418 Happon—The Actiniaria of Torres Straits. 
Transverse sections of one specimen showed between 60 and 70 pairs of 
mesenteries. Of these some pairs are very small, only about 44 pairs having 
longitudinal muscular plaitings; about 24 pairs reach the cesophagus. In 
some cases one mesentery of a pair is much smaller than the other of the 
same pair. In some places, owing to the extreme irregularity in the mesen- 
teries, it is hardly possible to recognise a distinctly paired arrangement of 
mesenteries. There seems to be only one pair of directives (?). The muscular 
plaitings even of the largest mesenteries are not strongly developed, and parieto- 
basilar muscles seem entirely wanting. In transverse section many of the 
tentacles show a crenated outline like that seen in Bunodes thallia. The longi- 
tudinal muscle of each tentacle is ectodermal. It is a curious fact that, in a good 
many cases, the central cavity of each tentacle is occupied by the termination of 
a mesenterial filament. The endoderm throughout contains zooxanthellae which, 
however, are most numerous in the tentacles. A longitudinal section shows a 
thin body-wall without endodermal saccules. (Pl. xxvi., fig. 5.) The upper 
part of wall is thinner and less contracted than the lower part. The 
thinnest part of body-wall is that which forms marginal spherules; towards the 
endoderm the mesoglcea is thrown into small plaits, on the sides of which endo- 
dermal muscle cells occur. These plaits are most numerous near the lower part 
of the wall, and are entirely absent in the marginal spherules. (Pl. xxv1., fig. 1.) 
The thinness of the wall of the spherules is due to diminution in thickness of all 
three layers. Between the marginal spherules and the outer tentacles there is 
a well-marked endodermal diffuse sphincter muscle (PI. xxv1., figs. 2, 3). 
Some of the tentacles which are cut obliquely show beautifully both the ecto- 
dermal longitudinal and the endodermal circular muscles. 
The ectoderm of the disk resembles that of the body-wall, and is slightly 
folded back and forward on itself. Near the mouth, the ectoderm becomes 
thicker, and its columnar cells do not reach quite as far as the outer border of 
mesogloea, but an intervening space is present which is filled by a fine granular 
nervous layer similar to that seen in transverse sections of the tentacles (Pl. xxv1., 
fig. 4) between the ectodermal columnar cells and the mesogloea. 
ANEMONIA, Risso, 1826, p. 288; Andr., 1884, p. 189. 
(Anthea, Johnst., 1838.) 
Actiniide with smooth column; no distinct acrorhagi; tentacles usually 
long, and not retractile ; endodermal sphincter muscle usually feeble, but 
variable. 
There is no doubt that this genus is very closely allied to Actinia, M*Murrich 
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