lian forholdsvis let adskilles ved tilstedeværelsen eller man- 

 gelen paa pigment i tunicaen. Den første pigmentfrie form 

 danner altid ganske tynde flade cormi, medens den anden 

 ofte er læbet eller klumpet. Hvorvidt selv disse er di- 

 stinkte arter er vel tvilsomt, da ingen constant forskjel kan 

 paavises i individernes anatomiske bygning. TidHgere op- 

 stillede karakterer som ingestionsaabningens 'mangel paa 

 tænder, tentaklernes forskjellige antal og andre afvigelser 

 har vist sig at bero paa iinøiagtige undersøgelser eller endog 

 sammenblanding med arter af andre genera. Jeg slutter 

 mig derfor til Lahilles udredning af denne genus. 



De norske diplosomer repræsenterer begge de ovenfor 

 anførte arter og af d. spongiforme 2 farvevarieteter. 



Diplosoma listerii. Lister, 1834 (Lahille, 1890). 



1842. Polyclimtvi, Lister, Some Obs. on the Str. and 



Eunc. of Tub. and Geil. Pol. and 

 of Ase. Phil. Trans. part. I. 



1890. Diplosoma listeri, Lahille. Eecherches sur les tuni- 



ciers des cotes de France. p. 104. 



Cormus altid tynd og transparent, saaat branchial- 

 stigmata og alle øvrige indre organer er fuldstændig synlige 

 uden nogen særegen præparation: 



var. D. gelatinosum-listeri, Milne-Edwards, 1842. 

 1842. Didemnnm. ;/elat>iiosn)n, M.-Edw., og 

 1842. Lepfodinuvt. gelafinosum, M.-Edw. Obs. sur les ase. 



compt. des cotes de la Manche. 



Mem. acad. sei. t. XVIII. 

 1862. DidemnuDi gélatino^ium, Gegeiibaur. Ueber Didem- 



num gelatinosum. Miiller, Archiv 



p. 149. 

 1890. Diplosoma gelatinosum-listeri, Lahille. Reeherches 



sur les tuniciers des cotes de 



France, p. 107. 



Denne varietet fandt jeg i 2 smaa cormi i juli maa- 

 ned ved Espevær i en dybde af 5 — 6 favne fæstet til lami- 

 naria sacharina. Af Hjort er der i november indsamlet 

 store kolonier ved Lervik paa Stordøen. I univei-sitets- 

 samlingen tindes exemplarer fra Solsvig ved Bergen. 



Diplosoma spongiforme, Giard, 1872. 



1872. Diplosoma spongiforme. Giard. Reeherches sur les 



Ase. comp. ou Synasc. Areh. Zool. 

 exper. t. I. 



1890. — — Lahille. Reeherches sur les tuni- 



ciers des cotes de France, p. 123. 



referred. They are distinguished with comparative ease by 

 the presence or absence of pigment in the tunic. The 

 first, unpigmented form is always in the form of quite thin, 

 flat cormi, while the seeond is often lobed or in lumps. 

 How far even these may be [distinet species is probably 

 doubtful, as no constant differenee can be shown in the 

 anatomical structiire of the animals. The characters for- 

 merly given, such as the absence of denticles at the bran- 

 chial 01'ifice, the differenee in the number of tentacles and 

 other variations, have proved to be due to inaccurate in- 

 vestigation or even confusion with species of other genera. 

 I therefore hold with Lahille in his interpretation of this 

 genus. 



Both the above-named species are represented by 

 Norwegian Diplosoma. D. spongiforme by 2 varieties of 

 eolour. 



Diplosoma listerii, Lister, 1834 (Lahille, 1990). 



1842. Polydimim, Lister. Some Obs. on the Str. and 



Fune. of Tub. and Geil. Pol. and 

 of Ase. Phil. Trans, part I. 



1890. Diplosoma listeri, Lahille. Reeherches sur les tuni- 

 ciers des cotes de France. p. 104. 



The cormus is always thin and transparent, so that 

 the branehial stigmata and all the internal organs are per- 

 fectly visil)le without any sjDecial preparation. 



var. D. gelatinosum-listeri, ^Milne-Edwards, 1842. 

 1842. Didemnuin gelatinosiint. M.-Edw., and 



1842. LeptorUnmn gelatinosum, M.-Edw. Obs. sur les Ase. 



comp. des cotes de la Manche. 



Mem. acad. sei. t. XVII. 

 1862. Didemnnm gelatinosum, Gegenbaur. Ueber Didem- 



num gelatinosum. Muller. Archiv. 



p. 149. 

 1890. Diplosoma gelatinosum-listeri, Lahille. Reeherches 



sur les tuniciers des cotes de 



France. p. 107. 



I found 2 small cormi of this variety in July at Espe- 

 vær, at a depth of 5 or 6 fathoms, attached to Laminaria 

 saccharina. Large eolonies have been found by Dr. Hjort 

 in the month of November at Lervik on Stordoen. In 

 the University eollection there are specimens from Solsvig 

 near Bergen. 



Diplosoma spongiforme, Giard, 1872. 



1872. Diplosoma spongiforme, Giard. Reeherches sur les 



Ase. comp. ou Synasc. Arch. Zool. 

 exper. t. I. 



1890. — — Lahille. Reeherches sur les tuni- 



ciei-s des cotes de France. p. 123. 



