CRUSTACKA LIBRAHT SMITHSONIAN INST. HBrUHR 10 W-119 FAUNA NORYEGIÆ Bd. I. BMSKimRLSK AF DE HIDTIL K.IENDTE NORSKE AliTEH AF UM)i:i!<»|!|)XERNE PHYLLOCARIDA og PHYLLOPODA VED G. O. SARS MED 20. TILDELS KARVETHYKTE PL.VNCMER CRUSTACSA VnBMKf cHinsTiAxiA aa«HtoFTAir inst. TRYKT 1 AKTIE-BOGTRYKKERIET (I'orhcn: Dit ILillinusko liogtrykkcri.J 1896 lacrws tc w-ii? 4 FAUNA NORVEGIÆ Vol. I. DKSCRIPTKlX.s of THl': XnU\\'i;(;iAX SPP:C1ES AT PRESi:XI' KNOWN BELONGING 'I'o THp: srP.-OHI)!:i!S PHYLLOCARIDA and PHYLLOPODA BY INVERTEETRATE ^' ^- ^^^^ \ ZOOLOGY .Crustacea WITH 20 PLATES. COLOUUEU AND UNCOI.OURED CIllilSlIANIA PRINTED BY THE JOINT-STOCK PRrNTING COMPANY (Formerly: Jift MulliDSKkn Bogtrykkcri.) 1890 FORTAL. PREFACE. Nærværende Værk, til hvis Udgivelse Staten liar bevilget de fornødne Midler, blev ])aal)egyndt for mere end et Decennitim siden; men forskjellige nforudseede Omstændigheder bar bevirket, at Ud- arbeidelsen af samme i længere Tid li ar maattet standses, saa at forst nu Værket kan udkomme i sin Helhed. Oprindelig var Bevillingen givet til den fortsatte Udgivelse af Fauna Utforalis Norvegice, hvoraf tidligere er udkommet 3 Bind, forfattede dels af min Fader alene, dels af ham i Forening med nu afdode Overlæge Danielssen og Konservator Koren. Da det forekom mig, at denne Titel paa en mindre heldig Maade vilde komme til at begrændse StoflFet, tillod jeg mig at foreslaa, at Benævnelsen littoraJifi udgik og at Værket herefter skulde ud- komme under don her anvendte Titel. Det af mig til nærværende Bind valgte Stof er ogsaa af den Art, at det vanskeligt vilde passe indonfor iiamme)i af den tidligere Titel, da jo her ikke blot Sodyi-, men ogsaa en Del ægte Fer.skvandsdyr er omhand- lede. Idethele syntes mig, at den mere omfattende Titel, Fauna Nonegiæ, bedre maatte kunne svare til sin Hensigt, da der herunder vil kunne leveres Bidrag til Belysning af hvilkensomhel.'it Branche af Vor Fauna, der maatte frembyde en særlig Interesse. I Overensstemmelse med de 3 udkomne Bind af Fauna littoral is, tror jeg at nærværende Værk Ijor indeholde Afhandlinger af en mere udforlig ana- tomisk-biologisk Character, behandlende visse ud- valgte Dele af vor Fauna og udstyTede paa en saa- vidt m-aligt tidsmæs.sig Maade, saavel hvad Text som Planeher angaar. I et andet, paa engelsk skre- vet Værk liar j.'g paabegyndt en Bearbeidelse af vor Fauna efier et herfra temmelig forskjelligt Brin- eip, idet dette Værk er nærmest beregnet paa at The present work, for the publication of which the Government has granted the necessary funds, was begun more than ten 3'ears 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 entirely. The grant was originally given for the continiied publication of Fauna Uttoralis Norvegice, 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 Jiftoralis should be struck out, and that the work should hereafter ajipear under the title here employed. The matter chosen b\' me for the pre- sent volume, is also of such a kind, tliat it could hardly be included under the former title, as iiot only marine animals, but also .some true fre.sh-water animals are here treated of. Upon the whole, it seemed to me that the more compi-ehen.sive title. Fauna Norvegiæ, would better answer its purpose, as under it, contriliutions might be made to the infor- nuition concerning any branch of our fauna that might oifer special interest. In accordance with the 3 published volumes of Fauna Uttoralis, 1 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 ])ossible in a manner suitable to the times, as regards text and plates. In another wiu-k, written in English, I have begun an account of our fauna on a very diflerent principle to this, as it is rather calculated to give, as far as possible, a brief. VI give en saavidt rauHgt kortfattet systematisk Over- sigt af samtlige bidtil kj endte norske Arter, hvor- ved der er lagt hovedsagelig Vægt paa dets prak- tiske Anvendeliglied 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 falde Berettigelse og N5'tte Side om Side, og skulde ogsaa af denne Grund onske, at Fauna Norvcrpo' blev forVteholdt mere ndforlige Monograpliier af enkelte mindre kj endte Dy ref ormer eller af begrændsede (Irujiper, der maatte frem- byde en særlig Interesse i anatomisk-biologisk Hen- seende. Plancherne til nærværende Bind er i sin Tid iidforte paa nu afdode Lithograf Lynghs Officin, og ved deres Udforelse er anvendt al den Omhyggelig- hed og Kunst, som da kunde præsteres, saavel hvad Lithographering som Farvetrykning angaar. Texten er i Lighed med de 2 sidste Bind af Fauna littoralis og med Nordhavs-Expeditionens Gener alb er etning, dobl)eltspaltet, den ene Spalte norsk, den anden en- gelsk. Oversættelsen afde 6forsteArk er l)esorget af nu afdode Translateur Wilson, Resten af Miss Jessie Muir. Idet jeg herved fremlægger for Offentligheden Iste Bind af Fauna ISorregiæ., sker det med det Haalj, at der maa gives vore fremtidige Zoologer Anledning til at fortsætte dette Værk med flere paafølgende Bind udstyrede paa en for vort Land værdig 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 mure detailed anatomical treatment of the various fonns. I tliink that zoological works written on these two principles are perfectly legitimate and useful side by side; and I therefore wish that jPa«wa Norvecjice could be ke])t 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 ])rinting-ofiice, and all the care and art of which that time was apable, both as regards lithography and coloai'-printing, were emijloyed in their execu- tion. The letter-press is similar to that of the last 2 volumes oi T'aiwa liltoraJis^ 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. In now presenting the first volume of Fauna Norvegice to the public, I do so in the hope that opportunity may be given to oirr future zoologists to continue this work with .successive volumes, got up in a manner worthy of our country. The Author. INDHOLD. lll.UcMlnill^ 1. Phyllocarida 4. F am. Nehaliida; 6. iW'W. Nebalia, Li'ach 7. 1. Xi-lialia liipcs Fahr li. 2. Xcl.alia tvplildjis, (J. (>. Sars 31. VhyJlopnda 35. Seel i 0 I. Anostraca :!'.i. Fain. 1. Branchipodi dæ 40. (icn. Branchinecta. Venill 40. Braiirhim-fta paludosa /Miilk'r 41. Fam. 2. Pol;/ arfcmiidæ .58. Gi'ii. Polyarlemia, Fit^i-hcv 58. I'olyarteinia forcii)ata, Fischer 59. Sectio II. Notostraca 60. Fam. Alio did æ (17. (icii. Lepidurus. Loacli (57. Lcpiilunis frhifialit- Kroyer) (18. Sectio III. Conchoslrnca 83. Fam. 1. Limnadiidæ . 84- Gen. Liinnadia, Brojjniart 85 Liiniiailia lenticularis Lin., 85 Fain. 2. Limnetidce IIG (ic'U. Limnetis, [.oven .... ] I (i Lininotis In'acliviinis Miill 11". CONTENTS. Fag. IntriMlnctiiiii j. I'hyllocarida 4. Fam. Nehaliidæ (i. (Tfn. Nebalia, Leaoh 7. 1. Xclialia l>ip^_■^^ (Fabr.; 9. 2. Xi-lialia tvjihlops, G. O. Sars 31. Pliyll opoda 35. Section I. Anostraca 39. Fam. 1. Branchipodidre 40. (ion. Brancliirwda, Vcrrill 40. Brant'hinec-ta pahidosa (Milller) 41. Fam. 3. Poly arfcmiidæ 58. (ten. Polyartania, Fischer 58. Polyarteniia forcipata, Fis-cher 59. Section II. Nofo.straca m. Fam. Apodidæ ti7. Gen. Lepidiirus. Feaoli U7. Lei)i(hn-us irhifialis Krøyer) tiS. Section III. Conchostraca 83. Fam. 1. Limnadiidæ 84. < i)ellation 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 motoi'ic 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 cari-ying to the mouth the nutriment upon which these animals feed; a function which kommeu typiske Branchiopoder vil vi fiude, at Lem- merne, ved Siden af sin Function som Respirations- organer, altid er af væsentlig Betydning for Til- veiebringelsen af Foden, idet de ved sine rythmiske Bevægelser frembringer en rontinuerlig Strømning af Våndet ind mod Mnnden, hvorved de Smaa- partikler, hvoraf Dyret lever, bringes iudeufor Mund- delenes Omraade. I ethvert Fald maa den oven- omtalte eiendommelige Modification af Lemmerne, hvortil vi egentlig ikke har uoget tilsvarende hos andre Crnstaceer, betragtes som den for de her om- handlede Dyr vigtigste og mest udprægede Cha- racter. Branchiopoderne indtager i flere Henseender en central Stilling inden Crustaceernes Classe, og Prof. Claus har endog fremsat den Hypothese, at alle nulevende Crnstaceer i sidste Instans nedstammer fra en phyllopodeagtig D\^reform (Protophyllopod). Skjondt denne Hj-pothese af andre Zoologer (Packard) har været bestindt, er der dog al Grund til at an- tage, at disse Dj^r har conserveret adskillige Cha- racterer, der efter al Sandsynlighed er i hoi Grad primitive og maaske endog skriver sig fra de ældste paa vor Klode optrædende Arthropoder. Allerede det i hoi Grad varierende og ofte excessivt forøgede Antal Kropssegmenter, samt disses ialmindelighed mindre skarpt udprægede Gruppering til distincte Kropsafsnit, synes at vise, at vi her har at gjore med Former af en kun lidet udarbeidet Character, hos hvem eudnu ikke det for Nutidens Crustaceer typiske Forhold rigtigt har fæstnet sig; og hvad Lemmernes B3'gning angaar, saa er vel alle enige i at de, ialfald hos de tj'piske Branchiopoder, repræ- senterer et mere primitivt Standpunkt end hos nogen af de ovrige Crustacegrupper. Ogsaa hvad den indre Organisation angaar, findes hos de lierhen horende Former kiin lidet fixerede Forhold, men derimod en Mangfoldighed af Modificationer i Bj'gningen af snart sagt alle Organer, hvad der ligeledes giver denne Crustacegruppe et ganske eiendommeligt Præg lige- overfor de øvrige Ordener. Endelig vil vi i disse Dyrs Levevis, Forplantning og Udvikling stode paa baade characteriske Forskjelligheder mellem de for- skjellige Former og tildels ogsaa hoist eiendomme- lige, fra samme hos andre Crustaceer afvigende For- hold. Et nøiere Studium af denne Crustacegruppe vil derfor ogsaa være af særlig Interesse, saavel i phylogenetisk som biologisk Henseende og vil pas- sende kunne tjene som Udgangspiinkt ved Bearbei- delsen af den her omhandlede Dyrclasse. 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 bj- 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 reallj' correspondent in other Crustaceans, must be considered to be the most important aiid prominent characteristic of the ani- malshere spoken of. f^ The Branchiopods occup}-, in several respects, a central position in the class of the Crustaceans, and Prof. Claus has even proposed the hj-pothesis, that all the now-existent Crustaceans may descend, in the final instance, from a phyllopodoirs animal-form (Protophyllopod). Although that hypothesis has been rejected b^- other zoologists (Packard), there is still every reason to assume that those animals have retained several characteristics which are, in all probabilitj- in a high degree primitive, and perhaps even emanate from the oldest Arthropods that have appeared on our Earth. The extremely vari- able and frei|uentl3^ 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 j-et 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 t3qiical Branchiopods, represents a more pri- mitive condition than in anj- of the other groups of Crustaceans. Also in regard to the internal or- ganization there is found, in the form.s belonging to this order, only little of permanent features but, on the other hand, a multitirde of modifications in the structure of, it maj' 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 ^ifi^erences between the various forms and parth-, also, highly peculiar features diff'ering from those in other Crustaceans. A closer study of this group of Crustaceans will, therefore, prove of special interest, both in phylogenetic and biological respects, and will serve as a suitable point of departure in the treatment of the animal- class here spoken of. f Branchiopodernes Orden lader sig naturligt ind- dele i 4 underordnede Grnpper, eller Underordener, der saavel livad den ydre Habitus som den anato- miske Bygning angaar, skiller sig temmelig skarpt fra hinanden. Disse Underordener er følgende: \)Fhyllo- carida, 2) Fliyllopoda, o) Cladocera og 4) Branchiura. De 2 første af disse Underordener vil blive gjoi'te til Gjenstand for en nøiere Behandling i nærværende Bind af Fauna Norvegice. The order of Branchiopods may be naturally divided into 4 subordinate groups or sub-orders, which, both in regard to external habitus and ana- tomical structure, distinguish themselves pretty sharply from each other. These sub-orders are, as follows viz ; 1) FhyUocarida, — 2) FhyUojwda, — 3) Cladocera, and — 4) Branchiura. The two first- named sub-orders will be made the subject of a closer treatment in the present volume of Fauna Norvegirr-. Subordo I. PHYLLOCARIDA (Leptostraca, Claus). Sub-Order I. Character. — Brancbiopoder med den forreste Del af Legemet dækket af et stort, mere eller min- dre udpræget tveklappet Rygskjold, forsynet fortil med en bevægelig Pandeplade. Den bagre Del af Kroppen cylindrisk, afsmalnende bagtil og endende med 2 bevægelige Grene (Furca), mellem bvilke der undertiden er en dolkformig Haleplade. Øinene stil- kede og bevægelige. Begge Par Folere vel udviklede, mangeleddede, 2det Par enkle, bverken locomotoriske eller prebensile. Alle Forkropslemmer bag Mnnd- delene udelnkkende respiratoriske ; Bagkropslem- merne meget ulig disse og fordetmeste locomotoriske, manglende paa de bagerste Segmenter. Havdyr. Alm. Bemærkninger. — Typen for denne Under- orden er den i mange Henseender hoist mærkvæi'- dige og anomale Slægt Nehalia, om hvis .systematiske Stilling der har hersket den største Uenigbed blaudt Zoologerae. Medens man før ialmindeligbed med Milne-Edvrards henregnede denne Form til Phyllo- poderne, har i den nyere Tid, navnlig efter de af Prof. Claus anstillede Undersøgelser, en ganske anden, allerede meget tidligt af enkelte Naturforskere ytret Opfatning vundet Overhaand, nemlig at denne Form slutter sig nærmest til de stilkoiede Krebsdyr, navn- lig til visse Schizopoder (Euphausiidæ), og at den saaledes snarere tilhører Malacostraoeernes Afdeling end Entomostaceerne. Jeg har paa et andet Sted *) nærmere udviklet mine Grunde til fremdeles at bi- beholde denne Slægt under Entomostraceerne, og blandt disse er Branchiopoderne de, hvormed nær- ') Report on the Phyltocfirifla, collected during the Expedition of H. M. S. «Challenger.. PHYLLOCARIDA (Leptostraca, Claus). Characters. — Branchiopods, with the foremost portion of the body covered by a large, more or less distinctly bi-lobate carapace, fiiinished anteri- orly' with a mobile frontal plate. The posterior por- tion of the body cylindrical tapering backwards, and terminating in 2 mobile rami (furca). between which there is occasionallj' a mucroniform caudal plate Eyes pedunculated and mobile. Both pairs of antennæ well developed, multiarticulate; 2nd pair simple, neither locomotory nor prehensile. All the appen- dages of the anterior division of the body behind the oral parts, exclusively respiratory. The appen- dages of the posterior division of the body very unlike the former and chiefly locomotor}^; absent on the posterior segments. Marine animals. General remarks. The tj-pe of this sub-order is — the in manv respects highly remarkable and anomalous genus — Kehalia, regarding whose sys- tematic position the greatest difference of opinion has prevailed among zoologists. Whilst, previously', zoologists in general agreed with Milne-Edwards in assigning this foi-m to the FliyUopods, there has prevailed in later times, especially since the result of the investigations made by Prof. Glaus, a quite different opinion, which already miti;h earlier was expressed b_y a few naturalists, viz; that this form approximates closest to the stalk-ej^ed Crusta- ceans, especially to certain Schizopods (Eupliausiidæ), and that it, therefore, pertains rather to the Malaco- stracan than to the Entomostracan division. I liave elsewhere ^) explained, in greater detail, my reasons for still retainins: this genus under the Entomo- ') Report on the Phyllocarida collected during tlie Esjieditiou of H. M. S. «Challensen.. værende Form viser mest Afinitet. At den imid- lertid ikke længere kan opfattes som en virkelig rhyllo])ode, derom kan der vel neppe for Tiden være mere end en Mening, efterat dens anatomiske Byg- ning, navnlig ved Prof. Claus's ndmærkede Under- søgelser. er bleven noiere udredet. Sporgsmaalet er nu, om de Eiendommeliglieder, denne Form viser i anatomisk Henseende, gjor det alisolut nedvendigt at skille den helt nd fra de ovrige Entomostraceer som Typen for en egen Orden. Saagodtsom samtlige Forskere synes for Tiden i Virkeligheden at være af denne Mening, og baade Packard's Benævnelse Fhyllocaricla og den af Claus foreslaaede Leptostraca er beregnet paa at udtrykke en distinct Orden. Undersoger vi imidlertid, hvorledes Forholdet er med de for Tiden ialmindelighed til Branchiopodernes Orden henførte Former, saa vil vi ogsaa her stode paa særdeles store og væsentlige Forskjelligheder i den anatomiske Bygning ; ja de saakaldte7?rrt«c/«'Mrer (Argulu.s), som vel de fleste Forskere nu er enige om at henføre til Branchiopodernes Orden, forekom- mer mig endog, saavel hvad den ydre Habitus som den indre Organisation og Levevis angaar. at skille sig endnu betj-delig mere fra de tj-piske Branchio- poder end Tilfældet er med Nehcdin. Hos denne sidste Slægt er der ialfald en Character, og det netop den for Branchiopodernes Orden mest beteg- nende, der staar i den bedste Harmoni med hvad vi finder som typiskt for denne Krebsdja-gruppe ; jeg mener Forkropslemmernes Bygning. Disse viser ikke blot ved sin udpræget bladdannede Form den storste Lighed med samme hos virkelige Branchiopoder; men, hvad der er af end større Vægt, deres respi- ratoriske Function er fuldkommen ligesaa tydeligt udpræget som hos de mest typiske Former blandt hine. Alene denne ene Character synes mig at maatte stemple Slægten XebaJia som en veritabel Branchiopode, og ialfald at være af adskillig større Vægt end Mesteparten af de Characterer, man har anført for at modbevise en saadan Antagelse, og hvoraf flere faktisk er fuldstændig ubrugelige. Efter min Mening bør derfor Slægten Nehalia henføres til Branchiopodernes Orden, om den end her maa danne Typen for en egen, i visse Henseender meget ano- mal Afdeling eller L'nderorden. for hvilken den først af Packard foreslaaede Benævnelse 1'hyUocarida vil kunne bibeholdes. I den nyere Tid har man troet i nogle, tildels kjæmpemæssige, fossile Former fra den palæozoiske Formation [Ceratiocaris, Dilhi/rocaris etc.) at gjeu- kjende visse for Slægten Nebalia eiendommelige Cha- racterer, saaledes Legemets almindelige Form. Ud- viklingen af Rygskjoldet og navnlig den meget characteristiske bevægelige Pandeplade* og, skjondt stracans, and among these the Branchiopods are tho.'^e with which the present form exhibits most affinity. That it ma}-, however, be no longer regarded as a genuine Phyllopod, there can, now be scarcelj' any diversity of opinion since its anatomical struc- ture has been preciselj' elucidated, especially through Prof. Claus"s admirable investigations. The question now is, whether the peculiarities this form exhibits in anatomical respects makes it absolutely neccessaiy to separate it entireh- from the other Entomostra- cans, as the type of a special order. Nearly all investigators appear, at present, to really entertain that view, and both Packard's appellation, FhjUo- carifla, and that proposed bj- Claus, Leptostraca, are intended to express a distinct order. If we, how- ever, investigate what the relations of the forms at present generalh- assigned to the order of Branchio- pods are, we will also here meet with particularly great and material divergencies in the anatomical structure; indeed the so-called i?/'flH(7;/;(»-a (Argulus), which most investigators are now, we think, unan- imous in assigning to the order of Branchiopods, yet appeal's to me, both in regard to external habi- tus, internal organization, and the mode of life, to distinguish itself even more considerably from the typical Branchiopods than is the case with NehaJia. In the latter genus there is, at any rate, one char- acter, and just the one most characteristic of the order of Branchiopods, which stands in the most perfect harmony with what we find to be tj^pical in that group of Crustaceans. I refer here to the structure of the appendages of the anterior division of the body. These exhibit, not only in their dis- tinguished foliaceous form the greatest similarity with the same limbs in genuine Branchiopods, but, what is of still greater importance, their respira- tory function is perfectl}- as prominent as in the most t3'pical form of Branchiopods. That single characteristic alone, it appears to me, must stamp the genus Xehalia as a true Branchiopod, and, in any case, is of considerabh- more importance than the greater part of the characteristics that have been adduced to 'disprove such an assumption, and some of which are really perfectly unserviceable. In my opinion the genus XeJialia ought, therefore, to be assigned to the order of Branchiopuds, even although it here must form the type of a special, in certain respects verj' anomalous division or sub- order, for which the appellation I'Jii/llocarida, first proposed by Packard, may be retained. In later times it has been thought, that we, in some parth^ gigantic fossil forms from the Paleo- zoic formation {Ceratiocaris, DitJn/rocaris &c.) were able to recognize certain characteristics peculiar to the genus Nebalia, for instance the general form of the body, the development of the carapace, and especiall\- the very characteristic mobile frontal disse Formers Organisatiou forovrigt kun er yderst ufuldstændigt kjendt (endnu kar man saaledes ingen- somhelst Kjendskab til Lemmernes BeskaiFenhed hos disse FormerX har Packard nylig indbefattet dem under samme Gruppe vOrden) som Nehalia. Uagtet jeg for flere af disse fossile Formers Vedkommende anser det for meget tvivlsomt, hvorvidt de lader sig henføre til denne Gruppe, har jeg dog forsøgt at give den ovenstaaende Diagnose af Uuderordenen en saavidt rummelig Character, at de nævnte fossile Former til Nod lader sig indbefatte uuder samme. De faa hidtil kjendte levende Former horer utvivl- somt alle til en og samme Familie, der passende vil kunne benævnes efter den forst opstillede og derfor typiske Slægt. plate; and although the organization of those forms is, otherwise, extremely imperfectly known (we have, for instance, not the slightest knowledge of the nature of the appendages in those forms), Packard has lately incliided them in the same group (order), as Nehalia. Although I, in regard to several of those fossil foi'ms, consider it very doubtful whether they can be assigned to that group, I have yet endeavoured to give the above diagnosis of the sub-order such a broad character, that the fossil forms referred to, may, if necessary, be included in it. The few hitherto known living forms all belong, undoubtedly, to one and the same famih', which may suitably be named after the first established and therefore typical genus. Fam. Nebaliidæ. Fam. Nebaliidæ. Character. — Legemet mere eller mindre for- længet, successivt afsmalnende bagtil. uden skarpt markeret Begrændsning mellem For- og Bagkrop. Eygskjoldet kun helt fortil umiddelbart forbundet med Legemet, sammentrykt, tveklappet, Valvlerne be- vægelige og sammenholdte ved en tydelig Addxictor- muskel; Pandepladen tungedannet, forbundet med Rygskjoldet ved et tydeligt Led. Truncus løst overdækket af Rj-gskjoldet og delt i 8 fuldstændige Segmenter af ens Udvikling. Bagkroppen bestaaende af 2 mere eller mindre tydeligt begrændsede Afsnit, hvert sa^nmensat af 4 Segmenter. Øinene fæstede tæt sammen under Basis af Pandepladen og diver- gerende til hver Side. Begge Par Følere kraftigt udviklede, subpediforme. Skaftet dobbelt knæboiet, Svoben mangeleddet; de ovre med et lamelleformigt børstebesat .Vedhæng ved Enden af Skaftet. Kind- bakkerne forholdsvis smaa, men 'med vel udviklet Palpe; T^'ggedelen hovedsageligt repræsenteret af Molarprocessen. Iste Par Kjæver med 2 indadret- tede Tyggelappe og en lang, børsteformig, bagudrettet Palpe; 2det Par lamellære, med mere eller mindre udviklet Palpe og Exognath. 8 Par mere eller min- dre udpræget bladdannede, respiratoriske Lemmer tilstede paa Forkroppen, bestaaende af Endo-, Exo- og Epipodit, den første mere eller mindre forlænget, med Inderkanten tæt borstebesat, men uden tyde- lige Enditer eller Flige De 4 forreste Par Bag- kropslemmer omformede til kraftige, tvegrenede Svømmefodder; de 2 følgende Par rudimentære. De 2 sidste Segmenter uden Buglemmer, Halegrenene simple, lineære eller lamellære, tæt borstebesatte Characters. — Body more or less prolonged, tapering backwards gradually, without sharply defined demarcation between the anterior and pos- terior divisions. Carapace attached, only quite in front, immediately to the body, compressed, bi- lobate, the valves mobile and kept together by a distinct adductor muscle. Frontal plate lingui- forra, attached to the carapace by a distinct joint. Truncus loosely covered by the carapace and divided into 8 perfect segments of uniform develop- ment. The posterior division of the body consisting of 2 more or less distinctly defined sections, each composed of 4 segments. E^^es secured close together below the base of the frontal plate, and divergent to each side. Both pairs of antennæ powerfully developed, subpediform, peduncle double-genicul- ated, flagellum multiarticulate ; the .superior ones with a lamelliform setous appendage at the ex- tremity of the peduncle. Mandibles relatively small, but with well developed palp; the mastica- tory part represented chiefly by the molar expan- sion. First pair of maxillæ with two inwardly dir- ected masticatory lobes and a long setaceous palp directed backwards; 2nd pair lamellar with more or less developed palp and exognath. Eight pairs of more or less prominently foliaceous respiratory appen- dages present on the anterior division of the body, consisting of endo-, exo-, and epipodite; the first more or less prolonged, with the inner edge closely beset with bristles but without distinct endites or laps. The 4 foremost pairs of appendages of the posterior division of the body transformed into ved Spidsen og i Inderkanten. Ingen median Hale- plade tilstede. Den indre Organisation nærmest lig samme hos Ampliipoderne. Æggene gjennemgaar sin Udvikling indenfor Rvgskjoldets Valvler, mel- lem Forkroppens Brancliialfodder. Ungens Udvikling directe, uden Metamorpliose. Bemærkninger. — Indtil for ganske nylig kjeudte man af nærværende Familie kun en eneste Slægt nemlig Slægten NehaJia. Under Cliallenger-Expedi- tionen blev imidlertid opdaget "2 lierlien hørende Former, der begge danner Typer for særskilte Slæg- ter og nærmere er omtalte i min Bearbeidelse af de under denne Expedition indsamlede Phyllocarider. Begge disse Slægter udmærker sig ved den eien- dommelige Udvikling af Branchialfodderne. Medens disse hos den ene Slægt, Faranehalin Claus, er, navnlig hos Hunnen, ualmindelig stærkt forlængede, saa at de i visse Henseender selv minder om For- kropslemmerne hos visse Sehizopoder (Euphausiidæ), er de hos den anden Slægt, Xehaliopsis Gr. O. Sårs, reducerede til meget smaa, utydeligt lappede, mem- branøse Plader, der viser endnu mindre Lighed med sædvanlige Fodder end hos de mest tj-piske Branchio- poder. Den 3die Slægtr Nebalia, staar i Henseende til Brancliialfoddernes Udvikling paa en Maade midt imellem hine 2 Slægter og repræsenterer saaledes det for Familien typiske Forhold. I Henseende til den ovrige Organisation sj'nes der ikke at være synderlig stor Forskjel mellem de 3 Slægter, oraend man ogsaa her forefinder Characterer af ixtvivlsom generisk Betydning. Alene den typiske Slægt. Xe- balia, er representeret i vor Fauna. Gen. Nebalia. Leach. powerful bifurcate swimming legs: the 2 succeeding pairs rudimentary. The 2 last segments without anj- ventral appendages. Caudal rami simple, linear or lamellar, closely beset with bristles at the tip and on the inner edge. No medial caudal plate. Internal organization approximating closest to that of the Am])hipods. The ova undergo their develop- ment inside the valves of the carapace, between the branchial legs of the anterior division of the Ijod}'. The development of the young direct, without an}' nietamorpho. Mediterranean form, X. Geoffroyi, M.Edw. of whieli I have had specimens for investi- gation, collected b}- my father off Naples, apjiears in no respect, whatever, to distinguish itself from our northern form, which is, undoubtedly, identical with Fabricius's species. Tiie same is also the case with A'. Ilirhslii Leach, and JS'. Moulagui Thompson. 10 son. Overhovedet synes kun denne ene Art at være observeret af andre Forskere. Fra den følgende meget nærstaaende, skjendt sikkert speoifiskt for- skjellige Form er den strax kjendelig ved de vel udviklede og med tydeligt Pigment og Synselementer forsynede Øine, samt ved Pandepladens forskjellige Form. Beskrivelse af Hunueii. Legemets Længde, regnet fra Spidsen af Pande- pladen til Enden af de sammenlagte Halegrene, er hos de største af mig observerede Exemplarer, tagne ved Lofoten, omtrent 12' mm. Exemplarer fra vor Syd- og Vestkyst er ialmindelighed noget mindre. Legemets Form (se Tab. I, Fig. 1 og 2) inaa idetbele siges at være temmelig slank, især naar man observerer Dyret i levende Tilstand. Paa de i Spiritus opbevarede Exemplarer synes ialmindelig- lied Legemet noget kortere og mere undersætsigt paa Grund af en ved Spiritusens Action frembragt kjendelig Contraction i Ledføiningerne mellem de forskjellige Segmenter; noget der ogsaa bemærkes paa de fleste af andre Forskere givne Figurer af dette D3^r. Hele den forreste Halvpart af Legemet dækkes mere eller mindre fuldstændigt af Rygskjol- det, bag hvilket den bagtil successivt afsmalnende og meget bevæ.gelige Hale rager frit frem. Den habituelle Lighed med en Copepode (navnlig visse Herjmcticider) er umiskj endelig og bliver endmere paafaldende, naar man observerer Dyret i levende Tilstand, idet Bevægelserne foregaar paa en fuld- kommen lignende Maade. Rygskjoldet er meget stærkt sammentrykt fra Siderne, saa at dets Brede kun lidet overgaar den halve Heide, og, da det desuden mellem sine Side- deie fuldstændig indeslutter ikke blot Munddelene, men ogsaa alle følgende Forkropslemmer (Branchial- fodderne), har det mere Lighed med en tveklappet Skal, saaledes som vi finder det hos visse Phyllo- poder og Cladocerer. Ogsaa i andre Henseender er denne Lighed tydeligt fremtrædende. Saaledes vil man finde, at dette Rygskjold kun paa et meget indskrænket Omraade helt fortil og oventil, dan- ner den umiddelbare Kropsvæg (se Tab. II, Fig. 1), medens det forøvrigt kun ganske løst dækker Le- gemet, som derfor frit kan bevæges indenfor samme. Endelig kan de 2 Sidedele, eller Valvler, ligesom hos de ovennævnte Branchiopoder, bevæges imod hinanden ved Hjælp af en stærk transversal Ad- ductormuskel (Tab. II, Fig. 7, ms), der lige bag Munddelene forbinder de 2 Valvler med hinanden. Insertionen af denne Adductornmskel er ogsaa ud- vendigt meget tydeligt at se i den forreste Del af hver Valvel, nærmere Dorsalsiden, i Form af en vel begrændset oval Area, hvori bemæi^kes en Ansam- Altogether, onl}' this single species appears to have been observed by other investigators. From the following very closely related, althoixgh certainly specifically diiferent, form, it is immediately distin- guishable by the well developed eyes furnished with distinct pigment and visual elements, and also by the difPerent form of the frontal plate. Description of tlie female. The length of the body measured from the tip of the frontal plate to the extremity of the folded caudal rami is, in the largest specimens that I have observed, taken off Lofoten, about 12 mm. Specimens from the south and west coasts. of Norway are generally somewhat smaller. The form of the body (see PI. I fig. 1 and 2) must be said to be, on the whole, rather slender, especially when the animal is observed in the liv- ing state. In specimens preserved in alcohol, the body appears, in general, to be somewhat shorter and stouter, owing to an appreciable contraction of the articulations between the various segments, pro- duced by the influence of the alcohol, a circumstance also noticed in the illustrations of this animal sup- plied by most other naturalists. The entire fore- most half of the animal is covered more or less completely by the carapace, behind which the grad- uall,y backwards-diminishing and very mobile tail projects freely. The habitual resemblance to a Copepod (especially certain Harpacticids) is unmis- takeable and becomes still more conspiciious when we observe the animal in the living state, as the movements occur in an exactly similar manner. The carapace is verjr strongly compressed from the sides, so that its breadth but little exceeds half the height, and, besides, as it comjiletely encloses between its lateral parts not only the oral parts but also all the succeeding appendages of the anterior division of the body (the branchial legs), it has more of resemblance to a bivalve shell, such as we find it in certain Phyllopods and Cladoceres Also in other respects is this resemblance distinctly pro- minent. We may thus observe that this carapace forms, only within a very limited space (juite in fi'ont and above, the immediate wall of the body (see PI. II fig. 1), whilst it, otherwise, only quite loosely covers the body, which can therefore move itself freely within it. Finally, the 2 lateral .parts or valves can, as in the above-mentioned Branchio- pods, be moved towards each other with the aid of a powerful transversal adductor muscle (see PI. 11 fig. 7, ms.) which immediately behind the oral parts connects the 2 valves to each othei\ The insertion of this adductor muscle may also be veiy distinctly observed from the exterior, in the foremost part of each valve next the dorsal side, in the form of 11 ling af klare Pletter (lucid spots), svarende til de enkelte Bundter af Adduftormuskelen (se Fig. 1 ms). Nogen virkelig Laasrand, saaledes som lios Ostra- coderne og enkelte Phjdlopoder (Estberia, Limnetis), er imidlertid ikke tilstede, idet de 2 Valvler dorsalt gaar umærkeligt over i liinanden med en jevn Krum- ning. Seet fra Siden (Tab. I, Fig. 1) bar Ryg.skjoldet en noget uregelraæssig oval, eller næsten rbombisk Form, med omtrent samme Hoide fortil som bagtil. Rygkanten er ganske svagt buet og danner med de skraat afskaarne bagre Kanter en meget stump Vin- kel. Fortil udgaar fra Rygskjoldet øverst den be- vægelige Pandeplade, som i denne Stilling tager sig xiå som et tilspidset, nogét nedadboiet Pandehorn. Lnellem denne og de forreste, noget udbuede Kanter af Rygskjoldet er der et smalt Indsnit, hvorfra Øinene rager frem. De nedre Kanter er i sin for- reste Del stærkt buede, længere bagtil næsten lige, og forbinder sig under en stærk Krumning med de bagre Kanter, hvorved fremkommer til hver Side en afrundetSidelap, der næsten rækker lige til Enden af Bagkroppens 4de Segment. Ovenfra seet (Fig. 2) viser Rygskjoldet sig meget smalt og stærkere af- smalnende fortil end bagtil, hvor det har en dyb, i Bunden smalt afrundet median Indbugtning, der skiller de 2 Sidelappe fra liinanden. Ved den for- reste Ende af Rygskjoldet sees Pandepladen, som nu viser en smal tungedannet Form, med Enden jevnt afrundet (se ogsaa Tab. II, Fig. 2). Den er forbundet med Rygskjoldet ved et tydeligt Led, saa at den ved særegne Muskler kan snart rettes lige fortil, snart indbøies mod Forkanten, i hvilket Til- fælde den lige.som et Laag dækker fortil for Ind- gangen til R3-gskjoldets Hule. Rj-gskjoldet er gan- ske glat, uden nogen tydeligt udpi-æget Sculptur og uden Børster eller Torner, af temmelig tynd, boielig, chitinøs Consistens og halvt gjennemsigtigt, saa at den indenfor liggende Krop tilligemed dens Lemmer kan skimtes igjennem samme. For noiere at kunne undersøge denne sidste, er det imidlertid hensigtsmæssigt at fjerne den ene af Rygskjoldets Valvler (se Tab. II, Fig. 1). Det viser sig da, at Legemet i sin hele Længde er t3'deligt segmenteret, og at Segmenterne grupperer sig til vel markerede Krojisafsnit. Man kan ialt adskille 4 saadanne Afsnit, livoraf de 2 tilhører Forkroppen, de 2 øvrige Bagkroppen. Det forreste Afsnit af Forkroppen kan jjassende benævnes Hovedet (Cepha- lon), da det, foruden Oinene, kun bærer de 2 Par Følere og d(> egentlige Munddele (Over- og Under- læbe, Kindbakkerne og 2 Par Kjæver). Dets dorsale Parti, der er af betydelig større Udstrækning end dets ventrale, er fast forbundet med Rygskjoldet, a well defined oval area, in which are observed a number of lucid spots corresponding to the indivi- dual bundles of the adductor-muscle (see fig. 1, ms). A true cardinal margin, such as appears in the Ostracods and some Piiyllopods (Estheria, Limnetis), does not, however, exist, as the 2 valves pass dor- sally, imperceptibly into each other by an even curvature. Viewed laterally (PI. I, fig. 1) the cara- pace has a .somewhat irregular oval or almost rhomboid form, having nearly the same height in front as behind. The dorsal margin is quite gently curved, and forms with the obliquely truncated posterior margins a ver}^ obtuse angle. The mobile frontal plate issues anteriorly from the upper part of the carapace, and in this situation appears as an acuminate, somewhat downwards-bent rostrum. Between it and the foremost somewhat bulging edges of the carapace, there is a narrow incision from which the eyes project. The lower edges are in their foremost portion greatly curved, but further back almost straight, and unite with a strong curve to the posterior edges, whereby- is formed on each side a rounded lateral lobe that almost extends to the extrem- ■ity of the 4th segment of the posterior division of the body. Viewed from above (fig. 2) the carapace ap- pears very narrow and diminishing more rapidly in front than behind, where occurs a deep median, sinus narrowly rounded at the bottom, which sepa- rates the 2 lateral lobes from each othei'. At the foremost extremity of the carapace appears the fron- tal plat(', which now exhibits a narrow linguiform shape with the extremitj^ eviuily rounded (see also PI. II fig. 2). It is connected to the carapace by a distinct articixlation, so that it can by means of special muscles be directed, now straight forward now bent in towards the anterior margin, in which case it, like a lid, covers in fi-ont the entrance to the cavity of the carapace. The carapace is per- fectly smooth, witliont any distinctly marked sculp- ture, and is devoid of bristles or spines; of rather thin, flexible, chitinous consistency and semi-trans- parent, so that the enclosed body with its appen- dages may be observed through it. In order to closely investigate the last-named, it becomes desirable to remove the one of the valves of the carapace (see PL II fig. 1); it then appears, that the body throughout its entire length is dis- tinctly segmented, and that the segments group themselves iato well defined sections of the body. We are able to distinguish in all 4 such sections, of which 2 pertain to the anterior division, and tlie other 2 to the posterior division of the body. The front section of the; anterior division of the body , may be suitably termed the head (cephalon). as it, be.sides the eyes, only bears the 2 pairs of antenna^ and the oral parts projier (anterior and posterior lips, the mandibles and 2 pairs of maxillæ). Its' 12 som her danner den umiddelbare Kropsvæg. Det følgende Afsnit, der forestiller livad man ialminde- lighed pleier at kalde «Truncus» eller «Thorax», men som raaaske mere passende bør kaldes Midtkroppen (mesosome), bestaar af 8, i sin hele Omkreds tyde- ligt sondrede, og ensformigt udviklede Segmenter, der hvert bærer et Par Branchialfodder. Omvendt hvad Tilfældet er med Hovedet, har dette Afsnit sin største Udstrækning ventralt, idet begge Afsnit forbinder sig med hinanden langs en meget skraat gaaende Linie. Maalt langs Dorsalsiden er det her omhandlede Afsnit derfor neppe læugere end Hove- det, medens det ventralt er næsten dobbelt saa langt. Bagtil forbinder det sig med Bagkroppen, viden at være afsat fra samme ved nogen mærkbar Indknibning. Det forreste Afsnit af Bagkroppen («Præabdomen», metasome) er sammensat af 4 Seg- menter, alle betydelig større end de til Truncus horende Segmenter, og hvert forsynet med et Par kraftigt udviklede Svommefodder. Det sidste af disse Segmenter har tydelige pladefornaige Epimerer, der ender bagtil med et retvinklet Hjørne. Hele Bagkanten af dette Segment er desnden regelmæs- sigt sagtakke t, og ogsaa paa det foregaaende Seg-, ment bemærkes i den dorsale Del en lignende, skiondt mindre udpræget Bevæbning af Bagkanten. Afsnit- tet, der successivt af smalnes bagtil, dækkes til Si- derne næsten fuldstændigt a,f Rygskjoldet, medens dets dorsale Del træder mere eller mindre frit frem indénfor den dybe Indbugtning i Rygskjoldets bagre Del (se Tal). I, Fig. 2). Angaaende Længden af dette Afsnit, saa er den noget forskjellig hos de 2 Kjøn. Hos Hunnen er det, ialfald maalt langs Ventralsiden, neppe længere end Truncus, medens det selv hos endnu ikke fuldt udviklede Hanner (se Tab. II, Fig. 1) al tid er betydelig storre, i Overens- stemmelse med den kraftigere Udvikling af Svømme- fødderne. Det ydre, meget bevægelige Afsnit af Bagkroppen («Postabdomen> , urosome), der gaar i Flugt med det forreste') og jævnt og hurtigt af- smalnes bagtil (se Tab. I, Fig. 1 og 2), bestaar lige- ledes af 4 Segmenter, hvoraf de 2 forreste er for- synede med rudimentære Buglemmer, medens de 2 bagerste ganske mangler saadanne. Det er af trind Form, næsten dobbelt saa langt som det forreste Afsnit og har Bagkanten af de 3 forreste Segmenter regelmæssigt sagtakket, ligesom paa de bagre Seg- menter af hint. Til Enden af sidste Segment er Halegrenene indleddede; de synes at svare til den saakaldte Furea hos Copepoderne og tør saaledes nærmest være at betragte som et i 2 Dele kløvet Endesegment. Under Basis af Halegrenene gaar sidste Segment ud i 2, ved et smalt mediant Indsnit ') Hos Sl. Paranehalia er di^fte Afsnit sl;ar|it afsat fra Præ- ab(iomeii. dorsal portion, which is of considerably greater extent than the ventral one, is firmty connected to the carapace, vphich here forms tlie immediate wall of the body. The succeeding section, which represents what is txsually termed the «truncus» or «thorax», but which might perhaps be more properly termed the middle section of the body (mesosome) consists of 8 uniformly developed segments, di- stinctly separated throughout their entire circum- ference, each of which carries a pair of branchial legs. This section, contrary to what is the case with the head, has its greatest extent ventrally, as both sections' are connected to each other along a very oblique line of union. Measured along the dorsal side, the section referred to here is, therefore scarcely any longer than the head, while the ven- tral part is almost twice as long. Posteriorly it connects to the posterior division of the body withovit being demarcated from it by any notewor- thy consti'iction. The front section of the posterior division of the body («præabdomen», metasome) is composed of 4 segments, all considerably larger than the segments pertaining to the truncus, and each furnished with a pair of powerfully developed swimming legs. The last of those segments has di- stinct lamelliform epimeræ that terminate behind in a right-angled corner. The entire posterior mar- gin of this segment is, further, regularly serrated, and also in the preceding segment there is observed, on the dorsal part, a similar although not so distinct armature of the posterior margin. The section, which diminishes gradually backwards, is almost comple- tely covered at the sides by the carapace, while the dorsal part appears more or less uncovered inside the deep sinus in the posterior part of the carapace (see PL I fig. 2). Regarding the length of this sec- tion, it is somewhat different in the 2 sexes. In the female it is, at any rate when measured along the ventral side, scarcely longer than the truncus, while it, in even not yet fully developed males (see PI. II fig. 1), is always considerabl}^ larger, in corre- sf)ondence with the more powerful development of the swimming legs. The outer, very mobile section of the posterior division of the body («postabdomen», urosome) which forms the immediate continuation of the anterior one ') and diminishes evenly and ra- pidly backwards (see PI. 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 ') In the gen. Paranehalia this section is sharply defined from the præabdomen. 13 skilte, tilspidsede Plader, der delvis dækker Anal- aabningen nedentil (se Tab. III, Fig. 12). Øinene (Tab. II, Fig. 1 og 7, 0, Fig. 3 og 4), der er fæstede temmelig nær sammen ved den forreste Ende af Hovedet, lige nnder Pandepladens Basis, er vel mlviklede og omtrent af Pandepladens halve Længde. De er tydeligt stilkede og meget frit be- vægelige, saa at de snart kan rettes ud til hver Side, snart lægges tæt ind mod hinanden og bøies nedad, i hvilket Tilfælde de ganske skjules mellem den forreste Del af Rygskjoldets Val vier. Af Form er de uoget sammentrykte, aflangt ovale, eller næ- sten halvmaanedannede, med den ydre Del noget udvidet og skjævt afrundet, endende nedentil i et vinkelformigt Hjørne. Forkanten afØiet er ganske glat, itden Spor af de stærke Sagtakker, som findes her hos Sl. Faranebaha. Øiepigmentet. der hos det levende Dyr er af en vakker purpurrod Farve, fyl- der næsten ganske den ydre Halvpart af Øiet, og fra det ndstraaler til alle Kanter talrige Synsele- menter, i Form af smaa stærkt lysbrydende Legemer (Krystalkegler) af kort pæredannet Form. Derimod mangler den Øiet omgivende Hud (Cornea) ganske ethvert Spor af nogen egentlig Facettering som hos de holere Crustaceer. Hvert Øie dækkes ved Roden af en fra Pandedelen nd.springende skjælformig, i en skarp Spids udgaaende Plade, der næsten rækker til Midten af Øiets Længde (se Fig. '6, 4). De ovre Folere (Tab. II, Fig. l,a', Fig. 5), der iidspringer lige under Øinene, er af kraftig, næsten fodformig Bygning og, lige ndstrakte, omtrent af af Forkroppens Lamgde. Man kan paa dem adskille et tykkere, dobbelt vinkelboiet Skaft og 2 terminale Vedhæng af ulige Form, hvoraf det ene har Ud- seendet af en skjælformig Plade, det andet af en forlænget, mangeleddet Svøbe. Skaftet bestaar af 4 Segmenter, hvoraf de 2 yderste er fast forbundne med hinanden, medens det foregaaende (2det) Led iiar en meget bevægelig Articulation saavel med Iste som SdieLed. Iste Led af Skaftet er, som det .'^ynes meget fast forbundet med Hovedet og kun lidet bevægeligt, 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 Borstevæbning og opfyldt med stærke Muskel- serrated, a.s in the posterior segments of the former. The caudal rami are articulated to the extremity of the last segment; thej' appear to correspond to the so-called furca of the Copepods, and ma}-, therefore, be most properly considered to be a bifurcated terminal segment. Below the base of the caudal rami the last segment projects into 2, bj' a narrow median incision, separated acuminate lamellæ which partly cover the anal aperture beneath (see PI. Ill fig. 12). The eyes (PI. 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 developed 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 ej'e is perfectly smooth without trace of the powerful sawteeth found in the gen. Paranehalia. The ocular pigment, which, in the liv- ing animal, has a beautiful purple-red colour, occu- pies almost completely the outer half of the e5'^e, and from it radiate numerous visual elements in all directions, in the form of small, strongly re- fractive bodies (crystal nones) of short pj-riform shape. On the other hand the enclosing integument (cornea) of the eye is quite deficient in every trace of an3^ real facets such as exist in the higher Cru- staceans. Each eye is covered at the base by a squamiform plate that issues from tlie frontal part, and terminates in a sharp point wiiich reaches nearly to the middle of the length of the eye (see figs. 3. 4). The superior antennæ (Pl.II, lig. 1 a', fig. 5), which issue just under the eji'es, 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 ap]3earance of a squamiform plate, the other of a pro. longed multi-articulate tlagellum. The peduncle con- sists of 4 segments, of which the two outermost ones are firmly attached to each other, while the ])receding joint (2nd) has a very llexible articulation both with the 1st and 3rd joints. The 1st joint of the ])eduncle is, apjuirently, ver^- firmly connected to the iiead and but little ilexible, hence it can with difficulty be obtained on dissection, in union with the remaining part. It is oval in form (see fig. 1, 14 knipper, der tjener til at bevæge den ovrige frie Del af Føleren. 2det Led, der ialmindeliglied er rettet lige fortil. dannende med Iste en mere eller mindre t^uleligt udpræget albuformig Boining, er omtrent saa langt som de 2 følgende tilsamnien og noget forstykket paa Midten, næsten tendannet. Det bærer i Midten af den ovre Kant en enkelt stærk Fjærbørste og i den nedre Kant, nærmere Enden, en Rad af omkring 8 saadanne, der hurtigt aftager i Længde udåd; ved Spidsen af Leddet findes des- ^^den et Knippe af divergerende simple Børster. 3die Led, der sædvanlig med det foregaaende danner en meget stærk, retvinkJet knæformig Bøining, er noget indknebet ved Basis, men iidvides suceessivt mod Enden, der er skjævt afskaaret i Retningen forfra bagtil. Det har i hver Kant, nær Enden, en Rad at cilierede Børster, hvoraf de i Bagkauteu er længst. 4:de Led er meget kort og bredt, næsten triangulært ug ligesom foregaaende skjævt afskaaret i Enden, men i modsat Retning, hvorved dets Bagkant bliver meget kort. Forkanten er bevæbnet med en Rad af korte Torner og ender med et noget sammentrykt, kort triangulæx"t Fremspring, der ved Spidsen bærer en noget ste ne Torn'). At de 2 terminale Vedhæng har det forreste Formen af en oval Plade, omtrent af samme Længde som Skaftets 3die Led, og langs Yderkanten og Spidsen tæt besat med fine haar- formige Børster ordnede i to Rader. Det bagre Vedhæng, der repræsenterer den egentlige Svobe, er omtrent af Skaftets Længde og afsuialnes suceessivt mod Enden. Den bestaar af omtrent 15 Led, hvoraf dog de 3 første ikke er tydeligt sondrede fra hin- anden. Hvert Led bærer ved Enden i Forkanten et Knippe 'af smaa Børster, hvoraf nogle har Charac- teren af Sandsevedhæng (Lugtepapiller), og i Bag- kanten en enkelt simpel Børste. Hos den endnu ikke slægtsmodent udviklede Han (Fig. 1) ligner disse Følere temmelig samme hos Hunnen, alene med den Forskjel, at Svøben er mere opsvulmet ved Basis og delt i et noget større Antal Led. De nedre Følere (Fig. 1, a-. Fig. (!), som ud- springer tæt bag de ovre, mangler ganske det blad- formige Vedhæng, men er forovrigt hyggede efter samme T3^pe som hine og har ligeledes Skaftet dob- belt geniculeret. Iste Led er, som paa de evre, meget fast forbundet med Hovedet, stærkt musculost ') Hos Sl. Paramhalia er dette Fremspring betydelig større og grovt sagtakket i Forkanten. fig. 7, a'), 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 usuallj^ 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 pi-eceding 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 tlie 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 tlie 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, llach joint carries at the extremity, on the anterior margin, a bundle of small bristles, of which some have the nature of sensor}^ appendages (olfactory papillæ), and on the posterior edge a single simple bristle. In the still incompletely sexually developed male (fig. 1) these antennæ resemble prett}^ much those of the female, with the sole difference, that the flagellum is more tumefied at the base and divided into a somewhat larger niimber of joints. The inferior antennæ (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 tj'pe as those, and have also the peduncle doubly geuiculated. The 1st joint is, as in the superior ones, very .firmly united to ') In the gen. Paranehalia, this prominence is considerably larger and coarsely serrated on the anterior edge- 15 og uden fiiiliver Borstebevæbning. 2det Led, der omtrent er af samme Størrelse som Iste, mangler ligeledes Børster, men gaar fortil nd i et kort tand- formigt Fremspring. Den ydre Del af Skaftet dan- ner ogsaa her en stærk knæformig Beining med fore- gaaende Led, men bestaar kun af et enkelt Led, paa hvilket dog en oprindelig Tvedeling er ant^'det ved en skarpt markeret Afsats baade fortil og bagtil ^). Til den bagre Afsats er fæstet en stærk Fjærborste, og langs Forkanten af Leddet findes en hel Del saa- (ianne Børster, tildels af betydelig Længde. navnlig ved Enden, hvor de delvis er krandsformigt stillede omkring Leddet. Desuden findes langs den øvre Halvpart af Forkanten en Rad af Smaatorner, der nedad siiccessivt tiltager i Længde, og en Del lig- nende Torner bemærkes ogsaa ved Enden af Leddet fortil niellem Børsterne. Svøben er betydelig (næ- sten dobbelt) længere end paa de ovre Følere og bestaar af omkring 20 børstebesatte Led, hvoraf dog de '^ eller 4 inderste er mindre tydeligt begrændsede. Hos den endnu ikke slægtsraodent ndviklede Han skiller disse Følere (Fig. 1, a^) sig væsentlig kun derved, at Svøben er meget tæt ringet, eller delt i et stort Antal, endnu ufuldstændisrt besrrændsede Led. Overlæben [Fig. 7, L. Fig. 8), der til Siderne ganske dækkes af de nedre Foleres Basalled. danner et tydeligt convext Fremspring af afrundet Form og med den bagre Kant svagt indhugtet i Midten samt her liesat med fine Haar. Underlæben (Fig. 7, 1, Fig. H) er meget liden og vanskelig at isolere. Den iiar 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. 1(») 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 fyJdt med de stærke. i Midten ved en chitin- agtig Sene forliundne Adductormnskler (se Fig. 10), og fra den bagre Kant udgaar en tynd Chitinsene, hvortil Kindbakkernes Rotationsmuskler fæster sig. Den næsten under en ret Vinkel med det ovrisre Corpus indboiede Tj-ggedel er (se Fig. 11) i Enden delt i 2 Grene, hvoraf den ydre har Formen af en liden triangulær Lamelle, der svarer til det tandede Parti (cTitting edge) hos andre Crustaceer, medens the head, strongly muscnlous, 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 ^vith 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, especialh' 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 extremitj' of the joint in front, between the bristles. The fla- gellum is considerably longer (nearly double) than on the siiperior antennæ, aaid 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 antennæ 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 tlie inferior antennæ, forms a distinctl}^ convex promi- nence of rounded form, witb the posterior margin faintly hollowed in the middle and l)eset here with delicate hairs. The posterior lip (fig. 7 1, tig. V) is verj^ small and difficult to isolate. It appears, however, to me, to present the appearance of a parth- ciliate lamella, deeply incised in the middle, as shown in fig. it. 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 jioint, 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 masticatorj- part, which is bent inwards almost at a right angle to tiie remaining corpus (see fig 11). is divided at the exti'emity into 2 rami, of which the outer has the form of a ') Ho.s SI. Kcbaliopiiis best.a.ir denne Del :if crrændsede Led. tvdeligt be- ') 111 the gen. Xchnliojistis this [lait consits of 2 distinctly detincd joints. 16 den indre og betydelig større Gren svarer til Molar- processen. Den første er ganske simpel og bar kun strax indenfor Spidsen et yderst lidet tandformigt Fremspring. Den sidste er af cylindrisk Form, lidt buet, og har som sædvanlig Enden fint riflet samt mere tvært afknttet paa høire end paa venstre Kindbakke. Palpen (Fig. 1, 7, Mp, Fig. 10). der ud- gaar fra Corpus noget fortil paa det Sted, hvor T3-ggedelen forbinder sig med den ydre, baadformige Del, er af særdeles betj'delig Størrelse, næsten 3 Gange saa lang som selve Corpus, og viser en Byg- nins idethele overensstemmende med samme bos høiere Crustaceer, navnlig Ampbipoderne. Den be- staar af 3 skarpt begrændsede Segmenter eller Led, alle omtrent af ens Størrelse, eller kun ganske lidt tUtagende i Længde udåd. Iste Led er simpelt cylin- driskt, dog noget fortykket i hver Ende, og mangler ganske Børster. Det forbinder sig med 2det Led paa en ganske egen Maade, saa at begge med bin- anden danner et Slag.': Knæ. 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 — o tynde Børster. Sidste Led, der er meget bevægeligt forbundet med 2det, er temmelig smalt, stærkt sammentrykt fra Siderne og ganske lidt bredere i sit ydre Parti, som er jevnt tilrundet i Enden. Det bærer langs den nedadvendte skarpe Kant en tæt Rad af fint cili- erede, toleddede Børster og har desiiden ved Spid- sen nok en E,ad af meget fine og stærkt krummede Børster. Leddets ovre Kant mangler Børster, men viser i sit bagre Parti en særdele.s fin Ciliering. I sin normale Situs convergerer de to Palper stærkt ved Basis (se Fig. 10), saa at 2det Led paa begge kommer til at ligge tæt sammen i Jiixtaposition, indenfor Basal leddene af de 2 Par Følere. Sidste Led paa hver divergerer igjen noget og træder frit frem enten foran eller mellem Følernes Rod (se Fig. 1, Mp). Iste Par Kjæver (Tab. II, Fig. 1 & 7. m', Tab. III. Fig. 1) er af afrundet Form og gaar indad ud i to korte, stumpt afrundede Tyggelappe, hvoraf den ydre er størst, næsten af øxedannet Form og, foruden med nogle tildels cilierede Børster, bevæbnet i sit bagre Parti med en Gruppe af smaa, i Enden tve- delte Torner (Fig. 1 a). Den indre Tyggelap er for- lioldsvis liden, af membranøs Beskaffenbed og paa den næsten tvært afkuttede Ende forsynet med en tæt Rad af særdeles fine cilierede Børster, foriiden en Del korte Torner. Fra Enden af disse Kjæver 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 isisiies 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- ciilarly large size, almost 3 times as long as the corpus itself, and exhibits a structiire 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 cylindrie 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 thej^ 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 vei-y delicate and strongly bent bristles. The u])per mar- gin of the joint has no bristles, but exhibits a parti- cularh- 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 antennæ. The terminal joint of each diverges again a little, and appears freely forward either in front of or between the bases of the antennæ (see fig. 1, Mp). The 1st pair of maxillæ (Pl. II, figs 1 and 7. m'; PI. Ill, 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. 1 a). The inner masticatory lobe is relatively small, of membi-anons nature, and fur- nished on the almost obtusely truncated extremity with a close series of delicate ciliate bristles besides 17 udgaar et besynderligt, stærkt forlænget Vedliæng (Tab. Ill, Fig. 1, p), som ifølge sit Udspring aaben- bart repræsenterer en eiendommeligt modificeret Palpe. Den bestaar af en noget tykkere, med en Del tynde Mi^skelbundter fyldt Basaldel, og en tynd Endesnært, som dog begge gaar ganske umærkeligt over i hinanden. Basaldelen, der paa 2 forskjellige Steder bar et Bundt af tynde divergerende Børster, viser strax ved sit Udspring en abrupt dobbelt vinkelformig Bøining udåd og bagtil, hvorfor den tynde, næsten borsteformige Endedel bliver rettet skraat bagtil og opad langs Siderne af Truncus, rækkende 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 fæstet circa 16 lange og tynde, ucilierede Børster og til Spidsen 3 lignende; alle Børster viser i Enden en eiendommelig, næsten korketrækkerformig Krumning og er temmelig stive, samt vende ialmindelighed nedad og indad. Angaaende dette eiendommelige Vedhængs Function, er der ingen Tvivl om, at det tjener til at rense Rygskjoldets Hule, og dermed ogsaa de tandre Branchialfodder, for fremmede i den indtrængende Dele, i Lighed med hvad Tilfældet er med det bagre Fodpar hos visse Ostracoder (Cypri- dinider, Cyprider). 2det Par Kjæver (Tab. II, Fig. 1 og 7, m-. Tab. III, Fig. 2) er udpræget pladeformige og af temme- lig compliceret Bygning, mest mindende om samme hos de holere Crustaceer (Podophthalmia). Man kan paa dem adskille en af 2 utydeligt begrændsede Segmenter bestaaende Basaldel og 2 fra denne fortil udgaaende Grene. Basaldelen har indad 4 børste- besatte Lappe, der utvivlsomt svarer til Tyggelap- pene paa Iste Par, med den Forskjel, at hverTygge- lap her altsaa er dobbelt eller delt i to. Den for- reste af disse 4 Lappe er imidlertid meget liden, knudefdrmig og bærer 6 lange, cilierede Børster. De 3 øvrige Lappe er ligeledes børstebesatte paa den tvært af kuttede Ende; men Børsterne er her meget kortere og tættere samt delvis ordnede i Uere Ilæk- ker. Den midterste af disse 3 egentlige Tyggelappe er betydelig smalere end de 2 øvrige, som omtrent indbyrdes er af ens Størrelse. Af de 2 Endegrene er den indre (p), der forestiller Endognathcn eller Palpen, af betydelig Størrelse, noget afsmalnende mod Enden og delt i 2 vel begrændsede Led, hvoraf det Iste er størst. Begge Led er i Inderkanten be- satte med talrige cilierede Borster, delvis ordnede i 2 Rækker, og en af de fra Spidsen udgaaende ad- mærker sig ved betydelig Længde. Den ydre Gren (ex), eller Exognathen, er l)otydelig mindre end den indre og rækker nepjTe udover dennes Iste Ijed. Don har Formen af en meget smal ellijitisk Plade, der langs liele Inderkanten og Spidsen er forsynet 3 — G. 0. Sårs: Fauna yorvcgix. a number of short spines. From the extremity of these maxillæ a strange, greatly prolonged appen- dage issues (PI. Ill fig. 1, p.) which judged by its origin evidently represents a peculiarly niodiiied 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 has a bundle of slender divergent bristles, exhibits, immediately 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, qiiite up to its dorsal surface (see PI. 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- screw-shaped bend and are rather stiff, and generally turn downwards and inwards Ret^irding 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 jienetrating, substances, like what is the case with the posterior pair of legs in certain Ostracods (Cypridinid.s. C3-prids). The 2nd pair of maxillæ (Pl. II, fig. 1 and 7, nr; Pl. III fig. 2) are of distinguished lamelliform shape, and of rather complex structure, reminding one most of the same maxillæ in the higher crustaceans (Po- dopthalmia). We can in them distinguish a — of 2 indistincth- 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 1st pair, with this dilierence, that each masticatory lobe is hei-e double or bifur- cated. The foremost of these 4 lol)es is, however, very small, nodiform, and carries (! long ciliated bristles. The 3 remaining lobes are also beset with bristles on the obtusely ti'uncated extremity; l)ut 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- ally of about the same size. Of the 2 terminal branches, the inner one (p) which represents, the endognath or the palp, is of considerable size, dimi- nishing somewhat towards the cxtreniit\', and divided into 2 well defined joints, of wliicli the 1st one is the largest. Both joints are on thr inner margin beset with numerous ciliated bristles, i)artly arrangeil in 2 sei'ies, and one of tlicm issuing from the point distinguishes itself by its great length. The outer branch (ex;, or the exognath, is considerably smaller 18 med en regelmæssig Rad af temmelig lange, fint cilierede Randljørster. De 8 Par Branchialfodder, som umiddelbart følger efter Kjæ verne, er alle byggede efter samme Type og ligger tæt ind mod hinanden i Form af tværstillede Plader, noget mere eonvexe fortil end bagtil (se Tab. II, Fig. 1). De tiltager noget i Stør- 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 fælles Basis udgaaende Ho- veddele, som vi, i Liglied med hvad man pleier hos andre Krebsdyr, kan benævne: Endopodit (p), Exopodit (ex) og Epipodit (ep). Den fælles Basaldel bestaar, som paa 2det Par Kjæver, af 2 nfuldkom- ment sondrede Segmenter, der i Inderkanten bar en dobbelt Rad af Børster, bvoraf de paa Iste Segment delvis udmærker sig ved betydelig Længde. Endo- poditen (p), der danner den umiddelbare Fortsættelse af Basaldelen, danner en mod Enden snecessivt af- smalnende Stamme, paa hvilken der er en svag An- tydning til Segmentering. Denne Del er hos den ægbærende Hun betydelig stærkere forlænget end hos yngre Individer af begge Kjøn og har sidste Led vel sondret, noget ombøiet og besat med sær- deles lange divergerende Fjærborster, der. delvis rager frem nedenfor Rygskjoldets Valvler (se Tab. I, Fig. 1 ). Forovrigt er Endopoditen langs hele Indei-- kanten besat med Borster, der fordetmeste er ord- nede i en dobbelt Rad og umiddelbart fortsætter de paa Basaldelen forekommende Børsterækker. Exo- poditen (ex), der er fæstet til Basaldelens 2det Segment, udenom Endopoditen, har Characteren af en l^red, 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 regelmæssig oval og i Yderkanten besat med en Rad af circa 18 tynde Børster, til- tagende i Længde mod Spidsen. Paa de følgende Par (Fig. 4, 5) bliver den successivt noget større og stærkere udvidet i Enden, som er skjævt afrundet og kun besat med faa og spredte Randbørster. Paa sidste Par endelig (Fig. 6) har den antaget en tem- melig smal elliptisk Form. Epipoditen (ep), der ved en kort Stilk er fæstet til Ydersiden af Basaldelens Iste Segment, er af særdeles betydelig Størrelse, saa at den mere eller mindre fuldstændigt dækker de øvrige Dele, naar disse Lemmer sees in situ fra Ydersiden (se Tab. II, Fig. 1). Den har Formen af en elliptisk eller næsten halvmaanedannet Plade og gaar ud i en dorsal og en ventral Lap, adskilte i Midten ved en tværs over E])ipoditen fra dennes Fæste løbende fortykket Ribbe. Ligesom Tilfældet var med Exopoditeu, er der ogsaa nogen Forskjel i Epipoditens Størrelse og Form paa de forskjellige than the inner one and scarcely extends beyond its 1st joint. It has the form of a very narrow elli])- 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 maxillæ, are all constructed on the same type, and lie close in to each other in the form of transversally placed lamellæ, rather more convex in front than behind (see PI. II, 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 PL III, figs. 3 — G) 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 maxillæ, 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 particixlarly long divergent and plumose bristles, which jiartly project below the valves of the carapace (see PI. 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 difterent in form in the various branchial legs. In the 1st pair (PI. Ill, fig. 3) it is regularly oval and beset on the outer edge Avith 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- ality, in the last pair (fig. H) 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 PI. 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 19 Par Branchialfødder. Dens Størrelse tiltagei' noget indtil 4de Par, hvor den er størst, og aftager saa igjen successivt paa de bagenfor liggende Par (se Tab. II, Fig. 1). Paa Iste Par (Tab. III, Fig. 3) er dens ventrale Lap betydelig større end den dor- sale og smalt tilløbende i Enden, medens hin er jevnt afrundet. Paa de følgende Par (Fig. 4, 5) bliver Forskjellen melleni de 2 Lappe efterhvert mindre, og paa sidste Par (Fig. fi) er Forholdet det omvendte af hvad det er paa Iste Par, idet den dor- sale Lap her er den største og mere smalt iidløbende end den ventrale. Saavel Exopoditen som Epipoditen, men især denne sidste, viser den for Cxjelleelemen- terne hos andre Krebsdyr charaeteristiske spongiøse Structnr, idet der mellem de 2 Lameller, hvoraf begge disse Vedhæng begrændses, findes et compli- ceret System af med hinanden anastomoserende Hul- rum, hvori der hos det levende Dyr foregaar en livlig Blodcirculation. At begge disse Vedhæng der^ for er af respiratorisk Betydning, er ganske ntvivl- somt, skjondt, som senere skal vises, ogsaa selve Rygskj eldet spiller i denne Henseende en vigtig Rolle. De 4 forreste Par Bagkropslemmer (seTab. II, Fig. 1) er overordentlig kraftigt udviklede Svømmeappa- rater, der i flere Henseender, og ogsaa i den Maade, hvorpaa de bevæges, minder om Copepodernes Svom- raefødder. De er alle hyggede efter samme Type og bestaar hvert (se Tab. III, Fig. 7 og it) af en med talrige sfærke Muskelbundter fyldt, noget affladet Basaldel, og to fra dennes Ende udgaaende, med filierede Svommeborster forsynede, enleddede Grene eller Aarer, hvoraf den ydre ialmindelighed er ret- tet stærkt udåd og i Yderkanten bevæbnet med kraftige Torner. 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 bevæbnet med et Antal, sædvanlig 4, krogformige Torner (Fig. 8 a). Ved disse Torner hægtes de 2 til samme Par horende Fødder ligesom sammen, saa at deres Bevægelser kun kan ske samtidigt. Iste Par Svommefødder (Fig. 7) skiller sig kjen- deligt fra de øvrige, saavel ved Basaldelens Form og Bevæbning som ved Beskatfenheden af den ydi'e Gren. Basaldelen, der ligesom paa de øvrige Par har et ganske kort Rodled, er her forholdsvis læn- gere og smalere, noget aftagende i Brede mod En- den, og bevæbnet med 4 lange Torner, hvoraf en er crosses the epipodite from its ]>oint 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 varions pairs of branchial feet. The size increases somewhat until the 4th pair, where it is greatest, and it then diminishes again, successively, in the pairs situated beliind (see PI. II, fig. 1). In the 1st pair (PI. Ill, 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 l,obes becomes gradually less, and in the last pair (fig. (i) the relation is the revei'se of what it was in the 1st 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 lamellæ by which the appendages of both are limited, there is found a complicated system of cavities, ana.?tomosing with each other, in which, in the living animal, an active blood cir- culation proceeds. That both these appendages are therefore of resjiiratory importance is perfectly indu- bitable, although, as will be subsequently shown, the carapace itself also plays an impoi'tant part in that respect. The 4 foremost pairs of the posterior appen- dages of the body (see PI. 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 constnicted on the same type, and consi.st, each (see PI. Ill, figs. 7 and !'), 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 ])art 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. 8 a). Tiie 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 1st ]mir of swimming feet (fig. 7) are per- ceptibly distin>;uished 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 wliich, as upon the other pairs, has a quite short basal joint, is here relatively longer and narrower, somewhat narrowing in breadth towards the extre- 20 fæstet helt oppe ved Basis til Yclerkanten. en anden helt nede ved det ydre Hjørne, medens de 2 ovrige ndgaar fra den nederste Del af Inderkanten. Den ydre Gren er temmelig smal, men snccessivt noget bredere mod Enden, og har langs Yderkanten en regelmæssig Ead af circa 20 korte Torner, hvorpaa følger, fæstet til en særegen Afsats, en betydelig stærkere saadan. Fra den noget skraat afkuttede Ende udgaar 3 stærke divergerende Torner, hvoraf den yderste er længst, den midterste kortest. Hele den indre Kant af Grenen er forovrigt besat med en tæt Rad af lange og tynde cilierede Børster. Den indre Gren er betydelig længere og ogsaa sma- lere end den ydre, næsten lineær, og viser ved Basis et ufuldstændigt sondret lidet Rodled. Den er i begge Kanter forsynet med en Rad af lignende Svommeborster som ])aa den ydre Gren og gaar ved Enden ud i en kort dolkformig Spids, indenfor hvil- ken en lang bagudrettet Torn er fæstet. Paa de øvrige Svømraefodder (Fig. 9) er Basal- delen kortere og bredere, mere affladet, og har Yder- kanten tilskjærpet samt endende nedad med et spidst udtrnkket Hjørne. Inderkanten er ligesom Yder- kanten nden Torner, men har 2 Knipper af meget fine Børster, skilte ved et længere Mellemrum. Mel- lem de 2 Grene danner Basaldelen et lancetformigt tilspidset Fremspring. Den ydre Gren er forholds- vis større og bredere end paa Iste Par og har langs Yderkanten 7 Afsatser, hver bevæbnet med 2 tæt sammenstillede divergerende Torner; fra Spidsen ud- gaar, som paa Iste Par, 3 Torner, som her sncces- sivt tiltager i Længde indad. Den indre Gren er kun' lidet længere end den ydre, men betydelig sma- lere, forovrigt af samme Beskaffenhed som ])aa Iste Par. Det bagerste Par skiller sig neppe fra de 2 foregaaende uden derved, at det er noget mindre. De 2 Par rudimentære Bagkropslemmer, der er fæstede til Bugsiden ved Enden af 5te og Gte Seg- ment (se Tab. I, Fig. 1), er begge af meget enkel Bygning og som det synes ganske ubevægelige. Iste Par (Tab. III, Fig. 10) er det største 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 Børster og har langs den skraat afskaarne Ende- rand en Rad af 7 Torner, hvoraf den yderste er længst; mellem Tornerne bemærkes ogsaa en Del fine lige uda together, onl}' connected by very short and thick longitudinal commissures, between whicli there is scarcely any interval. The ganglia 26 smeltede med hinanden og udsendende 2 stærke Sidestammer, der udbreder sig dels i Branchial- fødderne, dels i Kroppens Miiskulatur, De 4 i Bag- troppen beliggende Ganglier er betydelig større og ogsaa mere fjernede fra hinanden, med længere og mere tydeligt skilte Commissurer. I Halen løber 2 Nervestammer langs ad Bugsiden lige til Hale- grenene, og danner for hvert Par af de smaa Hale- fodder en liden ganglies Opsvulmning. En lignende synes ogsaa at tindes 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 Integnmenterne paa Grund af sin intense rødgnle Farve. De danner (se Pl. V, Fig. 1, Fig. 2, ov) 2 langstrakte Sække, der stræk- ker sig, til hver Side af Tarmen, igjennem hele Midtkroppen og Bagkroppen og rager endog et Stykke ind i Halen. I enhver af Sækkene findes kun en enkelt Række sig udviklende Æg, alle med tydelig Kimblære oggrovkornetBlommemasse. Ægge- 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 sammt Beliggenhed som Ovarierne og dan- ner ligesom disse simple Sække, men er betydelig smalere end disse. De munder, ifolge Claus ved Basis af sidste Par Branchialfødder. Ud vikling- Æggene optages, som ovenfor nævnt, efter at være komne ud af Ægiederne, i et Slags Rugehule, der ligger ind xinder Midtkroppen, omgiven af Ryg- skjoldets Valvler og delvis begrændset af Branchial- fødderne, hvis talrige krummede Endebørster hindrer dem fra at falde ud af Rygskjoldets Hule. De undergaar her sin hele Udvikling, og forst naar Tin- gerne er saa vidt komne, at de med Lethed kan be- • væge sig i Våndet, forlader de Klækkehulen. Ud- viklingen er nøiere studeret af den russiske Natur- forsker Kovpalewsky, og mine Undersøgelser stemmer i alt væsentligt overens med hvad der af denne ud- mærkede Forsker er meddelt. Æggene er umiddel- bart efter at være optagne i Klækkehulen, af rødgul 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 Størsteparten af themselves are relatively small and all alike in 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 jjass 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. Tiiey form (see PI. V, hg. 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 iirosome. 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 Clans 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 hatcliing cavity, which is sitviated in below the mesosome, surrounded by the valves of the carapace aud partly limited by tlie branchial feet whose numerous bent terminal bristles prevent them from falling out of the cavity of the carapace. They undergo here their entire development, aud 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 27 Æggets Blommemasse ikke undergaar nogen Klov- ning. Ifølge Kowalewsky dannes det blastodermale Cellelag ved den successive Klovning af en enkelt stor Polarcelle. Paa et temmelig tidligt Udviklings- stadium, som ei' fremstillet Pl. V, Fig. 6, finder vi, at Blommemassen i den ene Halvdel af Ægget er bægerformigt omgivet af et Lag af klare Celler, der navnlig i Kanten af Ægget tydeligt hæver sig af fra den mere iigjennemsigtige rodgule Blommemasse. Dette er den sig dannende Blastoderm. Det forste Anlæg til Embryonet antydes ved en svag trans- versal Indbngtning i Blastodermen, begrændset af 2 noget fremspringende Vulster. Den ene af disse Vulster forestiller Overlæben, den anden Haleenden (se Fig. 7 og 8). Til hver Side af den ovenomtalte Indbngtning viser sig noget senere S tværstillede langagtige Forbøininger, der forestiller Anlægget til de 2 Par Folere og Mandibularpalperne, og foran dem sees til hver Side en utydeligt begrændset rundagtig Udvidning, der aabenbart er Anlægget til Øienstilkene. Embr^'onet, der endnn er omgivet af Æggehinden, betinder sig nu i det saakaldte Nauplius- stadium. Senere optræder, bag de 3 Par ovenomtalte Lemmeanlæg, successivt en dobbelt Række af min- dre Forhoininger, der antyder Anlægget til de fol- gende Lemmer (se Fig. 7). Samtidigt bliver den transversale Indbngtning dybere, Haleenden sondrer sig tydeligere og stræber at fjerne sig ira Over- læben, hvad der tils-idst, i Forbindelse med Embry- onets Væxt, har tilfolge at Æggehinden 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 længere den oprindelige ventrale Krumning, men har strakt sig fuldt ud i Længden og endog antaget en svag dorsal Boining. Formen er næsten kolledannet, idet Legemet fortil ligesom er opblæst, 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 næsten kugle- formigt opsvulmet forreste Del, og en betydelig smalere, næsten ejdindrisk og bagtil i en stump Spids udgaaende Del. Den første svarer nærmest til Hovedet hos det voxno 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 Række af lemmolignende Fremspring, men af et endnu j^derst ufuldkomraent Udseende, kun dannende simple koniskt tilløbende Fortsatser. Størst og tydeligst sondrede er de 2 forreste Par (a', a"') som forestiller de 2 Par Folere. De har en næsten pølsedannet Form og er bøiede bagud langs Siderne af Foi-kroppen. Imellem dem i Midten sees et tydeligt klapformigt Fremspring (L), som er Overlæben, og foran dem til hver Side en a somewhat lighter colour and also become more transparent. Thej^ 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 extremit}- (see fig. 7 and 81 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 antennæ 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 siicceeding appen- dages (see fig. 7). At the same time the transversal in-curvature becomes deeper, the caiidal extremity sepai'ates itself more distinctly and endeavours to remove itself from the ujjper lip, with the eventual efl'ect, in connection with the growth of the embryon, that the skin of the ovum bursts and scales ofi'. 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 trans])arent 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 3'olk 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 jjart, and a considerabh* narr- ower, almo.st 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 niesosome. 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 Forhoining (0), Anlægget til Øienstilkene. Bag Følerne følger 3 Par ligeledes pølsedannede, men betydelig mindre Vedliæng, hvori man let erkj ender Anlægget til Mandibularpalperne (Mp) og de 2 Par Kjæver (mV ra"). Langs Siderne af den bagre Del af Legemet sees en uafbri\dt Række af ialt 11 Par simpelt koniske Fortsatser, hvoraf de s forreste er af fuldkommen ens Udseende og staar næsten 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 Udkrængninger af Larvebuden, og først indenfor dem sees Anlægget til et til- svarende Antal Lemmer. De forstnævnte 8 Par Fortsatser (brp) sjnies at svare til et lignende Antal Brancbialfødder, medens de o bager.ste 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 løst omgiver den bagre Del af Em- bryonets Krop, er allerede en tydelig Segmentering bemærkelig, og man kan herved temmelig noie be- stemme Grændsen mellem de forskjellige Kropsafsnit. Kun det bagerste Afsnit, Halen er endnu ufuldkom- ment segmenteret. I den forreste Del af Legemet sees til hver Side, ligeledes indenfor Lar vehi^den, en utydelig lialvcirkelformigt buet Linie (c), der fore- stiller den frie Kant af det sig udviklende Ryg- skjold, og helt fortil, umiddelbart ovenover Anlægget til Øienstilkene, er der et lidet knudeformigt Frem- spring (R), der aabenbart forestiller den sig \idvik- 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 følgende Udvik- lingstrin. Hvad der væsentlig adskiller dette Sta- dium fra det foregaaende, er, at Larvehuden nu er afkastet, saa at de forskjellige Kropsvedhæng alle er frit fremragende, ligesom Legemets Segmentering ogsaa udvendigt er tydelig. Den dorsale Krumning af Embryonet er nu saa stærk, at Legemet næsten beskriver en fuldstændig Halveirkel. De til Hove- det hørende Lemmer har voxet adskilligt i Størrelse, men er forøvrigt kun lidet forandrede. Dog bemær- kes paa det forreste Par (a^) en liden Bigren, som antyder det bladformige Appendix. Branchialfedderne (brp) er tilstede i .sit fulde Antal (8 Par) og viser sig alle dybt tvekløftede, samt lige nedadrettede. Derimod lindes der endnu kun anlagte 3 Par Svømme- fødder (pl), idet det 4de Par først 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 couically shaped prolongations, The 2 foremost pairs (a\ a'') which represent the 2 pairs of antennæ, 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 (0), tlie rudiments of the ocular stems. Be- hind the antennæ 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 maxillæ (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 S 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 (pi) 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 noticealile, 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 si;cceeding the pupa stage. What chiefly dis- tinguishes this stage from the preceding one is, that the larval skin is now thrown ofi", 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 Øienstil- kene (0) liar antaget en noget konisk Form samt viser i sin ydre Del den første svage Antydning til Dannelse af Synselementer. Til hver Side af Tar- men bemærkes i Midtkroppen en temmelig plump og kort cylindrisk Sæk, der aabenbart forestiller en af Leversækkene. Den dorsale Del af Forkroppen er endnu stærkt opblæst og fyldt af rødgul 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 tilbageværende Rest af Blommemassen opbruges lidt efter lidt, og samtidigt aftager den dorsale Opsvulning af Hovedet i Stør- relse, medens Rj^gskjoldets Valvler mei-e og mere voxer ud over Siderne af Midtkroppen. De forskjel- lige Kropsvedhæng udformes og indtager den for dem characteristiske Stilling i Forhold til Legemet, hvorved ogsaa meget snart Nebalia-Habitusen bliver fremtrædende. Fig. 12 fremstiller Ungen, naar den er færdig til at forlade Klækkehulen. Man har ingensombelst Vanskelighed med i den at erkjende en ung Nebalia. Den eneste væsentlige Afvigelse er, at der fremdeles kun er 3 Par Svømmefødder tilstede. Af det 4de Par sees kim et ubetj'deligt Anlæg bag de øvrige, i Form af et Par smaa knude- formige Fremspring (pM- Ungen kan nu bevæge sig frit i Våndet og ernære sig selv; men det varer endnu adskillig Tid, inden de forskjellige Vedhæng opnaar sin fulde Udvikling og faar sin normale rige- lige Børstebesætning. Af alle Vedhæng er 4de Par Svømmefødder 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 tiieir 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 (pi) in a rudimentary state, as the 4th pair only mucli later becomes developed. Neither is there any trace of caudal feet observed. The urosome itself has now, however, its full number of segments, and tlie 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 tirst faint indication of the formation of visual elements. In the mesosome, on each side of the intestine, there is noticed a prettj»- 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 lip, 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 ))air there is only seen a faint rudiment behind the others, in the shape of a pair of small nodular prominences (p'). The j'oung one can now move itself freely in the water, and nourish itself; but some time still passes, before the various appendages attain thi'ir full development and acquire tlieir nor- mal, abundant bristle-covering. Of all the append- ages, the 4tli pair of swimming feet are those which develope tliemselves latest. 30 Forekomst og Levevis. Den her omliaridlede mærkelige Dyreform fore- kommer ikke sjelden langs vor laele Kyst, fra Chri- stianiaf jorden til Vadsø, men synes idetbele at op- træde baade hyppigst og kraftigst udviklet i vor arktiske Eegion. I stor Mængde har jeg saaledes fundet den paa en Plads i Lofoten, Brettésnæs, hvor mange hnndrede Individer indsamledes i Lobet af et Par Dage, og ogsaa ved Finmarken har jeg paa sine Steder triiifet den i mængdevis. Den pleier at holde til paa maadeligt Dyb, fra 10 til 30 Favne, og helst paa saadanne Steder, hvor Bunden er dækket af forraadnende Tangarter, hvoraf den for en væsent- lig Del synes at ernære sig. Ligesom Tilfældet er med flere andre Crustaceer, synes Hannerne kun til visse bestemte Tider af Aaret at opnaa fiild Slægts- modenhed, og optræder da kun ganske enkeltvis. Der- imod er endnu ikke slægtsmodent udviklede Hanner at finde til enhver Tid af Aaret og næsten i samme Antal som Hunnerne. I Maaden at bevæge 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 stærkt, at Halegrenene kommer i Contact med Pandepladen. Bevæge] sen sker stodvis ved kraftige og temmelig rythmiske Slag af Svommefodderne, hvorved Lege- met drives frem med temmelig betydelig Fart. De slægtsmodne Hanner er overotdentlig raske i sine Bevægelser og foretager ofte længere UdHugter i Våndet. Derimod holder Hunnerne og de endnu ikke fuldt udviklede Hanner sig i Regelen ved Bunden og bevæger sig her mellem Bundmaterialet, ialmin- delighed paa Siden. De forstaar herunder med stor Behændighed at skjule sig mellem Mudret eller de hensmuldrende Tangrester, som bedækker samme, saa det slet ikke er saa let at finde dem frem, trods den ikke ubetydelige Størrelse. Lettest opdager man dem ved at slaa det optagne Bundmateriale ud i et Hadt Kar, med en ubetydelig Kvantitet af Sjø- vand. De tilstedeværende Exemplarer vil da, især naar man rorer lidt om i B\;ndsatsen, snart vise sig paa Overfladen af Våndet, og da de i Lighed med forskjellige andre Crustaceer ikke formaar at komme ned i Våndet igjen, etterat de først 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 Sjøvand under Mikro- skopet, kan man saa noiere studere de forskjellige Livsytringer og kan gjennem de halvt gjennemsigtige Integnmenter observere Hjertets Pulsationer, Tar- mens perestaltiske Bevægelser og Branchialføddernes Spil. Disse sidste, der ingensomhelst Inflydelse har paa Locomotionen. vil man i Regelen finde i en I)istril)iitioii and liabits. The remarkable animal form spoken of here appears not rarely along our entire coast, from the Christianiafiord to Vadso, 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, Brettesnæs in Lo- foten, where many hundreds of individuals were col- lected in the course of a couple of days; and also in Finmark I hav£, 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 iai 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 Harpacticidæ 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 ii^to 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 mxxd, or the decomposing remains of sea-weed which covers it, so that it is not at all eaisy to seai'ch them out, in spite of the not inconsiderable size. We find tliem 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 u]), soon show themselves on the surface of the water, and as the3^ 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 qviantity of sea-water, under the microscope, we can then more closely study the various features 31 regelmæssig svingende rythmisk Bevægelse, som kun foi" kortere Tid ganske kan stoppes. Denne Be- vægelse har væsentlig respiratoriske Formaal, men er ogsaa af stor Betj-dning for Næringsoptagelsen. Ved disse Lemmers Spil frembringes nemlig inden- for Rvgskjoklets Val vier en fertil gaaende Strøm- ning af Våndet, hvormed de Smaajiartikler, der tje- ner Dyret til Føde, hvirvles indenfor Munddelenes (^niraade. Våndet strommer lierunder i en conti- nuerlig Strøm ud fra Rygskjoldets forreste Ende, nedenfor Pandepladen. Derfor holdes denne altid, underBranchialfoddernesBevægelse, lige fortil strakt, medens den i Regelen, saasnart Bevægelsen stopper, bøies nedad, hvorved den som en Klap tillukker den forreste Aabning af Rygskjoldet. Udbredning. Arten sj-nes at have en ganske overordentlig vid geographisk Udbredning. Foruden ved Norges Kyster er den observeret i de ai-ktiske Have, ved Gronland, Spitsbergen og Island, frem- deles ved Nordamerikas Østkyst, ved de britiske Øer, og idetliele 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. 5J. Xebalia tyiililops, G. 0. Sårs. (Pl. 1, Fig. 4, Pl. IV, Fig. '.)— 19). Nehalia typhlops, G. O, Sårs, Nye Dybvandscrustaceer fra Lo- foten; Chr. Vill. Selsk. Forh. f. 1869. Artscharacteristik. Meget lig foregaaende Art i sin ulmiudelige Habitus, skjøndt maaske lidt mere undersætsig af Form. Rj'gskjoldet, seet fra Siden, af oval Form, lidt lavere fortil og med de nedre Kanter jevnt buede paa Midten. Pandepladen vel udviklet, aflang oval, stærkt hvælvet oventil og for- synet i. Enden med et spidst tornformigt Fremspring, Øinene yderst smaa og rudimentære, koniskt til- løbende i Enden, og uden Spor af Pigment eller Synselementer. De øvre Folere (hos Hunnen) for- lioldsvis kortere end hos foregaaende Art, med Svo- ben neppe længere end Skaftet og kun sammensat af 10 Led, det bladformige Appendix temmelig for- længet, næston halvt saa langt som Svøben. De nedre Folere omtrent som hos N. hipes. Branchial- fodderne med Endopoditen meget tynd og stærkt forlænget, omboiet i Spidscn og forsynet med lange divergerende Fjærbørster; 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 onlj- 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. B}' 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, b}' which action it, like a cover, closes the foremost aperture of the carajiace. 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. Xebalia typlilups^. G. 0. Sars. (PI. I, fip. 4, PI. IV, figs 9—19). Nebalia typhlops, G. O. .Sars, Nye Dybvaudscrustaceear fra Lo- foten; Clir. Vid. .Selsk. Fork, f 1S69. Specific Characters. Very like the preceding sjjccies 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 antennæ (in female) relatively shorter than in the preceding species, with the flagellum scarcely longer than the peduncle and only com])osed of 10 joints; the la- melliform appendage rather prolonged, almost half the length of the flagellum. Inferior antennæ about as in N. h'qies. Branchial feet with the endopodite very slender and greatly prolonged, m sale Lob betydelig storre end den ventrale. Første Par Svømmefodder med Yderkanten af den ydre Gren kun forsynet med 3 Smaatænder, umiddelbart ovenfor den Iste Endetorn. Halegrenene noget kor- tere end de 2 bagerste Segmenter tilsammen, Far- ven hvidagtig, uden Pigmentering. Dyrets Længde 9 mm. Bemærkninger. Den her omhandlede Art staar vistnok meget nær foregaaende, men er dog let kjendelig fra samme ved forskjellige vel udprægede Characterer, hvoraf navnlig maa fremhæves den rudimentære Beskaffenhed af Øinene og Pandepladens Form og Bevæbning. Ogsaa i Bygningen af de for- skjellige Kropsvedhæng vil man ved en noiere Sam- menligning kunne paavise en Del mindre Differentser fra samme hos N. hipes. Beskrivelse. Legemets Form hos Hunnen (se Pl. 1, Fig. 4) stemmer idethele temmelig nøie over- ens med samme hos foregaaende Art, skjøndt den maaske er noget mindre slank. Hannen er endnu ubekjendt. Rygskjoldet er som hos N. hipes stærkt sammentrykt og viser, seet fra Siden, en temmelig regelmæssig oval Form, med den største Høide, der er noget større end den halve Længde, omtent paa Midten. De frie Kanter af Valvlerne er nedentil jevnt buede og danner helt fortil en stærk Krum- ning, inden de støder sammen ved Basis af Pande- pladen. Bagtil viser de sig skraat afskaarne i Ret- ningen forfra bagtil, og de nedre bagre Hjørner af Rygskjoldet danner derfor, som hos foregaaende Art, til hver Side en smalt afriindet Lap, der dækker Siderne af Bagkroppen og næsten rækker til Begyn- delsen af Halen. Pandepladen (se Pl. IV, Fig. 9, 10) er vel udviklet og af meget smal tungedannet Form, temmelig stærkt livælvet ove^itil, og forsynet i En- den med et spidst tornformigt Fremspring, der dan- ner Fortsættelsen af en langs den nedre Side lebende Kjol. Sidste Bagkropssegment har, som hos fore- gaaende Art, et Par smaa afrundede Epimerer og er ligesom de 3 følgende Halesegmenter grovt sag- takket i den bagre Kant. Halegrenene er noget kortere end de 2 foregaaende Segmenter tilsammen, forøvrigt af fuldkommen samme Bygning som hos foregaaende Art. Øinene (se Pl. IV, Fig. 9, 11) udmærker sig i hoi Grrad ved sin ringe Størrelse og rudimentære Beskaffenhed, og rager kun lidet frem fra Rygskjol- det, hvorfor de let kan forbisees. De er, som hos N. hipes, dækkede oventil af en skjælformig, spidst udløbende Plade. Selve Øienstilken er af konisk recurved af 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 tlie 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 deiined characteristics,- of which may especially be noticed the rudimentary character of the eyes, and the shape aud armatiire 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. hipes. Description. The shape of the body of the female (see PI. 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 carapace is, as in N. hipes, 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 PI. 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 routuled epimera, and are, as well as the 3 succeeding caudal segments, coarsely sei'rated 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 PI. 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. hipes, covered above with a squamiform plate running 33 Fonn, Ilden nogen bemærkelig Opsvnlmning 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 læn- gere end Skaftet og kun sammensat af 10 Led. Det skjælformige Appendix er derimod forholdsvis storre end hos foregaaende Art, næsten halvt saa langt som Svøben, og af en mere aflang Form, forovrigt forsynet med en lignende kostformig Besætning af stive Børster. De nedre Folere (ibid.) stemmer idethele saa nøie overens med samme bos foregaaende Art, at en nøiere Beskrivelse er unødvendig. Ogsaa Munddelene viser en meget lignende Byg- ning, skjøndt 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 stærk Borste i den ydre Kant nær Spidsen. Første Par Kjæver (Fig. 13) er ligeledes noget svagere ud- viklede, men forovrigt paa det nærmeste af samme Udseende som hos N. hipes. Paa 2det Par Kjæver (Fig. 14) er Endognathens 2 Led kun ufuldkomment sondrede og næsten af ens Længe; Exognathen er neppe mere end halvt saa lang og har et ringere Antal Randborster end hos N. hipes. Branchialfodderne (Fig. 15, 16) udmærker sig navnlig ved Endopoditens Længde og Tyndhed. Paa de forreste Par overrager den betydeligt Exopoditen og har sidste Led stærkt omboiet samt besat med særdeles lange divergerende Fjærbjorster. Exopo- diten er af skjævt 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 Til fældet hos foregaaende Art. Som hos denne, bemærkes nogen For.skjel i de forskjellige Hoveddeles indbyrdes Forhold paa de forskjellige Par Brancliialfodder. Sidste Par (Fig. 16) har saa- ledes et fra Iste Par (Fig. lo) temmelig afvigende Udseende og skiller sig ogsaa kjendeligt fra det til- svarende hos X. hipes (Pl. Ill, Fig. 6). Endopoditen er her, i Modsætning til iivad Tilfældet er med de øvrige Par. meget kort og uden nogen tydelig Led- deling, og Exopoditen er ligeledes forholdsvis min- dre end hos N. hipes og i Yderkanten forsynet med (!n Had af cilierede Børster. Fem lignende Fjær- boi'ster findes ogsaa paa den korte og tilrundede ventrale Lap af Epipoditen. Svømmefodderne forholder sig i alt væsentligt som hos N. hipes; kun er de idethele af en noget ^ — G. 0. Sårs: /'anna Xorfef/i:f. out to a ])oint. 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 vi.sual elements to be discovered. The superior antennæ (see Pl. IV, lig. 9) are rela- tivel}' shorter than in the preceding species, other- wise of a very similar structure. The flagellum is only a little longer than tlie peduncle and is composed of only 10 johits. 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 su])pl\' of stitf bristles. Tlie inferior antennæ (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 ver}' 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 2nd joint has only a single, verj'' strong bristle on the oviter edge, near the tip. The first pair of maxillæ (fig. 13) are likewise some- what more faintly developed; but otherwise pretty nearlj' of the samme appearance as in N. hipes. In the 2nd pair of maxillæ 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. hip)es. The branchial feet (fig. 15, 16) especiall}' dis- tinguish themselves hj the length and slenderness of the endopodite. In the foremost pairs it considerably overreaches the exopodite, and has the terminal joint strongly recuiwed, and also beset with parti- cularly long, diverging plumose bristles. The exo- podite is of ol)li(iue, 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. Tlie last pair (fig. 16) have thus a pretty divergent ajjpearance from the 1st pair (fig. 15), and distinguish themselves perceptibly from the coji'res- ponding pair h\ N. hipes (,P1. Ill, 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 relative!}' smaller than in .V. hipes, and is furnislied 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, tlie same structure as in X /(//k.?; only that they 34 mere smækker 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. hipes hele denne Kant er tæt og regelmæssigt pigget. De 2 Par rudimentære Halefodder (Fig. 18, 19) viser ligeledes et Udseende, meget nær 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 bemærkelig Pigmentering. Integiimeilterne er tynde og gjennemsigtige, saa de indre Organer tem- melig tydeligt skinner igjennem. Æggene i Klækkehulen er forholdsvis store og af en meget bleg gulagtig Farve. Længden af den ægbærende Hun er kun 9 mm., Størrelsen er altsaa betydelig ringere en hos N. hipes. 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 Hvitingsø, udenfor Stavanger, det 2det i Trondhjemsf jorden, 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 udpræget Dybvandsform, hvad der ogsaa kan sluttes af de ufiildkomment 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, howevei', the diffe- rence, that the outer edge of tlie outer branch has, immediately above the outermost spine, only 3 small spikes, whilst in N. hipes 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 tlie number of spines on both is somewhat smaller. The colour in the living state of tlie 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. hipes. 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 Hvitingsø, 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. Suboi'do IL PHYLLOPODA. Character. Branchiopoder af meget forskjellig Kropsform, dels uden, dels med Rygskjold, det sidste undertiden irdviklet i Form af 2 voluminose, det hele T>yT omsluttende Valvler. Legemets Segmenta- tion forskjellig hos de forskjellige Former. Øinene dels stilkede, dels sessile, undertiden næsten sammensmel- tede; et mediant Enkeltoie ^ocellus) tilstede. Følerne i Regelen meget ulige xrdviklede; Iste Par som oftest meget smaa og udelukkende sensitive; 2det Par af forskjellig Bygning, snart rudimentære (hos det voxne I>yr), snart udviklede til kraftige 2grenede Aarer, eller til tangformige Griberedskaber (hos Hannen). Ovorla^bcn v(d udviklet, klajiformig; Under- læl)en i Regelen manglende. Kindbakkeinc hos det udviklede Dyr uden Palpe. To Par Kjæver tilstede, begge smaa og af foi'holdsvis sim])el J>ygiiing Alle bag Munddelene følgende Lemmer respiratorisko, af tilnærmelsesvis uniform Bygning og bladdannet lap- p(!t Form; deres Tal meget forskjelligt, undertiden abnormt stort. Udviklingen i Regelen en eompli- ceret Metamorphose, begyndende med et fritNau])lius- Stadium. Lidlandsdyr. Bemærkninger. Denne Underorden omfatter et ikke meget stort Antal Dyreformer, der imidlertid viser meget væsentlige Forskjelligheder, saavel hvad det ydre Udseende som den indre B^'gning angaar. Hvad der hovedsageligt characteriserer denne Af- deling af Branchiopoder, og har givet dem sit Navn, er Structuren af de bag Munddelene følgende Lem- mer, der alle viser et lignende bladformigt og lappet Udseende som de til Midtkroj)pen hos Phyllocariderne horende saakaldte Branchialfodder. Da de tillige i sin Function er udpræget respiratoriske, benævnes Sudordo II. PHYLLOPODA. Characters. Bi-anchiopods 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. Antenuæ, as a rule, very unequally developed; 1st pair most frequently very small and exclusively sensitory; 2nd pair of vari- able structure, sometimes rudinientar}^ (in the adult animal), sometimes developed to powerful, 2-branched oars, or to pincer-sha])ed prehensile apparatus (in the male). Anterior lip well developed, tlap-formed; posterior lip, as a rule, wanting. Mandibles, in the developed animal devoid of palpi. Two ])airs of max- illæ present, both small and of relatively simple structure. All tlie ap])endages placed behind the oral ])arts 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 Xauplius-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 appearance as well as in the internal structure. Wliat chietly characterizes this division of Branchiopods and lias gevin.to it its designation is, the structure of the a])pendages placed behind the oral parts, whidi all exhibit a similar leaf-sjiaped and lobed ajijiearance as the so-called branchial-feet pertaining to the mesosome in the Pliyllocarida. As tiiey are, besides, in their function ])rominently 36 ile ogsaa lier paa samme Maade. Forskjellen er altsaa, at lier alle bag Munddeleiie følgende Lemmer er ægte Branchialfodder, medens dette hos Phyllo- cariderne kun er Tilfældet med en Del af dem. I Følernes Bygning er der saa stor Forskjel hos de forskjellige Former, at intet andet bestemt fælles Charaetertræk kan anføres end, at det 1 ste Par ude- lukkende er sensitive og derfor af en meget tander Structur. Ogsaa Øinenes 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 Tilstedeværel- sen af et mediant Enkeltoie (ocellus). Angaaende Munddeleues Structur, kan fremhæves Mangelen af Palper paa Kindbakkerne, og den forholdsvis simple Bygning af de 2 Par Kjæver. De hidtil bekjendte Phyllopoder vil passende kunne fordeles paa 3 større Afdelinger. for hvilke jeg allerede i 1867') har foreslaaet følgende Benæv- nelser: Anosfraca, Notosfraca og ConcJtostraca. 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 tillægges en langt høiere systematisk Værdi (Tribus eller Sectioner). Til enhver af disse Grupper hører et meget beg)'ændset Antal af Slæg- ter, som delvis lader sig fordele paa flere Familier. De herhen hørende Slægttypers Faatallighed og i Regelen overordentlig skarpt udprægede For- skjel, i Forbindelse med deres sporadiske Forekomst paa vidt adskilte Localiteter, synes at tyde ben paa, at vi i Phyllopoderne har de sidste divergerende Grene af en uddoende Dyrgruppe, som rimeligvis, at domme efter flere palæontologiske Fund, har været langt rigere repræsenteret i tidligere Jordperioder. Ogsaa af disse Dyrs Organisation og Udvikling .synes man at være berettiget til at slutte, at de maa være af meget gammel Oprindelse. Det yderlig variable Antal af Kropssegmenter og af Lemmer, disse sid- stes uniforme Bygning, den oftest kun lidet skarpt udprægede Sondring af Legemet i tydeligt begrænd- sede Kropsafsnit, alt dette er Characterer, der aaben- bart henpeger paa primitive Tilstande, hvori endnu ikke de hos de moderne Crustacegrupper gjældende Forhold rigtigt har fixeret sig. Phyllopoderne min- der i denne Henseende ikke saa lidet om de æld- 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, Sårs, Histoiie naturelle de.s Criistacés d'eau doiice de Norvége, I. respiratory, they are also named here in the same manner. The diiference, therefore, is, that here all the appendages placed behind the oral parts are real branchial feet, while in the Phj'-llocarida that is only the case with a part of them. In the structure of the antennæ 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 1st ])air are exclusively sensitoi\y and there- fore of a very delicate structure. The structure of the eyes also is very difi'erent. 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 raaxiliæ. The Phyllopods hitherto known may suitably be assigned to 3 large divisions, for which the author, as early as 18(37^), proposed the following designations: Anosfraca, Notostraca and ConcJiostraca. 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 occurrence 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 palæontological 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. 0. Sars, Histoire naturelle ries Crustacés d'eau douce de Norvége, I. 37 Dolkiialer (Xiphosura). Det synes altsaa som om disse Dyr, uagtet deres Organisation idethele liar naaet et forholdsvis meget heit Udviklingstrin, dog ved Siden lieraf har conserveret flere af de primitive Characterer, der maa antages at have ndmærket de ældgamle Stamformer, hvorfra alle de moderne Cru- staceer i sidste Instans har tåget sit Udspring. Ogsaa Udviklingen synes at støtte denne baade af Prof Clans og Dr. Dohrn fremholdte Ansknelse. Saagodtsom hos alle Phyllopoder begynder nemlig den frie Udvikling med det overordentlig simple saakaldte Nau])lius Stadium, og Larven gjennemgaar derpaa en Række af snceessive Omformninger, der lidt efter lidt forbereder Pindlopodestadiet. Det bar dog her bemærkes, at Dr. Packard i sit fortjenst- fulde Værk over Noi-damerika s Phyllopoder hævder en herfra meget forskjellig Anskuelse. Efter denne Naturforskei's Mening er Ph^dlopoderne tværtimod af meget ny Oprindelse og fremstaaet ved en videre Udvikling af Cladocer-Typen. Dette kunde maaske til Nod lade sig hore, hvor der er Spørgsmaal om den ene af Phyllo])odernes i5 Sectioner, de saakaldte Conchostraca. budy-divisions well mai'- ked off. Head of moderate size, evenly rounded in front in both sexes. Tail considerably longer than the ])art 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 closel}' edged with ciliated bristles. Second pair of an- tennæ, in female, almost the length of the head, very obliquely truncated at the extremity, with the posterior corner drawn out to a shai'p point. Same antennæ in male more than twice as long: shaft somewiiat curved at the base, thick cylindrical, with a series of small teeth along the inner edge; terminal ])art a little shorter, somewhat curved in the middle, and narrowing evenh- towards the point. 42 Hunnen kort triangulær, hos Hannen betydelig stær- kere uddraget og næsten leformig indadkrummet. Hunnens Ægbeholder særdeles forlænget, rækkende næsten til Enden af næstsidste Halesegment. Han- nens ydre Kjønsvedliæng cylindriske, forsynede ved Basis fortil med 2 fremspringende Flige, mellem hvilke der er en dyb Indbugtning. Legemet hos begge Kjøn gjennemsigtigt, med et mere eller min- dre tydeligt grenligt eller rodligt Anstrog. Hun- nens Længde indtil 18 mm., Hannens 23 mm. Bemærkninger. Denne Art er allerede i 17. Hos Hunnen er det forreste af disse Segmenter noget opsvulmet fortil, og det bagerste danner nedentil, ved Basis af Ægbeholderen, 2 rundagtige Fremspring der navnlig er meget tydeligt fremtrædende, naar Dyret sees ovenfra eller nedenfra (se Tab. VI, Fig. 4, Tab. Vni, Fig. 11). De folgende 5 Segmenter er alle af ens Udseende og ogsaa af tilnærmelsesvis samme Storrelse, simpelt cylindriske, med Længden betydelig større end Breden. Næstsidste Segment er deriniod betydelig længere end de ovrige, og sidste omvendt meget kort, neppe mere end halvt saa langt som næstsidste. Det er (se Tab. VI, Fig. 10) tvært 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 større M(dlem- rum, er fæstet de smalt laneetformige Halegrene, der maaske, i Lighed med den saakaldte Furca hos Copepoderne, kan betragtes som frendvomne ved Klov- ningen af et terminalt Segment, num som dog vel uorrectest vil kunne beskrives som et Bar omformede Lemmer. Hunnens Længde gaar op til IS mm. Hannen er i llcgelen kjendelig større og opnaar ofte en Længde af indtil 2i'> mm. Begge Kjon er dcsuden let kjendelige ved den meget forskjellige Udvikling af 2det Par Følere, samt ved Beskatfenheden af de ydre Kjonsvedliæng. Disse vil passende kunne be- skrives paa dette Sted. maxillæ issne ventrally from the cervical seg- 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. Tliese last follow after each other at regular short intervals, forming with their varioiis lobes and numerous bristles a broad fringe on either side. In this wa}' 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 extraordinarilj' slen- der, considerably narrower than the mesosome, and of regular cylindrical shape. It occupies appreciably, more than half tlie entire length of the body, and is composed of 9 segments besides the caudal rami. Of tliese 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 tlie outer sexual appendages. These 2 tii'st segments of tlie tail ma^-, 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 PI. VI, fig. 4, PI. VIII, tig. 11). The succeeding 5 segments have all a uniform appearance, and are also of approximately the same size, plain cylin- drical, with the length considerabl}^ greater tlian the breadtli. The penultimate segment is, on the contrary, considerably longer than the others, while, on the other hand, the last is ver}' short, scarcely more than half as long as the penultimate one. It is (see PI. VI, fig. 10) transversally truncated at the extremity, and in the middle of tlie posterior edge shows a quite faint sinus. On either side of this, and se])arated in the middle by a lar- gish interval, tlie luirrow lanceolate caudal rami are attached, wliich, perhaps, like the so-called furca in the Copepods, may be considered as pro- duced by the s])litting of a terminal segment, but which, however, probably more correctly may be described as a pair of transformed ajipendages. Tlie length of the female reaches up to 18 ni. ni. 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 ditferent development of the 2nd pair of antennæ. and by the character of the outer sexual ajipendages. These may be conveniently described here. 44 Hos Hunnen (Tab. VI, Fig. 3, 4) danner de ydre Kjonsvedhæng en enkelt bagudrettet, po.seformig Be- holder af meget smal, næstert cylindrisk Form, dog gradvis noget tiltagende i Tykkel.se mod Enden. I sin fiilde Udvikling rækker den næsten til Enden af næstsidste Halesegment; men er ofte en Del kor- tere. Sædvanligvis sees i dens indre et storre eller mindre Antal af Æg af morkegron Farve, ordnede i 2 eller flere Rader. Enden af Ægbeholderen er noget koniskt tillobende og bestaar af 2 ved sær- egne Muskler bevægelige Klapper, der begrændser en tværliggende spaltformig Aabning, bvorigjennem Æggene udstodes. Den ventrale Klaji 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 Kjøns- liængene dobbelte og meget smaa. De iidspringer (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 nær sit Ud.sjiring en dybt indstikkende Bugt, som begrændses oventil af en sammentrykt triangulær Lap, nedentil af en konisk tilspidset Fortsats. Den ydre Del af Ved- hænget er simpelt cylindriskt, og fra dens stumpt tilrundede Ende sees undertiden en uregelmæssig sagtakket Vorte at skyde frem, egentlig en Udkræng- ning af vas deferens. Legemet er hos begge Kjøn i hoi Grad gjennem- sigtigt, saa at de indre Organer, navnlig den med rødgult Indhold fyldte Tarmkanal, tydeligt skinner igjennem de tynde Integamenter. Farven er noget vekslende efter Lokaliteterne, snart meget bleg, hvidagtig, snart med et mere eller mindre tydeligt rijdligt eller grønligt Anstrøg. Beslivivelse af Kroppens Yedliæiig. Øinene (Tab. VI, Fig. it; Tab. VIL 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 Bevægelighed er langt mere begrændset. Af Form er de næsten kolledannede, idet de gradvis udvides mod Enden, der er noget skjævt tilrundet. Den egentlige Øienglob, der indtager omtrent Vs af Øiets Længde, indeholder en oval eller elliptisk An- samling af mørkt Pigment, omgivet udåd 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 Nehalia. — Midt imelleni Øinene sees i det Indre af Hovedet en dyb sort Pigmentplet, som er det saakaldte Ocellus eller enkle Øie. 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 (PI. 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. Tliey 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 (PI. VI, fig. 9; PI. VII, rigs. 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 Nehalia, although their mobility is far more limited. They are almost claviform \\\ shape, as they become gradually dilated towards the extre- mity, which is somewhat obliquely rounded. The real ocular globe, which occupies about ^'a of the eye, contains an oval or elliptical collection of dark pigment, surrounded outwards by a clear zone in which the oiiter refracting portions of the visual elements have their position (see PI. VIII, fig. 6). Any external facetting is just as little present here as in Nebalia. Midway between the e^-es there is seen, in the interior of the head, a deep black pigment-patch, which is the so-called ocellus or simple eye. 45 Første Par Folere (Tab. VI, Fig. i), a' ; Tab. VII, Fig. 1, 2, a') er meget smaa og simpelt byggede, dannende hver en meget smal cylindrisk, eller næ- sten traadformig Stamme, paa hvilken ingen tyde- ligt udpræget Leddeling kan paavises. De er sæd- vanligvis rettede skraat fortil og udåd (se Tab. VI, Fig. 1 — 4), men kan ogsaa til en vis Grad bevæges i andre Retninger, ligesom de idethele er meget boielige. Paa Spidsen, der er noget skraat afskaa- ret, bærer de (se Tab. VIII, Fig. 2) en Gruppe af 8 yderst smaa og delikate Sandsevedhæng, som ved stærk Forstørrelse (Fig. 3) viser en stavdannetForm, med et kort, dobbelt contureret Fodstykke og en liden klar Blære ved den stumpt afrundede Spids. Ifølge sin Bygning maa disse Vedhæng nærmest betragtes som Lugtepapiller ; medens de 'o betydelig længere, og i en fin Spids udgaaende Vedhæng, som iidspringer i nogeu Afstand fra hine fra en afrundet Forhoining, utvivlsomt er at anse som ægte Fole- borster. Andet Par Feiere, der udspringer fra Hovedets nedre Flade umiddelbart nedenfor og lidt indenfor det Iste Par, er meget forskjellige hos de 2 Kjøn. 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 ubevægelige fra Hovedet nedhængende pladeformige Flige. De er omtrent af samme Længde som Øinene og næsten triangulære 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 uogle yderst smaa Foleborster, men er forovrigt ganske ubevæbnede. — Hos Hannen er disse Folere (se Tab. VI, Fig. 1, 2; Tab. VII, Fig. 2, a') langt stærkere udviklede og omformede til kraftige Gribe- redskaber, hvormed Hunnen fastholdes under Co])u- lationen. I Hviletilstand er de mere eller mindre stærkt ombøiede mod Bugsiden og rækker i denne Stilling omtrent til Midten af Forkroppen. Man kun l>aa dem adskille to skarpt begrændsede Afsnit: et tykt cvlindriskt og stærkt muskuløst Skaft, og en tynd kloformig Endedel. Skaftet viser ved Basis flere circulære Indsnoringcr, der antyder .'5 til 4 ufuldstændigt sondrede Led. Yderdelen af Skaftet har indad en noget tilskjærpet Kant, forsynet med en Række af smaa Tænder, og ved Enden, indenfor Endedelens Insertion, åndes en liden konisk tillobende Knude, eller rettere Bigren. Endedelen er noget kortere end Skaftet og meget smalere, men af sær- deles fast cliitinos Consistens. Den er bevægeligt articuleret med Skaftet og mere eller mindre stærkt indbøiet, samt gradvis afsmalnende mod Spidsen, som er stumpt tilrundet. I Modsætning til hvad Til- fælde er hos Hunnen, er disse Følere hos Hannen The iirst pair of antennæ (Pl. VI, fig. 9, a'; Pl. VII, figs. 1, 2, a') are very small and simple in structure, eauh forming a ver}- narrow CNdindrical or almost filamentous stem, upon which no distinctly distinguished articulation can be shown. They are usually directed obliqueh^ forwards and outwards (see PI. 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 ri. Vill, fig. 2) a group of 8 extremely small and delicate sensory appendages, which on a power- ful magnification ifig. 3) exhibit a rod-like shape, with a short, double-contoured foot-piece, and a small clear vesicle at the bluntly rounded point. From their structure those appendages must be chiefi}'' considered as olfactory papilla», whilst the 3 considerably longer, and to a tine ^loint 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 antennæ, which issue from the lower surface of the head immediately below and a little inside of the 1st pair, are very dirterent in the 2 sexes. In the female they are (see PI. VI, fig. 9, a'-'; PI. VII, fig. 1, a-) relatively small and simple, forming a pair of apparentl}' perfectly im- moveable plate-formed flaps hanging from the head. The}' are of about same length as the eyes, and almost triangular in shape, as they issue with a pretty broad base and graduall}'- diminish in breadth towards the extremit}', which is very obliquely trun- cated, with the posterior corner drawn out to a sharp ])oint. On tlie foremost edge the}- have a few extremely small sensory bristles, but are othei'wise ])erfeetly unarmed. In the male these antennæ isee PI. VI, fig. 1. 2, PI. VII, i\g. 2, a-) are far stronger developed, and are transformed into powerful prehen- sile organs by which tlie female is firmly held during copulation. In a condition of repose they are more or less greatly recurved towards the ventral side, and in tlmt position extend to the middle of the anterior body. AW are able to distinguish upon them two sharply defined divisions; a thick cylind- rical and strongly musculous shaft, and a thin claw-shai)ed terminal part. The shaft exhibits se- veral circular constrictions at the base, which indi- cate 3 to 4 imperfectly separated jidnts. The outer part of the shaft has, inwards, a somewhat sharp- ened edge, furnished witii a series of small teeth; and at the extremity, to the inside of the insertion of the terminal purt, 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 40 meget bevægelige og kan tilsammen virke som et meget kraftigt tangforraigt Griberedskab. Af Munddelene er Overlæben og de 2 Kind- bakker let iøinefaldende. Derimod er de 2 Par Kjæ- ver meget vanskeligere at opdage og lader sig egent- lig kun nøiere undersoge ved Dissection. Overlæben (Tab. VI, Fig. !), L; Tab. VII, Fig. 1, L; Fig, 3) har Formen af en aflang Lap, der fra Ho vedets Ventralside strækker sig bagtil, og sædvan- ligvis fuldstændig dækker overKindbakkernesTygge- dele (se Tab. VI, Fig. 'J). Den viser paa Midten en svag Udvidning og ender med en stump Spids, hvis Kanter er fint cdlierede. Dens ydre Flade er noget convex, medens den indadvendte Flade er plan eller concav og laadden af fine, tildels gruppevis ordnede Haar. Ved Hjælp af flere stærke Muskler, som fra Hovedet passerer igjennem dens Indre, kan den snart løftes op fraKindbakkerne, snart præsses ind mod dem igjen. Ind under dens Basis ligger (se Tab. VII, Fig. 3) Mundaabningen i Form af en tvær- oval Spalte, der bagtil begrændses af en ubetydelig fremspringende, haaret Kant. Nogen egentlig Under- læbe 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 Grændsen mellem dets forreste og bagerste Parti. Det convexe baadformige Corpus, der saa- godtsom fuldstændig udfyldes af de kraftige, indad convergerende Tyggemuskler, ender oventil i en Spids, der er bevægeligt indleddet til Hovedets Inte- gument ved Enden af den dorsale Sutur, der be- grændser Nakkesegmentet fortil. Den ventrale Ende, eller den egentlige Tyggedel, er (se Tab. VII, Fig. 4) stærkt indboiet og begrændset fra Corpus ved en svag Indknibning eller Hals. Den er stumpt af kuttet i Enden og har en oval Tyggeflade, der ved stærk Forstoi'relse (Fig. 5) viser sig fint riflet paatværs, med den ydre Del af Riflerne noget grovere og besat med Rækker af tæt sammentrængte tandformige Fremspring. Af nogen egentlig skjærende Del, er der imidlertid intetsomhelst Spor. De 2 Par Kjæver kommer forst tilsyne, naar man betragter Dyret fra Bugsiden, efterat de for- reste Branchialfødder er fjernede eller lagte om til Siderne (se Tab. VI, Fig. U, mi— m"; Tab. VII, Fig. 1, m' — ra-). De er begge forholdsvis smaa og af enkel Bygning. — Forste Par (Tab. VII, Fig. ti) bestaar articulated with the shaft and more or less strongly incurved, and gradually diminishes in breadth to- wards the point, which is bluntty rounded. In con- trast to what is the case in the female, these antennae are, in the male, very mobile, and can act together as a very powerful forceps-formed prehensile ap- paratus. Of the oral parts, the iipper lip and the 2 man- dibles are readily visible. On the other hand, the 2 pairs of raaxillæ are much more difficult to dis- cover and can, in reality, only be closely investigated upon dissection. The anterior lip (PI. 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 VI, 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 flufiy with fine hairs arranged partly in groups. With the aid of several strong muscles wliich from the head pass through its inside, it can easily be raised irp 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 pi'ojectant hirsute edge. Any real posterior lip is, on the contrary, not present. The mandibles (PI. VI, fig. 9, M; PI. 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 liead, at the ex- tremity of the dorsal suture which limits the cer- vical segment in front. The ventral extremity, or the veal masticatory part, is (see PI. VII, fig. 4) strongly incurved and defined from the corpus by a faint constriction or neck. It is bluntly truncated at the extremity, and has an oval masticatory sur- face wliich upon powerful magnification (fig. 5) shows itself to be finely fluted transversally, with the outer ])art 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 maxillæ 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 PI. VI, fig. 9 m.^ — m.-; PI. VII, fig. 1 m.' — m."). They are both rela- tively small and of simple structure. — The first 47 af en tyk muskulos Basaldel og en raed denne be- vægeligt forbunden og stærkt indljoiet Endedel. Denne sidste har Formen af et triangulært Blad. der paa sin frie, lige afskaarne Rand er besat med en Kække af stive Borster, tiltagende i Længde indad. Enhver Børste 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 tæt cilieret Endedel. — Andet Par Kjæ- ver (Fig. 8) er langtfra saa kraftigt udviklede og synes heller ikke ifolge sin Stilling at kunne spille nogen væsentlig Rolle ved Næringsoptagelsen. De udspringer (se Fig. 1, m'-) lidt bag Iste Par og er, ganske i Modsætning til hine, rettede udåd. Basal- delen har paa den nedre Side 3 tykke Fjærbørster. Endedelen synes kun at være lidet bevægelig og viser en noget oval Form. Dens udadvendte Side er tæt besat med stive, kort cilierede Borster, der staar i flere Rækker og divergerer til alle Sider. Den forreste Borste er noget grovere end de ovrige og fæstet i nogen Afstand fra disse til et kort Fremspring. Branchialfodderne (se Tab. VII, Fig. ',)— 13) er alle udpræget bladformige og af temmelig bred Form, med den forreste Flade noget hvælvet 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 næten ens Brede overalt. I dens Indre sees for- skjellige hinanden delvis kr\'dsende Muskelbundter, der dels tjener til at boie selve Stammen, dels vir- ker ])aa de forskjellige Vedhæng. Stammens ydre Kant er noget fortykket og viser ved Basis nogle svagt> lud- og Udbugtninger som en Antydning til en Slags ufuldstændig Leddeling. Dens indre Kant er delt i 5 korte Lappe, de saakaldte Enditer, hvoraf den bagerste, eller øverste, er meget bred og langs sin halvmaaneformigt buede Rand besat med en tæt Ra thick plumose Ijristles 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 foi'emost bristle is somewhat coarser than the others, and is attached at some distance from them to a short ])rojection. The branchial feet (see PI. VII, figs. d—Vd) are all prominently foliaceous and of pretty broad form, with the foremost surface somewhat convex, and the backmost one more or less concave. AVe can distinguish in them the same chief parts as have already been described above concerning the branchial feet of Nebah'a. 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 ])artly traversing each other, which serve partly to bend tlie stem itself, partly act on tlie various appendages. The outer edge of the stem is somewhat thickened, and at the base ex- hibits a few faint in- and out- curvatunjs, as an indication of a kind of imperfect articulation. Its inner edge is divided into a short lobes, the so-called endites, of whicli the backmost or uppermost one is very broad, and along its semi-lunary arcuate _ margin is beset vrith 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 otlier lobes are much smaller, almost mammilli- form in shape, and beset witli similar curved brist- les, and besides, in front of them, with a fascicle of considerably coarser setæ. Thi> 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 setæ, which at tlie tip and along the inner edge succes- sively assume the character of short spines, ciliated only on the one edge. The exopudite (ex) which is 48 har Formen af et ovalt Blad, rundt om besat med en Rad af Fja'rborster. I nogen Afstand fra. Exo- l^oditeu, omtrent ved Midten af Stammens Yder- kant, er Epipoditen (ep) fæstet. Den repræsente- res af et forholdsvis ikke meget stort, simpelt, aflangt, sækdannet Vedhæng, der er rettet skraat nedad og bagud. I sin finere Structur skiller den sig noget fra de ovrige Vedhæng, idet den er af mere spongiøs Beskaffenhed, og antager paa Spiri- tusexemplarer meget snart et temmelig opakt Ud- seende. Foruden de iiævnte Hoveddele, som alle ogsaa er tilstede hos Nebalia, kommer her endnu til et særegent Vedhæng, der er specielt eiendomme- ligt for Gruppen Anostram., og som jeg ovenfor har benævnt «Dækpladen», for at antyde dets Bestemmelse, der nærmest synes at være den, til en vis Grad at erstatte det manglende Rygskjold ved at dække over Roden af Branehialfodderne. Dette Vedhæng (b) udgaar ligeledes fra Ydersiden af Stammen, men lige ved dennes Rod, og har For- men af en meget tynd og gjenuemsigtig oval Plade, regelmæssigt sagtakket i Kantei-ne. — Undersøger man noiere de 11 Par Branchial fodder og sammen- ligner dem med hverandre, vil man finde enkelte mindre Dilferentser i deres Bygning. Hvad for det første Størrelsen angaar, saa tiltager de gradvis noget i Længde fra Iste til omtrent ote Par, for saa jevnt at aftage i Størrelse bagtil, saa at sidste Par neppe er halvt saa stort som 5te og noget min- dre end Iste. Det forresti^ Par (Fig. 1») skiller, sig fra de følgende ved en noget ringere Udvikling af Exopoditen, medens Endopoditen er forholdsvis stær- kere fremspringende, mindre indadrettet, og kun for- synet med en enkelt Torn i Inderkauten. Sidste Par (Fig. 12) udmærker sig fra de øvrige derved, at Epipoditen har antaget Characteren af en tynd Plade, besat i Kanterne med cilierede Borster, og derved at Dækpladen ganske mangler. Endopoditen er paa dette Par meget kort og af afrundet Form, medens Exopoditen er vel udviklet. — Hos Hannen skiller Branehialfodderne (Fig. 13) sig kjendeligt fra samme hos Hunnen ved Endopoditens betydelig stær- kere Udvikling. Den er navnlig paa de midterste "Par stærkt fremspringende indad, næsten 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 Branchialfødderne derved delvis kan fun- gere som et Slags Griberedskaber og derved under- støtte 2det Par Antenner i deres Function at fast- holde Hunnen under Pai-ringen. movabl}' articulated to a separate ledge of the stem at the outer side of the endopodite, has the form of au oval lamella, beset all round with a row of plu- mose setæ. At some distance from the exopodite, about in the middle of the outer edge of the stem, the epipodite (ep) is secured. It is represented by a, comparatively, not very large, simple, oblong vesicu- lar ap])endage, which turns obliquely downwards and backwards. In its microscopical structure it differs somewhat from the other ap])endages, exhibiting a more spongious character, and in alcoholic specimens it very soon assumes a rather opaque appearance. Besides the above named chief parts, which are all also present in Nehnlia, 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 a])pendage (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, regularh' 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 1st 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 5tli and also somewhat smaller than the 1st. 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 co\'ering 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 prodiaced inwards, almost falciform in shape, and provided with a great num- Ijer 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 antennæ in their function to retain hold of the female during copulation. 49 Indre Oriraiier. .I)cii indre Organisiitioii er luis nærværende Forni ikke saa særdeles vanskeli.i;- at studere, da Dyrets store Gjennemsigtighed gjor det muiigt at observerte saagodtsom alle indre Organer i sin Situs, uden at nogen Dissection er tornoden. Paa. de lier givne Habitiisfigurer (Tab. VI, Fig. 1 — 4i er de vig tigste indre Organer antydede, saaledes som de visei' sig ved en svag Forstørrelse. Paa Tab. \'ll rv af- bildet Detailler af Nervesystemet, Fordoielses.syste- niet og Kjonssystemct i stærkere Forstorrelse. Fordøielsessystemet. — Tarmti'aetus l)estaar at ."> tvdeligt begrændsede l_)ele, nemlig Spiserør. Chy- lustarm og Endetarm. 8|>iserøret er meget kort, stærkt mnskulost. og stiger lodret o|) fra Mund- aabningen til don forreste, i Hovedet beliggende DA af Tarmen. Denne sidste Del er noget udvidet og viser, overensstemmende med Legemets Konturer, en svag Ivrunmiug, men gaar forovrigt nmærkeligt over i den bagenfor liggende Del af Tarmen, uden at væi'e l)egrændset fra samme som nogen virkelig Mave. Fortil ndsender denne Del til hver Side en afrundet blindsækiorniig Udvidning, som bedst sees, iiaar Legemet betragtes ovenfra (Tab. VI, Fig. 4). Ved nærmere Undersogelser viser enhver af disse Ildvidninger sig stærkt foldet (se Tab. VIII, Fig. 10), eller ligescra bestaaende af et Antal uregelma^ssige secrindære Udposninger, alle indvendigt beklædte med et kjertelagtigt Epithel, der delvis ogsaa fort- sætter sig ind i selve Tarmen. Der er ingen Tvivl om, at disse 2 blindsækformige Udvidninger af Tar- men er homologe med det lios andre Phyllopoder i Hovedet beliggende eomplicerede kjertelagtige Organ, man ialmindelighed har kaldt Leveren, men som hos nærværende Grrup|)e er stærkt redueeret og saa- ledes ])aa en Maade danner Overgangen til de simple blindsadvformigeAp[)endiees, der forefindes ])aa samme Plads hos visse Cladocercr. Ijigeleiles maa de oven- for beskrevne saakaldte Leversadvke iios Ncbglia an- tåges at liore ind under samme Kategori, skjcnidt K'un et 1'ai' at disse strækker sig ind i selve Hove- det. Tarmen danner forovrigt (se Tab. VI. Fig. 1 — 1) et sini])(dt eyliudriskt, med sta'rludetai'men. Denne sidste (se Fig. 10), der altsaa kun er ind- skrænket til sidste Halesegment, er, som det ovi'ige 'I'armroi', forsynet med sta-rke Ringmuskler og des- uden ved straalefiu-niigt til dens Overllade gaaende ]\rnskelHbi'e lixeret i sin Stilling. \'ed lijadp af alle disse Muskler bliver denne Uel af Tarmtraetus meget bevægelig og kan \exeK-is sta^rkt indsnores og ndvides. hvad der har sin Bi'tydning ved Ud- tomnndseii af Fxerementerne. Gledens Dyret lever, obser\'eres paa Tarmroret meget energiske pei-istal- v — (i. 0. Sårs; Funna Xonr'jkf Internal Organs. Tiie internal organisation in the jiresent i'orm is not espeeially diftieult to study, as the animal's great transpareuey renders it ])ossible to observe almost all the internal organs in situ, without tlie necessity of dissection. In the habitus figures liere given (PI \'[. tigs. 1 — 4), the most important inter- nal organs arc; shown as they aj)pear under a low power of the microscope. On PI. Vil, details of the nervous, the digestive and the sexual s\-stems are given, more highly magnified. Digestive system. — The intestinal ti-act con- sists of o elearly-detined portions, viz, the (eso- phagus, the chyle-intestine and the rectum. The o'sophagus is very short and muscular, and ascends vci-tically from the oral oritice to tlie anterior ])or- tion of the intestine, which is situated in the head. This portion is somewliat expanded, and, in agree- ment with the contour of the body, exhibit^ a slight curve, passing then imperceptibly into that part of the intestine lying behind, without being defined fiv.im it as a true stomach. In front this portion sends out to eatdi side a rounded, cæcal dilatation, which is Ijest seen on viewing the body from above (1*1. VI, fig. 4). On a clo-ser examination, each of these dilatations |)rovcs to be very much folded (see PI. VIII, fig. 10), or to consist, a.-s it were, of a number of irregular .seiiondary lobules, all lined interiorly with a glandular epithelium whieh also partly extends into the intestine itself There is no doubt that these two cæcal dilatations (jf the intes- tine are homologous with the complicated glandular organ found in the head of other Pliyllopoda, wliich has generally been called the liver, luit which, in the present grouj), is vi'r\- much reduced, thus form- ing, to some extent, the transition to the simple cæcum-like ai)pendages found in the same place in certain Chfiocera. The jireviously-described biliary cæca in Nehalia may similarly be sup])osed to come under the same category, although only two of them extend a-! far as into the head itself. Tlie rest of the intestine (see PI.V'I, figs. 1 — 4) is in the form of a sinijde cylindrical tube furnished with stritng annular mus- cles, and extending, without an\- windings, through the animaPs axis a< far as the last .segment of the tail, where it unites with the rectum. This last (see fig. lOV which is thus confim^d to the last caudal segment, is, like the rest of the intestinal tube, furnished with strong anntilar nuiscl(>s, and is also fixed in its ))osition by nuis(de-fibres radiating towarils the outer surface. By the aid