Part IT.—Stichodactylinee and Zoanthee. 149 
The base is very spreading, irregular in outline, and firmly fixed to coral 
rock, adapting itself to the irregularities of the surface ; in diameter it is larger than 
the column. A brownish, cuticular layer occurs between the ectoderm of the base 
and the surface of attachment, and may either be detached with the polyp or 
remain adhering to the rock. The internal, radiating mesenterial lines are clearly 
indicated through the thin basal-wall. 
The column is short, thin-walled, and semi-transparent, the mesenterial lines 
showing through; the surface is smooth, and thrown into delicate longitudinal 
ridges and furrows, and occasionally transverse wrinklings are indicated. The 
limbus is spreading and irregular, and the polyps are generally constricted a little 
above the middle. The upper region of the column and the disc usually overhang 
so as to hide the parts below. Individual polyps are generally oval in outline in 
transverse sections. 
A single cycle of very short tentacles occurs at the apex of the column or 
margin of the disc, a longer tentacle alternating with a short one, or there may be 
two or three of the latter between two longer ones. Much irregularity occurs in 
this respect. In shape the tentacles may be shortly acuminate, or cylindrical and 
rounded at the tips. A small, nearly horizontal, tentaculiform outgrowth projects 
from near the base of many of the larger tentacles, and, occasionally, from the 
middle tentacle of an alternating three. 
The dise is divisible into two regions: a peripheral, naked area, limited out- 
wardly by the marginal cycle of tentacles; and a larger, inner area bearing the 
branching outgrowths described as tentacles. The peripheral portion of the dise is 
very thin, and sometimes stands as a distinct parapet or collar around the inner part; 
at other times it is entirely reflexed (Pl. x., fig. 3). The discal tentacles are very 
short, thick, columnar outgrowths which divide towards the apex into numerous— 
6 to 12—small, tubercular, finger-shaped, or pointed processes. A few, irregularly 
arranged examples may occur near the mouth, or they may be practically absent 
from this region. ‘The organs are capable of assuming the flaccid condition, or 
one of distension, independently of one another. They may be distributed over the 
whole disc except near the margin, but are always less numerous centrally. The 
distinction between the discal and the perioral series is not always apparent. 
Usually the tentacles appear irregularly disposed, but occasionally an arrange- 
ment in cycles, or, more often, in radial series, is evident. It is doubtful if 
more than two or three ever communicate with the same mesenterial chamber 
GAL Ky ms, BB), 
In the living condition the disc usually overhangs so as to hide the base and 
column; but the peripheral, naked portion of the dise may be vertically elevated 
as much as 4 mm. above the central part. In retraction the capitular part of the 
column closes over the rest of the disc as a thin, radiately marked, semi-trans- 
TRANS. ROY. DUB. SOC., N.S. VOL. VII., PART VI. Z 
