 6) have the same position as the ovaries, and resemble them exactly as regards the arrangement of the follicles (see fig. 12). Here, however, the latter are all of about the same size, and of a somewhat irregular shape; each contains a cavity communicating with the central channel, and in whose walls the very small, cellular seminal elements are developed. The opening of the vasa deferentia appears to lie at about the same place as the mouth of the oviducts in the female. Development. — I have unfortunately not had an opportunity, personally, of studying the develop- ment of this Phyllopod; but, according to Grube’s investigations, it seems, in several essential points, to differ from that of other Phyllopoda. The larva has a very peculiar appearance, somewhat resem- bling that of Cirripedia. Even in the earliest stage observed by Grube, which, from the condition of the limbs, is unquestionably a nauplius stage, the body is covered above by a very large flat cara- pace, and has a similar, but smaller shield below, which represents the labrum. The head has a very peculiar shape, for it projects in 3 cruciformly-placed a 129 stillede Fortsatser, hvoraf den midterste forestiller Rostrum. Forekomst og Leyevis. Det eneste Sted her i Landet, hvor denne Phyllo- pode hidtil er observeret, er i Ostfinmarken ved Matsjok, en Biflod til Tana, hvor Prof. Collett fandt den i Sommeren 1885. Da jeg nogle Aar senere, i 1888, bereiste Finmarken, undlod jeg ikke at besoge denne Lokalitet, og var ogsaa saa heldig at finde den her i Slutningen af August meget almindeligt i en grund, med talrige Vandplanter bevoxet Groft. Alle Exemplarer var da fuldt udviklede og syntes at have opnaaet sit Maximum af Storrelse. Skjondt jeg noie undersogte alle Damme og Grofter i Om- egnen, var det mig dog ikke muligt at finde noget Spor af den andetsteds end netop i den omtalte Groft, der saaledes maa have frembudt serlig gun- stige Forhold til dette Dyrs Trivsel. 1 Lobet af nogle faa Dage indsamledes her et betydeligt Antal Exemplarer, ligesom Observationer anstilledes over det levende Dyr i mine Excursionsglasse. Dyrets Bevegelser er temmelig klodsede og lidet udhol- dende, bestaaende i et noget ujevnt og ligesom rul- lende Lob gjennem Vandet, hvorunder snart Ryg, snart Bug vendes opad. Under Beveegelsen er Ho- vedet helt fremstrakt af Skallen, saa at Aarerne fuldt kan virke, og Valvlerne er herunder vidt aabne neden- til. Jeg kunde ikke observere, at Dyret nogensinde, som Tilfeeldet er med Limnadia, feestede sig til de i Vandet veerende Gjenstande. Naar Bevegelsen op- horte, sank Dyret hurtigt til Bunden, og laa her ofte i lengere Tid ubevegeligt paa Siden, for saa igjen at foretage en kort Udflugt i Vandet. Hanner og Hunner forekom nesten i samme Antal og saaes ofte i Copulation, hvorunder Hannen med sine Gribe- fodder med stor Kraft omfatter Kanterne af Hun- nens Valvler nedentil. Selve Parringsakten fik jeg dog ikke observere. At domme efter Kindbakkernes Beveebning, synes Dyrets Nering at vere mere -animalsk end Tilfeeldet er med de ovrige bivalve Phyllopoder, og bestaar rimeligvis for en stor Del af mindre Entomostraceer. Udbredning. — Denne Phyllopode blev forst opdaget af O. F. Miiller i Damme ner Kjobenhavn, og er ogsaa senere her gjenfunden. Foruden i Dan- mark er den observeret ved Danzig af Liévin, ved Dorpat af Grube, i Lillerusland ved Charkow og i Ungarn ved Pest, endelig ogsaa i Sibirien. I sin Udbredning synes den saaledes idethele, i Modseet- ning til Limnadia, at vere en ostlig Form, og det er aabenbart ad den Vei, nordenom den _ botniske Bugt, at den har udbredt sig til vort Land. processes, the middle one of which represents the rostrum. Occurrence and Habits. The only place in this country (Norway) where this Phyllopod has hitherto been observed is in Kast Finmark, near the Matsjok, a tributary of the Tana, where Prof. Collett found it in the summer of 1885. When some years later, in 1888, I travelled through Finmark, I did not fail to visit this locality, and had also the good fortune to find it there at the end of August, very plentiful, in a shallow ditch where numerous aquatic plants grew. All the spe- cimens were then fully developed, and seemed to have attained their maximum size. Although I care- fully examined all the ponds and ditches in the neighbourhood, I did not succeed in discovering any trace of it anywhere except in the said ditch, which must thus have offered conditions especially favo- rable to this animal’s well-being. Ig the course of a few days, a considerable number of specimens - were collected here, and observations made of the living animal by watching them in my collecting- jars. The animal’s movements are rather awkward, and not very persevering, consisting in a some- what uneven and, as it were, rolling course through the water, sometimes with the dorsal, sometimes with the ventral side uppermost. During the movement the head is stretched right out of the shell, so that the oars can have their full effect, the valves meanwhile being wide open below. I never observed the animal attaching itself to objects in the water, as is the case with Lim- nadia. When the motion ceased, it sank quickly to the bottom, and often lay there a long time on its side, motionless, then again making a short ex- cursion through the water. Males and females are found in almost equal numbers; and are often seen in copulation, during which the male, with its pre- hensile legs, embraces with great power the lower edges of the female’s valves. The act of copulation itself, however, I have not witnessed. Judging from the armature of the mandibles, the animal’s food appears to be more animal than is the case with the other bi-valve Phyllopoda, and probably consists to a great extent of smaller Entomostraca. Distribution. — This Phyllopod was first disco- vered by O. F. Miiller, in ponds near Copenhagen, and has also been found there again subsequently. Besides in Denmark, it has been observed by Liévin at Danzig, by Grube at Dorpat, at Charkow in Little Russia, at Pesth in Hungary, and lastly in Siberia. It therefore appears, in opposition to Lim- nadia, to be, in its distribution, an eastern form, and it is evidently by way of the north of the Gulf of Bothnia, that it has spread to our land (Norway). 17 — G. O, Sars: Fauna Norvegie. srr Sd Living: Sy eeeg 7 Piers wide bite sonoma Apidos vit tt ave ourlad AFP oe ormltbp wed baqn ted eit adie Adjata Gitstem Arete ; ewan “s\n techy aah ta T aa donor + -bell4yernd Daa hak watak else sine nl cofvenit tiehe ot Het*dod Gib f emt mad ai bai of sgmttcol foog sit onle funk sthwita. arisni Pte “aio sara Pe Tu Bate beypz Ob? LA rote erring serene uyrerracegiir real qe Od Panes brs chayolrebte iin de Sty eric y iets orks £ derodt lel — sete vieeerteane sbalt? Paaiad te yd da univ) emnfad ib Jaa hina ett Be) baat. ilbat Pitan Sete savour ler basses tho ier Bors (odibeteir diiter wdotiinhie edd at pears er ohyprms te fo Siietl t ‘alte een 6b. wren Sia a “hy eMail Tae ‘ Oe taka’ x ere oe rina atiwhP au vobis0e abies bo Banat fae nodvnimitisat + tu Amaeinede Soewigte ibe?" allay? cr eT fit Lotte B radises AL Stee” eh 'Kaat HAs amend tacwab di! pale fstanratt shit fe giblad ePakee TeV ge, lite — puitShvieer? ogee burgh A ta a Hear tol Thor raonteonh te nari ut nd bebionges “eth tet hact fers ix Seni she deone | lnieewwer aft el ogntaldise: Afuntemt =id}ote ahderr atinnines?: ty adorn allerbietos a anh wat sift ty alms. oitmisads freeroll harsstion’ ae x gothistiod pac ai mods dotihaew ch Merida eat Tales venobet oe etree einlins all Cah | -yitos git yyrithietho .auitrevodtap ea dome hae dhowdt enor giftos ano) dks” bine eaten jmki ehovitumo’ syheaib © dicots Aaihisvaroe Ling ai ade etruishl) +. GEE Se pou neue Diakeeotnas nbd vols china 1) seMin (in) init SowtP des letamarkty Aye vee, = ra orofet caqe shin Qed sititeagey esl ay) Yheatt gnitengte Loner aft froverarde tram, J tidy sitive. nail ts ah air alent eret ae 7 . Par, 1) ! ’ - b ‘ Faqs m ‘ REL ac eA feet | = ae Pere. we SSR mur tt Samp ete rite ‘ : "= |Z 1 cheplatiad ~ “a *, ; 9S hue So Aug Ke Se a, ae Fig lene ee ae: | ad . i + ~ a Pie ae + aS = int ee ee Lae se ¥ { are a Fig. 1. >» 2 a, Be Fig. 4 Fig. 1 7 2, > 3. > 4, a Oi > 6. 2) JE wm eos + dle > 10. oon te 12. vs , Thal ‘Fig. 1. FORKLARING AF PLANCHERNE. Tab. I. Nebalia bipes (Fabr.) ZEgbeerende Hun, seet fra venstre Side. Samme seet ovenfra. Slegtsmoden Han, seet fra hgire Side. Nebalia typhlops, G. 0. Sars. JEgbeerende Hun, seet fra hoire Side. Tab. II. at Nebalia bipes (Fabr.) Storsteparten af Legemet af en ung, endnu ikke slegtsmoden Han, seet fra venstre Side. Venstre Halvdel af Rygskjoldet er borttaget, for at vise de underliggende Dele. — ms Insertionen for Skallens Lukkemuskel; r Pandepladen; O Ginene; a! 1ste Par Folere; a* 2det Par Folere; M Kindbakkerne; Mp Mandibularpalpe; m* 1ste Par Kjever; m* 2det Par Kjeever. ; ; Pandepladen seet ovenfra, steerkere forstorret. QMinene med det tilhgrende Segment, seet ovenfra. Venstre Gie seet fra Siden.’ En af iste Par Folere hos Hunnen. En af 2det Par Felere do. Forenden af Legemet med Mundregionen, seet neden- fra. Af Folerne er blot Basaldelen tegnet. —r Pande- pladen; O @inene; a' iste Par Folere; a* 2det Par Folere; Mp Mandibularpalper; Z Overleben; J Un- derleben; m! iste Par Kjver; m? 2det Par Kjzever. Overleeben steerkere forstorret. ~ Underleben. Kindbakkerne med sine Palper, seede forfra. “Tyggedelen af en Kindbakke.- ‘Endeleddet af en Mandibularpalpe. Tab. ITI. Nebalia bipes (Fabr) 9 En Kjeeve ‘af 1ste Par; p Palpe. » 1a. En af Tornene paa Tyggelappen, steerkt forstorret. En Kjeve af 2det Par; p Endognath; ex Exognath. Fig. Fig. Fig. Fig. vwwvyvyv vows se ew Fig. See Ra eS i EXPLANATION OF THE PLATES. Plate I. Nebalia bipes (Fabr.) Ovigerous female, seen from the left side. Same, seen from above. Sexually mature male, seen from the right. Nebalia typhlops, G. 0. Sars. Ovigerous female, seen from the right. Plate I. Nebalia bipes (Fabr.) Greater part of the body of a young, not yet sexu- ally mature male, seen from the left. The left half of the carapace is removed to show the parts beneath. — ms, insertion of the adductor muscle of the shell; r, frontal lamina; O, eyes; a1, first pair of antenne; a*, second pair of antenne; M, mandibles; Mp, mandibular palpi; m', 1st pair of maxille; m*, 2nd pair of maxille. Frontal lamina, seen from above, more highly mag- nified. Eyes, with the segment appertaining to them. Left eye, seen from the side. One of the ist pair of antennz in the female. One of the 2nd f Anterior end ‘of the body with the oral region, seen from below. Only the basal part of the antenne is drawn. — r, frontal lamina; O, eyes; a’, first pair of antenne; @*, 2nd pair of antenne; Mp, mandibular palpi; Z, labrum; 7, posterior lip; m', Ist pair of maxille; m*, 2nd pair of maxilli. : Labrum, more highly magnified. Posterior lip. Mandibles with their palpi, seen from the front. Masticatory part of a mandible, —»— — Terminal joint of a mandibular palp. Plate II. Nebalia bipes (Fabr.) Q A maxilla of the 1st pair; p, palp. One of the spines on the masticatory lobe, highly magnified. A maxilla of the 2nd pair; p, endognath; ew, exognath. v_ vw we we Fig. vwvwyve 11. 12. OIA MS go Be te Se En Branchialfod af 1ste Par. En Branchialfod af 5te Par; p Endopodit; podit; ep Epipodit, En Branchialfod af 7de Par. En Branchialfod af 8de (sidste) Par. En Svommefod af Iste Par. Den ved Enden af Basaldelen indad udgaaende Fort- sats, steerkere forstorret. ex Exo- . En af de terminale Hager paa samme, meget steerkt forstorret. En Svommefod af 4de Par; x den indre Fortsats. Det forreste Par rudimentere Halefodder. Det bagerste Par Halelemmer. Sidste Halesegment, med venstre Halegren, seet ne- denfra. Tab. IV. Nebalia bipes (Fabr.) 3 En Foler af iste Par. En Foler af 2det Par (kun den basale Del af Svo- ben tegnet). En Kjeeve af iste Par. En Kjeeve af 2det Par. En Branchialfod af 5te Par. En Halefod af 1ste Par. En Halefod af 2det Par. Enden af sidste Halesegment med venstre Halegren, seet nedenfra. Nebalia typhlops, G. 0. Sars. Q Den forreste Del af Legemet seet fra hgire Side; (hgiere Halypart af Rygskjoldet borttaget). Pandepladen, seet ovenfra. Minene med det tilhgrende Segment, ovenfra seet. Venstre Kindbakke med Palpe. En Kjzeve af iste Par. En Kjeve af 2det Par. En Branchialfod af 1ste Par. En Branchialfod af sidste Par. En Svommefod af Iste Par. En af de forreste rudimentzere Halefodder. En af de bagerste Halefodder. Tab. V. Nebalia bipes (Fabr.) Skematisk Figur af en Hun, seet fra hoire Side, med de vigtigste indre Organer indtegnede i samme og angivne med. szerskilte Farver. Tveersnit af Dyret over Midtkroppen. De indre Or- ganer angivne med samme Faryer som paa Fig. 1. C Rygskjoldet;. ¢ Tarmen; Cv, Cd Tarmens Blind- seekke (Leverseekke); g Bugganglion; ¢ Hjerte; Mv ventrale Kropsmuskler; Md dorsale Kropsmuskler; ov Ovarier; bpr Branchialfodder. Tarmens Chitinskelet, seet fra venstre Side. Samme nedenfra, Et Stykke af Buggangliekjeeden. Et Ag, paa hyilket netop Blastodermen er dannet, indtagende den nedre Halydel. Et Zg med indesluttet Embryo, seet fra venstre Side. Fig. 3. > 4, eit. > 6. » he, » 8a > 9. >» 10. dae 22 » 12, Hig: A: a? >» 3. > 4, » 65. » 6. er | +; FS Fig. 9. > 10, ae 6 bs te bd >» 13. >» 14, > 26. >» 16. es > 18. >» 19. Fig. 1. weer f a Bs oe A 2b; wae. Hip Sip A branchial leg of the 1st pair. A branchial leg of the 5th pair; p, endopodite; ex, exopodite; ep, epipodite. A branchial leg of the 7th pair. A branchial leg of the 8th (last) pair. A natatory leg of the 1st pair. The inward-pointing projection at the end of the basal part, more highly magnified. . One of the terminal hooks on the same, very highly magnified. A natatory leg of the 4th pair; jection. The foremost pair of rudimentary caudal legs. The hindmost pair of caudal limbs. Last caudal segment, with the left caudal ramus, seen from below. a, the inner pro- Plate IV. Nebalia bipes (Fabr.) ¢ An antenna of the Ist pair. An antenna of the 2nd pair (only the basal part of the flagellum drawn). é A maxilla of the Ist pair. A maxilla of the 2nd pair. A branchial leg of the 5th pair. A caudal leg of the Ist pair. A caudal leg of the 2nd pair. End of the last eaudal segment with the left caudal ramus, seen from below. Nebalia typhlops, G. 0. Sars. The foremost part of the body seen from the right (right half of the carapace removed). Frontal lamina, seen from above. Eyes, with the segment belonging to them, seen from aboye. . Left mandible with palp. A maxilla of the 1st pair. A maxilla of the 2nd pair. A branchial leg of the 1st pair. A branchial leg of the last pair. A natatory leg of the 1st pair. One of the foremost rudimentary caudal legs. One of the hindmost caudal legs. Ww Plate V. Nebalia bipes (Fabr.) Diagrammatic drawing of a female, seen. from the right, with the most important organs shown in dif- ferent colours. Transverse section of the dnimal through the meso- some. The internal organs represented in the same colours as in fig.1. ©, carapace; i, ‘intestine; Cv, Cd, intestinal cxca (biliary ceca); g, ventral ganglion; c, heart; Mv, ventral muscles of the body; Md, dorsal muscles of the body; ov, ovaries; bpr, bran- chial legs. Chitine skeleton of the intestine, seen from the left. The same, from below. A piece of the ventral ganglion chain, An egg, in which the blastoderm is just Soria: ae occupies the lower half. An egg, with enclosed embryo, seen from the left, m\< 10. aH 12. 2 8 TASER Se be O Anlegeet til Ginene; L Overleben; a', a? Folerne; Mp Mandibularpalpe; « Haleenden. Samme ‘2g seet nedenfra. Bogstaverne som paa foregaaende Figur. Et Embryo, nogen Tid efterat AZghuden er afkastet, seet ovenfra. O QMinene; a! 1ste Par Folere; a* 2det Par Folere; brp Anleg til Branchialfodder; pl Anleg til Svommefgdder; uw Haleenden. Samme Embryo seet fra yenstre Side. RK Pande- pladen; Z Overleben; Mp Mandibularpalpe; m', m? de 2 Par Kjever. De ovrige Bogstaver som paa fore- gaaende Figur. Et videre udviklet Embryo, seet fra hgire Side. staverne som paa foregaaende Figur. Unge feerdig til at slippe ud af Moderens Klekke- hule, seet fra hgire Side. Ms Insertionsareaen for Skallens Lukkemuskel; pla sidste Par, endnu ikke udviklede Svemmefedder; c', c? de 2 rudimentzere Halefodder. De ovrige Bogstaver som paa de 2 fore- gaaende Figurer. Bog- Tab. VI. Branchinecta paludosa (Miiller.) Fuldt udviklet Han, seet nedenfra. Samme fra venstre Side. Jigberende Hun, seet fra hgire Side. Samme oventra seet. Larve i sidste Stadium, seet fra venstre Side. Samme ovenfra seet. Hoyedet af en Unge i 1ste postlarvale Stadium, seet nedenfra. O de sammensatte Gine; o det enkle Gie; a' iste Par Folere; a? 2det Par Folere; L Oyerleben; M Kindbakkerne. En af 2det Par Folere af samme, steerkere forstorret. Hovedet af en fuldt udviklet Hun, seet nedenfra. m', m? de 2 Par Kjever. De ovrige Bogstaver som paa Fig. 7. Enden af Halen med Halepladerne, seet ovenfra. Genitalsegmenterne med den tilstodende Del af For- kroppen og Halen af en fuldt udviklet Han, seet fra venstre Side; e¢ Hjerte; t Testes; p ydre Kjonsved- heeng. Sperma-Celler ved meget steerk Forstgrrelse. Tab. VII. Branchinecta paludosa (Miller.) Forenden af en fuldt udyiklet Hun, med Overleben leftet op fra Kindbakkerne, seet nedenfra. O de sammensatte Mine; 0 det enkle Gie; a' 1ste Par Fo- lere; a? 2det Par Folere; LZ Overleben; M Kindbak- kerne; m' iste Par Kjever; m? 2det Par Kj:ever; p* Iste Par Branchialfodder. Hovedet af en fuldyoxen Han, seet forfra, Bogsta- _ yerne som paa foregaaende Figur. ‘ Overleeben (LZ), med den bagenfor liggende Chitin- hud. M Stedet hvyor Kindbakkernes Tyggedel har ligget; m' Stedet, hvor Iste Par Kjever har veeret feestede. En Kindbakke seet forfra. Sammes Tyggeflade steerkt forstorret. En Kjeve af iste Par. | Pixs! Fig. 8 yet > 10. pA I » 12. Fig. 1. > 2. ches > 4. >» 6. > 6. SD ty Go > 8. + 9, > 10. “egg o. Aa. Fig 1. & > 3. » 4, > «aby an 6S O, eyes in process of formation; Z, labrum; antenne; Mp, mandibular palpi; Same egg, seen from below. a‘, a*, u, end of the tail. Lettering as in fig. 7. An embryo, some time after the egg-skin is cast, seen from above. O, eyes; a', Ist pair of antenne; a*, 2nd pair of antennz; brp, rudiments of branchial legs; pl, rudiments of natatory legs; wu, end of tail. Same embryo, seen from the left. R, frontal lamina; DL, labrum; Mp, mandibular palpi; m', m*, the 2 pairs of maxille. The rest of the lettering as in fig. 9. A more deyeloped embryo, seen from the right. Lettering as in fig. 10. Young one ready to emerge from the mothér's incuba- tory cayity, seen from the right. Ms, area of inser- tion of the adductor muscle of the shell; pla, last pair of the not yet developed natatory legs; c', ¢?, the 2 rudimentary caudal legs. The rest of the let- tering as in the 2 preceding figures. - Plate VI. Branchinecta paludosa, (Miiller.) Fully developed male, seen from below. Same, from the left. Ovigerous female, seen from the right. Same, seen from aboye. Larva in the last stage, seen from the left. Same, seen from above. Head of a young one in the 1st post-larval stage, seen from below. O, compound eyes; 0, ocellus; a‘, ist pair of antennie; a*, 2nd pair of antenne; ZL, labrum; M, mandibles.. One of the 2nd pair of antenne of the same, more highly magnified. Head of a fully-developed female, seen from below. m*, m*, the 2 pairs of maxilla. The rest of the let- tering as in fig. 7. End of the tail, with the caudal lamellz, seen from above. Genital segments with the adjacent part of the an- terior part of the body and the tail of a fully-deve- loped male, seen from the left. c, heart; ¢, testes; p, external sexual appendage. Sperm cells, very highly magnified. Plate VIL. Branchinecta paludosa (Miller.) Anterior end of a fully-developed female, with the labrum raised from the mandibles, seen from below. O, compound eyes; 0, ocellus; a‘, 1st pair of antenne; L, \abrum; M, mandibles; m', 1st pair of maxille; m*, 2nd pair of maxille; p', ist pair of branchial legs. “Head of a full-grown male, seen from the front. Lettering as in fig. 1. Labrum (Z), with the chitinous skin lying behind it, M, place where the masticatory part of the mandi- bles has been; m', place where the 1st pair of max- ille have been attached. A mandible, seen from the front. Masticatory surface of the same, highly magnified. A maxilla of the 1st pair. Fig. Fig. % 10. 11. 12. 13. 15. SF ON Fede En af de paa samme festede Borster, steerkt for- storret. En Kjeeve af 2det Par. En Branchialfod af iste Par hos Hunnen; end Endo- podit; ex Exopodit; ep Epipodit: b Basalplade. Et Stykke af Kanterne af den inderste Endit med de tilhorende leformigt krummede Borster, stzerkere for- storret. En Branchialfod af 5te Par. Fig. 9. En Branchialfod af sidste Par. En Branchialfod af 5te Par hos Hannen. som paa Fig. 9, 11 og 12. Bogstaverne som paa Bogstaverne Tab. VIII. Branchinecta paludosa (Miiller). Legemet af en Hun, med indtegnet Nervesystem, seet fra Bugsiden. Enden af en Feler af iste Par, steerkt forstorret. En Lugtepapille fra samme, endnu sterkere for- storret. Hjernegangliet med de fra samme udspringende Ner- ver, seet ovenfra. o det enkle Mie; aa Sandsegruber i Hovedets Integument; a‘ Basis af iste Par Folere med den tilsvarende Nerve; O Synsnerverne; a? Ner- verne for 2det Par Folere. Et Stykke af Buggangliekjeeden. Den ydre Del af et af de sammensatte Mine i Leengdesnit. 2 Synselementer isolerede. d Neryefibrer fra Syns- neryen; ¢ Synsstav; b Krystalkegle; @ lindseformigt fortykket Del af samme. : Sidedelen af et Halesegment, med 2 Hudnerver. Hudpapiller med Foleborster, steerkt forstorret. Den forreste Del af Tarmen med sine 2. Blindseekke, seet ovenfra. Genitalsegmentet af en Hun med Agbeholderen og Ovarierne (oy), seet nedenfra. Et Stykke af Kitkjertelen. Et g med begyndende Kloyning. Et andet Ag uden Kloyning. En Larye i et af de tidligere Stadier, seet fra Bug- siden. En Larve i et senere Stadium, vee fra Bugsiden. Forenden af Legemet hos et lidt senere Larvestadium, seet nedenfra. O de sammensatte Oine; o det enkle @ie; at Iste Par Folere; a* 2det Par Folere; LZ Over- leben; M Kindbakkerne; p Mandibularfodderne; m’', m*® Kjeeverne. Tab. IX. Polyariemia forcipata, Fischer. Fuldyoxen, «gbzerende Hun, seet fra hgire Side. Samme, seet ovenfra. Fuldvoxen Han, seet nedenfra. Samme fra yenstre Side. Spidsen af en af Gribeantennernes Grene, sterkere forstorret. Enden af Halen med Halepladerne, seet ovenfra. En Larve i et af de tidligere Stadier, seet nedenfra. vv wow 12. 13. or One of the bristles attached to the same, highly magnified. A maxilla of the 2nd pair. A branchial leg of the 1st pair in the female; end, endopodite; ex, exopodite; lamella. A piece of the edge of the innermost endite with. its falciformly curved bristles, more highly magnified. A branchial leg of the 5th pair. Lettering as in fig. 9. A branchial leg of the last pair. A branchial leg of the 5th pair in the male. tering as in figs. 9, 11 and 12. Let- Plate VIII. Branchinecta paludosa (Miller). Body of a female with the nervous system drawn in, seen from the ventral side. Extremity of one of the 1st pair of antenne, highly magnified. An olfactory papilla on the same, still more highly magnified. Cerebral ganglion with the neryes issuing from it, seen from above. 0, ocellus; aa, sensory pits in the integument of the head; a', base of the first pair of antennz, with the corresponding nerves; O, optic nerves; @*, nerves for the 2nd pair of antenne. A piece of the ventral ganglion chain. The outer part of one of the compound eyes in longitudinal section. Two visual elements isolated. d, nerye fibres from the optic nerve; ¢, optic rod; 0, crystalline cone; a, lenticularly thickened part of the same. Lateral part of a tailsegment, with 2 cuticular nerves. Cutaneous papillz, with sensory bristles, highly mag- nified. ; The anterior part of the intestine with its 2 czeca, seen from above. The genital segment of a female with marsupium and ovaries (ov), seen from below. A piece of the glutinous gland. An egg with cleavage commenced. An egg without cleavage. A larva in one of the earlier stages, seen from the ventral side. A larva in a later stage, seen from the ventral side. Anterior end of the body in a rather more advanced larval stage, seen from below. O, compound eyes; o, ocellus; a}, 1st pair of antenn®; a@*, 2nd pair of optennei L, labeuat M, mandibles; p, mandibular legs; m1, m*, maxilla, | Plate IX. Polyartemia foreipata Fischer. : Full-grown, ovigerous female, seen from the right Same, seen from above. uk Full-grown male, seen from = enh Same, from the left. i Point of one of the rami of the Sermese antennee, more highly magnified. End of tail, with the caudal lamelle, seen bie: aose A larva in one of the earlier stages, seen from below. ep, epipodite; 6, basal . —<_war”|6lUll. —— Tab. X. Polyartemia forcipata, Fischer. ‘Hovedet af en Hun seet nedenfra. O de sammen- satte @jne; o det enkle Mie; a Iste Par Folere; a® 2det Par Folere; Z Overleeben; M Kindbakkerne; m', m® Kjeeverne. Hovedet af en Han, seet forfra. En Foler af iste Par. Overleben med Spisergret (¢), seet fra venstre Side. De samme Dele, seet ovenfra. En Kindbakke, seet forfra. En Kjeve af iste Par, En Kjeeve af 2det Par- En Branchialfod af 1ste Par. En Branchialfod af 11te Par. En Branchialfod af sidste Par. Den bagre Del af Legemet af en fuldvoxen Hun; med Agbeholderen og de gjennemskinnende Ovarier, seet fra hoire Side. Oyarierne med Kitkjeertelen, seet ovenfra. A rialtuberne; ovd Aglederne; gl Kitkjeertelen. Et af Ovarierne med den tilsvarende Mgleder, isole- ret og seet fra Siden. Et modent Ag, steerkt forstorret. Den bagre Del af Legemet, uden Halepladerne, af en fuldyoxen Han, seet fra venstre Side. vd vas deferens; p ydre Kjonsvedheeng. “www ww ve oe vy wy ov Ova- vow eet So t Testes; Tab. XI. . Lepidurus glacialis (Kroyer). Fig. 1. Fuldyoxen Hun, ovenfra seet. > 1a. Samme i naturlig Storrelse. 2. Samme seet nedenfra, ie Ege: Samme seet fra vere Side, med Kroppen steerkt foroverbgiet. En Larve, seet ovenfra. En anden Larve i et noget senere Stadium, seet oyenfra. Fuldyoxen Han, bvbatea seet. Samme i naturlig Storrelse. ie i samme Forsterrelse som ‘Tab. XII. Lepidurus glacialis (Kroyer.) Forenden af Legemet, seet nedenfra. a‘ iste Par Folere; a* 2det Par Folere; DL Overleeben (oploftet); M Kindbakkerne; J Underleben; m* iste Par Kjx- ver; m* 2det Par eee p* iste Fodpar. , En Foler af iste Par. Et Stykke af Endedelens nedre Kant med de paa- siddende Lugtepapiller, sterkere forsterret. En Lugtepapille, meget steerkt forstorret. fn En Foler af 2det Par. 6, 7. Samme Foler af 2. andre, Fxemplarer, for at vise Va- riationerne i Form og Storrelse. 8. En Kindbakke, seet forfra, 9. Den inderste, Tand af samme, steerkt forstorret. og. lete Es Kjeever (m 2) i sin natur- ge Forbincelee ane hinanden, snaprene Mere Spiseroret (o seet bagfra, — r a 135 | Fig. 1. OK > 8. >» 4, Ee ae | > 6. oP) Ap) IT. >» 8. > 9. > 10. IDS een > 13. ay st. >» 16. > 16. Fig. 1. > ole wo D > 38. at; Sy ae nb, > 6. >» 6a Fig. 1. + aan & %3. » 4 > 6 > 6,7 > 8B. > 9% >» 10. Plate X. Polyartemia forcipata, Vischer. Head of a female, seen from below. O, compound eyes; 0, ocellus; a‘, Ist pair of antenns; a*, 2nd pair of antenne; Z, labrum; M, mandibles; m', m?, maxillze. Head of a male, seen from the front.. One of the Ist pair of antennze. Labrum, with cesophagus (9), seen from the left. Same parts, seen from above. A mandible, seen from the front. One of the Ist pair of maxille. One of the 2nd pair of maxille. One of the 1st pair of branchial legs. One of the 11th pair of branchial legs. One of the last pair of branchial legs. Posterior part of body of a full-grown female, with marsupium, and the ovaries shining through, seen from the right. Ovaries with the glutinous gland, seen from above. ov, ovarial tubes; ovd, oviduct; gl, glutinous gland. One of the ovaries with its corresponding oviduct, isolated, and seen from the side. A mature ovum, highly magnified. Posterior part of the body, without caudal lamellie, of a full-grown male, seen from the left. f¢, testes; vd, vas deferens; p, external sexual appendage. Plate XI. Lepidurus glacialis (Kroyer.) Full-grown female, seen from above. . Same, natural size. Same, seen from below, magnified with the same power as fig. 1. Same, seen from the left, with the body bent very much forwards A larva, seen from above. A larva in a rather more advanced stage, seen from above. Full-grown male, seen from above. . Same, natural size. Plate XII. Lepidurus glacialis (Kroyer. Anterior end of body, seen from below. a', Ist pair of antennie; a*, 2nd pair of antenne; LD, labrum (raised); M, mandibles; 1, posterior lip; m', 1st pair of maxille; m*, 2nd pair of maxille; p', Ist pair of legs. An antenna of the Ist pair, A piece of the lower edge of the terminal part, with its olfactory papillee, more highly magnified. An olfactory papilla, very much magnified. “An antenna of the second pair, . Same antenna in 2 other specimens, to show the variation in form. and size. A mandible seen from the front. The innermost denticle of the same, highly mag- nified. Posterior lip (2) and Ist pair | of maxillee (m") in their natural _connection with ope ‘another, and cesophagus (oe), seen. from behind, ay Fig. Fig. vwwwvw wow 1}. 16%. 19. Underleben med Spisergret, seet forfra. En Kjeeve af iste Par. En Kjeve af 2det Par; p Palpe. En Fod af 1ste Par. m Coxallappen; 1—5 Enditerne; ex Exopodit. En Fod af 2det Par. gaaende Figur. En Fod af 10de Par. En Fod af lite Par. sluttet eg. En Fod af 12te Par. En Fod af et af de bagerste Par ved samme For- storrelse. Samme Fod betydelig steerkere forstorret. En Fod af sidste Par; samme Forsterrelse som Fig. 19. Samme Fod sterkt forstorret. de foregaaende Figurer. Den bagre Del af Legemet med Halepladen og Basis af Haletraadene, seet ovenfra. Samme Del seet nedenfra. Sidste Segment, med Halepladen, af et ualmindelig stort Exemplar, seet oventfra. Samme Del af 2 andre Exemplarer, for at vise Varia- tionerne i Halepladens Form. Bogstaverne som paa fore- ov Agkapselen med et inde- Bogstayerne som paa Tab. XIII. Lepidurus glacialis, (Kroyer.) Dorsalt Vue af en Hun, paa hvilket Rygskjoldets frie Del er borttaget, for at vise de underliggende Dele, seet oyenfra. Ved lengere Tids Indlegning i Glycerin, er Legemet gjort halvt gjennemsigtigt, saa at de indre Organer delvis skinner igjennem. O de sammensatte Gine; oc det enkle Gie; a Postocular- knuden; M Kindbakkerne; p' Iste Fodpar; p" 1lte Fodpar med Aigkapslen; J Tarmrgret; / Leveren; ¢ Hjertet; ov Ovarierne. Lateralt Vue af et andet Exemplar, paa hvilket ven- stre Halypart af Rygskjoldet er borttaget. a‘ Iste Par Folere; a* 2det Par Folere; L Overleben. De ovrige Bogstaver som paa Fig. 1. Endefliger af Leveren, steerkt forstorret. Skalkjeertelen. De sammensatte Mine, med det enkle Bie (oc) og Hjernegangliet (g), ovenfra seet. En Krystalkegle seet fra den ydre Ende. Et enkelt Synselement, med Forgreninger af Syns- nerven yed Basis. Postocularknuden. Et Stykke af Buggangliekjeedens forreste Del. Et andet Stykke lengere bagtil, samme Forstorrelse. Den bagre Ende af Buggangliekjeden, samme For- storrelse. Et Stykke af et Ovarium med paasiddende Aig- follikler. To af de mindste Agfollikler isolerede. To videre udviklede ®gfollikler. En endnu mere udviklet Agfollikel. Et modent ASg udtaget af Agkapselen. Et Stykke af A®gskallen, sterkt forstorret. Et Stykke af en Szdstok. Nogle Seedfollikler, steerkere forstorret. Seedelementer, meget steerkt forstorret. En Fod af 11te Par hos Hannen. Fig. 1. ve wees ve ee vee 18. 14. 15. 16. 161, 17. 18. 19. 20. Posterior lip and esophagus seen from the front. A maxilla of the Ist pair. A maxilla of the 2nd pair. p, palp. A leg of the 1st pair. m, coxal lobe; 1—5, endites; ex, exopodite; ep, epipodite. A leg of the 2nd pair. Lettering as in fig. 14. A leg of the 10th pair. A leg of the 11th pair. an egg. A leg of the 12th pair. A leg of one of the hindmost pairs, magnified with the same power. Same leg, under a much higher magnification. A leg of the last pair; magnified with the same power as fig. 19. ov, egg-capsule, containing Same leg, highly magnified. Lettering as in the pre-— ceding figures. Posterior part of body with caudal lamella and base of caudal filaments, seen from above. Same part, seen from below. Last segment, with caudal lamella of an unusually large specimen, seen from above. Same part of 2 other specimens, to show variations in the shape of the caudal lamella. Plate XII. Lepidurus glacialis, (Kroyer.) Dorsal view of a female, seen from above, the free part of the carapace being removed to show the parts beneath. By being kept for some time in gly- cerine, the body has been rendered semi-transparent, so that the internal organs are partly visible through. O, compound eyes; oc, ocellus; x, post-ocular tubercle; M, mandibles; p', Ist pair of legs; p', 11th pair of © legs, with egg capsule; J, intestinal tube; J, liver; c, heart; ov, ovaries. Lateral view of another pisehuieth from wish the left half of the carapace is removed. a', 1st pair of antenne; a@*, 2nd pair of antenne; L, labrum; the rest of the lettering as in fig. 1. Terminal lobes of the liver, highly magnified. Shell-gland. Compound eyes, with the ocellus (0c) and cerebral ganglion (g), seen from above. A crystalline cone seen from the outer end. A single visual element, with ramifications of the optic nerve at the base. Post-ocular tubercle. Piece of the foremost part of the ventral ganglion chain. Another piece, farther back, same » athgdsbenbion. The posterior end of the ventral Senter: chain, same magnification. A portion of the ovary with a egg-follicles. Two of the smallest egg- follicles isolated. Two more developed egg-follicles. A still more developed egg-follicle. A mature egg removed from the egg-capsule. A piece of egg-shell, highly magnified. A piece of the testes. Some sperm-follicles, more highly magnified. — Sperm elements, very much magnified. © A leg of the 11th pair in the male. isl is _ aabningen. Forenden af en Larve, seet nedenfra. O de sammen- satte Gine; oc det enkle Mie; a‘ 1Iste Par Folere; a* 2det Par Folere; LZ Overleeben; M Kindbakkerne; l Leversekke. En Fod af iste Par af samme Larve En Fod af 2det Par. En Fod af i1te Par. En af de bagenfor liggende Fodder. En af de allerbagerste Fodder. Den bagre Del af Legemet af samme Larve, seet ovenfra. Bagenden, med Basis af Haletraadene, af en eeldre Larve, oventra seet. Tab. XIV. Limnadia lenticularis, (Lin.) Fuldyoxent, «egbzerende Exemplar, seet fra hgire Side. Samme ovenfra. Samme nedenfra. En kun lidt over 1 mm. lang Unge, seet fra ven- stre Side. En anden noget storre Unge, fra samme Side. Et Exemplar, paa hvilket den forste Veextstribe har dannet -sig, seet fra venstre Side. Tab. XV. Limnadia lenticularis, (Lin.) Dyret liggende i sin naturlige Situs i hoire Valvel. Venstre Valvel borttaget. Det forreste Afsnit af Legemet seet fra venstre Side, steerkere forstorret. Aarerne er borttagne. r Rost- rum; af Fastheftningsorgan; O de sammensatte Gine; oc det enkle Mie; a‘ Iste Par Folere; LZ Overleben; M Kindbakkerne; m' 1ste Par Kjzever; m* 2det Par Kjeever; i Tarmen; J Leveren; ms Insertionsareaen for Skallens Lukkemuskel; ¢ Forenden af Hjertet. Samme Del, med Basis af Aarerne, seet ovenfra. Bogstaverne som paa foregaaende Figur. . Samme Del, uden Aarerne, seet nedenfra. Bogsta- verne som paa de 2 foregaaende Figurer. En Foler af iste Par. En af de paa samme festede Lugtepapiller, steerkt forstorret. Overleben seet fra venstre Side. En Kindbakke, seet forfra. En Del af den ventrale Flade, umiddelbart bag Mund- M Stedet, hvor Kindbakkernes Tygge- dele har ligget; m* 1ste Par Kjzever; Kjeever; oes Spiseroret. En Kjeve af 1ste Par. To af de paa samme feestede pigtoninige Borster, m?® 2det Par _steerkt forstorret. - En Kjeve af 2det Par. Samme Kjeve sterkere forstorret. Tab. XVI. _ Limnadia lenticularis, (Lin.) En Aare (Foler af 2det Par). Tre af de til Forsden at den yare Gren festede Pigge, steerkere forstorret. G. 0. Sars Fauna Norvegiz. 137 Fig. 21 » 22. >» 238. >» 24, >» 26. >» 26, >» 27. » 28. Fig. 1. Ko ZB +> BS: we 7s > 6, + 16; Fig. 1. int jae are >» 4. 1 OF 4 & ae Ts 2 18s » 9 >» 10. ssh » 12. > 13. Fig. 1. rae > Anterior end of a larva, seen from below. O, com- pound eyes; oc, ocellus; a‘, Ist pair of antenne; a’, 2nd pair of antennze; LZ, labrum; M, mandibles; /, biliary ceca. A leg of the Ist pair of the sama larva, A leg of the 2nd pair. A leg of the 11th pair. One of the legs farther back. One of the hindmost legs. Posterior part of the same larva, seen from above. Posterior end of an older larva, with the base of the caudal filaments, seen from above. Plate XIV. Limnadia lenticularis, (Lin. Full-grown, ovigerous specimen, seen from the right Same, from above. Same, from below. A young one, only a little over 1 mm. in length, seen from the left. A somewhat larger young one, from the left. A specimen in which the first line of growth has been formed, seen from the left. Plate XV. Limnadia lenticularis, (Lin.) The animal, lying in its natural position in the right valve: left valve removed. The anterior part of the body, seen from the left, more highly magnified. The oars are removed. r, rostrum; af, affixing organ; QO, compound eyes; oc, ocellus; a', Ist pair of antenne; Z, labrum; M, mandibles; m*, Ist pair of maxille; m*, 2nd pair of maxille; i, intestine; J, liver; ms, area of insertion of the shell's adductor muscle; c, anterior end of the heart. Same part, with the base of the oars, seen from above. Lettering as in fig. 2. Same part, without the oars, seen from below. Let- tering as in figs. 2 and 3. An antenna of the Ist pair. One of the olfactory papille on the same,. highly magnified. Labrum seen from the left. A mandible, seen from the front. Part of the ventral surface, immediately behind the oral aperture. M, place where the masticatory part of the mandibles has been; m', 1st pair of maxille; m*, 2nd pair of maxille; 0¢8, cesophagus. A maxilla of the 1st pair. Two of the spiniform bristles on the same, highly magnified. A maxilla of the 2nd pair. ‘Same maxilla more highly magnified. Plate XVI _ Limnadia lenticularis, Lin.) An oar (antenna of 2nd pair). Three of the spines affixed to the front of the outer ramus, more highly magnified. : Fig. 3. 10. 11. 12. 13. 14. 15. 16. ay 18. 19. En Fod af 1ste Par; 1—5 Endopoditen med sine En- diter; ew Exopoditen; eat dens dorsale Lap; ep Epi- poditen; ma Coxallappen. En Coxallap isoleret og steerkere forsterret, seet fra Indsiden. En Fod af sidste (23de) Par, ved samme Forstorrelse som Fig. 3. Samme Fod, stzrkere forstorret. Bagenden af Legemet, seet fra venstre Side. Halen seet bagfra. Hjernegangliet med de fra samme udgaaende Nerver og det enkle Mie, seet fra yenstre Side. ¢ selye Hjerne- gangliet; opt Synsnerven; a' Nerver for lIste Par Fo- lere; a? Nerver for Aarerne; oc det enkle Mie; x det- tes forreste Ligament. Hjernegangliet tilligemed de sammensatte @ine (0), seet ovenfra. m Qiemuskler. De ovrige Bogstaver som paa foregaaende Figur. Det enkle Mie seet forfra. Samme bagfra. Samme nedenfra, En Del af Buggangliekjeeden, seet nedenfra. Et Ovarium af et ganske ungt Individ. Et Ovarium af et xldre Individ, kort efter at Ag- gene fra Folliklerne er indkommen i Ovarialrgret. a glederen. Et Stykke af et andet Ovarium, med A%gfollikler i forskjellig Udvikling. Forskjellige Agfollikler, isolerede. Et Ag udtaget af Ovarialrorene. begyndt at danne sig. Skallen har netop 20—22. Et fuldfeerdigt AZ{g med sin Kapsel, seet i 8 for- Fig. 23. skjellige Stillinger. Et Stykke af den ene vingeformige Udvidning af Agkapselen, steerkt forstorret. Tab. XVII. Limnadia lenticularis, (Lin.) (Udvikling). En netop udklekket Larve, seet nedenfra. oc det enkle Gie; @! 1ste Par Folere; a* 2det Par Folere (Aarerne); Mp Mandibularfodderne; Z Overleben; f Haleindsnittet. En Larve efter iste Hudskiftning, ovenfra seet. Eldre Larve seet nedenfra. Et senere Stadium, paa hvyilket det forste Anleg til de sammensatte Oine, Rygskjoldet og Fodderne kan adskilles, seet ovenfra. ZEldre Larve, seet nedenfra. En Feler af 1ste Par, steerkt forstgrret. Et noget eldre Stadium, seet fra venstre Side. stre Aare er udeladt. Sidste Larvestadium, ovenfra seet. Unge i iste postlarvale Stadium, seet ovenfra. Ven- Samme seet fra venstre Side. Tab. XVIII. Limnetis brachyurus, (Mill.) Fuldyoxen, «gberende Hun, seet fra venstre Side. Samme nedenfra. : Fuldyoxen Han, seet fra hgire Side. Hovedet af en Hun, seet forfra. Fig. 3. » 11. Ocellus, seen from the front. » 12. Same, from behind. >» 13. Same, from below. >» 14. Part of the ventral ganglion chain, seen from below. >» 15. An ovary from a yery young animal. >» 16, An ovary from an older animal, soon after the eggs from the follicles have entered the ovarial-tube. a, oviduct. ; >» 17. Piece of an ovary, with egg-follicles in different stages of development. » 18. Various egg-follicles, isolated. . » 19. An egg taken out of the ovarial tube. The shell has just begun to form, » 20—22. A complete egg with its capsule, seen in 3 diffe- rent positions. » 283. Piece of one wing-like expansion of the egg- pig vans. highly magnified. Plate XVII. Limnadia lenticularis, (Lin.) (Development). Fig. 1. A newly-hatched larva, seen from below. oc, ocellus; a‘, 1st pair of antenne; a?, 2nd pair of antenne (oars); Mp, mandibular legs; LZ, labrum; f, caudal emargination. >» 2. » 4. A later stage, in which the earliest rudiments of the compound eyes, the carapace and the legs are dis- tinguishable: seen from above. » § Older larva, seen from below. » 6a. An antenna of the 1st pair, highly magnified. » 6, A somewhat later stage, seen from the left. Left oar omitted. » 7 Last larval stage, seen from above. >» § Young one in the last post-larval stage, seen | from: above. ; >» 9, Same, seen from the left. Plate XVIII. Limnetis brachyurus, (Mill.) Fig. 1. Full-grown, ovigerous female, seen from the left. >» 2. Same, from below. >» 3. Full-grown male, seen from the right. > 4 Head of a female, seen from the front. _ - 12. 139 . 5. Hovedet af en Han i samme Stilling. 6. Skallen af en Hun, med Valvlerne tet lukkede, seet fra venstre Side. 7. Samme ovenfra. Tab. XIX. Limnetis brachyurus, (Mill.) . 1. Legemet af en Hun liggende i sin naturlige Situs i hgire Valvel; venstre Valvel borttaget. ovs en af de kageformige ASgmasser. 2. En Foler af 1ste Par. . En af de paa samme festede Lugtepapiller, sterkt forstorret. 3. En Foler af 2det Par (Aare). 4. Mundregionen seet nedenfra; Overleeben borttaget. M Kindbakkerne; m! 1ste Par Kjeever; m? 2det Par Kjeever; oes Spiseroret. 5. En Kjeve af Iste Par. . En af de paa Spidsen af samme feestede Pigge, steerkt forstorret. ; 6. En Kjeeve af 2det Par. 7. Haledelen seet fra venstre Side. 8 9 h Hijertet; Samme nedenfra. Den bagre Del af Legemet seet ovenfra, fl de om- formede dorsale Lappe af Exopoditerne paa 9de og 10de Fodpar; 7 de bladformige dorsalePlader; % Hale- fligene. Hjertet seet ovenfra. 11. Det forreste Afsnit af Legemet af en Hun, seet fra venstre Side (Aarerne udeladte). O de sammensatte Mine; oc det enkle Mie; p dettes forreste Ligament; ol Sandsegruber; « Fastheftningsorgan(?); a! 1ste Par Folere; L Overleeben; M Kindbakkerne; m' iste Par Kjeever; m? 2det Par Kjeever; ms Insertionsarea for Skallens Lukkemuskel; J Tarmen; lv Leveren. En Sandsegrube seet ovenfra. Hjernegangliet med de fra samme udgaaende Nerver, tilligemed de sammensatte Gine (0) og det enkle Mie (oc), seet nedenfra; opt Synsnerven; a‘ Nerver for lste Par Folere; a* Nerver for Aarerne. Samme Del (uden de sammensatte @ine), seet fra venstre Side. Bogstaverne som paa foregaaende Figur. Det enkle @ie seet forfra. Skalkjeertelen med Muskelareaen. 13. 14. 15. 16. Tab. XX. Limnetis brachyurus, (Miull.) En Fod af 3die Par hos Hunnen. 1—5 Endopoditen med sine Enditer; ma Coxallappen; ex Exopoditens ventrale Lap; ex dens dorsale Lap; ep Epipoditen. la. En af de til nestsidste Endit feestede Torne, steerkt forstorret. 1b. Coxallappen isoleret, og seet fra den indre Side. 2. En Fod af 8de Par. 8. En Fod af 9de Par. 3a. Enden af Exopoditens dorsale Lap, sterkt foratorret. 4. En Fod af lite Par. 5. En Fod af 12te (sidste) Par. 6. Legemet af en Han liggende i sin naturlige Situs i venstre Valyel (hgire Valvel borttaget). 7. En Fod af 1ste Par hos Hannen. Fig. . 6. Head of a male, in the same position. with the valves closely shut, seen > Shell of a female, from the left. 7. Same, from above. Plate XIX. Limnetis brachyurus, (Mull.) 1. Body of a female, lying in its natural position in the right shell; left valve removed. h, heart; ovs, one of the cake-like egg-masses. 2. An antenna of the 1st pair. 2a. One of the olfactory papille on the same, highly magnified. 3. An antenna of the 2nd pair (oars). 4. Oral region, seen from below: labrum removed. M, mandibles; m', 1st pair of maxille; m*, 2nd pair of maxille; oes, cesophagus. 5. » §. The same, from below. « 9. Posterior part of the body, seen from above. jl, the transformed dorsal lobes of the exopodites in the 9th and 10th pairs of legs; J, the leaf-like dorsal lamellee; u, caudal lobes. >» 10. Heart, seen from above. >» 11. Anterior part of the body of a female, seen from the left. (Oars omitted). O, compound eyes; oc, ocellus; p, its front ligament; ol, sensory pits; @, affixing organ(?); a@', Ist pair of antenne; JZ, labrum; M, mandibles; m1, 1st pair of maxille; m*, 2nd pair of maxille; ms, area of insertion of the adductor muscle of the shell; J, intestine; lv, liver. » 12. A sensory pit, seen from above. » 18. Cerebral ganglion with the nerves issuing from it, and the compound eyes (Q) and ocellus (0c), seen from below. opt, optic nerve; a', nerves for the Ist pair of antenne; a*, nerves for the oars. » 14, Same part (without the compound eyes), seen from the left. Lettering as in fig, 13. » 15. Ocellus, seen from the front. >» 16. Shell-gland with muscular area. Plate XX. Limnetis brachyurus, (Mill.) Fig. 1. » 9. En Fod af 2det Par hos Hannen. os" dite but one, 1 > 9a, Nestsidste Endit, sterkere forstorret- > 9b. One: of the peculiar s » 9b. En af de til samme feestede eiendommelige Pie, highly magnified. endnu sterkere forstorret. >» 10. Caudal part of a jones » 10. Haledelen af en Han, seet fra hoire Side. » 11. Some sperm e > 11. Nogle Sedfollikler, sterkt forstorrede. >» 12. Piece of one of > 12. Et Stykke af en af Sedstokkene. » 13. Anterior part of > 18. Det forreste Parti af et Ovarium. f » 14—17. - Egg-follicles | > 14-17, Mefollikler i forskjellig Udvikling. abi > 18. A group of eggs | > 18. En Gruppe af Hg tagne fra en af ey kagetormige ny egg-r . /Egmasser. - bd ie > 19. Et Stykke af Buggangliekjeeden, seet” nedentra. “Agree ney 7 SIU ; mes ee = anaes hehe inne isa ooh x r i pet hy (dis oe at tas Atel } ‘a i . Et kay , oe. - fag {HOM Viupeh eT SCANS ay cL y, ” . rt; ‘ohieerin ie. oe AEs iy hei Gate 85. = / “ P. F / é : ; . i ’ f < id } i re , - . ‘ “ . me. 3 *f 7 7 £ 4 ~» } i , & 5 < 2 wae Lil : m 3 ae oe, eon hard a assy y esr ey, z ee Tarps r > a aa ¢ Ps OHA sila tk Lew saeaannd pia pied A. a te te ee. £g SS “ie ‘bat mht ee yd, 7 ai, y Oa eri) ee eae mas +) ae iar i om, aie bent Rape wrt ab et je | PACNA Norvyears,. : 9 . (Crustacea) ws Phyllocarida.: al hi es = . M.Dyng* lith Anst Cirrtsttania By. 4-3 Nebatia bipes, Fabr. 3 & 8. ame # ee ctiphlane: G.0.Sars? . P= ¢ | ad FAUNA NORVEGIA. Phyllocarida (Crustacea) Tab TT G.O Sars, del. L Sars, de : M. Lyng lith Anst Christiunia Nebalia bipes (Fabr/ a 3 . x s a ' eS > é ae iS > © = ee o ~ So .2° AR a 2 - H = is = ed wf a ea = ts os cd a a o a RS Ay Faywa Norveaia. (Crustacea) Phyllocarida yy) eee + jt 72 PO SE ay ee a hee 5 ane BP wee oh a a - | “Big 1-8 Nebalia bipes,(Fabr) 8. Fig. 9-9 —_ —_ typhlops, .0.Sars ?. = Fauna NoRvVEGIR.. Tab. V. (Crustacea) Phyllocarida M.Lyngs lith Anst. Christionin. G.O.Sars del. Nebalia bipes,(Fabr) 2 (Crustacea.) llopoda y ‘sy 7, Pp + Christiania. M. Lyag’s lith Anst Branchinecta paludosa, (Milter). ie *s eS | > ena e