231 
There is a basal septum across the entire breadth of the polyp at the polypar periphery; 
it is attached to the usually free border of the primary transversal mesenteries. 
The mesogloea, which is a homogeneous layer, is very thick, viz. tentacles: at the top 
7 y., at the base 66 u ; bodywall: ± 13 y. but very variable; oral cone: max. 25 u .; actino¬ 
pharynx: 35 u ; mesenteries: 4 y or less; basal septum: 7—8 y. 
29. Stichopathes aggregata sp. n. (PI. VII, figs. 5, 6 and 7). 
Tentacles, dhe ectoderm (40 y) is papillose and contains a small number of nema- 
tocyst-batteries, surrounded fiy a large number of deeply staining, homogeneous glandcells, which 
are also present in other parts of the ectoderm. The nervous layer is separated from the 
mesogloea by a clear space. There are no musclefibres or they are only very slightly developed. 
The mesogloea (10 y) is a homogeneous layer, with circular ridges on the entodermal side. 
The entoderm (20 y) contains no other glandular elements besides the hyaline glandcells. 
There are no musclefibres. 
The bodywall has layers of the same structure, minus the batteries, as the tentacles; 
the thickness is resp. 20, 3 and 10 y. The layers are thicker in the oral cone viz. 26, 10 and 
13 y. The polyps are separated by an inter zooidal septum. 
The axis, a very thin-walled tube with a very wide lumen is broken in most of the sections, 
tearing up the tissues rather badly. — The epithelial layers are resp. 7, less than 1 and 5 y. 
The ectoderm is thicker at the base of the spines, thinner at their top ; its thickness increases 
towards the top of the colony. 
Actinopharynx. The ectoderm (26 y) has actinopharyngeal glandcells only. There is 
no pigment, even in the lower part of the actinopharynx. The ectoderm is very deeply folded. 
The mesogloea is less than 1 y; the entoderm (13 y) is the same as elsewhere. 
The mesenteries are normal in course and number. There are no musclefibres. The 
entoderm is 7 y and the mesogloea less than 1 y. The secondary mesenteries descend to a 
slightly lower level at the actinopharyngeal side. 
The mesenterial filaments are straight along the primary sagittal mesenteries. Along 
the primary transversal ones they are straight at first, but at a little distance from the actino¬ 
pharyngeal border the filaments get convoluted and branched (PI. Adi, figs. 5, 6 and 7). There 
is no pigmentation. 
Reproductive organs, ddiey are absent and in connection with this it is remarkable 
that the gastral cavity is very large and roomy when compared to the axis-diameter. While 
in other species this cavity is a narrow slit only, it is very wide here (PI. VII, fig. 7). For this 
reason the polyps are cushionshaped, which is accentuated by the gastral cavity narrowing 
distinctly at the periphery of the polyp (PI. VII, fig. 6). The absence of reproductive organs in 
this case is a proof of the incorrectness of the opinion of some authors as if the different size 
of the polyps could be explained by the presence or absence of genital products. It is plain 
that for sure this is not the only factor, if it is one, for here the gastral cavity is a large 
empty room, only for a very little part filled with mesenterial filaments. 
