201 
The muscular layer is usually absent; in some places there are musclefibres, very few in 
number, but much thicker than in other species. The mesogloea (7 p„) is very thin, when 
compared with the ectoderm and the entoderm and the heavy structure of the entire polyp. 
This layer is fibrillar through the basal ends of the epithelial cells. There are no connective 
tissue cells (PI. IV, fig. 6). The entoderm (55 p,) does not contain any deeply staining 
glandcells, but very numerous hyaline ones. The structure of the entoderm is very much like 
the ectoderm, except for the absence of batteries and musclefibres. 
Bodywall (PI. IV, fig. 3). The ectoderm (110 p.) does not contain any nematocyst- 
batteries, except on the oral cone. There is no layer of musclefibres. The nervous layer is 
found at a higher level in the entoderm than in the tentacles. There are no deeply staining 
glandcells or only a few. The hyaline glandcells are very numerous. In front of the connecting 
septum there is a group of nuclei, deep in the entoderm, below the nervous layer (PI. IV, 
fig. 3). The mesogloea (7 p.) is a homogeneous layer. The entoderm (40 p.) has the 
same structure as elsewhere. 
The Axis-layers have almost entirely disappeared, since the polyps are loosened from 
the axis. The connecting septum remains with parts of the axis-layers (PI. IV, fig. 3). The 
axis-entoderm (13 p.) is rather thin with the rounded entodermal type of nuclei. The mesogloea 
is only a few p. thick; the mesogloea of the connecting septum is much broadened at the side 
of the axis and it contains a large number of cells. These cells are oval shaped or irregularly 
rounded, but never stellate. 
Actinopharynx. The mesogloea and the entoderm are the same in structure and have 
o 
the same thickness as in the bodywall. The entoderm contains numerous actinopharyngeal 
glandcells in a superficial layer. The structure of these glandcells is visible in PI. IV, fig. 1 
(mesenterial filament). Each cell is filiform, but near the entodermal surface the cell is swollen 
and granular, which part is the only visible part at a low magnification. I he actinopharynx 
contains no pigment. The entoderm is folded; these folds concur with the interstices between 
the places of attachment of the mesenteries. 
Mesenteries (PI. IV, figs. 1, 2 and 4). They are normal in number and course. The 
mesogloea is very thin; the entoderm is the same as in the bodywall. There is no mesenterial 
musclesystem; mesogloeal lamellae are entirely absent. 
Reproductive organs. There are testes in the primary transversal mesenteries (PI. IV, 
figs. 2 and 4). Each testes-follicle is enclosed in a thickwalled mesogloeal capsule, which 
separates the folliculi one from the other and from the surrounding entoderm. I here are young 
follicles with spermatocytes only, but also ripe testes with bundles of spermatozoa. 1 he dia¬ 
meter of a follicle is 55 p„. The young testes are found in the middle of the mesentery, but 
the ripe ones are found near the entodermal surface. In this case the mesogloeal capsule- 
wall is reduced in thickness and the bundle of spermatozoa is turned with its tails towards 
the entodermal surface. In some cases I saw the spermatozoa being liberated into the gastral 
cavity through the rupture of the epithelium. I saw no very young follicles with spermatogonia, 
still without mesogloeal capsule, unless the rounded cells, which I have figured in the mesen¬ 
terial entoderm, near the mesenterial filaments (PI. IV, fig. 1), are to be considered as such. 
26 
SIBOGA-EXPE DITIE XVII. 
