95 



Det er hovedsagelig paa Clavulavia crassa og petri- 

 cola samt Synrpodiuin coralloides de to nævnte Natur- 

 forskere have anstillet deres [agttagelser, og da Clavularia 

 crassa er æglæggende have de kunnel forfølge Udviklingen 

 Skridt for Skridt, indtil Ungerne bave sat sig fast. Den 

 Omstændighed, at Alcyoniderne i Regelen føde levende 

 Unger, og at Blommedelingen foregaar i yderst kurt Tid, 

 — allerede efter en halv Times Porløb er Morbærstadiet 

 indtraadt hos Clavularia crassa — har bidtil lagt de største 

 Hindringer iveien for at kunne observere de første Stadier 

 af Udviklingen. Det er derfor, a( Clavularia crassa har 

 leveret et yderst brugbart Materiale, idet Æggene, netop 

 befrugtede og indesluttede i en sei- Slim. udgydte gjennem 

 Munden, strax kunne iagttages, og altsaa fra den Stund 

 Observationerne kunne anstilles fra Minut til Minut. 



Af de mangfoldige Æg, jeg havde til Undersøgelse. 

 var en god Del ikke undergaaet nogen Deling, og hvor 

 denne var indtraadt, havde den naaet Morbærformen, 

 Tab. XII, Fig. 60; de mellem denne og det begyndende 

 Embryo liggende Stadier kunde ikke opdages uden hos 

 nogle faa Æg. hvor Delingen var fuldendt og et periphe- 

 risk Cellelag. Ectoblast. dannet. Tab. XIII. Fig. 35, a. 

 [ndenfor dette ydre Kimblad sa.aes paa Tversnit en Samling 

 af Blommemasse uden Ordning. Fig. 35, /'. I det peri- 

 phere Cellelag havde Cellerne en unget aflang Funn og 

 vare forsynede med en tydelig, tiæsten rund Kjerne, der 

 fremtraadte skarpt ved Farvning af Hamanns eddikesure 

 Karmin. Fig. 35. a. Paa et lidt mere udvoxet Embryo, 

 hvis hele Overflade bar Cilier, Tab. XII, Fig. 62, viste 

 Tversnittet en dobbelt Række periphere Celler meil Kjerner, 

 en tydelig Ectodermdannelse, Tab. XIII. Fig. 36. 37. a. 

 samtidig med, at en skarp, gjennemsigtig Linie var op- 

 staaet. Tab. XIII. Fig. 37. b. 38. a. inden for hvilken 

 saaes dannet en Cellerække, bestaaende at runde Celler 

 med Kjerne. Entoderm (indre Kimblad), Fig. 38. b. Efter 

 dette at dømme ser det ud, som om den nævnte Linie 

 der representerer den saakaldte Membrana propria, ei- et 

 Sekret af Ectodermet og ikke. som at' Kowalevsky og Marion 

 antaget, af Entodermet; thi paa et Par Æg saa det ud. 

 som om den var dannet tor det indre Kimblad. Imidlertid 

 maa det erindres, at jeg kun har havt med Spiritusexem- 

 plarer at gjøre, imedens de nævnte Forskere have anstillet 

 sine Undersøgelser paa levende Individer og have saaledes 

 kunnet forfølge Udviklingen ganske anderledes, end jeg har 

 været istaud til. ilen hvorom Alting er. saa er denne 

 Fundamentalmembran (Membrana propria) et virkeligt 

 Sekret af et af de to Kimblade og kan ikke betragtes som 

 et tredie, oprindeligt opstaaet, cellulært Kimblad (Meso- 

 derm. Mesenchym); den undergaar heller ikke nogen 

 væsentlige Forandringer, men adskiller strængt de to Kim- 

 blade fra hinanden og synes endog senere hen i Udvik- 

 lingen at kunne delvis forsvinde. Hos ældre Larver. Tab. 

 XII. Fig. 63. 65, saaes paa Tversnit et smalt, hvalint, 

 gelatinøst Belte, der ufeilbarligt var afsondret af Ectoderm- 

 cellerne og havde skudt Fundamentalmembranen indad 



It is. principally, upon Clavularia crassa aud petri- 

 cola also Sympodiivm coralloides, that the two Naturalists, 

 above-named, have made their observations, and as Clavu- 

 laria crassa is oviparous, they have been able to follow up 

 the development, stage by stage, until the young have be- 

 come frrmlj adherent. The circumstance that the alcyon- 

 oids. usually, produce living young. and that the segmenta- 

 tion takes place with extreme rapidity — in the course of 

 half an hour. even. the morula stage is attained in Clavu- 

 laria crassa - - has. hitherto, placed the greatest difficulties 

 in the way of observing the first stages of development. 

 It is for this reason, therefore, that Clavularia crassa has 

 furnished an extremely useful material, because the ova 

 just impregnated, and enclosed in a tough mucous discharged 

 througb the oral aperture, may immediately be observed 

 aud. consequently, from that moment, observations may be 

 made from minute to minute. 



Of the innumerable ova whieh I had for examina- 

 tion. a. large number had undergone no segmentation , and 

 when this had appeared. it had attained the morula 

 form (Pl. XII. fig. 60). The stages between that and the 

 initial embryonal stage could not be detected, except in a 

 lew ova where the segmentation was completed and a 

 peripherical cellular laver (epiblast) formed (Pl. XIII, 

 fig. 3."i. a). Inside of this epiblast was seen, upon transver- 

 sal section, a collection of yoke-substance devoid of arrange- 

 ment (Pl. XIII, fig. 35, b). In the peripherical cellular 

 laver, the eells had a somewhat oblong form. and were 

 furnished with a distinct, almost globular, nucleus. whieh 

 came prominently out on colouration by Hamanns acetic 

 carmine (Pl. XIII. tig. 35, «). In a somewhat more devel- 

 oped embryon. whose entire surface was covered with ciliæ 

 (Pl. XII. tig. 62), the transversal section showed a double 

 series of peripherical eells with nuclei, a distinct ectoderm- 

 formation (Pl. XIII. hg. 3b. 37, a), and at same time. also, 

 a clearly defined, translucent, line had appeared (PL XIII. 

 hg. 37. //. 38, ii) inside of whieh a cellular series was 

 sien to be formed. eonsisting of globular eells with nucleus 

 (hypoblast) (Fl. XIII. tig. 38. 6). To judge from this, it 

 appears as if the line referred to, whieh represents the 

 so-called membrana propria, is a secretion of the ectoderm, 

 and not of the hypoblast as supposed by Kowalevsky and 

 Marion, because, in a couple of ova it appeared as if it had 

 been formed previous to the hypoblast. However, it must 

 be remembered that I have only had to do with specimens 

 preserved in alcohol, whilst the Naturalists above-named 

 have made their observations on living individuals. and have 

 thus been in a position to follow up the development in a 

 perfectly different manner from what 1 have been able to 

 do. But however the case may be. this fundamental mem- 

 brane (membrana propria) is a genuine secretion of the 

 germinative bladder and can not be considered to be a third 

 original cellular germ (Mesoblast, Mesenchym); neither 

 «loes it undergo any essential changes. but sharply separ- 

 ates- the epiblast from the hypoblast. and seems, even at 

 a later stage of the development, capable of partially dis- 

 appearing. ln older larvæ (Pl. XII, figs. 63 65). there 



