196 J. E. DuerpEN—Jamaican Actiniaria: 
the oval nuclei of which are arranged at different heights in the different cells, so 
that a distinct, deeply-staining, nuclear zone is produced in sections (PI. xv., fig. 4). 
In transverse sections, a little above the stomodezeal termination, the reflected 
ectoderm is thrown into a few short vertical folds, and centrifugally is free from 
the mesentery, while centripetally it can be traced in continuity with the ectoderm 
of the stomodeum. 
This continuity is, however, not one of exactly similar tissues throughout, but 
is interrupted at places by a tissue of a different nature. The cell nuclei of this 
are rounded, and not arranged in a distinct zone, and the whole stains less deeply 
and contains zooxanthelle and granular gland cells. To this tissue, as met with 
in Zoantius chierchie, von Heider (1895, p. 129) has applied the term Driisen- 
wulst.” Though its presence can be easily recognized in P. tunicans, it is not so 
well developed as in the genus Zoanthus, where, owing to the increased size and 
length of the polyps, the reflected ectoderm and mesenterial filaments are better 
displayed and more favourable for study. 
As shown in PI. xv., fig. 4, a filament is a complex structure, the sagittate or 
lanceolate form in transverse sections being characteristic of the Zoanthese. The 
outer border of the lateral lobes is constituted of ciliated, extremely narrow 
cells, the associated nuclei forming a very regular, densely-staining zone. It 
is to this tissue that I consider the term ciliated streak or Flimmerstreif should 
be restricted, and not applied to the lateral lobe as a whole, as is usually done. 
The inner layer of the lobes is formed of endoderm cells, indistinguishable from 
the epithelium of the mesentery. The tissue occurring around the termination 
of the middle lobe is made up of ciliated supporting cells, granular gland cells, 
and nematocysts. The term glandular streak, Driisenstreif, or Nesseldriisenstreif 
should, in my opinion, be employed only for this part of the middle lobe, the 
intermediate streak coming between it and the ciliated streak. Towards its 
termination the mesogloea is slightly swollen, and delicate muscular fibres border 
it anteriorly. 
The mesenteries exhibit the macrocnemic arrangement, that is, the dorsal, 
or sulcular pair of imperfect directives has a pair of mesenteries on each side— 
of which the first 1s a perfect mesentery, and the other an imperfect—and the 
succeeding pair consists of two perfect mesenteries (Pl. xv., fig. 4). Beyond these 
the pairs consist of an imperfect and a perfect mesentery until the neighbourhood 
of the ventral or sulcar directives is reached, when the arrangement in pairs 
becomes a little irregular, this bemg the region in which new mesenteries are 
added. In one polyp eight perfect mesenteries occurred on each side, while 
in another eight were present on the left and six on the right side. 
The mesenterial musculature is extremely feeble, and the parieto-basilar is 
clearly distinguishable. ‘The mesogloea is broad at its origin in the column-wall, 
