3 
sarc is particularly conspicuous on one side of the pedicel, viz. 
on the side turned towards the support. On this side the thick- 
ening stops abruptly at the sharp basal bending of the pedicel; on 
the other side it is continued over the “foot” of the pedicel. The 
thickened mesosarc is shown in PI. I, fig. 2 and, still more expli- 
citly, in the cross-section, fig. 5. — The muscular elements of the 
pedicel are much stronger than in ordinary hydroids; this is rel¬ 
evant to the longitudinal muscular fibrils of the ectoderm as well 
Pigs. 1 and 2. — Transverse (fig. 1) and longitudinal (fig. 2) sections of the pedicel ot 
a nutritive polyp, showing the thickened mesosarc (mes.) and the ectodermal (eet. m.) 
and endodermal (end. m.) muscular fibrils. — eet. ectoderm, end. endoderm. 
as to the circular fibrils of the endoderm. Both systems are about 
equally developed all around the body. The muscular fibrils are 
more or less sunk into the mesosarc (PI. I, fig. 5 and textfigs. 1 
and 2). — The structure of the mesosarc, as described above, 
must lend a considerable amount of firmness and elasticity to the 
pedicel, and on account of the high development of the muscula- 
ture, the polyp must be able to move very easily in all directions. 
On one side of the pedicel, at the base of the hydranth, there 
is usually a fold, more or less deep, in which the mesosarc is 
considerably thickened (PI. I, fig. 3). I am not absolutely sure, 
whether this fold is present in all the polyps of the colony, but I 
have found it in the four or five specimens, which I have isol- 
ated for further examination, and also in several of the polyps in 
situ. It corresponds to a sharp bending of the hydranth. Some of 
the polyps are irregularly twisted and contracted owing to the pre- 
servation, but in most cases the hydranth is clearly seen to be 
bent in the same direction as the basal part of the pedicel. 
The hydranth is spindle-shaped or nearly cylindrical, with a 
i* 
