Saalænge dette Stadium 1 Udviklingen vedvarer, er endnu 
ingen Madreporplade dannet.; efterhaanden som Aabningen 
i Huden lukkes, udvikler Madreporpladen sig, og da nu 
Stenkanalens ydre Ende vedbliver. at være. fastvoxet til 
Huden, kan Madreporpladen ikke udvikle sig der, hvor den 
ellers pleier at findes hos Holothuriderne, men maa frem- 
staa paa et andet Sted af Stenkanalen, som jo ogsaa virke- 
lig ere Tilfældet hos Trochostoma. 
Stenkanalens histologiske Bygning afviger ogsaa noget 
ira Holothuridernes og synes at nærme sig mere Asteri- 
dernes. . forsaavidt den er kjendt, idet nemlig det indre 
ilimrende Lumen er omgivet af tæt tilsluttende Kalkringe, 
der dog ikke som hos Asteriderne sende Forlængelser ind 
i selve Hulheden, hvorved denne bliver mere kompliceret, 
men kun tjener som Støtte for det enkelte Lumen. Ogsaa 
Madreporpladen danner et Slags Overgangsled imellem 
Holothuridernes og Asteridernes, men synes at nærme sig 
mest til de sidstes Madreporplade. 
Vi have tidligere kun i Forbigaaende nævnt Tentak- 
lerne; vi skulle nu omtale dem noget nærmere. Som alle 
Tentakler ere de hule cylindriske Rør, som paa deres 
øverste frie Ender ere tredelte, Tab. VII, Fig. 4.” Den 
midterste Papille er den største og bredeste; Sidepapillerne 
ere smalere og næsten lancetformige. Tentaklerne ere yderst 
korte og rage knapt 2”” over Mundskiven. Deres ydre 
Flade er beklædt med en yderst tynd, vandklar Cuticula, 
under hvilken et'enkelt Epithellag, bestaaende af Cylinder- 
"celler, findes. Indenfor dette sees en temmelig fast Binde- 
vævshud, hvis Fibriller krydse hverandre i alle Retninger, 
og 1 hvis intermediære Substants ere indleirede en Mengde 
kugleformige Kalkkorn, ' der ligge meget tæt sammen uden 
dog at berøre hverandre, og som tidligere ere beskrevne. 
Til denne Bindeveyshud fester Muskelhuden’ sig, som dan- 
nes af cirkulere og langsgaaende Fibre, hvilke tildels ana- 
stomosere med hverandre: 
Indenfor Længdemuskellaget iagttages et hyalint Binde- 
væv, der er temmelig smalt, indeholder en stor Mængde 
aflange kornede Celler (Sempers Slimceller) og enkelte for- 
grenede Bindevævslegemer. Til dette Bindevævslag fæster 
sig Tentakelkarret med sit flimrende Cylinderepithel, hvis 
Cilier rage ind i Hulheden. Som tidligere neynt ligge 
disse yderst smaa Tentakler næsten skjulte 1 de før beskrevne 
aflange Gruber, og kunne saaledes vanskeligen tjene som 
Bevægelsesorganer, og heller ikke synes de paa Grund af 
deres Lidenhed at kunne benyttes til Gribeorganer eller 
til at føre Føden hen til Mundaabningen. En Funktion 
maa de imidlertid have, men hvilken denne nu er, vide vi 
ikke. 
Kropshulheden er overalt beklædt med et flimrende 
Epithel og er ved Vandkarrmgen forsaavidt afbrudt, som 
denne danner Grændsen imellem Svælgsinus og den egent- 
ige Kropshulbed: Idet Ringkanalen, som ovenfor angivet, 
58 
the water in which the animal is immersed. During 
this stage of development the madreporic body does 
not exist: it begins to form as the-opening in the skin 
gradually closes; but the outer extremity of the sand- 
canal contmuing to be connate with the integument, the 
madreporic body cannot develop where it is commonly ° 
observed in Holothurians; it must needs form on some 
other part of the sand-canal, which indeed is the case with’ 
Trochostoma. pe 
The histological structure of the sand-canal differs 
somewhat, too, from «that in other Holothurians, approxi- 
mating apparently that in the Asteridæ, — so far at least 
is known, — the inner vibratile lumen being furnished 
with tight-fitting calcareous rings, from which, however, 
unlike those in the Asteride , no prolations extend 
into the cavity itself; they merely serve to strengthen the 
particular lumen they encircle. Moreover, the madreporic 
body constitutes a kind of transition link between the 
Holothurians and the Asteride, but would seem to bear 
most resemblance to the madreporie body in the latter 
family. 
We have already occasionally mentioned the tentacles; 
we will now proceed to describe them. They consist — 
as do all tentacles — of hollow, cylindric tubes, which, at 
their free extremities, are tripartite, Pl. VII, fig. 4.. The 
middle. papilla is the largest and broadest; the lateral 
papillæ are narrower and almost lanceolate. These ten- 
tacles are exceedingly short, projecting at most 2”” above 
the oral disk. Their outer surface is invested with an 
- exceedingly: thin transparent cuticle, under which extends 
a single epithelial layer, consisting of cylindric cells. Under- 
neath the latter is seen a layer of comparatively firm connec- 
tive tissue, with fibrils interlacing in all “directions, and 
haying, embedded in its intermediary substance, numbers 
of globose calcareous granules, very closely arranged, but 
not contiguous, similar to those already described. To this 
layer of connective tissue is webbed the muscular integument: 
consisting of circular and longitudinal fibres. some of which 
anastomose one with the other. 
Underneath the longitudinal muscular layer is seen a 
layer of hyaline connective tissue, comparatively narrow, and 
containing a large number of oval granulous cells (Sem- 
per’s mucous cells) and a few ramose corpuscles of connective 
tissue. To this layer of connective tissue is attached the 
tentacular vessel, with its vibratile cylindric epithelium, 
the cilia of which project into the cavity. As pre- 
viously stated, these minute tentacles are almost con- 
cealed in the elliptic-shaped cavities described above; and 
hence they can hardly serve as locomotory organs, nor, 
being so small, are they, it would seem, adapted for seizing 
prey or conveying food to the mouth. Some function they 
must however have, but what that function is, we are 
unable to state. 
The perivisceral’ cavity, invested. over the whole 
of its surface with vibratile epithelium, is intersected 
by the water-vascular ring, inasmuch: at least as the 
latter constitutes the boundary between the pharyngeal 
