20 



Kapitel 2. 

 Kiiopanhviiget hos de forskjellige grujtper. 



De forskjellige familier af sammensatte Ascidier af- 

 viger i væsentlige anatomiske karakterer fra hinandeii. 

 Dette forhold har i den systematiske zoologi fort forfatterne 

 til den opfatning, at hver større gruppe fylogenetisk har 

 udviklet sig paa en forskjellig maade fra den fælles stam- 

 form, saa at enkelte familier endog viser større anatomisk 

 overensstemmelse med de enkle (ikke knopskydende) Asci- 

 dier end indhyrdes. Herdmnn siger saaledes: ,.The Asci- 

 diæ Compositæ or Synascidire are polyphyletic, liaving heen 

 derived from the Simple Ascidians or their ancestors at 

 three distinct points. The resiilt of this is that the Com- 

 pound Ascidians form three groups (1) the Polystijélidæ. 

 (2) the Botrijllidæ and (3) the remainder, which are more 

 nearly related to particular groups of Sin}ple Ascidians 

 than tliey are to one another-'. „Pyrosonia, although iiow 

 a pelagic free-swimming organism, was derived from the 

 fixed Compound Ascidians". (24). 



I nedenforstaaende fig. har Herdninii gjengivet sin oj)- 

 fatning af de enkelte gruppers sla^gtskubsforhold. Fami- 

 lierne Perophora og Clavelina antages at være primitive 

 former, der er vidt forskjellige fra de andre familier. Po- 

 lycliniderne danner en begrændset gruppe, de staar nærmest 

 Dklemniderne. BotnjlJideDie er maaske den bedst liegrænd- 

 sede gruppe, og de synes at staa de enkle Ascidier som 

 Ciona. Ascidia nærmere end Polydlniderne. 



Chapter II. 

 The Hu(l-ni(liineiit iu tlie Varioiis Groups. 



The various families of Comiiound Ascidians differ 

 from one anotlier in essential anatomical characters. This 

 circumstanee has led writers on systematic zoology to the 

 opinion that each large group has developed phylogeneti- 

 cally in a different way from the common primitive form. 

 so that certain families even show greater anatomical har- 

 mony witli the Simple (non-bud-producing) Ascidians, than 

 with their own group. Thus H<'rd)nan says: ,.The Asci- 

 diæ Compositæ, or Synascidiæ, are polyjihyletic, iiaving been 

 derived from the Simple Ascidians, or their ancestors, at 

 three distinct points. The resnlt of this is that the Com- 

 pound Ascidians form three groups, (1) the Polystyelidæ, 

 (2) the BotryUidæ and (3) the remainder, which are more 

 nearly related to particular groups of Simple Ascidians 

 than they are to one another". ..Pyrosoma, although now 

 a pelagic, free-swimming organism, was derived from the 

 fixed Compound Ascidians." (24). 



In the figure below, Herdman has reproduced his 

 idea of the relationship of the different groups. The fami- 

 lies Peropliora and Qai-elina ari' assumed to be primitive 

 forms that differ widely from the otlier families. The Po- 

 hjdinidæ form a limited group, standing nearest to Didem- 

 nidæ. The BotryUidæ are perhaps the best defined gi-ouj), 

 and tiiey seem to stand nearer to such Simjjle Ascidians 

 as Cioiiri and Ascidia, than to the Pohjclinidd'. 



Choriiocomus 



-ThylaciuTl 



Ogsaa knopskydningen viser derfor hos tie forskjellige 

 familier store forskjelligheder. Hos Clavelina og Penqdiora 

 udvikler knoppcrne sig fra de lange cylinderformige stole- 

 ner, hos Polydinidfrne dannes de fra postabdomen, hos 

 DisiaiiHia ved en udbugtning af tarmen, hos Botryllideiiw 



Euctfélium 



Leptoolinum 



Fig. G. 

 Efter Herdman (24, pag. 1'0). 



Budding therefore also shows great differences in tlie 

 various families. In Clareliiia and Perojdiora, the buds 

 are developed from the long cylindrical stolons; in Poly- 

 dinidæ, they are formed from the post-abdomen; in Distap- 

 lia by an evagination of the intestine; in Boiryllidæ, by 



