g ACTINIARIA 



cysts of the column in fertile specimens partly 12 — 29 X 1,5 — 2 //, partly 8 — 12 X i ,«, very sparse, especially 

 the latter; those of the tentacles 17 — 34 X 2 — 2,5 /^, partly 12 — 17 X 1—1,5 /a the latter very sparse, those 

 of the actinopharynx very numerous, 45 — 91 X 4,5 — 7 u. 



The genus Urticina now is easily distinguished from other Cribrinids by aid of the nematocysts. 

 It is more difficult to say, whether we have to do with more than one Urticina-species in the Northern and 

 Arctic seas. There is no doubt that in those seas there are different Urticina-ionns which are certainly 

 rather easily distinguished from each other alive, but whether these form are different species (Carlgren 

 1902) or variations of one and the same species (Mc. Murrich 191 1) is a question. For practical reasons it 

 is more suitable to accept the latter view, as the different forms in contracted and badly preserved state are 

 difficult to distinguish. I, therefore, here treat the Northern and Arctic Urticina-iovms as varieties of a single 

 species: Urticina felina (I,.). To my mind there are 4 varieties of this species. 



i) Urticina felina crassiconiis = Rhodactinia davisii Agas. = "the true Urticina crassicornis of the 



North" (Verrill 1868 p. 470 note). The column of tliis variety is smooth, without verrucae, the 



embryos develop unto a stadium with numerous tentacles in the coelenteric cavity, the tentacles are 



uniformly coloured or almost so. An Arctic and Boreoarctic form. 



2) Urticina felina lofotensis = Urticina crassicornis f. laevis Carlgren in Appellof 1900 p. 4). The 

 column is provided with very small verrucae, in contracted state often inconspicuous. The develop- 

 ment of the embryos does not take place in the coelenteric cavity. The tentacles are furnished with 

 more or less indistinct transverse bands, or are sometimes uniformly coloured. A large Boreal form 

 from the littoral area, but also from deeper water. 



3) Urticina felina coriacea = U. coriacea Rapp = U. papulosa Ehr. The verrucae of the column large. 

 Development of the embryos probably as in the previous form. Tentacles with more or less distinct 

 transverse bands. A Boreal-Lusitanic form of the littoral area. 



4) Urticina felina tuberculata = U. tuberculata Cocks (compare Walton 1908 p. 218). Verrucae smaller 

 than in U. felina coriacea. Otherwise as the former variety, but of greater size. A Boreal form from 

 deep-water. 



Of these forms coriacea and tuberculata are probably most closely related. In the review of the liter- 

 ature I have put them together. As the verrucae display a different appearance in different states of contraction 

 it is sometimes difficult to determine the varieties with certainty. I have therefore added lofotensis to the 

 list of occurrence of coriacea and tuberculata. The varieties, which I believe I have been able to determine with 

 certainty, I have designated (c) = coriacea, (1) = lofotensis. The other forms from deep water are most prob- 

 ably tuberculata. 1 myself have seen only coriacea and lofotensis (Appellof's specimens in Bergen, spec- 

 imens from Drontheim fiord and i specimen in Bohuslan) in living state. 



From an anatomical point of view these varieties seem to be equal, except as far as the presence or 

 absence of verrucae is concerned. It is possible that the difference in size between the larger nematocysts 

 of the tentacles and those of the actinopharynx is somewhat greater in coriacea and tuberculata than in lofo- 

 tensis and crassicornis, but this question demands a closer examination of numerous specimens, determined 

 in living state. Concerning the size of the larger nematocysts in the tentacles and of those in the actinopha- 



