34 
egentlige Kanal taber sig, Fig. 7, c. Stenkanalen dannes 
af en meget bred Bindevævsskede, hvori er afsat en Mængde 
Kalk; selve Kanalen bestaar af et fastere Bindevæv, der 
er uden Kalk. å AR 
Farven bleg rosenrød med brunlige Tentakelblade. 
Stat. 270. 
Med Hensyn til Oligotrochus vitreus, saa maa vi til- 
staa, at vi i længere Tid have været 1 Tvivl om, hvorvidt 
den kunde opretholdes som særegen Slegt; men af Mangel 
paa tilstrækkeligt Sammenligningsmateriale maatte vi lade 
Afgjørelsen staa hen til en gunstigere Tid. Denne kom, 
idet vi fra Nordhavsexpeditionen blev forsynet med en stor 
Mængde Exemplarer af Myriotrochus Rink og et velkon- 
serveret Exemplar af Huxleys Myriotrochus (Chirodota) 
brevis. 
Vi tog. nu fat paa at undersøge Oligotrochus vitreus, 
og fandt, at de Kjendetegn, der skulde karakterisere Slæg- 
ten, faldt fuldstændig sammen med dem, der tilhøre Myrio- 
trochus. Hjulene ere vistnok ikke stilkede; men paa de 
Exemplarer, vi have undersøgt, ere de tilstede 1 ligesaa 
stor Mængde som hos Myriotrochus. Ligesom Tilfældet er 
«hos denne, at Bugfladen kan stundom være ganske fri for 
Hjul, og altid, naar de findes der, ere de yderst sparsomme, 
— saaledes forholder det sig ogsaa hos Oligotrochus. 
Har altsaa Sars undersøgt mest Bugfladens Hud, saa 
lader det sig forklare, hvorledes det er gaaet til, at han 
har fundet saa faa Hjul. Denne Omstændighed 1 Forening 
med at Hjulene vare stilkløse, har motiveret Sars til at 
opstille en ny Slægt. Men, som vi have seet, har M. bre- 
vis heller ikke stilkede Hjul, hvilket Sars dengang ikke 
kjendte til. Selv vaklede han imellem at danne en ny 
Slægt, eller at henføre den til Steenstrup's Myriotrochus; 
men han bestemte sig til det Første. Vi have ikke fundet, 
hverken i de ydre eller i de anatomisk-histologiske Kjende- 
tegn, Noget der kan adskille den fra Myriotrochus, og vi 
ere saaledes nødsagede til at mddrage Slægten Oligotrochus. 
Hvad nu Arten angaar, saa falder den ganske sam- 
men med Myriotrochus brevis. At Sars dengang antog den 
for at være forskjellig fra Rink, var jo 1 sm Orden, og 
da han ikke har kjendt Huxley's Ohirodota brevis, saa faldt 
det af sig selv. at han gav den et nyt Navn. Men efter 
de Undersøgelser, vi have anstillet over Oligotrochus ‘vitreus, 
I 
calcareous spicules give a rough surface, the canal itself 
coalesces, fig. 7, c.. The sand-canal is enclosed in an ex- 
ceedingly broad sheath of connective tissue, strengthened 
by an abundance of calcareous deposit; the canal itself 
consists of connective tissue, firm in texture but without 
calcareous deposit. . 
Colour a pale rosy red; the tentacular pinnæ brownish. 
Station 270. 
We must confess we have long felt very doubtful as 
to whether Oligotrochus vitreus would in the end be found. 
to constitute a separate genus; but the materials before us 
being insufficient for pronouncing a decided opinion, we 
deemed it. best to defer our judgment till a more favourable 
opportunity should enable us to institute conclusive obser- 
vations. Nor did we wait in vain; for on the return of 
the North-Atlantic Expedition, numerous examples of Myrio- 
trochus Rinkii and a well-preserved specimen of Huxley's 
Myriotrochus (Uhirodota) brevis were submitted to us for 
examination. 
We forthwith renewed our observations on Oligotro- 
chus vitreus, and were not surprised to find, that the cha- 
racters said to distinguish the genus do not m any respect 
differ from those of Myriotrochus. True, the wheel-shaped 
spicules are not pedunculate; but in the specimens we have 
examined: they are as numerous as in Myriotrochus. And, 
as is the case with the latter, the ventral surface in Oli- 
gotrochus has sometimes not a trace of these spicules, 
which, when they do occur there, are always very sparingly 
distributed. 
Supposing, then, that Sars confined his observations 
chiefly to the integument of the ventral surface, the fact 
of his haying found so few wheel-shaped spicules is at 
once accounted for. It this paucity of spicules 
in conjunction with ,their non-pedunculate character that 
induced Sars to establish a new genus. But neither are, as 
we have seen, the wheel-shaped spicules in M. brevis pedun- 
culate, a feature of which Sars was at that time ignorant. 
Was 
Nay, he himself wavered between establishing a new spe- 
cies or referring the animal to Steenstrup’s Myriotrochus ; 
but the balance dipped in favour of the former alternative. 
Neither in the exterior nor in the anatomical-histological 
characters have we lighted on any generically distinctive 
feature which it does not share with Myriotrochus; and 
hence the genus Oligotrochus should, we opine, be no longer 
retained. 
And as regards the species, it agrees in every respect 
with Myriotrochus brevis. In deeming it specifically distinct 
from Rinkii, Sars is found to have been quite correct, and 
as Huxley’s Chirodota brevis was unknown to him, it was 
but natural he should give it a new name. But, ac¢ording 
to our observations Oligotrochus vitreus and Myrvotrochus 
