18 



Xogen nærmere Undersøgelse af dette mærkelige For- 

 hold, er saavidt vides, endnu ikke foretagen; det maa dog 

 bemærkes, at Lyman, efter at have omtalt Sars*s An- 

 givelse, tilfoier: ,.An observer is apt to take the erease in 

 the disk. elose to the arm, for a true opening, while there 

 may be none at all - '. Hvem Lyman her sigter til. hal- 

 det desværre ikke været muligt at faa Rede paa. 



De af mig undersogte Exemplarer viste folgende : 

 Hos alle mindre Exemplarer, selv om de havde fuldt ud- 

 viklede Kjonsprodukter, var det ikke muligt at opdage 

 nogen Genitalspalte selv med den stærkeste Loupeforstør- 

 relse; Forholdet svarer saaledes ganske til det af Sårs 

 iagttagne. Hos ældre Exemplarer med en Skivediameter 

 af 6'"'" sees derimod undertiden en fin Spalte eller rettere 

 en Fold, svarende til de ovrige Ophiuriders Grenitalspalte; 

 det er muligens denne Fold ovennævnte „observer - ' har 

 iagttaget og tåget for ,.a true opening". 



Yi har her imidlertid ikke nogen Aabning for os', 

 den viser sig nemlig under Loupen at være lukket og ikke 

 at staa i Forbindelse med de indenfor liggende Organer. 

 Som senere skal vises, maa Folden nærmest betragtes som 

 en Ardannelse efter tidligere Udtømmelser af Generations- 

 produkterne. Denne Fold er imidlertid ikke karakteristisk 

 for alle ældre Individer, meget ofte mangler ogsaa de den 

 ganske. 



Snittes et Individ op i Vertikalsnit, tinder man ved 

 Armene en Bursa, som ender blindt og som paa sin ydre 

 Flade er forsynet med talrige Genitalsække, der er fyldte 

 med Æg i forskjellige Udviklingsstadier; det Billede, man 

 saaledes faar, ligner ganske det. Ludwig l ) og Hamann -') 

 giver af Generationsorganernes Bygning hos Ophioglypha, 

 Amphiura ete. Hvad der imidlertid adskiller < >phii>ptts 

 arctic/is fra dem, er at dens Bursa ogsaa er lukket udad- 

 til; et tyndt Cellelag, som synes at skrive sig fra Krops- 

 væggens Pladeepithel, dækker nemlig Genitalspaltens ydre 

 Munding (Fig. 15; Snittet har truffet Bursaens Væg, 

 saaat kun den nederste Del af denne kan sees, ligeledes 

 er kun mindre Dele af et Par af Ægkapslerne synlige 

 paa Tegningen). 



Naar Generationsprodukterne er blevne modne, ud- 

 tommes de paa normal Maade 'i Bursaen, hvorpaa de, 

 hvis de skal kunne blive frie og udvikle sig, maa bryde 

 sig Yei gjennem det Cellelag, der dækker Genitalspalten. 

 Efter Udtommelsen voxer saa Genitalspalten igjen til; 

 men har dette gjentaget sig nogle Gange, er det klart, at 

 der vil opstaa en Ardannelse paa Gjennembrudsstedet og 

 den ovenfornævnte Fold fremkommer. Hvad der synes at 

 støtte den Antagelse, at Folden er en Ardannelse, er, at 

 skjont Ophiopus arctieus er fuldt forplantningsdygtig. naar 



') Beitrage zur Anatomie der Ophiuren, Zeitschr. f. wiss. Zool., 



Bd. XXXI, pag. : ; !T4. 

 "-) Beitrage zur Histologie der Eehinodermen, Heft IV, pag. 44. 



Anv minute investigation of this remarkable relation 

 has, so far as is known. not yet been undertaken; 

 it must. however, be noted that Lyman, after having 

 mentioned Sars's report, adds. "An observer is apt to take 

 the erease in the disk, elose to the arm, for a true open- 

 ing. while there may be none at all". To whom Lyman 

 in that remark refers, it has unfortunately not been pos- 

 sible to obtain anv enlightenment. 



The specimens investigated by me showed the follow- 

 ing features: in all the smaller species, even although they 

 eontained f uliv developed sexual products, it was impos- 

 sible to discover any genital fissure, even with the most 

 powerful magnifying glass; the relation quite corresponds 

 therefore with what has been observed by Sårs. In older 

 specimens with a disc-diameter of ti""" there is, on the 

 ut her hand, occasionally observed a fine fissure, or more 

 correctly a fold, corresponding to the genital fissure in the 

 other Ophiurideans; it is. possibly, that fold the above- 

 named "observer" has remarked and assumed tu be "a true 

 opening". 



We have, however. here no opening before us; it is 

 seen. namely. under the magnifier. to be closed, and not to 

 stand in connection witli the organs lying inside. As shall 

 subsequently he shown. the fold must chietiv be considered 

 tu lic ;i scar-formation, following upon previous evacuation of 

 the reproductive products. This fold is ; however. not 

 characteristic of all older individuals, very frequently they 

 are entirely deficient in it. 



If an individual is cut up in vertical section. wc tind 

 at tlie arms a bursa, which terminates blindly, and is fur- 

 nished mi its nuter surface with numerous genital-sacs 

 filled witli ova in various stages of development; the 

 picture we thus obtain resembles exactly that given hy 

 Ludwig 1 ) and Hamann-) of the structure of the repro- 

 ductive organs in Ophioglypha, Amphiura&c. What. how- 

 ever, distinguishes Ophiopus «rettens from tliem is. that 

 its bursa is also closed ontwards; a thin layer of cells, 

 which appear to be derived from the epithelial plate of 

 the wall of the body. covers, namely, the outer aperture 

 of the genital fissure (fig. 15; the section has struck the 

 wall of the bursa, so that only its lowest part can he 

 viewed ; likewise there can only be seen on the drawing, 

 small portions of a couple of the ova-capsules). 



When the reproductive products have become mature, 

 they are evacuated in the normal way into the bursa; 

 thereafter they must. in order to become free and develope 

 themselves, force a way through the cellular laver that 

 covers the genital fissure After the evacuation, the genital 

 fissure grows together again. but when that has been 

 repeated a few times it is evident that a scar-formation 

 will arise at the point of rupture, and the ahove-named 

 fold will be produced. What appears to support the as- 

 sumptinn that the fold is a scar-formation is the fact, 



') Beitrage zur Anatomie der Ophiuren, Zeitschr. f. wiss. Zool., 



Bd. XXXI, pag. :!T4. 

 '-) Beitrage zur Histologie der Eehinodermen, Heft I\ , pag. 44. 



