54 



m^ 



Fordybninger er en Tentakel fæstet. Alle Spidser staa i 

 lige Afstand fra hinanden med Undtagelse af de paa 

 de 2 før nævnte Kalkstykker siddende dobbelte, hvilke ere 

 noget, skjønt ikke betydeligt, mere nærmede til hinanden 

 indbyrdes end de øvrige. — Ved nærmere Betragtning finder 

 man i Svælgringen af vort Dyr meget tydelige Spor af bi- 

 lateral Symetri. Denne viser sig ikke alene i Tilstede- 

 værelsen af de 2 med dobbelt Spids forsynede Kalkstyk- 

 ker, et paa hver Side af det, sigesom de 7 øvrige, kun med 

 en enkelt Spids besatte midterste dorsale Stykke, men og- 

 saa deri, at disse 3 Stykker, især det midterste, ere lavere 

 eller kortere end de øvrige, hvilke efterhaanden blive høiere 

 jo mere de fjerne sig fra hine, saa at de 2 lige overfor hine 

 beliggende midterste ventrale Stykker (Fig. 9 — 11, v) hvis 

 nederste Rands Indbugtninger derved ogsaa blive dybere 

 end paa de øvrige) næsten have den dobbelte Høide, nemlig 

 1-J- Mm., af hine, af hvilke det midterste kun er J Mm. høit. 

 Den midterste ventrale Længdemuskel er fæstet imellem 

 de 2 høieste Stykker af Svælgringen, hvis laveste Stykker 

 ere dorsale. Disse sidste ligge ogsaa noget længere fortil 

 end hine, idet Ringen er i dens dorsale Del lidt bøiet og 

 derved her mere fremragende end i ventrale. 



Af det Anførte er det klart, at Kalkringen af vort Dyr 

 paa det nærmeste stemmer overens med samme af Myrio- 

 trochus Rinkii efter Lutkens Beskrivelse (Grønlands Echino- 

 dermata p. 22), med Undtagelse af, at den danske Forsker 

 intet nævner om nogen Forskjel i Størrelsen af de Ringen 

 sammensættende Stykker. 



Ambulacralsy steinet s Centraldel bestaar af en Spiserøret 

 omgivende, tæt under eller bag Svælgringen beliggende 

 Ringcanal (Fig. 12, 13, 1), hvis Omrids er noget bugtet i 

 Form af en Polygon, og det som det syntes en 8kantet, 

 dog med ulige store Sider; Polygonens stumpt afrundede 

 Hjørner ere fæstede til Kalkringens bageste Rand, men 

 dens Sider ere frie og indbugtede samt indleirede i Mund- 

 skivens Bindevævslag. Fra Ringcanalens forreste eller 

 øverste Flade udgaa 12 blinde Forlængelser ind i Tentak- 

 lerne, hvis Hule de beklæde. Ambulacralkar fattes ligesom 

 hos alle Synaptider. Fra den bageste Flade af Ringcana- 

 len, lige indenfor en af de 5 Længdemuskler, hænger en 

 eneste, anselig (omtrent 3 Mm. lang), efter dens forskj el- 

 lige Contractionsgrad snart naskeformig snart kølledannet, 

 hyalin (med enkelte brune Pigmentpunkter i dens Endedel 

 besat) Polisk Blære (Fig. 12, 13, p) frit ind i Kroppens Hule, 

 samt en tæt ved eller i det dorsale Mesenterium siddende 

 liden (lidt over \ i Diameter holdende) opak hvid Madre- 

 portuberkel (Fig. 12, r), (som indeholdt en blød, ikke synlig 

 kalkagtig Masse) baaren paa en kort cylindrisk, hyalin Stilk 

 (Stencanalen), ligeledes frit fremragende. Hos nogle Indi- 

 vider var der endnu en eller endog to mindre Madrepor- 

 tuberkler (Fig. 13 r, r) i nogen Afstand paa den ene eller 

 begge Sider af den første. 



and in each of these depressions there is attached a ten- 

 tacle. All the points are equidistant excepting the double 

 points on the 2 calcareous pieces before mentioned, which 

 are somewhat, although not considerably, nearer to each 

 other than the others. On closer examination we find in 

 the calcareous ring of our animal very evident traces of 

 bilateral symmetry. This symmetry appears not only in 

 the presence of the 2 double-pointed calcareous pieces one 

 on each side of the middle dorsal piece, which, like the 7 

 others has only one point — but also in these 3 pieces 

 especially the middle one, being lower or shorter than the 

 others, which latter gradually become higher the further 

 they recede from the former; so that the 2 middle ventral 

 pieces (üg. 9—11 v.) (the lower marginal sinuosities of 

 which thereby become deeper than those of the others) 

 are nearly twice as high as the middle dorsal, namely II 

 Mm., the central dorsal piece being only J Mm. high. The 

 medial ventral longitudinal muscle is attached between the 

 2 highest pieces of the calcareous ring, the lowest pieces 

 of which are dorsal. These lowest dorsal pieces are also 

 somewhat more in front than the others; the ring being a 

 little bent forward in its dorsal part, which therefore projects 

 beyond the ventral part. 



From what has been said it is evident that the calca- 

 reous ring of our animal corresponds most closely with the 

 ring of Myriotrochus Rinkii according to Liitken's descrip- 

 tion (Grønlands Echinodermata p. 22) excepting that the 

 Danish naturalist does not mention any difference in the 

 size of the pieces of which the ring is composed. 



The central part of the ambulacral system consists of 

 an annular canal (fig. 12, 13, 1) encircling the esophagus 

 close under or behind the calcareous ring; the outline of 

 this canal being somewhat bent in the form of a polygon, 

 and apparently 8-sided, but with sides of unequal length. 

 The obtusely rounded angles of rhe polygon are attached 

 to the posterior margin of the calcareous ring; but its 

 sides are free and curved invards and also imbedded in 

 the layer of connecting tissue of the oral disc. From the 

 anterior or upper surface of the circular canal, there issue 

 12 cæca-like continuations entering into the tentacles and 

 lining their cavity. The ambulacral vessel is wanting as 

 in all Synaptidæ. From the posterior surface of the cir- 

 cular canal, just to the inside of one of the 5 longitudinal 

 muscles, there hangs a single ambulacral vesicle (vesicle of 

 Poli) (fig. 12, 13, p) of considerable size (about 3 Mm. 

 long) in the cavity of the body. This vesicle is, according 

 to its different degrees of contraction, sometimes bottle- 

 shaped, sometimes club-shaped, and hyaline (with isolated 

 brown pigmentary points at its extremity; and close to it, 

 or in the dorsal mesentery, there is a small (rather more 

 than V 3 Mm. in diameter) opaque white Madrepoic tubercle 

 (fig. 12, r) which contains a soft, white, not percep- 

 tibly calcareous mass and is supported on a short cylin- 

 drical hyaline stalk (the stone canal) also projecting freely. 

 In some specimens there appeared one or even two smaller 

 Madreporic tubercles (fig. 13 r, r) at some distance on one 

 or on both sides of the former. 



