CiiAP. IV. CORYMORPIIA TENDULA. 277 



the base upwards to about one third the height of the stem, but from this point 

 it either disappears altogether, or exists as a mere iihn [Fiff. 8, //' h'') over the 

 upper part of the stem and on the head. The lower, j)ointed base of the stem, 

 is not so simple as might at first be supposed. The question naturally arises, 

 whence are derived the numerous filamentary rootlets of the horny sheath? and, 

 \\\nn\ close examination, avo find that the lower fiftii of the stem is covered by 

 small processes, varying from mere papilhe above, to extremely elongate filaments 

 at the end of the stem. These processes excrete the filamentary rootlets of the 

 horny sheath, and may be traced to the finest terminations of the latter. Tliey 

 are hollow, and are permeated by prolongations of the chymiferous tubes of 

 the stem. 



Before proceeding to describe the details of the diflerent organs of this Ilydroid, 

 we would say a word in regard to the attitudes which it assumes from time to 

 time. Owing to the flexible, plastic nature of the horny sheath, and also to its 

 distensibility, the stem of this Ilydroid is cap.able of assuming almost any form, 

 without restraint. At one time we may see it swollen to its fullest extent, from 

 top to bottom, with the head nearly erect, and, perhaps, in a few minutes, the 

 whole aspect is changed, iind the stem is contracted to one fourth, or even to 

 one sixth, of its former diameter, when it is sometimes very much elongated, 

 though it may also contract without elongating. At other times the upper part of 

 the stem becomes quite slender and elongated, and the head droops to a greater or 

 less degree {Figs. 7-17). The proboscis also shares largely in these changes, but, 

 in this respect, it does not differ from the proboscis of other Tubularians, except, 

 perhaps, in the extent of its changes ; at one moment it has a globular I'orm 

 {Fig. 9), and soon afterwards assumes the opposite extreme, and hangs suspended 

 by a slender neck {Figs. l.S and 14). Between these extreme limits of its plasticity 

 it assumes, at intervals, numerous other forms, a few of which we have reproduced 

 among our illustrations {Figs. 7-17). 



An examination of the stem from the outside, already leads us to suspect that 

 it has a structure similar to that of Tubularia; but we notice that, in addition to 

 the longitudinal tubules {Fig. 8, i^), about thirty in number, which extend along 

 the whole length of the stem, there are, in the lower half, transverse communi- 

 cations from one tubule to the next on either side. These transverse chamiels are 

 very simple about the middle region of the stem, but lower down they are irreg- 

 ular in their course, and communicate with each other as well as with the lon- 

 gitudinal tubules; and at the base of the stem the longitudinal tul)ules become 

 very irregular in their course, and reduced in size, so that they cannot be dis- 

 tinguished from their transverse connections, with which they form an irregular 

 network. Now, upon making a transverse section of the stem, we find that it 



