17 



lidet lulviklede Gonoferer 02; de irit svoniinonde INIeduser. 

 Nedenstiineiulc Træsnit (Fig. 2) viser schoniatisk Gono- 

 forernes forskjellige Udvikliiig hos Arter af denne Familie. 



can i>e hetter denionstrated here thaii7in any otiier faniily. 

 Fig. 2, below, is a dia;j;rani showing the different forms of 

 development in diflerent species of this family. 



Fiir. ■-'. 



Schematisk fremstilling at Gonofdrerne inden Fam. 'Tiibiilai-idæ. 

 a, Styloid Gon. (G-ymuog. cvassicornis); h, Anlæg af 'Glk' (fællcs for 

 Medusoide orr Pseudomedusoide Gon.); c,d,d' Pseudoined. Gonnfor 

 (Lampra), (f, Udviklingsstadium ; d, fuldt iidviklet Gonofor; rf', Tver- 

 snit af samme); e — i Medusoide Gonoforer; (e, udv. Stad ; /, fuldt ud- 

 viklede Gonoforer; /' og /", Tvcrsnit af Gonoforer uden og med 

 Radialkanaler; g, Gonofor med fuldst. Kanakystem), — Overgangs- 

 stad, til /(, fastsiddende , — eller til i, fri Meduse). 



Diagram of tlie gonophores in fam. Tuhularidae. a, Sti/loid 

 gonophorc (Gymnog. crassicornis); b, rudiment of 'Glk' (common to 

 medusoid and pseudo-mediisoid gonophores); c, d, d' , pseudo-medusoid 

 gonopliore (Lampra); (c, developmental stage, d, fuUy-developed gono- 

 pliore, (/', transverse seotion of the same); c — i, medusoid gonojihores ; 

 (e, developmental stage, /, fully-developed gonophore, f, f", trans- 

 verse seotion of gonophore without and with radial canals; g, gono- 

 phore Vi'ith complete canal system, — transition to li, fixed, — or i, 

 free-siriiiuiiiiig medusd ). 



Gi/mnogoiios crassicorms (29) viser det aller enkleste 

 Forhold (Styloide Gonoforer), idet Gouoforcriic her kun 

 bestaar i en simpel Udhugtning af Hydrantheiis to Lag, 

 og Generationsstofferne ligger her i Ektodermen, kun be- 

 skyttet af et enkelt Lag af dennes Celler. 



Ingen andre af de hidtil kjeudte Arter bliver staa- 

 ende paa dette Stadium, men faar gjennem Anlæg af 

 „Glockenkern" en mere komi)liceret Bygning. Udviklingen 

 gaar imidlertid fra dette Punkt i forskjellige Retninger. 

 De almindelig udbredto og vel kjendte Medusoide Gono- 

 forer, hvis Anlæg det er overflødigt her at beskrive, repre- 

 senteres ved den nedre . Række af Figurer. Gonoforer 

 uden Radialkanaler, hvor de to Entodermlag i)aa Snit kun 

 viser sig som et. tindes f. Eks. hos Titbularia larynx, 

 medens Arter som Tnbidaria obl/qua, T. indirisa, T. varia- 

 bilis, Corji)ii(irp]i(i gJacialis, 0. &., har Gonoforer. i hvis 

 Vægge der tindes et forskjelligt Antal Radialkanaler. og 

 af hvilke nogle udvcndig bærer Tentakler eller Ribber. 



Paa et hoiere Udviklingstrin opnaar de medusoide 

 'orer fuldstændig Meduseforra, og som Regel river de 



Den norske Nordhavsexpodition. Kristine Bonjievie: Hydroida. 



Gymnoffonos crassiconyis (29) exhibits the very sim- 

 plest eonditions (styloid gonophores), the gonophores here 

 consisting of only a sirajjle evagination of the two layers 

 of the hydranth; aud the reproductivo elements lie in the 

 ectoderra, only protected by a single layer of the ectoder- 

 nial cells. 



No otlier hitherto known species stops at this stage; 

 they all aciiuire, in the rudimentary „glockenkern", a more 

 complicated structure. From this point, however, the 

 development proceeds in various direetions. The uuiver- 

 sally-distributed, and well-known medusoid gonophores, whose 

 rudimentary stage it is unnecessary to describe here, are 

 represeuted by tlu' lower row in the tiguri'. Gonophores 

 without radial canals, where the two endodermal layers, 

 in section, only appear as one, are found, for instance, in 

 Tnbidaria larynx, while the species Tubularia obliqna, T. 

 indivisa, T. variabilis, Corymorpha gJacialis, and others, 

 have gonophores in whose walls are found a varying number 

 of radial canals, and some of which have tentacles or ribs 

 externally. 



At a higlier stage of development, the medusoid 

 gonophores acquire a complete medusa-form, and as a rule, 



