TUBULAEIDyE. 85 



appear to anastomose, making a sort of network from which free stalks 

 shoot up here and there, sometimes to the length of three inches or 

 more, sending forth the polyp -branchlets irregularly on all sides. The 

 creeping fibre, the stalk, and the branchlets are seen under the micro- 

 scope to be tubular ; and the two latter are marked throughout their 

 course with close-set rings or false joints, apparently produced by the 

 annular infolding of a small portion of the integument. The tube is of 

 a yellowish-brown colour, sufficiently translucent to reveal a core or 

 central axis of flesh running along its centre and sending oif branches 

 into the polyp -branchlets, from the open lips of which the flesh emerges 

 in the form of a thickened oblong head, somewhat club-shaped, whence 

 the name Coryne (from Kopvvr], a club). The tube or sheath becomes 

 membranous, or rather gelatinous, at its margin, the ultimate three or 

 four rings being evidently soft and scarcely consistent, of undefined out- 

 line, and larger than the rest. The club-shaped head of the polyp is 

 studded with short tentacles, of curious and beautiful structure. These 

 vary much in number in each polyp ; but the full complement appears 

 to be from twenty-five to thirty, arranged somewhat in a whorled manner 

 in four or five whorls, which, however, especially the lower ones, are 

 often irregular and scarcely distinct. The tentacles spring from the 

 axis, with a graceful curve ; they are rather thick and short when con- 

 tracted, but slender when elongated, and nearly equal in diameter, 

 except at the termination, where each is furnished with a globose head 

 studded all over with tubercles, each of which is tipped with a minute 

 bristle. The neck or body of the tentacle is perfectly transparent, and 

 appears to be a tube with thin walls, but containing a colourless thickish 

 axis freely permeating its centre, marked with delicate parallel rings. 

 The tentacles are endowed with the power of free motion, and they fre- 

 quently throw themselves to and fro with considerable energy. The 

 whole polyp likewise can be tossed together from side to side at pleasure. 

 (194.) TUBTJLAKID^E. In the Tubular Hydrozoa the structure of the 

 tentacula is widely different from what has been described in Tubijpora 

 mmica and other anthozoic polyps. When the Tubularia is expanded, 

 its protruded portion is seen to be furnished with two circles of arms, 

 one placed around the opening of the mouth, the other at a considerable 

 distance beneath it (fig. 41, l) ; and, nearly on a level with the inferior 

 circle, a second aperture (fig. 41, l, a) is observable, communicating 

 with that portion of the body which is lodged within the tube, and re- 

 sembling a second mouth. A remarkable action has been observed to 

 take place in these parts of the polyp, producing a continual variation 

 in their form*: a fluid appears, at intervals, to be forced from the lower 

 compartment into the space intervening between the two rows of tenta- 

 cula, which becomes gradually dilated into a globular form (fig. 41, 2,3). 



* Lister, " On the Structure and Functions of Tubular and Cellular Polypi," 

 Phil. Trans. 1834. 



