200 REPORT ON THE PENNATULIDA. 



" knowing very little indeed about natui-al history at the time"; an 

 observation which consisted in looking over the side of a ship and 

 seeing something phosphorescent in the water, whose shape he was 

 unable to make out, but which the sailors told him was a Sea-pen. 



We are acordingly of opinion that the statements concerning 

 Pcmnitula swimming freely cannot be accepted unless fresh evidence 

 from direct observation is brought forward. 



Assuming then that Poinatiila does not swim, there still remains 

 the question as to what is the natural position of the pen ; it un- 

 doubtedly dwells at the bottom of the sea, but is it planted upright or 

 does it lie horizontally on the bottom ? 



Sir John Dalyell, a very careful observer, expresses an opinion, 

 though by no means a decided one, that the horizontal position is the 

 natural one. He is however much troubled by the stem, whose use on 

 his theory he is unable to understand.* A few other zoologists have 

 adopted this view, prominent among whom is again Dr. Grant,! who 

 says : — " the slow contraction of the Pennatula phosphorea coils up the 

 thin flexible extremities of its calcareous axis, and moves the 

 I'etroverted spines of its exterior surface so as to push the animal slowly 

 along a rough surface." 



Our own opinion is very strongly in favour of the now generally 

 accepted view that Fennatula lives erect, planted in the sea-bottom. 

 The absence of polypes on the stalk, the presence of the supporting 

 calcareous stem, and especially the proportions of this stem in 

 different parts of its length, and the pale colour of the stalk speak 

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

 by the undoubted fact that in Virgularia the stalk is 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 an-anged 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 evident from 

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

 liable to be washed away by cun-ents 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 

 Vh'guluria. 



2. Phosphorescence. — The majority of the Pen)iatuUda are phosphor- 



* Dalyell: " Rare and Remarkable Animals of Scotland," vol. ii., 1848. 

 + Grant : " Outlines of Comparative Anatomy," 1841, pp. 132-133. 



