BRITISH ZOOPHYTES. 81 



Gosse,* "who liumorously alludes to tlie alternation of 

 generations caused by the production of these medusi- 

 form zooids, and states that any individual is not like 

 its mother or its daughter, but exactly like its grand- 

 mother and granddaughter. 



Genus II. Obelia, Peron and Leseur. 



Stems branching, plant-like, rooted by a creeping 

 stolon. Hydrothecce campanulate, without operculum. 

 Gonothecce borne on the stem and branches. Repro- 

 ductioti by free medusiform zooids. Gonozooid (at time 

 of liberation) depressed and disc-like ; marginal ten- 

 tacles numerous. Lithocysts borne on the inner side of 8 

 tentacles near the base. — T. H. 



1. 0. GENicuLATA, Liuuceus. Plate TV. fig. 3. 



Sertularia geniculata {Linn., Pal., Lh.,Miill.,E.a7idS., 

 Berk., Turt., Stew., Pose, Hogg), Laomedea geniculata 

 (Lamx., Temp., De P., P. K G., G. J., B. Q. C, D. L., 

 McA.), Campauularia geniculata {Flem.), Monopyxis 

 geniculata {Ehr.), Eucope diaphana {Ag.), E. alternata 

 [Ag.). 



Hab. : Generally distributed on seaweeds near low- 

 water marks. Height 1 in. 



" Stem zigzag, white, jointed at each bend and 

 thickened immediately below, so as to form a series of 

 projections or elbows." Calycles bell-shaped, with 

 entire rims borne on short ringed pedicels. Gonothecee 

 urn-shaped, borne in the axils between the pedicels 

 and the stem. Polypites with about 12 tentacles and 

 a large proboscis. 



This is the " knotted thread coralline " of Ellis, who 

 likens the gonothecee to oil jars with necks to them. 



* " Devonshire Coast," 299. 



G 



