15 



ducere Medusegemmer, hvilke, bestemte til at løsrive sig 

 fra Amme dyret for at føre et selvstændigt Liv, derfor 

 udrustedes med en til saadan Levemaade svarende fuld- 

 komnere Organisation, — De af C. glacialis opammede 

 Medusegemmer derimod ere og blive sessile d. e. de løsne 

 sig aldrig, men forblive i continuerlig Forbindelse med 

 deres Ammedyr. Derfor ere de ogsaa langt simplere orga- 

 niserede. De have vel den almindelige Meduseform, den 

 klokkeformige Kappe og den ind i dennes Hule fremra- 

 gende Mave (Manubrium); men Kappen er overalt tilsluttet, 

 saaledes som den er hos hine alene paa et tidligere Ud- 

 viklingstrin, uden Tentakler (Randtraade), det hele Kar- 

 system fattes ganske, og endelig mangle de al eiendom- 

 melig Bevægelse. 



De ere altsaa yderst ufuldkomment organiserede Me- 

 duser, og ligne saaledes ganske de hos mange Coryneer, 

 Tubularier og Sertularier forekommende saakaldte "Gene- 

 rationskapsler", hvilke længe af Zoologerne holdtes for 

 Organer og navnlig Kjønsorganer, men nu almindelig aner- 

 kjendes som Kjønsdyr, ufuldkomne Meduser eller den 

 anden Generation af alle disse Generationsvexelens Lov 

 underkastede Dyr. 



Vi gaa nu over til den nærmere Beskrivelse af disse 

 Medusegemmer hos vort Dyr. 



De ere af tvende Slags, mandlige og kvindelige. Vor 

 Corymorpha, det isoleret levende Ammedyr, producerer 

 altid kun Medusegemmer af clet ene Kjøn. Det samme, 

 vide vi, finder ogsaa Sted hos alle til Colonier forenede 

 Hydroider, hvor Kjønnene altid ere fordelte paa forskjel- 

 lige Colonier. 



Begge Slags Gemmer ligne hinanden meget; dogere 

 de mandlige (Tab. 2, Fig. 9—13) i udviklet Tilstand sæd- 

 vanlig mere langstrakte eller elliptiske (Fig. 12, 13), de 

 kvindelige (Fig. 5 — 7) derimod noget kortere og mere 

 bugede eller ovale. I meget ung Tilstand (Fig. 4, a', 

 Fig. 10) ere Kjønnene ikke til at adskille. Disse frem- 

 spirende unge Gemmer ere nemlig ovale, den gjennem- 

 sigtige svagt rødlige Kappe ligger tæt til den store ellip- 

 tiske opakrødlige Mave (&), og Stilken (s), med hvilken 

 de ere fæstede, er tykkere end den senere bliver; endelig 

 er Kappens ydre Ende altid simpelt tilrundet. — Hos de 

 udviklede Gemmer, hvis Kjøn let kan erkj endes af deres 

 Indhold, bemærker man paa den ydre Ende af Kappen 4 

 meget smaa, undertiden, og som det synes hos de mand- 

 lige Gemmer (Fig. 12, 13), mindre tydelige, rundagtige 

 eller coniske lave Knuder, mellem hvilke der, naar Gem- 

 merne ere komne til fuld Modenhed, dannes en Aabning 

 (Fig. 5, 6, q) for Udtømmelsen af Kjønsstofferne. 



Mellem den gjennemsigtige dobbelt conturerede Kappe 

 (af Allman kaldet Ectoderm), som har udviklet sig bety- 

 deligt (Fig. 5 — 7, p), og den ved Kappens Væxt tilsyne- 

 ladende mindre blevne, nu mere cylindriske opakrødlige 

 Mave (&) (Endoderm Allman), er der nu et stort Hulrum, 

 (som svarer til Svømmehulen hos de frie Meduser), og i 

 dette er det at Kjønstofferne dannes, i de kvindelige 



which all produce gonozooids destined to disconnect 

 themselves from the parent animal and to lead an inde- 

 pendent life, and therefore furnished with a perfect orga- 

 nisation corresponding to such a mode of life. The 

 gonozooicls reared by the C. glacialis are, and remain 

 sessile, i. e. they never loosen themselves, but continue 

 in connexion with their parent animal. Therefore they 

 are much more simply organised. They have indeed the 

 usual medusa form, the bell-shaped umbrella, and the 

 prominent stomach (manubrium) enclosed in its cavity; 

 but the umbrella is everywhere closed — as in an earlier 

 stage only of the species previously described. They are 

 without tentacles (marginal filaments) entirely without 

 any vascular system, and finally they are without any 

 peculiar movement. 



They are therefore very imperfectly organised medusæ, 

 and resemble entirely the so-called "generative capsules" 

 occurring in many of the Corynidæ Tubulariidæ and Ser- 

 tulariidæ, which were for a long time considered by the 

 zoologists as organs, and particularly sexual organs, but 

 are now generally recognised as sexual animals, imperfect 

 medusæ or the secondary generation, all these animals 

 being subject to the law of alternate generation. 



We now proceed to describe more minutely these 

 gonozooids in our animal. 



They are of two sorts, male and female. Our Cory- 

 morpha, the isolated living parent, produces always gono- 

 zooids of one sex only. We know that the same takes 

 place also in all Hydroids united in colonies, where the 

 sexes are always distributed in different colonies.. 



Both sorts of gonozooids resemble each other very 

 much; but the males (Tab. 2, fig. 12 — 13) are, when fully 

 developed, usually more elongated or elliptical (fig. 12 — 

 13); the females (fig. 5 — 7) are somewhat shorter and 

 more swollen or oval. In a very young state (fig. 4, a', 

 üg. 10) the sexes can not be distinguished. These nascent 

 young buds are oval; the transparent light reddish um- 

 brella lies close round the large elliptical opaque-reddish 

 manubrium (&); and the stem (s) by which they are atta- 

 ched is thicker than it afterwards becomes; and lastly 

 the outer end of the umbrella is always simply rounded. 

 In the developed gonozooids, the sex of which is easily 

 known by their contents, there may be observed at the 

 outer end of the umbrella 4 very small tubercles, which 

 are sometimes, mostly in the males (fig. 12— 13) not very 

 distinct. These tubercles are roundish or low-conical; 

 and between them, when the gonozooids arrive at matu- 

 rity, an opening is formed (fig. 5, 6, q) for the discharge 

 of the sexual matter. 



Between the transparent doubly-contoured umbrella 

 (called by Allman the Ectoderm) which is considerably 

 developed (fig. 5—7, p.) and the opaque reddish manu- 

 brium (&) (Endoderm Allman) which becomes apparently 

 smaller and more cylindrical during the growth of the 

 umbrella, there is in the mature gonozooids a large cavity 

 (answering to the swimming cavity in the free medusæ); 



