19 



den har en Skivediameter paa 3'" m . har jeg dog ikke 

 kunnet finde Folden hos noget Individ, der har en Skive- 

 diameter under ti'"". Sandsynligvis har de af Lyman om- 

 talte Slægter Ophiocymbhvm og OphiotJiamnus, som ogsaa 

 mangler en ydre synlig Grenitalspalte, en Bygning, der 

 ligner den her omtalte. 



Bursaens histologiske Bygning ligner den hos Ophio- 

 glypha : Flimmerceller har jeg imidlertid ikke kunnet paa- 

 vise hos Ophiopus arcticus, muligens skriver dog dette sig 

 fra, at jeg blot har havt ca. 15 Aar gammelt Spiritus- 

 materiale til mine Undersøgelser. 



Genitalsækkenes Vægge dannes af et Pladeepithel med 

 et indenforliggende tyndt Bindevævslag, hvori Emærings- 

 vædsken cirkulerer. 



Dette Bindevæv er imidlertid saa tyndt. at det kun 

 med stor Vanskelighed lader sig paavise; ofte ser det 

 endog ud. som om det ganske manglede og at Pladeepit helet 

 stod i umiddelbar Forbindelse med Urkimcellerne. Tyde- 

 ligst fremtræder det der. hvor der ligger Æg lige under 

 Genitalsækkens Vægge, og disse er omgivne med et enkelt 

 Tjau Celler. 



De fuldmodne Æg er mere eller mindre ovale og 

 har en Størrelse af indtil 0.224™™, Nucleus maaler 0.064""". 

 Mellem Æggene ligger Urkimcellerne spredte, snart i større 

 eller mindre Partier, snart dannende fuldstændige Follikler 

 omkring Æggene. Medens Holothurierne og Asteriderne 

 ifølge Hamann har et fuldstændigt Follikelepithel, er deri- 

 mod Æggene hos denne Art ligesom hos de øvrige Ophi- 

 urider omgivne af saakaldte Pseudo-Follikler. De er nemlig 

 som oftest kun delvis omgivne af et sammenhængende Celle- 

 lag. saaat store Partier af dem kan komme til at ligge 

 umiddelbart mod hinanden med kun en og anden mellem- 

 liggende Celle (Fig. 17) '). Man kan dog undertiden finde 

 Genitalsække. hvor samtlige Æg er omgivne med et fuld- 

 stændigt Follikelepithel. Ligesom Ophiuriderne har Cri- 

 noideme 2 ) og Echiniderne 3 ) kun Pseudo-Follikler, men 

 ogsaa hos disse kan man stundom fijide Æg med et fuld- 

 stændigt Follikelepithel. 



') Hamann, op. cit. Tab. VI, fig. 3. 



2 ) Danielssen, Crinoida, Norske Nordhavsexpedition, vol. XXI, 

 pag. 18. Tab. IV, fig. 5 & 6. 



3 ) Hamann, op. cit. Heft III, pag. 98. Tab. VI. fig. 10. 



that although Ophiopus arcticus is perfectly capable of 

 reproduction when it has a disc-diameter of 3""", I have 

 been unable to find the fold in anv individual with a 

 smaller disc-diameter than ti""". Probably the genera 

 Ophiocymbium and OphiotJiamnus mentioned hy Lyman. 

 which are also deficient in an outer perceptible genital 

 fissure. have a structure resembling the øne spoken of here. 



The histological structure of the bursa resembles that 

 of Ophioglypha ; I have, however, been unable to observe 

 ciliated cells in Ophiopus arcticus; possibly that is due to 

 the fact that I have only had about 15 years old alcoholic 

 material at my disposal for investigation. 



The walls of the genital sacs are formed of a laminar 

 epithelium. with a thin connective-tissue laver lying inside, 

 in which the nutritory fluid circulates. 



This connective-tissue is. however. so thin that it 

 is only with diifieulty it can be observed; it frequently 

 even appears as if it were entirely al>sent and the laminar 

 epithelium were placed in immediate connection with the 

 original germinative cells. It appears most distinctly at 

 the poiut where ova are situated. right below the walls of 

 the genital sac. and these are enclosed by a single layer 

 of cells. 



The fully mature ova are more or less oval, and are 

 as ■ mucli as 0.224""" in size; the nucleus measures 0.064""". 

 The original germinative cells lie spread between the ova. 

 sometimes in larger or smaller quantities, sometimes form- 

 ing perfect follicles around the ova. Whilst the Holothur- 

 ians and Asterideans have. according to Hamann. a perfect 

 follicular epithelium, the ova, on the contrarv, in this 

 species as well as in the other Ophiurdeans, are sur- 

 rounded by so-called pseudo-follicles. They are, namely. 

 most frequently only partially enclosed by a continuous 

 cellular layer, so that large portions of them may come 

 to lie immediately opposite each other. with only an 

 occasional intermediate cell (fig. 17) : ). We may, however, 

 sometimes find genital sacs where the whole of the ova are 

 enclosed by a perfect follicular epithelium. Just as the 

 Ophiurideans, have the Crinoideans -) and Echinoideans s ) 

 pseudo-follicles only, hut also in these we may occasionally 

 find ova with a perfect follicular epithelium. 



') Hamann, op. cit. Pl. VI, fig. 3. 



2 ) Danielssen, Crinoida, Norske Nordhavsexpedition. vol. XXI 

 pag. 18. Pl. IV, figs. r.&fi. 



3 ) Hamann, op. cit. Heft III, pag. 08. Pl. VI, fig. 16. 



3* 



