Tentakelkransen Ijestaar af 8 alternerende længere og 

 kortere tentakler. 



Branchialsækken ined 2 X 12 stigmata i hver af de 3 

 rækker, der optager hele dennes længde. 



Kloakaabnin2,erne er forholdsvis talrige, smaa og runde. 



De modne æg og larverne, der næsten er af ventri- 

 kelens størrelse, ligger frit og enkeltvis i den fælles tunica, 

 i koloniei- af cylinderform samlede mod dennes axe i de 

 skorpeformige cornii nedenfor individerne. 



Yas deferens er spiralforniig snoet 12 gauge rundt 

 testikelen. 



Ved koloniernes ovorflade forekommer meget liyppig 

 ved kloakaabningernes udmunding smaa kugle- eller lindse- 

 formige legemer gnlhvide af farve med en diameter af 

 1 — Smm Disse er omgivne af en tynd mod overfladen tyk- 

 kere hinde og er fyldte med en utallig mængde smaa ovale 

 kiselsyreplader ordnede i ovale klumper, der synes at antyde 

 smaa parasiters tilstedev/erelse og disses form. Disse op- 

 træder meget almindelig hos denne art, sjeldnere har jeg 

 fundet dem hos leptocliner og diplosomer. 



Dideniiioidcs lariahile forekom almindelig i juni — juli 

 maaned ved Espevær og Bømmeloen i en dybde af 3 — 6 

 favne. Paa de samme lokaliteter er den funden af Hjort 

 ogsaa i marts. Ved Andenæs fandt jeg denne art alminde- 

 lig (juli). I universitetets samling findes exemplarer sam- 

 lede af M. Sårs ved Hammerfest. Trouiso og Solsvig. 



En varietet, som jeg vil benævne [/elathiosa blev fun- 

 den i den bohusliinske skjærgaard a f Floderns (juli). Denne 

 adskiller sig fra typeformen hovedsagelig ved sin gelatinøse, 

 bløde consistens og ved iudividernes tættere og mere uregel- 

 mæssige stilling til hinanden. Ligeledes mangler her det 

 abdominale pigment. 



Dideninoides inarii/afiiiii, Drasciie og d. fortnosnm, 

 Drasche er vistnok begge meget nærstaaende former, af hvilke 

 jeg dog ikke tor identificere nogen med denne, idet disses 

 beskrivelse væsentlig refererer sig blot til farven og andre 

 ydre karakterer. 



Didemnum, Saviguy, 1816. 

 Didemnum roseum, Sårs, 1851. 

 1851. Didemnum ruseitiii, Sårs. Nyt Mag. for Nat. Bd. VI. 

 Sars's kortfattede beskrivelse skal jeg supplere med 

 nedenstaaende tilføielser : 



Kolonien danner ialmindelighed tykke skorpeformige 

 betræk eller sjeldnere uregelmæssige klumper paa indtil 1 

 cm.s tykkelse omvoksende hydroider og alger. Det største 

 exemplar havde en længste udstrækning af o..J cm. 



The fringc of tentacles consists of 8 alternately long' 

 and short tentacles. 



The branchial sac has 2 X 12 stigmata in eaeh of 

 the 3 rows, which occiipy its entire leugth. 



Tlie cloacal apertnres are small and round, and com- 

 paratively numerous. 



The mature ova, and the larvæ, which are almost as 

 large as the veiitricle, lie free and singly in the common 

 tunic, in the cyhndrical colonies congregated towards the 

 axis in the crust-hke cormi, below the members. 



The vas deferens is spiral, winding 12 times round 

 the testicle. 



On the upper surface' of the colonies, at the mouth 

 of the cloacal apertnres, small spiierical or lentiform bodies 

 of a yellowish white colour, and with a diameter of from 

 1 to 3'"", are of very fre(iuent occurrence. They are sur- 

 rounded liy a thin membranc increasing in thickness towards 

 the upper surface, and are filled with innumerable small, 

 oval, silicic acid plates, arranged in oval masses whicli 

 seem to indicate the presence and form of small parasites, 

 They are of very general occurrence in this species, w hile 

 I have less frcipieutly found them in Leptoclinum and 

 Diplosoma. 



Didemnoides rariabile was comuionly fouud in .June 

 and July off Espevær and Bommeloen, at depths of from 

 3 to li fatlioms. Dr. Hjort has also found them in the 

 same localities in March, while I have found the species 

 to be common at Andenæs in July. In the University 

 collection there are specimens collected by Prof. M. Sårs 

 at Hamuierfest, Tromsø and Solsvig. 



One variety, which I will call gehitiiiom, was found 

 on tile Bohusliin belt of rocks by Floderns in July. This 

 is distinguished from the type-forms principally by its ge- 

 latinous, soft consistency, and by the closer aud more ir- 

 regular arrangement of the individual members in i-elation 

 to one another. The abdominal pigment is likewise ab- 

 sent here. 



DideDiiioides inarinatuni, Drasche and D. fortnosimi, 

 Drasche are witliout doul)t very nearly-allied forms, hut I 

 will not venture to identify either of tliem witli the type- 

 form, as their description has i'eference chiefly to colour 

 and other external characters. 



Didemnum, Saviguy, 1816. 

 Didemnum roseum, Sårs. 1851, 

 1851. Dideinniiiii roseum, Sårs. Nyt Mag. for Nat. Bd. VI. 

 I will supplement Sars's brief account with the follow- 

 ing remarks: 



The colonies generally form a thick crust-hke covering, 

 but sometimes, though less frequently, irregular lumps to 

 the thickness of 1 cm. investing hydroidæ and algæ. The 

 extent of the largest specimens was 5..' cm. 



