19 



Par Branchialfødder. Dens Størrelse tiltager noget 

 indtil 4de Par, hvor den er størst, og aftager saa 

 igjen suecessivt 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 afn^ndet. Paa de følgende Par (Fig. 4, 5) 

 bliver Forskjellen melleni de 2 Lappe efterhvert 

 mindre, og paa sidste Par (Fig. 6) er' Forholdet det 

 omvendte af hvad det er paa Iste Par, idet den dor- 

 sale Lap her er den største og mere smalt udlobende 

 end den ventrale. Saavel Exopoditen som Epipoditen, 

 men især denne sidste, viser den for Gjelleelemen- 

 terne hos andre Krebsdyr characteristiske spongiose 

 Structnr, idet der raellem de 2 Lameller, livoraf 

 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 

 Rygskjoldet sjiiller i denne Henseende en vigtig 

 Rolle. 



De 4 forreste Par Bagkropslemmer (se Tab. II, Fig. 

 1) er overordentlig kraftigt udviklede Svømmeappa- 

 rater, der i flere Henseender, og ogsaa i denMaade, ■ 

 hvorpaa de bevæges, minder om Copepodernes Svøm- 

 mefødder. De er alle hyggede efter samme Type 

 og bestaar hvert (se Tab. III, Fig. 7 og 9) af en med 

 talrige stærke Muskelbundter fyldt, noget affladet 

 Basaldel, og to fra dennes Ende udgaaende, med 

 cilierede Svømmeborster forsynede, enleddede Grene 

 eller Aarer, hvoraf den ydre ialmindelighed er ret- 

 tet stærkt udåd og i Yderkanten bevæbnet med 

 kraftige Torner. Paa alle Par iindes ved Enden af 

 Basaldelen paa den indre Side en eiendommelig 

 indadrettet Fortsats (Fig. 8), der møder 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 hørende Fødder ligesom sammen, saa at deres 

 Bevægelser kun kan ske samtidigt. 



Iste Par Svømmefødder (Fig. 7) skiller sig kjen- 

 deligt fra de øvrige, saavel ved Basaldelens Form 

 og Bevæbning som ved Be.skaffenheden af den ydre 

 Gren. Basaldelen, der ligesom paa de øvrige Par 

 har et ganske kort Eodled, 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 point of attachment. 

 As was the case with the exopodite, there is also 

 some difference in the size and form of the epipo- 

 dite in the various pairs of branchial feet. The size 

 increases somewhat until the 4th pair, where it is 

 greatest, and it then diminishes again, siiccessively, 

 in the pairs situated behind (see PI. II, fig. 1). In 

 the Lst 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 lobes 

 becomes gradually less, and in the last pair (fig. 6) 

 the relation is the reverse 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, anastomosing with each other, 

 in which, in the living animal, an active blood cir- 

 culation proceeds. That both these appendages are 

 therefore of respiratory importance is perfectly indu- 

 bitable, although, as will be subsequently shown, 

 the carapace itself also plays an important part 

 in that respect. 



The 4 foremost pairs of the posterior appen- 

 dages of the body (see 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 constructed on the same 

 type, and consist, each (see PI. Ill, figs. 7 and 9), 

 of a somewhat flattened basal part filled with nu- 

 merous strong bundles of miiscles, and two branches 

 or oars, issuing from its extremity and furnished with 

 ciliated swimming-bristles. Of these branches the 

 outer one is usually directed strongly outwards, and 

 is armed on the outer edge with powerful spines. 

 In all the pairs there is found, at the extremity of 

 the basal part on the inner side, a peculiar projec- 

 tion directed inwards (fig. 8), which meets the corre- 

 sponding one of the other side, and is armed at the 

 point with a number — usually 4 — uncinate spines 

 (fig. 8 a). The 2 feet pertaining to the same pair 

 are, as it were, hooked together by these spines, so 

 that their movements can only take place simul- 

 taneously. 



The 1st pair of swimming feet (fig. 7) are per- 

 ceptibly distinguished from the others, both by the 

 form and ai-matiire of the basal part as well as by 

 the nature of the outer branch. The basal part 

 which, as upon the other pairs, has a quite short 

 basal joint, is here relatively longer and narrower, 

 somewhat narrowing in breadtli towards the extra- 



