70 



Zooider; de staa tæt sammen, og paa Grenene er det især 

 omkring Polyperne, at de sees tydeligst. Tab. VIII, Fig. 1. b. 



Zoanthodemets anatomisk-histologiske Bygning. 



Stammen og Grenene ere paa den ydre Flade be- 

 klædte med et bredt Ectoderm, der bestaar af flere Lag 

 polyædriske Celler, 0.008""" med en rund. næsten central 

 Kjerne. 0.002""" med Kjernelegeme, Tab. VIII. Fig. 2. a. 

 I de dybere Lag ere Cellerne tildels mere aflange og 

 Protoplasmaindholdet rigere. Imellem Ectodermcellerne 

 sees hist og her næsten pæreformige Celler med et kornet 

 Indhold, encellede Slimkjertler, fuldkommen lig dem, jeg 

 har beskrevet hos Slægten Drifa. I dette tykke Ectoderm- 

 lag ere Spiklerne indleirede, saaledes at hver Spikel er 

 ligesom indkapslet af Ectodermcellerne. Xaar man har 

 fjernet Spiklerne sees dette bedst. idet enhver Spikel efter- 

 lader et tomt Rum i Ejjithelet. Fig. 2. 1. 



I Almindelighed ere i Alcyonidernes ydre Hud Spik- 

 lerne placerede i Bindevevet og dækkede af Ectodermet : 

 men hos Nannodendron er det som paavist helt anderledes. 

 og hvor enkelte Spikler hos denne ligge i Bindevævet, der 

 er Ectodermet forlænget ned i den Bindevæyshulhed, som 

 optages af Spikelen og omgiver denne ganske. Hos denne 

 SLægt synes Spikeldannelsen at være udelukkende afhængig 

 af Ectodermet os er visselig et Produkt af dette. 



Indenfor Ectodermet er et bredt, hvalint Bindevævslag, 

 hvori sees Ernæringskanaler med deres Epithel. Fig. 2. c, 

 samt Bindevævsceller nu-d to eller flere Udløbere, Fig. 2. </. 

 som korrespondere med de finere Nutritionskanaler. Pra 

 dette Bindevævs indre Væg ndgaa en Mængde tykkere 

 eller smalere Forlængelser, der anastomosere med hver- 

 andre og danne, ikke alene de Længde- og Tverkanaler, 

 der udgjøre Coenenchvniet. som her er meget bredt, 

 Fig. 2. e. men ogsaa Hovedkanalerne, hvori Polyperne 

 aabne sig. Det er dette Bindevæv. der udgjør Stokværket 

 i Kolonibygningen. Samtlige Kanaler ere beklædte med 

 et Endothel. dannet af lidt aflange Celler med en næsten 

 rund Kjerne og Kjernelegeme, samt et rigt Protoplasma- 

 indhold. Fig. 2, e. 



I disse Bindevævsforlængelser sees, foruden de alniin- 

 delige Bindevævslegemer, større og mindre Ernærings- 

 kanaler, beklædte med aflange Endothelceller, der ganske 

 udfylde de fineste af dis>e Kanaler, Fis. 2. /. 



close together. and. on the branches. it is especiallv round 

 about the polyps that thev are distinctly observed 

 (Pl. VIII. fig. 1. &). 



Anatomo-histological structure of the Zoanthodem. 



The stem and the branches are clad. on the exter- 

 ior snrface, with a broad ectoderm consisting of several 

 layers of polyhedrical cells measuring 0.008""". and contain- 



ing a round, almost central nucleus, measuring 0.002 , 



with a nucleus body (Pl. VIII, fig. 2, a). In the deeper 

 layers the cells are. partly, more oblong, and the proto- 

 plasmic contents are richer. Between the ectoderm cells, 

 piriform cells are, here and tliere. observed, which contain 

 a granular substance, unicellular mucous glands exactly 

 like those I have described as pertaining to the genus 

 Drifa. In this thick ectoderm-layer, the spicules are 

 entrenched in sueh manner, that each spicule is. as it 

 were. encapsuled by the ectoderm-cells. That is best ob- 

 served when we remove the spicules. because each spi- 

 eule leaves then. behind it. a vacant space in the epithe- 

 lium (Pl. VIII. fig. 2. 6). 



Usually, in the exterior integument of the Alcyonoids, 

 the spicules are placed in the connective-tissue, and are 

 covered l>.\ the ectoderm ; hut in Nannodendron, the case is. 

 as we have shown, quite different; where. in it. a fe w 

 spicules are placed in the connective-tissue, the ectoderm 

 is. tliere. prolonged down into the connective-tissue cavity, 

 which is occupied liv the spicule and quite encompasses 

 it. In. this genus, the spicular formation appears to be 

 exelusivelv dependent on the ectoderm. and is evidentlv 

 its product. 



Inside of the ectoderm, tliere is a broad layer of 

 hyaline connective-tissue in which nutritorv ducts with 

 tlieir epithelium are observed (Pl. VIII, fig. 2, c) also, 

 connective-tissue cells with two or more prolongations 

 (Pl. VIII. fig. 2. d), which correspond with the more 

 minute nutritorv ducts. From the inner wall of this 

 connective-tissue, a multitude of thicker. or narrower. pro- 

 longations proceed; these anastomoze with each other, and 

 form. not only the longitudinal and transversal ducts that 

 compose the sarcosoma, which is. here. very broad (Pl. 

 VIII, fig. 2, e) but, also, the main ducts into which the 

 polyps discharge themselves. It is this connective tissue 

 that composes the framework of the structure of the 

 colony. All of the ducts are clad with an endothelium 

 formed of slightly oblong cells containing an almost round 

 nucleus and nucleus body, and a rich protoplasmic substance 

 (Pl. VIII. fig. 2. e). 



In these connective tissue prolongations, there are 

 observed, besides the usual connective-tissue corpuscles. 

 also, larger, and smaller. nutritorv ducts, lined with oblong 

 endothelial cells that completely fill the minutest of the 

 ducts i Pl. VIII. fig. 2. f). 



