IIEPORT ON THE PENNATULIDA. 



The integument of both stalk and rachis is, according to KoUiker, 

 thick, and closely studded with minute fusiform calcareous spicules.* 



In stating that the stalk is, in the natural condition, inserted in 

 the mud of the sea bottom, we rely mainly on the very definite state- 

 ment of Forbes, who says :t " It lives erect, its lower extremity, as it 

 were, rooted in slimy mud." Additional evidence on the point is 

 yielded by the anatomical arrangement of the parts, especially of the 

 stem (as will be noticed immediately) ; and by the fact that the allied 

 genus Virgidaria is known to live erect. ^ Sir Wyville Thomson^ 

 also speaks of " passing over a forest " of Fuuiciiliiia, clearly implying 

 that they live erect. 

 2.— The Stem— 



The Stem (Fig. 2) extends from the top of the rachis to within a 

 short distance of the lower end of the stalk. As shown in Fig. 3 c, it 

 is quadrangular in section, but the sides are not perfectly iiat. The 

 dorsal surface is slightly convex (flat in some specimens) along the 

 greater part of its length, but becomes concave in the stalk : the ventral 

 surface is slightly concave ; while the lateral surfaces, which are 

 rather narrower than the dorsal and ventral ones, are decidedly concave. 



The stem is thickest at the junction of the rachis and stalk, 

 where its transverse diameter is 0-10 in., its dorso- ventral diameter 0'08 in. 

 From this point it tapers towards the upper end, at first very gradually, 

 then more rapidly ; its upper part being very slender and flexible : 

 towards the lower end it tapers gradually for a short distance, and 

 then rapidly, ending in a fine flexible and imperfectly calcified point 

 which enters the bent portion of the stalk, and ends a very short 

 distance from its extremity. 



It is thus seen that the thickest part of the steni is at the point 

 where the fleshy coenenchym is thinnest ; indeed, as is seen from the 

 measurements given above, the total thickness at this point — the 

 junction of rachis and stalk — is due almost entirely to the stem, which 

 is here covered by a layer of cceuenchym so thin that the quadrangular 

 shape of the stem is very evident on mere inspection. 



A point of much greater interest, and one on which we think some 

 stress should be laid, is that the proportions of the stem at various 

 points of its length are such as, mechanically considered, to adapt 

 it most perfectly to what we regard, for the reasons stated above, as its 

 normal position, i.e., planted erect with the stalk buried in muds and 

 the rachis projecting freely above it into the water. In this position the 

 thickest and strongest portion of the stem is at the point where most 

 strength is needed, i.e., at the surface of the mud. The gradual 

 tapering downwards in the first part of the stalk gives a firm, rigid 

 support, while the gradual and steady tapering towards the upper end 

 of the rachis provides the requisite strength in the lower part with 



* Kiilliker, op. cit, p. 253, aud Plate XVIII., Fig. 154. 



t "Johnston's British Zoophytes," 2ud edition, 1817, Vol. i,, p. 165. Cf. also 

 Eichiardi, " MoiioRrafla della PainiKlia dei Peniiatiilarii," p. 91, 

 t Darwin, " Naturalists' VoyaRo Kound the World," IbGO, p. 99. 

 § Thomson, " Depths of the Sua," 1873, p. 14'J. 



