Nervesystemet. 
Nerveringen omgiver den øverste Del af Svælget, er 
uregelmæssig rund, temmelig smal og er indesluttet 1 en 
Skede (Nervekarret). Den har en temmelig stærk gul 
Farve, og har et ydre Cellelag og et indre Fiberlag. For- 
uden en Mængde mindre Grene, som afgives til Spiserøret, 
Tentaklerne og Mundskiven, udgaa 5 Hovedstammer (Ra- 
‘dialstammer) fra den. Disse gaa ud igjennem det lille Hul, 
som findes paa hvert af Kalkrmgens Radialstykker, og naar 
de komme paa den ydre Flade af dem, løbe de over Radial- 
musklen hen til Huden, hvor de fortsætte sit Løb imellem 
denne og Ringmusklerne til omtrent Midten af Kroppen, 
hvor de kun dækkes af Længdemusklerne, idet, som tidligere 
bemærket, Ringmusklerne her ophøre noget indenfor Længde- 
musklens Rand uden at gaa over Radialnerven. Længere 
bag paa Kroppen indtræder atter det tidligere Forhold, og 
nu er Radialnerven dækket af baade Ring- og Længde- 
muskelen lige til Analaabningen. Der 
træder ind i Kalkringens Radialstykke, findes paa hver Side 
af den en rund klar Blære, der dannes af en temmelig fast, 
gjennemsigtig Membran, hvis Indhold var en klar Vædske 
uden Otolither. Disse Blærer svare til de saakaldte Høre- 
organer, der findes i større og mindre Mængde hos Elpidi- 
derne, og som baade Dr. Théel og vi tidligere have paa- 
vist, — kun er Forskjellen den. at de hos Acanthotrochus 
ingen Otolither have, hvilket, ifølge Théels Angivelser. og- 
saa skal være Tilfældet hos den af ham beskrevne Trocho- 
derma elegams. Er dette et mere primitivt Stadium af 
Høreorganet, eller skulde det tyde hen paa, at disse Blærer 
ingenlunde ere specielle Sandseorganer? 
indesluttede i et forholdsvis vidt 
Kar, der paa Nervens indre Flade er sammenyoxet med 
denne, Tab. V, Fig. 9, g, medens Karret paa den ydre 
Side er aabent, Fig. 9, h. Dette Forhold er ganske mod- 
sat af det Dr. Teuscher angiver at være Tilfældet hos Cri- 
noiderne, Echiniderne og Holothuriderne. hvor Radialnerven 
med sin ydre, brede Flade er sammenvoxet med Karvæg- 
gen. Om Karret er forsynet med Endothelceller skulle vi 
ikke med Sikkerhed kunne afgjøre; thi det var os ikke 
muligt, selv under meget stærk Forstørrelse, at opdage saa- 
danne. Selve Nervestammen bestod af et lysere, bredere 
Lag, Fig. 9, 7, og et mørkt smalere. Fig. 9, k, der vendte 
indad og var sammensmeltet med -Karvæggen. Nerven be- 
stod af et peripherisk Cellelag og et centralt Fiberlag. Fra 
Radialnerverne udgik langs hele Løbet en Mængde Grene 
til Musklerne og Huden. 
Radialnerverne ere 
Generationsorganerne. 
De faa Exemplarer (4), vi have havt til vore Under- 
søgelser, vare samtlige Hunner. Kjønsorganet hos Hunnen 
hvor Radialnerven 
40 
fibrous layer. 
Nervous System. 
The neryous ring surrounds the upper portion of 
the esophagus; it has a somewhat irregular cireular form, is 
rather narrow, and is enclosed in a membranous sheath (the 
nervous vessel). It has a rather deep, yellow colour, and 
is furnished with an outer cellular layer and an inner 
Exclusive of numerous smaller ramifications 
passing to the cesophagus, the tentacles, and the oral disk, 5 
large stems (the radial stems) proceed from the outer mar- 
gin of the ring. These stems project through the small 
aperture on each of the radial segments composing the cal- 
careous ring; and after reaching their outer surface, they 
extend across the radial muscle to the integument, from 
whence they continue their course between the latter and 
the annular muscles nearly to the middle of the body, 
where they aré covered by the longitudinal muscles alone, 
the annular muscles, as before stated, terminating here a 
little within the margin of the longitudinal muscle, with- 
out crossing the radial nerve. Farther down the body, the 
radial nerves are covered both by the annular and the 
longitudinal muscles till they reache the. anal opening. 
Where the radial nerve pierces the radial segment of the cal- 
careous ring, on either side of the nervousstem, is seen a round, 
bright vesicle, consisting of a firm, transparent membrane; 
they contained each a limpid fluid, without Otoliths. These 
vesicles correspond to the so-called auditory organs that 
occur — more or less numerous — in the Elpidide, and 
to which attention has been previously ealled both by Dr. 
Théel and by ourselves, — with this difference, however, 
that in Acanthotrochus they have no Otoliths, which, accor- 
ding to Dr. Théel’s description of Trochoderma elegans, 1s 
also the case with that species. Does this characteristic 
feature represent an earlier stage in the development ot 
the auditory organ, or are we rather to infer, that these. 
vesicles have no sensorial function whatever ? 
The radial nerves are enclosed in a comparatively 
capacious vessel, which, on the inner surface of the nerve, 
is connate with the latter, Pl. V, fig. 9, g, and open on 
the outer surface, fig. 9, h. This feature is exactly the 
reverse of that stated by Dr. Teuscher as characteristic of 
the Crinoidea, Echinoidea, and Holothwroidea, in which the 
outer broad surface of the radial nerve is connate with the 
wall of the vessel. Whether the vessel be furnished with 
endothelial cells, is a question to which we can give no 
conclusive answer, seeing it was impossible to detect any, 
even with the aid of a powerful magnifier. The nervous 
stem consisted of a light, broad layer, fig. 9, 7, and of a 
dark, narrow one, fig. 9, å; the latter was directed in- 
wards, and coalesced with the wall of the vessel. The nerve 
was composed of a peripheral cellular layer and a central 
fibrous layer. From the radial nerves — throughout their 
entire length — numerous offshoots proceeded to the mus- 
cles and the skin. 
Generative Organs. 
The few specimens (4) we have had the opportunity 
of examining were all females. The generative organ in 
