2 35 
ectoderm contains only a few deeply staining glandcells, except sometimes in the oral cone. 
The actinopharyngeal ectoderm is rich in glandcells and stains much more deeply than the 
bodywall, as is the normal case in other species. There is a broad lip of actinopharyngeal 
ectoderm (PI. VI, fig. 7); the oral cone is constricted at its base. There is no pigment any¬ 
where. The mesenteries have no musclefibres or mesogloeal lamellae. The mesenterial filaments 
occur along the primary transversal mesenteries only, and they are straight and unbranched. 
The polyps of station 53 have a small number of nematocyst-batteries in their tentacular 
ectoderm, and a large number of supporting cells. This ectoderm contains longitudinal muscle- 
fibres. I he bodywall-ectoderm has locally crowded, deeply staining glandcells, which are very 
numerous in the oral cone, which is basally constricted. The actinopharynx-ectoderm forms a 
narrow lip. I here is no pigment in any part of the polyp. I he mesenterial musclesystem is 
absent or too slightly developed to permit a clear view of the musclesystem. The mesenterial 
filaments are found along all the primary mesenteries, convoluted along the transversal ones. 
There are symbiotic Algae in the ectoderm of the tentacles, the oral cone and the bodywall 
(PI. VII, fig. r); they occur in the entoderm also but very rarely. At the top of the colony 
the axis-ectoderm (PI. VII, fig. 1) is thickened to 37 p.; it is a cylindrical epithelium with basal 
nuclei, which are large, oval or round, and not very deeply staining. The entoderm (12 p) 
is a cubical epithelium with smaller, more deeply staining nuclei. The nuclei of the bodywall- 
ectoderm are of the small, dark and elongated type, which is typical for ectoderm. The 
formation of the axis takes place in the same way as in the type of this species. 
The following tabel gives a review of the numerical data of the thickness of the various 
layers in the examined colonies. 
Station and Variety 
TENTACLES 
BODYWALL 
ORAL CONE 
ACTINOPHARYNX 
ec 
me 
Cll 
ec 
me 
en 
ec 
me 
en 
ec 
me 
e?i 
Saleyer. 
50 
4 
35-44 
70 
13 
60 
70 
13 
60 
70 
13 
60 
var. asperispina 
7 . 
33 
4 
16 
IO 
3 
6 
17 
4 
7 
24 
1 
6 
53 . 
50 
4 
20 
50 
4 
20 
5 ° ^ 
4 
20 
20 
1 
7 
var. lotigispina. 
260 . 
318 j 
40 
4 
30 
15 
4 
IO 
40 
4 
30 
33 
4 
15 
var. lissispina . . . . 
var. lissispina minor. 
Banda > . . . . 
1 17 ' 
47 
1-13 
35 
15 
7 
7 
40 
13 
7 
24 
1-2 
I I 
The mesenterial entoderm varies from 6—12 p, its mesogloea from 1 — 2 p ; the axis- 
ectoderm 3—6 p, its mesogloea 1 p. or less, its entoderm 3 — -7 p. 
REVIEW OF MICROSCOPICAL ANATOMY. 
The results of microscopical examination of the various species have many points in 
common with Brook’s results. However there are important deviations from or complements 
to Brook’s data to be found, especially in the mesogloea, in the mesenteries, as well their 
