49 



des: ..Allein (las Faktum, dass dieselhe innero P.lasc. die 

 nur aus einein Keimblatt der Larve herstanimt so ver- 

 schiedene Organe, wie den Darm und das Xervensysteni 

 bilden kami. scheiut geniigeiid /.u /.eigen, dass ilir Keim- 

 blatt nicht als Kcimbl.itt im grwJihnliclieii Sinne aufziifassen 

 ist.-^ 



Det hele kuDpankeg maa derl'i)i- tænkes væsenstbr- 

 skjelligt fra ethvert stadium at emlii-vonaludviklingen og 

 den indre blære bestaar af celler, der er kvalitativt indifte- 

 reiite som det æg, hvorfra de i sidste instants dannes. 



Til samme opfatning har Ritier og Caidh-nj sluttet 

 sig. medens Sulensl;y. Pizon og (Tdrsfang har sogt at op- 

 retholde den opfatning, at knnpudviklingen dog lader sig 

 fore tilbage til den embryonale udvikliiigs principer. Da 

 de resultater, hvorpaa disse sidste forskere støtter sin op- 

 fatning, punkt for punkt er behandlede dels i den fore- 

 gaaende afhandling, dels i dette arljeidcs specielle del, 

 forbigaar jeg det her. 



Jeg vil kun kort berøre knopskydnins^en andetsteds i 

 dyreriget. Det vil være almindelig bekjendt, at de fleste 

 tidligere undersøgere overalt i dyreriget har sogt at føre 

 knopskydningen tilbage til en art delingsproces, der ifølge 

 den v. Kennrl-LangsJce knopskydningstheori oprindelig har 

 været fremkaldt ved ydre skadelige angreb, men efterhaan- 

 den er gaaet over til en normal ]>roces. De dele, hvori 

 ..moderdyrot'' deles, tænkes da at danne nye individer ved 

 regeneration. Da man nu fremdeles har ment. at al rege- 

 neration i dyreriget har den tendents at recapitulerc den 

 embryonale udvikling og danne nye organer af lige organer 

 eller af lige organers kimblad, saa har man ved overordent- 

 lig indgaaende undersøgelser søgt at finde en overensstem- 

 melse mellem knopskydning og larvendvikling. En saadan 

 overensstemmelse har ogsaa i de fleste tilfælde vist sig at 

 være tilstede. Hos AniielideriiP regenereres de nye organer 

 efter de fleste forfattere ud fra de gamle, hos Hijdrnidenie 

 Inigter begge kimblade sig ud til dannelse af knoppen. 



Imidlertid foreligger der dog ogsaa afvigende medde- 

 lelse. Foriulen hvad jeg har meddelt her hos Asc/dierue 

 meddeler Braeni, at knopskydningen hos Bryozoeriie alene 

 udgaar tra ektodermen (5) og Clutii har synlig paavist at 

 hele knopanlægget hos visse meduser, Murr/clider, er af ren 

 ektodermal oprindelse (11). 



Det siger sig selv, at knopskydningen ogsaa i dette 

 tilfælde kan opfattes som en regeneration. Kun maa man 

 da tænke sig at Aiwpsk\dninf/en ndr/aar fra et mere iwimi- 

 tivt anlcBfi, i hvilket modeydijreta organisationsplan ildn saa- 

 ledes fra første stadium af kan paavlses, som i de tilfælde, 

 hvor knopskydningen virkelig er en deling (TiirheU arier, 

 AinicVider), eller hvor knopanlægget dannes ved udbugtning 

 af Ilegge moderdyrets kropsmembraner, kimblade [Hijdroi- 

 denie). 



Kurqisl-gdiiingeii er lier virkelig udvikling ikke idene 

 regeneration. 



Den norske Nordliiwse.xpedition. Jcih.in Hjort: KinililaJsttulic-r p.ia gn 



as follows: .. Allriu das Faktum dass dieselbe innere Blåse, 

 die nur aus einem Keimblatt der Larve herstanimt so ver- 

 se hiedene Organe wie den Darm und das Nervensystem 

 bilden kann, scheint geniigend zn zeigen, dass ihr Keim- 

 blatt nicht als Kcimlilatt im gewiihnliehen Sinne auizufassen 

 ist." 



The whole rudiiniMitary bud in its nature must there- 

 fore be considered as essentially diflerent from any stage 

 of embryonic development, and the inner vesicle consists 

 of cells that are (^ualitatively indifierent like the ovum 

 from which they are ultimately formed. 



Bitter and Canllrrg have subseribcil to the same view, 

 while Salenskg. Fizoii and Garstang have tried to maintain 

 the theory that the bud-development does admit of being 

 traced back to the principles of embryonic development. 

 As the results with which these latter writers support their 

 view is discussed point by point partly in the foregoing 

 paper, partly in the special section of this paper, I will 

 jiass them by hei'e. 



I will only briefly touch upon the subject of budding 

 clsewhere in the animal kingdom. It will be generally 

 known that most of the earlier investigators of all parts 

 of the animal kingdom have attempted to trace budding 

 back to a kind of dividing process, which, accordiug 

 to the /■. Kennel-Lang theory of budding, has originally 

 been occasioned by external injury, hut by degrees has 

 passed into a normal process. The parts into which tlu; 

 jiarent animal is divided. are then supposed to form new 

 individuals by regeneration. As it is still thought that all 

 regeneration in the animal kingdom has a tendency to re- 

 capitulate the embryonic development, and form new organs 

 from similar organs, or from the germ-layers of similar 

 organs, endeavours have been made by e.xceedingly minute 

 investigations to establish a harmony between budding and 

 larval development. Such a harmony has indeed in most 

 cases been proved to e.\ist. In the AniuAids. the new organs 

 are regenerated, according to most writers from the old 

 ones. In Hydroids, both the germ-layers bulge out to 

 form the bud. 



There are, however, also varyiug statements. Besides 

 what I have stated here of Ascidiæ, Braeni states (5) that 

 in Bryozoa, budding in-oceeds only from the ectoderm. and 

 Llinn has recently demonstrated (11) that the entire bud- 

 rndiment in certain medusæ — Margelidæ — is of purely 

 ectodermal origin. 



It is selfevident that butlding in this instance too, 

 niav be regarded as a regener.itiun : but then it must be 

 considered that budding avises from a more primitive rndi- 

 ment, in ivliicli tlie parent-unimaVs plan of organisafion 

 cannot he tJius demonstrated from the earliest stage onward, 

 as in the cases where budding is really a division. (Tur- 

 hellii rians. An)ielids), or where the rudimentary bud is formed 

 liy an evagination of both tiie body-membranes of the 

 parent animal, germ-layers (Hydroids). 



Budding is here actual dcvelnjintent not simjily rege- 

 neration. 



undlug iif Ascidiernes ndvikling. 7 



