yet there never are more than 3 or 4 to be seen in one vertical cross-section. — Their 
diameter is 250 p.. Each ovum is surrounded by a firm mesogloeal capsule, 4 p. thick and 
more at the joining of the capsules. 
25. Stichopathes gracilis (Gray) emend. (PI. VI, figs. 8 and 12). 
Tentacles. The ectoderm varies in thickness around 60 p.; the nematocyst-batteries 
are surrounded by deeply staining glandcells. There are only a few hyaline glandcells. The 
nervous layer lies at a very low level. There are no longitudinal musclefibres. The mesopdoea 
is about 40 p. thick (!). There are rather numerous transversal fibres from ectoderm to entoderm; 
these fibres may be branched. The entodermal side shows circular ridges. The mesogloea is 
homogeneous, without any cells. 1 he entoderm contains only a few deeply staining glandcells 
and also only a tew hyaline ones. I here are no musclefibres. 
The bodywall is badly preserved. It has the same structure as the tentacles, but the 
nematocyst-batteries are absent. The mesogloea is yet 30 y, but the other layers are decidedly 
thinner than in the tentacles. In the oral cone however, they are thicker and richer in glandular 
elements, especially in deeply staining glandcells. There is an interzooidal septum, 
without secondary ones. 1 he axial layers are very thin. 
Actinopharynx. Ihe ectoderm is folded with mesogloeal thickenings at the bases of 
the folds. The actinopharyngeal glandcells are rather abundant; also the hyaline ones. There 
are very slightly developed longitudinal musclefibres. A pigmentation is to be found only in 
the lowest part of the actinopharynx, in the immediate neighbour¬ 
hood of those sides where the primary transversal mesenteries are 
attached.— Ihe mesogloea is thin, and it contains a large number 
of fibrillae and oval cells. The entoderm is of the same structure 
as elsewhere. 
The mesenteries have nothing remarkable in their structure 
except some stellate connective tissue cells in the mesogloea of the 
primary transversal mesenteries near the bodywall. In the top of the 
oral cone the mesenterial mesogloea is very thick. The mesenterial 
musclesystem is well developed, so that there can be no doubt about 
its exact position. Ihe system of these longitudinal musclefibres is 
given in fig. 260; on the primary sagittal mesenteries they are found 
on the averted sides of the mesenteries. On the secondary mesenteries 
they are directed towards the primary transversal mesenteries and 
on the latter they are found on both on the same side of the mesentery. 
The mesenterial filaments are highly branched along the 
primary transversal mesenteries. They contain pigment. 
Reproductive organs. The fertile part of the primary transversal mesenteries, which are 
the only ones containing testes, is folded, especially in the peripherical p art Q f t j ie mesentery 
(PI. VI, fig. 8). In the higher part of the oral cone this fold is again united with the mesentery 
Fig. 260. Stichopathes gracilis Gray) 
emend. System of the longitudinal 
musclefibres on the mesenteries. 
SIBOGA-EXPEDITIE XVII. 
29 
