BUGULA PURPUROTINCTA. 91 



ments. The older portions of the zoarium are brown, and 

 coarse in appearance ; but the newer terminal portions of 

 the shoots are of the most delicate whiteness and perfectly 

 transparent. This in itself gives a very peculiar and di- 

 stinctive appearance to the species. The material of which 

 the cells and ovicells are composed is very thin and papy- 

 raceous. The cells are much longer than those of B. plu- 

 mosa, and with something of a cylindrical character ; and 

 the aperture occupies a larger proportion of the front. 

 The stout, cylindrical, and jointed spine at the top of the 

 cell differs widely from the sharp and rather slender spike 

 of the other species, with which indeed, as Alder has re- 

 marked, it hardly corresponds. The true equivalent of 

 the latter is clearly the small denticle, which usually rises 

 in front of the larger spine from the free angular extremity 

 of the margin. The avicularium of the present species is 

 very large, as long as the breadth of the cell, and differs 

 in shape from that of B. plumosa. Perhaps the most 

 striking difference is found in the shape of the ovicell, 

 which in the latter is globular and of the usual type, while 

 that of B. fastigiata is extremely shallow; as seen in 

 profile (PI. XII. fig. 12) it is hemispherical, the aperture 

 occupying nearly the whole of the front and looking 

 straight outwards. So shallow is it that it only partially 

 covers the embryo in its later stages. 



When dry B. fastigiata takes on a rich purplish-red 

 colour, a peculiarity which has suggested the specific name, 

 and by which it may be at once recognized. 



The polypide has, according to Sars, 14 tentacles, while 

 Daly ell gives the number at 16-18. 



The present species rises from a dense mass of inter- 

 twining fibres to a height of about 3 inches. It is a 

 northern form, not occurring on our southern and western 

 coasts. 



