98 



Unger, etterat de have forladt Moderen, kan jeg ingen 

 Besked give; thi jeg har ikke kunnet følge dem saa langt. 

 Men Kowalevsky og Marion have iagttaget, at Ungerne hos 

 de Arter, de have observeret, altid satte sig fast ved den 

 brede|Ende, som de forresten vare tilbøielige til at antage 

 for Ungens Hovedparti (region eéphalique), naar de toge 

 Hensyn til den Maade, paa hvilken den bevægede sig, 

 nemlig altid ' med den brede Del foran. De angive ikke, 

 at der i den brede Ende var en Mundaabning, men tvert- 

 imod, at Mundaabningen dannede sig i den smale Del, forst 

 etter at Ungerne havde fæstet sig. Dersom de af mig iagt- 

 tagne Unger skulde fæste sig ved den brede Ende, maatte 

 Larvemunden forsvinde og en ny Mund dannes, en For- 

 vandling, der jo ikke er fremmed for de lavere Dyr, men 

 endog temmelig almindelig hos de fra (Joelenteraterne 

 ikke saa fjernt staaende Echinodermer. De nysnævnte 

 Forskeres Udtalelser med Hensyn til Befæstningsmaade 

 staar forresten i Strid med Kowalevsky's tidligere gjorte 

 Iagttagelser over Udviklingen af Sympodium coralloides; 

 thi i hans Athandling: ,,Zur Entwickelungsgescb.icb.te der 

 Aleyoniden" l udtrykker han sig saaledes: „Wåhrend der 

 Verwandlung heftet sich die Larve bekanntlich mit ihrem 

 vorderen zugespitzten Ende an und ziebt den hinteren 

 mehr ausgebreiteten Pol ein, wobei aus demselben der 

 Magen entstebt." — Jeg er dog tilbøielig til at antage, at 

 mine Larver fæster sig ved den smale Ende, at Larve- 

 munden bliver permanent, og at, idet den tidligere omtalte 

 In dkrængning af Ectodermet forlænger sig og danner Svæl- 

 get, læste Skillevæggene (Mesenterierne) sig paa dette. Jeg 

 paaviste, at i et temmelig fremrykket Larvestadium udgik 

 der fra Mavehulheden en Mængde listeformige Forlængelser : 

 de begyndende Mesenterier. Enten smelter flere af disse 

 sammen, eller flere af dem forsvinde (absorberes), saa at 

 Antallet bliver det regulære, nemlig 8. Det er jo netop i 

 Larvens brede Ende, at disse Skillevægge optræde, og det 

 tør ogsaa af den Grund være antageligt, at Ungen fæster 

 sig ved den smale Ende og altsaa ikke undergaar den 

 Metamorphose, som vikle være Tilfældet, om Befæstelsen 

 skede ved den tykke Del (Hoveddelen). 



Det er ganske mærkeligt, at Spikeldannelsen hos 

 disse Arter optræder saa overordentlig tidligt, længe før 

 Larven har forladt Ægget, hvilket ikke tidligere har været 

 observeret; thi ifølge Kowalevskys og Marions Iagttagelser 

 indtræder Spikeldannelsen, først efter at den fritsvømmende 

 Unge har sat sig fast. Men den Omstændighed, at Spik- 

 lerne optræde saa tidligt hos den i Ægget indesluttede 

 Larve, kort Tid efter Ectodermet er dannet, og førend 

 nogen Antydning til Bindevæv kunde iagttages er, saa 

 forekommer det mig, et stærkt Bevis for, at Spiklerne ere 

 Produkter af Ectodermeellerne og ikke af Bindevævet. 



Zoologischer Anzeiger. '_' Jahrg. pag. 491. 



young ones, after they have abandoned the parent animal, 

 is a subject upon which I can give no information, as I 

 have been unable to follow them so far. But Kowalevsky 

 and Marion have remarked, that the young of the species 

 which they have observed always became adberent by 

 the broad extremity, which, however, they were disposed 

 to assume to be the cephalic part of the young one (region 

 eéphalique), wben they regarded the manner in which it 

 moved itself, that is. always with the broad extremity in 

 advance. They do not state that there was an oral aperture 

 in the broad extremity lint. on the contrary, that the oral 

 aperture was iormed in the narrow part, and not till after the 

 young ones had secured tbemselves tast. If the young 

 ones, observed by me, were to secure themselves fast by 

 the broad extremity, the larva mouth would necessarily dis- 

 appear and a new mouth be forined, a change which, indeed, 

 is not unknown in tbe lower animals, but is, even, rather 

 common in the JEchinodermata, not so very distantly related 

 to the Coenteralata. The report ni' the Naturalists just 

 named. with reference to the mode of attachment stands. 

 however, in opposition to the observations previously made 

 by Kowalevsky, on the development of Sympodiwm coral- 

 loides, because in his Memoir ,,Zur Entwickelungsgeschichte 

 der Aleyoniden" 1 be tims expresses himself. ..Wahrend der 

 „ Verwandlung heitet sich die Larve bekanntlich mit ihrem' 

 „vorderen zugespitzten Ende an und zieht den hinteren" 

 ..mehr ausgebreiteten Pol ein, wobei aus demselben der" 

 „Magen enststeht." 1 am, however, disposed to assume that 

 my larvæ fasten themselves by the narrow extremity, and 

 that the larva mouth is permanent; further, that whilst the 

 depression in the ectoderm, previously spoken of, beeomes 

 prolonged and forms the gullet, the divisional walls (Mesen- 

 teries) secure themselves to it. 1 showed that, in a tol- 

 erably advanced larva-stage, there proceeded from the ven- 

 tral eavity a number of fillet-formed prolongations - the 

 rudimentary mesenteries. Either, several of these jiass 

 into eaeh other, or several ut' them disappear (an' absorbed) 

 so that the number beeomes the usual one, that is 8. It 

 is just in the broad extremity of the larva that these 

 divisional walls appear, and it may, for that reason, be 

 presumed that the young one tastens itself by the narrow 

 extremity and, therefore, does not undergo such a meta- 

 morphosis as would be the case if the attachment was 

 made by the thick part (the cephalic part). 



It is cpiite remarkable that the spicular formation in 

 these species appears sd extremely early, long before the 

 larva has abandoned the ovum, a taet which has not been 

 previously observed; according te Kowalevsky and Marions 

 observations. the spicular formation does not appear, till 

 after the freelv-swimming young one has secured itself fast. 

 But tire circumstance that the spicules appear so early in 

 the larva enclosed in the ovum, a sbort time after tin 1 form- 

 ation of the ectoderm, and previous to a ny indication of 

 conneetive-tissue being observed is, it appears to me, a 

 strong proof that the spicules are products of the ectoderm 

 cells. and not of the conneetive-tissue. 



Zoologischer Anzeiger. '-' Jahrg., pag. 401. 



