190 J. E. Duerpen—Jamaican Actiniaria : 
A peculiarity connected with the Zoanthean filament is that the Flimmers- 
treifen extend for some distance up each face of the perfect mesenteries, just 
before the latter cease their connexion with the stomodzum; the middle portion 
is folded and in actual contact with the mesentery, while the two ends, or at any 
rate the centrifugal end, may hang freely in transverse sections. The whole 
structure has been denominated by Haddon and Shackleton (1891, p. 619), the 
‘reflected ectoderm,” these authors regarding it as representing a portion of the 
stomodeeal ectoderm which has become transferred to the face of the mesenteries. 
In the adult the reflected ectoderm and mesenterial filaments are always found in 
absolute continuity with the ectoderm of the stomodzeum. And it has also been 
demonstrated by M*Murrich (1891) and others, that even at an early stage in the 
development of the embryo such a relationship can be recognized. 
While not inclined to accept the ectodermal origin of the “ reflected ecto- 
derm,” or of any portion of the mesenterial filaments, the former term may be 
employed for the present as referring to parts now well known in Zoanthean 
morphology. The Hertwigs (1879) first emphasized the fact that trifoliate 
mesenterial filaments may appear on mesenteries of the lower orders which never 
reach the stomodeeum, and in all their structural details are indistinguishable 
from those occurring on the first order; and this appears to me to militate most 
strongly against an ectodermal origin to any part of the Actinian filament. I 
regard the continuity of the strongly ciliated stomodeeal ectoderm, reflected 
ectoderm, and the Flimmerstreifen and Driisenstreif of the mesenterial filaments 
as having a physiological rather than a morphological significance, as being 
necessary, in fact, for the proper maintenance and regulation of the imternal 
circulation of the respiratory and digestive fluids in the mesenterial chambers of 
and around the stomodeeal region. 
The histological characters of the tissues point to this, while the similarity of 
structure is not so great as is sometimes assumed. The uniform nature of the 
cells composing the Flimmerstreifen certainly contrasts strongly with the variety 
met with in the stomodeeal ectoderm, with the exception of those lning the 
gonidial grooves. The grooves are usually more strongly ciliated, and but few 
glandular or stinging cells occur amongst the supporting cells. 
Less differences exist between the Driisenstreif and stomodeal ectoderm, 
while the Entodermwucherung shows no histological relationship with the latter. 
The ciliation of the gonidial grooves, reflected ectoderm, and the Flimmers- 
treifen is more pronounced than that of any other region of the Actinian polyp, 
and usually persists in preserved specimens even when not observable elsewhere. 
The histological elements are also more specialized, pointing to a specialized 
function. The cells are almost entirely of the extremely narrow ciliated type, 
each with an oval-shaped nucleus, often larger in diameter than the cell itself, 
