Gr. T. and A. F. Dixon — On Bunodes thallia, etc. 315 



so thrown into folds as to have five corners. These corners were per- 

 manent in position, and were probably each marked by the presence 

 of a groove, but of this we could not be certain. When killed, the 

 specimen contracted so unequally that we could make no transverse 

 sections of it which would be of any use. This was very unfor- 

 tunate, as of course longitudinal sections gave no information as to 

 the number of grooves and directive mesenteries. One specimen 

 had four, another three, and the remainder either one or two 

 grooves. 



The warts of Bunodes thallia are frequently used as suckers. 

 They may be employed to moor the animal temporarily in the 

 same way as the suckers are used in Sagartia nivea, Grosse [vide 

 these Proceedings, antea, p. 123), or for the purpose of attaching 

 minute extraneous particles of shells or sand. The specimens 

 obtained by Gosse at Lidstep were not troglodyte in habit, but 

 adherent to the open rock, and therefore easily detached. Those 

 to be found at the Ore Stone, Torquay, on the contrary, are gene- 

 rally fixed in small clefts and rock-borings, with only their disk 

 and tentacles expanded above the surrounding levels, and are 

 consequently very hard to procure. They extend a considerable 

 way above the extreme low water-mark, and may be obtained at 

 any tide, some of the specimens we examined having been pro- 

 cured when the -moon was seven days old. 



Structure. 



Tentacles. — Examination of a transverse section of a tentacle 

 which does not present the fluted appearance described above, 

 shows the usual three layers, endoderm, mesogloea, and ectoderm, 

 concentrically arranged and equally distributed, the mesogloea 

 being slightly pleated on its ectodermal side. But if a section be 

 made across a tentacle presenting the fluted appearance, it offers a 

 very different aspect. The endoderm is slightly and the ectoderm 

 deeply crenated along their outer edges, while down the centre of 

 each crenation of the ectoderm there are prolonged strong pleatings 

 of the mesogloea, and the mesogloea itself rises in strong ridges at 

 points corresponding to the centre of each crenation of the 

 ectoderm, and to the depression between those of the endoderm. 

 The crenations of the ectoderm and endoderm, also the ridges of 

 the mesogloea are tolerably regular in size and position all round 



