the Actiniarian Family Aliciide. 9 
latter layer is very thin. The endoderm is narrow and 
contains zooxanthelle. 
In several specimens sectionized the endoderm is divisible 
into two portions—a proximal, which is largely reticular in 
character, and a more internal part crowded with nuclei and 
zooxanthellae (figs. 3, 4). The separation of this reticular 
layer, sometimes on the endodermal side and sometimes on 
the ectodermal side of the mesogloea, is a well-marked feature 
of some examples and is found practically throughout the 
whole polyp. The reticulum appears to be formed of the 
nervous and perhaps muscular and mesogloeal elements, 
probably separated more distinctly by the unequal contraction 
of the mesogloea and the two other layers, but is not a con- 
stant feature of the species, being evidently partly dependent 
upon the method of preservation. In vertical sections of the 
base the mesogloea borders directly on the ectoderm, and the 
reticulum is on the endodermal side, whereas in the tentacles 
it is on the ectodermal side. 
Column-wall.—The column-wall is very delicate and much 
broken up below by the outgrowths forming the vesicles. 
The nuclei in the ectoderm are uniformly distributed ; nemato- 
cysts apparently do not occur, except a few, similar to those 
of the tentacles, in the capitulum. An ectodermal muscle on 
small mesoglceal plaitings can be distinguished. The meso- 
gloea is thicker than at the base and contains a few isolated 
cells. The endoderm has abundant nuclei and zooxanthelle. 
The vesicles are hollow outgrowths of the body-wall, but 
their structure differs somewhat. The thickenings and 
tubercles seen externally are shown in sections to be batteries 
of nematocysts. ‘The stinging-cells are very long, extending 
across the ectoderm, and are limited to the enlarged areas. 
Many cysts present a fine internal beaded character, due to the 
spiral thread seen in optical section, while others, mostly in 
the deeper parts, show no thread and may have the contents 
staining deeply, being evidently only in process of development. 
Small oval nuclei are, more particularly in the thickened 
regions, arranged in a narrow belt just below the surface. 
The remaining area is much vacuolated in places. ‘The ecto- 
derm ot the vesicles where devoid of nematocysts is very thin. 
The mesogloea is narrow. The endoderm contains zooxan- 
thelle, but not pigment granules such asare abundant in A. coste 
and A. mirabilis. A slight endodermal muscle can be distin- 
guished. In the difference in the characters of the nemato- 
cysts in the vesicles and those of the column-wall and tentacles 
Bunodeopsis agrees with the two species of Alicia examined. 
‘They are, however, larger in the latter genus. 
Sphincter muscle.—'The sphincter muscle is of the diffuse 
