ACTINIA. 9 



are present in relation with the mesenteries of the first cycle in small specimens, including 

 directives, and in large specimens, with the mesenteries of two cycles ; but I was not 

 able to determine to my satisfaction if present in relation with the third complete cycle. 

 Both ova and spermatozoa are present, often associated together in relation with the 

 same mesentery (PI. 3, Fig. 19). Occasionally fertile mesenteries are found showing 

 ova or spermatozoa alone, but in all the specimens examined microscopically the 

 hermaphroditic condition is constant. Embryos in various stages of development are 

 present in the body-cavities of many. 



Genus Rhodactinia, Agassiz. 



Cribrinidse (Tealiidse, Bunodidee, Bunodactidse), with well-developed foot disc; 

 distinct verrucse present on body- wall ; radial muscles of oral disc and longi- 

 tudinal muscles of the tentacles meso-ectodermal to mesogloeal ; tentacles simple ; 

 strongly circumscribed endodermal sphincter. 



Rhodactinia crassicoknis. 



Actinia crassicornis Miiller, Prod. Zool. Dan. (1776), p. 231. 



Actinia elegantissima Brandt, Prod, descriptionis animalium ab H. Mertensio observatoram (1835), p. 13. 



Rhodactmia davisii Agassiz, L., Comptes Kendus, XXV. (1847), p. 677. 



Rhodactinia davisii Verrill, A. B., Mem. Soc. Nat. Hist. Boston (1864), p. 18. 



Urticina crassicornis Verrill, A. E., Proc. Essex Instit. VI. (1869), p. 469. 



Leiotealia spitzlergensis Kwietniewski, Zool. Jahrb. (Syst.) (1898), p. 1, p. 121. 



Carlgren in 1902, in his report on "Die Actiniarien der Olga Expedition" 

 (2, p. 39), thought it necessary to revive the old genus of Agassiz, Rhodactinia, 

 and has taken for its type the well-known and widely distributed Actinia crassicornis, 

 Miiller. The principal distinguishing character given for the genus is that the radial 

 muscles of the disc and the longitudinal muscles of the tentacles may be meso- 

 ectodermal to mesogloeal, and under R. crassicornis Carlgren places a number of 

 synonyms, including Actinia elegantissima, Brandt, and Leiotealia spitzhergensis, 

 Kwietniewski. I have previously been struck with the variation in the degree in 

 which the muscles of the tentacles are imbedded in the mesogloea, in specimens of 

 crassicornis examined by me, from a well-known local habitat, Ililbre Island, at the 

 mouth of the Dee. The text-figures (2, p. 41) given by Carlgren are most 

 instructive, and from Hilbre Island specimens I can produce examples in which the 

 longitudinal muscles are quite as much meso-ectodermal as Carlgren's figure 4, if not 

 as much as his Fig. 3. In my examination of the ' Southern Cross ' Antarctic 

 Actinians (3, p. 294), I was convinced of the many close resemblances to the type 

 species crassicornis, seen in the specimens then under observation ; and notwithstanding 

 that the longitudinal muscles of the tentacles were not imbedded in the mesogloea, 

 I decided to include these species under the genus Urticina. I feel therefore some- 



