214 THE MICROSCOPE. 



long, of a purplisb-red colour, except at the base of the smooth stalk, 

 which is a pale yellow, from, as the fishermen say, this part being im- 

 bedded in the mud at the bottom of the sea. They are built up in 

 the same manner as the former. The papillse on the back of the rachis, 

 and between the pinnse, are disposed in close rows, and do not differ 

 from the polyp-cells except in size. The latter are placed along the 

 upper margin of a flattened fin ; they are tubular, and have the aper- 

 ture armed with eight spinous points, which are movable, and contract 

 and expand. at the will of the animated inmates. These are fleshy, 

 white, provided with eight rather long retractile tentacula, beautifully 

 ciliated on the inner aspect with two series of short processes, and 

 strengthened moreover with crystalline spicula, there being a row of 

 these up the stalk, and a series of lesser ones to the latter cilia. The 

 mouth, in the centre of the tentacula, is somewhat angular, bounded 

 by a white ligament, a process from which encircles the base of each 

 tentaculum, which thus seems to issue from an aperture. The ova lie 

 between the membranes of the pinnse ; they are globular, of a yellow- 

 ish colour, and by a little pressure can be made to pass through the 

 mouth. 



Dr. Grant writes : " A more singular and beautiful spectacle could 

 scarcely be conceived than that of a deep purple Pennatula phosphorea, 

 with all its delicate transparent polyps expanded and emitting their 

 usual brilliant phosphorescent light, sailing through the still and dark 

 abyss, by the regular and synchronous pulsations of the minute fringed 

 arms of the polyps." The power of locomotion is doubted by other 

 writers, and the pale blue light is said only to be emitted when under 

 the influence of some painful irritation. 



In some genera, Yirgularia mirabUis and pavonaria, to which the 

 name of Sea-rushes has been given, the central stem is from six to ten 

 inches long (see fig. 103). Sowerby describes them as like a quill stripped 

 of its feathers. The base has some resemblance to a pen, as in the other 

 species, swelling a little from the end, and ihen tapering. The upper 

 part is thicker, with alternate semicircular pectinated swellings, larger 

 towards the middle, tapering upwards, and terminating in a thin bony 

 substance, which passes through the whole. Professor Grant writes : 

 • " Their axis is calcareous, solid, white, brittle, flexible, cylindrical, of 

 equal thickness throughout, and exhibits no mark of attachment at 

 either end. When broken, it exhibits a radiated surface, like the 

 broken spine of an echinus. The axis appears to have little connection 

 with the fleshy part, and to consist of concentric layers deposited by 

 the soft parts surrounding it. When a portion of the axis is broken 



