Indre Organer. 
Den indre Organisation er hos nerverende 
Form ikke saa serdeles vanskelig at studere, da 
Dyrets store Gjennemsigtighed gjor det muligt at 
observere saagodtsom alle indre Organer i sin Situs, 
uden at nogen Dissection er fornoden. Paa de her 
givne Habitusfigurer (Tab. VI, Fig. 1—4) er de vig- 
tigste indre Organer antydede, saaledes som de viser 
sig ved en svag Forstorrelse. Paa Tab. VII er af- 
bildet Detailler af Nervesystemet, Fordoielsessyste- 
met og Kjonssystemet i steerkere Forstorrelse. 
Fordgielsessystemet. — Tarmtractus bestaar af 
3 tydeligt begreendsede Dele, nemlig Spiserer, Chy- 
lustarm og Endetarm. Spiseroret er meget kort, 
sterkt muskulost, og stiger lodret op fra Mund- 
aabningen til den forreste, i Hovedet beliggende Del 
af Tarmen. Denne sidste Del er noget udvidet og 
viser, overensstemmende med Legemets Konturer, en. 
svag Krumning, men gaar forevrigt umerkeligt over 
i den bagenfor liggende Del af Tarmen, uden at 
vere begrendset fra samme som nogen virkelig 
Mave. Fortil udsender denne Del til hver Side en 
afrundet blindsekformig Udvidning, som bedst sees, 
naar Legemet betragtes ovenfra (Tab. VI, Fig. 4). 
Ved nermere Undersogelser viser enhver af disse 
Udvidninger sig sterkt foldet (se Tab. VII, Fig. 10), 
eller ligesom bestaaende af et Antal uregelmessige 
secundere Udposninger, alle indvendigt bekledte 
med et kjertelagtigt Epithel, der delvis ogsaa fort- 
setter sig ind i selve Tarmen. Der er ingen Tviv] 
om, at disse 2 blindsekformige Udvidninger af Tar- 
men er homologe med det hos andre Phyllopoder i 
Hovedet beliggende complicerede kjertelagtige Organ, 
man ialmindelighed har kaldt Leveren, men som 
hos neerveerende Gruppe er steerkt reduceret og saa- 
ledes paa en Maade danner Overgangen til de simple 
blindseekformige Appendices, der forefindes paa samme 
Plads hos visse Cladocerer. Ligeledes maa de oven- 
for beskreyne saakaldte Leverseekke hos Nebalia an- 
tages at hore ind under samme Kategori, skjondt 
kun et Par af disse strekker sig ind i selve Hove- 
det. Tarmen danner forovrigt (se Tab. VI, Fig. 
1—4) et simpelt cylindriskt, med steerke Ringmuskler 
forsynet Ror, der uden nogen Bugtninger strekker 
sig gjennem Dyrets Axe indtil Halens sidste Seg- 
ment, hvor den forbinder sig med Endetarmen. 
Denne sidste (se Fig. 10), der altsaa kun er ind- 
skrenket til sidste Halesegment, er, som det ovrige 
Tarmror, forsynet med steerke Ringmuskler og des- 
uden ved straaleformigt til dens Overflade gaaende 
Muskelfibre fixeret i sin Stilling. Ved Hjelp af 
alle disse Muskler bliver denne Del af Tarmtractus 
meget bevegelig og kan vexelvis sterkt indsnores 
og udvides, hvad der har sin Betydning ved Ud- 
tommelsen af Excrementerne. Medens Dyret lever, 
49 
Internal Organs. 
The internal organisation in the present form 
is not especially difficult to study, as the animal’s 
great transparency renders it possible to observe 
almost all the internal organs in situ, without the 
necessity of dissection. In the habitus figures here 
given (Pl. VI. figs. 1—4), the most important inter- 
nal organs are shown as they appear under a low 
power of the microscope. On Pl. VI, details of the 
nervous, the digestive and the sexual systems are 
given, more highly magnified. 
Digestive system. — The intestinal tract con- 
sists of 3 clearly-defined portions, viz, the «so- 
phagus, the chyle-intestine and the rectum. The 
gsophagus is very short and muscular, and ascends 
vertically from the oral orifice to the anterior por- 
tion of the intestine, which is situated in the head. 
This portion is somewhat expanded, and, in agree: 
ment with the contour of the body, exhibits a slight 
curve, passing then imperceptibly into that part 
of the intestine lying behind, without being defined 
from it as a true stomach. In front this portion 
sends out to each side a rounded, cecal dilatation, 
which is best seen on viewing the body from above 
(Pl. VI, fig. 4). On a closer examination, each of 
these dilatations proves to be very much folded (see 
Pl. VUI, fig. 10), or to consist, as it- were, of a 
number of irregular secondary lobules, all lined 
interiorly with a glandular epithelium which also 
partly extends into the intestine itself. There is no 
doubt that these two cecal dilatations of the intes- 
tine are homologous with the complicated glandular 
organ found in the head of other Phyllopoda, which 
has generally been called the liver, but which, in 
the present group, is very much reduced, thus form- 
ing, to some extent, the transition to the simple 
cecum-like appendages found in the same place in 
certain Cladocera. The previously-described biliary 
ceca in Nebalia may similarly be supposed to come 
under the same category, although only two of them 
extend as far as into the head itself. The rest of the 
intestine (see Pl. VI, figs. 1—4) is in the form of a simple 
cylindrical tube furnished with strong annular mus- 
cles, and extending, without any windings, through 
the animal’s axis as far as the last segment of the 
tail, where it unites with the rectum. This last 
(see fig. 10), which is thus confined to the last 
caudal segment, is, like the rest of the intestinal 
tube, furnished with strong annular muscles, and is 
also fixed in its position by muscle-fibres radiating 
towards the outer surface. By the aid of these 
muscles, this portion of the intestinal region becomes 
very mobile, and can be alternately contracted and 
expanded, thus assisting in the evacuation of the 
excrements. While the animal is alive, very vigor- 
observeres paa Tarmroret meget energiske peristal- | ous peristaltic movements of the intestinal tube may 
7 —G. 0. Sars: Fauna Norvegix. 
