PENNATULA PHOSPHOREA. 49 



strongly in support of this view, to sa\ nothing of the evidence yielded 

 by the undoiibtecl fact that in Vivijuluria the stalk i« known to be 

 planted in the mud of the sea-bottom. 



In connection with this question we would direct special attention 

 to the powerful system of longitudinal muscles present in the stalk of 

 Pennatula. These muscles, as previously noticed, are arranged round 

 the stalk, not in a simple ring, but in a deeply corrugated layer, and 

 the disposition of the muscular bands is such as to suggest the power 

 not only of a considerable longitudinal contraction, but also of a 

 partial lateral or spiral contraction. We are in fact disposed to view 

 these muscular bands as affording a means whereby a slight wriggling 

 movement of the stalk could be effected, such as would enable the 

 Pennatula to burrow down into the soft mud to a certain extent ; and 

 that the pen is probably possessed of such a power is supported by 

 the consideration that the mud in which it is planted must always be 

 liable to be washed away by currents and other causes, in which 

 case the Pennatula, if it had no power of burrowing, would fall 

 prostrate at once, in consequence of the small total depth of its 

 insertion in the mud. We shall return to this point when dealing with 

 Virgularia. 



2. Phonphoi-c'scence. — The majority of the Pennatulida are phosphor- 

 escent, and P.'plio.-iphorea receives its specific name from the fact that 

 it exhibits this phenomenon in an exceptional degree. 



This was well seen in the Oban specimens while living; the more 

 perfect female specimen when suspended in a jar of sea-water in the 

 dark, and irritated or excited by gently brushing the leaves, exhibited 

 a fine display of phosphorescence, the different polypes when touched 

 showing minute brilliant points of light which appeared to flash over 

 the whole surface of the feather in rapid irregular corruscatious. 



Edward Forbes made some interesting obsei"vations on the phos- 

 phorescence of Pennatula, his main results being as follows: — The 

 pen is phosphorescent only when irritated by touch ; the phosphores- 

 cence appears at the place touched, and proceeds thence in an undulat- 

 ing wave to the extremity of the rachis, but never in the opposite 

 direction ; it is only the parts at and above the point of stimulation 

 that show phosphorescence ; the light is emitted for a longer time from 

 the point of stimulation than from the other luminous parts ; detached 

 portions may show phosphorescence. Forbes also says that " when 

 plunged in fresh water, the Pennatula scatters sparks about in all 

 directions — a most beautiful sight ; but when plunged in spirit it does 

 not do so, but remains phosphorescent for some time, the light dying 

 gradually away, and, last of all, from the uppermost polypes. One 

 remained phosphorescent for five minutes in spirit." 



Dr. Wilson,* who, at the request of Forbes, made a direct investiga- 

 tion of the phosphorescent properties of Pennatula, came to the con- 

 clusion that the phosphorescence was not an electrical phenomenon, but 

 was probably due to some " spontaneously inflammable substance." 



* Vide Johustou's "British Zoophytes," ^d Ed., 1847, vol. i., pp. 150—155. 



