tiske Bevegelser, der med stor Regelmessighed for- 
plantes langs ad dens hele Lengde, ialmindelighed 
i Retningen bagfra fortil. 
Circulationssystemet. — Hjertet danner (se Tab. 
VI, Fig. 2, 3, 11 ce) et overordentlig langstrakt, med 
bestemte Mellemrum indsnoret Ror, der strekker sig 
ovenfor Tarmen fra Nakkesegmentet og bagtil lige 
ind i Halens nestsidste Segment. Det er ved fine 
Muskeltraade festet til Indsiden af Ryggens Inte- 
gument, og viser for hvert Segment et Par venose 
Spaltaabninger, hvorigjennem Blodet optages i Hjer- 
tet. Den samlede Blodmasse, som paa denne Maade 
trenger ind i Hjertet, udstedes dels fra den forreste, 
dels fra den bageste Ende, og kommer derpaa ind i 
veglose Hulrum mellem de forskjellige Organer. 
Skjondt saaledes et egentligt Karsystem, bestaaende 
af Arterier og Vener, ganske mangler, circulerer dog 
Blodet med stor Regelmessighed omkring i Lege- 
met, idet det folger visse bestemte Baner. Blodet 
er, som sedvanligt, farvelost og indeholder en 
Mengde smaa, tildels amosboide Blodlegemer, * hvis 
Gang let lader sig forfolge hos det levende Dyr 
under Mikroskopet. Hjertets Pulsationer, hvorunder 
Spaltaabningerne afvexlende aabnes og Iukkes, er 
seerdeles livlige, saa det er meget vanskeligt at 
telle, hvormange der sker i Minuttet. 
Nervesystemet. — Centraldelene af Nervesyste- 
met bestaar; som hos andre Crustaceer, af et dorsalt 
Parti, det ovre Svelgganglion eller Hjernegangliet, 
og af en ventral Del, den saakaldte Bugganglie- 
kjede, begge forbundne ved en omkring Spiseroret 
lobende Commissur (se Tab. VIII, Fig. 1). 
Hjernegangliet (se Fig. 1, 4, 17), der. har sin 
Plads i den forreste Del af Hovedet, lige foran Be- 
gyndelsen af Tarmen, er af temmelig’ betydelig Stor- 
relse, og bestaar af 2, i Midten med hinanden for- 
bundne symetriske Halvdele. Oventil danner det 
flere Lappe, der delvis omfatter Basis af det enkle 
Mie (se Fig. 4), og til hver Side fortsetter det sig 
ji den megtigt udviklede Synsnerve (0), efterat have 
udsendt en tynd Nerve til lste Par Antenner (a’). 
Et andet Par Nerver sees at udgaa fra Hjernegang- 
liet leengere fortil, til hver Side af det enkle Gie. 
De ender hver med en liden ganglios Opsvulmning 
umiddelbart under en liden grubeformig Fordybning 
i Hovedets forreste Integument (a), rimeligvis sva- 
rende til de omtrent paa samme Sted hos Limnetis 
forekommende cilierede Gruber, der ialmindelighed 
ansees for et Slags Sandseorgan. Nerverne for 2det 
Par Folere (a*), der hos Hannerne er betydelig 
sterkere end hos Hunnerne, udspringer fra den for. 
reste Del af Svelgcommissurerne. Disse sidste for- 
bindes, inden de omfatter Spiseroret, ved en tynd 
Tvercommissur (se Fig. 1 og 4), der ligger ved Basis 
af Overleben. 
50 
\ 
be observed, these being transmitted with great 
regularity throughout its entire length, generally 
from behind forwards. 
Circulatory system. — The heart (see Pl. VI, 
figs..2, 3, 11¢) consists of an exceedingly elongated 
tube, constricted at regular intervals, and extending 
above the intestine from the cervical segment back- 
wards into the penultimate segment of the tail. It 
is attached by fine muscle-fibres to the inside of the 
dorsal integument, and exhibits, in each segment, 
a pair of venous ostia, through which the blood 
is received into the heart. The accumulated mass 
of blood, which thus forces itself into the heart, is 
expelled partly from the anterior, partly from the 
posterior end, and then enters the several cavities 
between the various organs. Although there is thus 
a total absence of a true vascular system consisting 
of arteries and veins, yet the blood circulates with 
great regularity through the body, following certain 
fixed courses. The blood is, as usual, colourless, 
and contains a number of small, partly amcbous 
blood-corpuscles, whose course may be easily traced 
under the microscope. The pulsations of the heart, 
during which the ostia alternately open and close, 
are exceedingly rapid, so that it is very difficult to 
count the number occurring in a minute. 
Nervous system. -- The central portion of the 
nervous system consists, as in other Crustaceans, 
of a dorsal part, the supracsophageal or cerebral 
ganglion, and of a ventral part, the so called ventral 
ganglion chain, connected with one another by a 
commissure round the cesophagus (see Pl. VIII, fig. 1). 
The cerebral ganglion (see figs. 1, 4 and 17), 
which is situated in the anterior part of the head, 
just in front of the commencement of the intestine, 
is of considerable size, and consists of 2 symmetri- 
cal halves connected with one another in the middle. 
Above, it forms several lobes which partially sur- 
round the base of the ocellus (see fig. 4), and, after 
sending out a fine nerve to each of the first pair of 
antennee (a), continues on each side in the form of 
the powerfully developed optic nerve (0). A second 
pair of nerves are seen to issue from the cerebral 
ganglion farther forward, on each side of the ocellus. 
They each end in a little ganglionic protuberance 
immediately below a small pit-like depression in the 
anterior integument of the head (a) probably ‘an- 
swering to the ciliated pits occurring in about the 
same place in Limmetis, and which are generally 
considered to be a kind of organ of sense. The 
nerves for the second pair of antenne (a*) which 
are considerably stronger in the males than in the 
females, originate from the anterior part of the 
cesophageal commissures. These, before they encircle . 
the esophagus, are connected by a thin transverse 
commissure (see figs. 1 and 4) lying near the base 
of the anterior lip. 
