ikke meget brede, men tiltage i Bredde, saa at de ere 
bredest henimod Midten af Kroppen, hvorfra de aftage i 
Tykkelse, «indtil de mod den bagerste Ende blive yderst 
fine. Enhver Radialnerve løber imellem hvert Par Længde- 
muskler, under Radialkarret, kun adskilt fra dette og Hu- 
den ved et tyndt Lag Bindevæv, Tab. VIII, Fig. 12. 
Fra Radialnerverne udgaa en Mængde Grene til Hu- 
den. Disse ere ved deres Udspring temmelig tykke, men 
forgrene sig meget snart og danne dels ganglionære Op- 
svulmninger, Fig. 13,c, dels fine, udbredte anastomoserende 
Net i Corium, Fig. 13. b, hvorfra udsendes Smaagrene dels 
til Musklerne, dels til det ydre Fpithellag, hvor de for- 
svinde. 
-Radialnerverne have den samme histologiske Bygning 
som Nerveringen. De have en Skede, indenfor hvilken 
findes et lysere Cellelag, der ligesom dækker det indre Lag, 
som synes at være stribet, Fig. 12, a. Uagtet al anvendt 
Møie har det ikke været os muligt at kunne konstatere for 
Trochostomas Vedkommende Sempers Iagttagelser med Hen- 
syn til den finere histologiske Bygning af ‘Radialnerverne 
hos Molpadiderne. Han angiver, at Radialnerven hos disse 
Dyr er sammensat af 3 flade Baand, tydelig adskilte ved 
et tyndt Bindevævsseptum og indesluttet i en Skede. Hos 
Trochostoma findes kun to Lag, og disse ere ingenlunde ad- 
skilte ved Bindevæv, men gaa umiddelbart over i hinanden. 
Kjønsorganerne. 
Slægten Trochostoma har adskilt Kjon, og afviger 
saaledes fra de øvrige Molpadider, som ere antagne for at 
være Hermaphroditer. I Dyrets Ydre er der Intet, som 
angiver Kjønnet, men i den indre Bygning adskiller Hannen 
sig tydeligt fra Hunnen, idet nemlig Kjønsorganerne ere 
saa forskjellige i deres Form, at man strax kan afgjore, 
hvilket Kjøn man har med at gjøre. 
Kjønsorganerne ere fæstede til den fortykkede Del af 
det dorsale Mesenterium, lige ved Tarmens Begyndelse, og 
danner to store Stammer, som forene sig til en fælles Ud- 
førselsgang, Tab. IX, Fig. 39, 40. Den ene Stamme er 
altid noget længere end den anden. 
«Hos Hunnen udgaar fra den længste Stamme, der 
indtager omtrent Kroppens halve Længde, 28—30 dels rør- 
formige, dels kolbeformige Udvidninger, der have en for- 
skjellig Længde og dele sig dichotomisk, og fra den korte 
Stamme udgaa 15—18 lignende Forlængelser, Fig. 40, a. 
Hos Hannen bestaar den længste Stamme af en utallig 
Mængde lignende Rør, som hos Hunnen, — kun ere de 
meget længere og tyndere, og indtage, idet de ligeledes 
dichotomisk dele sig, hele Dyrets Længde. Den kortere 
61 
to the mtegument of the oral disk, and to the tentacles; 
also 5 large branches, which constitute the radial nerves. 
The latter are not very thick at their origin, but increase 
in diameter, being thickest near the middle of the body; 
from whence they begin to diminish, till, towards the 
posterior extremity, they terminate remarkably slender. 
Hach radial nerve extends between each pair of longitudi- 
nal muscles, under the radial vessel, separated from the 
latter and from the imtegument by a thin layer of con- 
nective tissue, Pl. VIII, fig. 12. 
Numerous branches proceed from the radial nerves 
to the integument. At their origin these branches are 
comparatively thick, but soon divide, forming ganglionic 
protuberances, fig. 13, c, and fine-meshed, anastomosing 
network in the corium, fig. 13, b, from which subsidiary 
branchlets are sent off, some to the muscles, others to the 
outer epithelial layer, where they disappear. 
The radial nerves exhibit the same histological strue- 
ture as the nervous ring. They are furnished with a sheath, 
beneath which extends a lighter-coloured cellular layer, cover- 
ing up, as it were, the inner layer, which would seem to 
have a striate structure, fig. 12, a. As regards Trochostoma 
we cannot, we regret to say, though no trouble has been 
spared to arrive at conclusive results, confirm Semper's 
observations, according to which the radial neryes in the 
Molpadide are distinguished by greater complexity.in their 
histological structure. ‘According to that zoologist, the radial 
nerve in these animals is composed of 3 flat bands, distinctly 
separated by a thin septum of connective tissue, and invag- 
inated in a sheath. In Trochostoma there are but two 
layers, not separated by a connective membrane, but con- 
tiguous, passing one into the other. 
Generative Organs. 
The genus Trochostoma has the sexes separate, and 
differs therefore from all other Molpadidæ, which are re- 
garded as bisexual. In the habitus of the animal there is 
nothing to indicate the sex; but with regard to its inner 
organisation, males may be readily distinguished from fe- 
males by the obvious difference in form characterising the 
generative organs. 
These organs are attached to the inspissated portion 
of the dorsal mesentery, in immediate proximity to the ori- 
gin of the intestine, and constitute two large stems, which 
unite to form a common eferent duct, Pl. IX, fig. 39, 
40. One of the stems is invariably longer than the other. 
In the female, from. 28 to. 30 expansions,: some 
tubular, some clavate, varying in length and dividing dicho- 
tomously, proceed from the longer of the stems, which ex- 
tends about half the length of the body; and from the 
short stem proceed 15—18 similar prolations, fig. 40, a. 
In the male, the longer stem consists of a countless 
number of tubes similar to those in the female; they 
are, however, much longer and slenderer, and extend, too, 
dividing dichotomously, throughout the whole length of the 
