3^8 Dr Grant on the Structure and Nature ofFlustrae. 



accessible at ebb tide, though, from the immense quantities 

 of it which I have found drifted alive on our eastern and 

 western coasts, and constantly brought up by the dredges from 

 oyster-beds, it appears to be the most abundant species on the 

 British shores. It generally adheres to shells or stones, on the 

 surface of which it first spreads like a sessile species with a single 

 plain of cells, then rises up in the centre of the expanded base 

 in a branched form, when its branches are always composed of 

 a double plain of cells. It is a very large species, its branches 

 often amounting to many hundreds, and presenting on their 

 two surfaces some hundred square inches of cells. It has a strong 

 and pleasant odour of violets, which it retains for some time after 

 being taken from the sea, and it is probably the species which the 

 inhabitants of Iceland are said to chew as a substitute for tobacco. 

 The branches have a thick, opaque, and coarse appearance, gene- 

 rally a yellowish-grey colour, and a rough surface covered with 

 minute reverted spines ; they are variously subdivided, but most 

 frequently present a broad palmate form, terminated by nume- 

 rous rounded and expanded digitations. The sides of the stems 

 and lower branches do not present the thickened, opaque, and 

 compact margins we find in the F, truncata and F. carbasea^ 

 which are much more delicate species. The tips of the branches 

 are thin, soft, and transparent, as in other branched species, and 

 as in the anterior margin of sessile species, from their containing 

 little calcareous matter, and from the polypi in that situation be- 

 ing young, colourless, and translucent. The boundaries of the 

 cells on the opposite plains do not coincide, nor have they any 

 determinate relation to each other in their position. The broad 

 rounded extremity and the aperture of the cells are always 

 above, the contracted and flat base always below. The cells 

 are arranged on each surface, as in the F, carbasea ; the 

 opaque sides of the cells form continuous ramified lines from the 

 base to the apex of the branches ; and the first cell of a new 

 series in the middle of the branch is always smaller than the 

 cells which surround it, being confined to a small angular space, 

 formed by the bifurcation of the opaque lateral wall of a per- 

 fect cell. The tips of the branches are never bounded by a 

 smooth continuous line, as we observe them in the F. carbasea 

 and F. truncata, but are terminated by the round bulbous ex- 



