70 



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

 omkring Polyperne, at de sees tydeligst, Tab. VIII, Fig. 1, 6. 



Zoanthodemets anatomisk-histologiske Bygning. 



Stammen og Grenene ere paa den ydre Made be- 

 klædte med et bredt Ectoderm, der bestaar af flere Lag 

 polyædriske Celler, 0.008 m '" 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. Naar man har 

 fjernet Spiklerne sees dette bedst, idet enhver Spike! efter- 

 lader et tomt Rum i Epithelet, Fig. 2. b. 



I Almindelighed ere i Alcyonidernes ydre Hud Spik- 

 lerne placerede i Bindevævet og dækkede af Ectodermet; 

 men hos Nannodendron er det som paavist helt anderledes, 

 og hvor enkelte Spilder hos denne ligge i Bindevævet, der 

 er Ectodermet forlænget ned i den Bindevævshulhed, som 

 optages af Spikelen og omgiver denne ganske. Hos denne 

 Slægt synes Spikeldannelsen at være udelukkende afhængig 

 af Ectodermet og er visselig et Produkt af dette. 



Indenfor Ectodermet er et bredt, hyalint Bindevævslag, 

 hvori sees Ernæringska naler med deres Epithel, Fig. 2, c, 

 samt Bindevævsceller med to eller flere Udløbere, Fig. 2, d, 

 som korrespondere med de finere Nutrition skanaler. Fra 

 dette Bindevævs indre Væg udgaa en Mængde tykkere 

 eller smalere Forlængelser, der anastomosere med hver- 

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

 der udgjøre Coenenchymet, som her er meget bredt, 

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

 aabne sig. Det er dette Bindevæv, der udgjør Stokværket 

 i Kolonibygnirigen. 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 almin- 

 delige Bindevævslegemer, større og mindre Ernærings- 

 kanaler, beklædte med aflange Endothelceller, der ganske 

 udfylde de fineste af disse Kanaler, Fig. 2, /. 



close together, and, on the branches, it is especially round 

 about the polyps that they are distinctly observed 

 (Pl. VIII, fig. 1, 6). 



Anatomo-histological structure of the Zoanthodem. 



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

 ior surface, 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. Till, 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 there, 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 such 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- 

 cule leaves then, behind it, a vacant space in the epithe- 

 lium (Pl. VIII, fig. 2, b). 



Usually, in the exterior integument of the Alcyonoids, 

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

 covered by the ectoderm ; but in Nannodendron, the case is, 

 as we have shown, quite different; where, in it, a few 

 spicules are placed in the connective-tissue, the ectoderm 

 is, there, prolonged clown into the connective-tissue cavity, 

 which is occupied by the spicule and quite encompasses 

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

 exclusively dependent on the ectoderm, and is evidently 

 its product. 



Inside of the ectoderm, there is a broad layer of 

 hyaline connective-tissue in which nutritory ducts with 

 their 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 nutritory 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, nutritory ducts, lined with oblong 

 endothelial cells that completely fill the minutest of the 

 ducts (PL VIII, fig. 2, /). 



