THE GLAUCOUS PIMPLET. 197 



closely like those of the Gem. Like the latter, it expands 

 under the stimulus of the light, rather than in darkness, 

 indicating a habitually exposed mode of life. Like gem- 

 macea, it frequently erects itself when closed, in the form 

 of a pillar ; and throws off successive rings of mucus from 

 its body, which accumulate around its base, if not removed. 

 The action of the waves would wash these away in a state 

 of freedom ; in a tank they should be detached by means 

 of a stick or hair-pencil. 



I have never seen the warts of gemmacea used as suckers ; 

 but in specimens of the present species, I observed this 

 function exercised by them very signally ; not in the way 

 of attaching extraneous fragments to the body, like 8. belli's 

 and T. crass icornis, but in taking hold of a firm support, 

 like 8. troglodytes. The suckers of the column adhered 

 with force to the side of the glass vessel, and by contrac- 

 tion were stretched as above described. 



The specific name " ihallia" (not Thalia, as M. Milne 

 Edwards misquotes it) I adopted in allusion to the elon- 

 gated form and glaucous colour, from daXkla, an olive- 

 shoot. The same idea recurs in the epithets which distin- 

 guish the varieties, — as if the glaucous, the dull brown, and 

 the chocolate, were the twig as green, dry, and scorched. 



It is possible that the immature specimens, found by 

 Templeton in Belfast Lough, and named by him Act. 

 monile* were the young of this species ; though they have 

 been generally attributed to gemmacea. 



gemmacea. 



THALLIA. 



[xanthogrammica], 

 [Artemisia]. 

 T. crassicornis. 



* Loudon's Mag. N. H. ix. 303 ; fig. 49. 



