Part II.—Stichodactyline and Zoanthee. 143 
As already ascertained by M*Murrich, there is no special concentration of the 
endodermal muscle to form a sphincter; indeed, the musculature, if anything. 
becomes more feeble towards the apex. 
The verrucee are readily distinguished from the rest of the column by the 
absence of gland cells from the ectoderm, and by the nuclear zone being broader 
and staining more deeply. 
Sections through the acrorhagi reveal a thinner wall, an absence of gland 
cells, and small nematocysts. 
In the tentacles, both the ectodermal and endodermal muscles are well- 
developed on mesogleal plaitings. The nematocysts in the former layer are 
extremely small, and, in both, the fibrillar layer extends for some distance from 
the mesoglea. Zooxanthelle are abundant in the inner layer. Where the 
sections include one of the tentacular swellings, the enlargement is seen to be due 
to a slight increase in thickness of the endoderm, but more especially of the 
mesoglea. 
The dise is much like the tentacles in structure, but thinner-walled, and fewer 
nematocysts occur in the ectoderm. The mesogleea is thrown into elongated 
branching folds to serve as an additional support to the endodermal circular 
muscle. 
Sections through the wart-like projections reveal slight, hollow upgrowths of 
the disc; the mesogloea and musculature become so attenuated as to be with 
difficulty recognizable, and the ectoderm is thinner than elsewhere, but ap- 
parently does not exhibit any new structural elements. Like M*Murrich, I 
have been unable to determine if the tubercles are actually perforated, but the 
delicacy attained by both the mesogloea and ectoderm at the apex is an indication 
that the production of a temporary opening by any pressure from within would be 
a matter of very little difficulty. It has already been noted that water may be 
emitted in the living condition. M*Murrich (1889, pl. iv., fig. 11) gives a 
figure of a section through one of the disc tentacles. 
The stomodzum is very elongate and oval-shaped in transverse sections, and 
extends almost across the ccelenteron, the pair of directives at each extremity 
being much shorter than the lateral complete mesenteries. In longitudinal 
sections, the stomodzum is comparatively short. Its walls are thin, and the 
ectoderm is thrown into irregular vertical folds, partly followed by the mesogleea. 
The gonidial grooves are clearly indicated at each end, their walls unfolded, 
and not much thicker than the rest of the stomodeum. At each end the groove 
is prolonged for some distance below the lateral walls, the directives remaining 
attached all the way. All the other mesenteries, however, are very deeply 
concave along their free edge towards their attachment to the stomodeal wall, so 
that in transverse sections through this region a short portion of each mesentery 
Y 2 
