52 



i de medusoide Gouoforer angaar, stemmer mine Eesul- 

 tater luldstændig overens med War/ners. Jeg skal dog 

 give en kort fremstilling af Gonoforernes Anatomi, og her- 

 under paca enkelte Punkter supplere Wagners. 



Gonoforerne, der i sin ydre Form ligner en Kegle, 

 eller kanske heller eu firkantet Pyramide, der staar fæstet 

 med Spidsen nedad, viser i sit Indre alle en Meduses 

 Organer, men i en saadan Form, at jeg anser det for 

 sikkert, at Medusen aldrig løsriver sig. Man finder saa- 

 ledes et fuldstændigt Kanalsystem — fire Radialkanaler og 

 Eingkanal, — men disse Kanalers Vægge er saa sterkt 

 fortykkede, at deres Hulrum l)lir forsvindende; dette gjælder 

 især Ringkanalen, men ogsaa Radialkanalerne viser sig ofte 

 paa Snit ikke som Kaualer, men som Fortykkelse af Gono- 

 forernes Vægge, idet Entodermlaget paa deres sulirumljrale 

 Side er saa sterkt udviklet, at det fylder Kanalen og sam- 

 tidig ogsaa rager frem i Klokkehulrummet. Fig. 2 b viser 

 et af de faa Snit, paa hvilke en Eadialkanal tydelig til- 

 kjendegiver sig som saadan. Den subumbrale Ektoderm 

 danner langsetter Radialkanalerne en næsten cylinderformet 

 List, der tjener som Stotte for Generationsorganerue, og 

 fra hvilken den tynde Hinde udvikles, der omgiver disse. 

 Hermaphroditisme forekommer ikke; men man finder Indi- 

 vider af begge Kjøn forenede i en og samme Koloni. 

 Generationsstofferne ligger, som ovenfor nævnt, langs Radial- 

 kanalerne, i 8 Sække, der parvis er forbundet ved de om- 

 talte Ektodermlister. 



Manubriet er kun rudimentært, findes som en liden 

 Knap helt nede i Gonoforernes Stilk. Det undgik Meresch- 

 JiOivshjs Opmerksomlied, medens War/iicr har seet det og 

 givet en Afbildning af det (Tab. IX, Fig. 14). Da denne 

 Afbildning imidlertid ikke gir noget klart Indtryk af Manu- 

 briets Stilling og Størrelse i Forhold til Gonoforen, sup- 

 plerer jeg den med en anden (Fig. 2 c), udført efter et 

 Længdesnit, og som viser, at Manubriet kun findes som 

 en liden Udbugtning nede i Gonoforernes smaleste Del, 

 og at det ikke engang rager op til det Sted, som man, 

 efter den ydre Form at dømme, vil betragte som Over- 

 gangen mellem Stilk og Gonofor. 



Monobrachiums medusoide Gonoforer hører efter sin 

 Bygning til Lept om cd i iser ne. idet Generationsorganerue har 

 sin Plads langs Radialkanalerne og ikke paa Manubriet; 

 og dette anviser dem en Plads i Systemet paa Grænsen 

 mellem de athecate og de thecate Hydroider, paa samme 

 Tid som dens eiendommelige Bygning, baade hvad Hydranth 

 og Gonofor angaar, holder den i Afstand fra de øvrige 

 kjendte Familier af begge disse Grupper. 



Pindested. St. 374. 



structure of the colonies, and the arrangement of the organs 

 in the medusoid gonophores, agree in every particular witli 

 those of Wagner. I shall, however, give a short descrip- 

 tion of the gonophores, and in so doing supplement Wagners 

 description on certain points. 



In external appearance, the gono^jhores resemble a 

 cone, or rather a quadrilateral pyramid standing upon its 

 apex, while internally it exhibits all the organs of a 

 medusa, but in such a form. that I regard it as certain 

 that the medusa never becomes detached. There is, for 

 instance, a complete canal system — 4 radial canals and 

 a ring-canal — but tlie walls of these canals are so greatly 

 tliickened, that their cavity almost disappears. This is 

 especially the case with the ring-canal, but the radial 

 canals often appear in section not like canals, but like a 

 thickening of the walls of tlie gonophore, as the endo- 

 dermal layer on their subumbral side is so greatly deve- 

 loped that it fills the canal and also projects into the bell- 

 cavity. Fig. 2 b shows one of tlie few sections in which 

 a radial canal distinctly appears to be what it really is. 

 The sub-umbral ectoderm forms an almost cyliudrical fillet 

 along the radial canals, which serves as a support for the 

 generative organs, and from wiiieh tiie thin memlirane sur- 

 rounding them is developed. Herma[)hrodites do not occur, 

 l)ut persons of both sexcs are found united in one colony. 

 The generative organs, as already stated, lie beside the 

 radial canals in 8 rows united in pairs by the above men- 

 tioned ectodermal fillets. 



The manubrium is only rudimentary, and is visible 

 as a small Imd at the bottom of the gonophore's stem. 

 It cscaped Merc-<diJ:oicsky's observation, whereas Wagner 

 saw it, and has given an illustration of it (Pl. IX, fig. 

 14). As, however, this does not give a clear idea of the 

 ])osition and relative size of tlie manubrium, I supjilement 

 it with another (fig. 2 c), made from a longitudinal section, 

 which shows that the manubrium is only like a little swel- 

 ling on the narrowest part of the gonophore, and does 

 not even reach up to the place which. from its external 

 shape, would appear to be the transition from stem to 

 gonophore. 



From their structure, the medusoid gonophores of 

 Mo)iohracJiiiiin belong to the Lcpio-medusæ. the generative 

 organs being situated beside the radial canals, and not 

 on the manubrium. This gives it at place in the system 

 upon the boundary line hetween athecate and the thecate 

 hydroids, while the 23eculiar structure of both hydranth and 

 gonophore separates it from the other already known fami- 

 lies of these two groujis. 



Locality. Station 374. 



