The Morphology of Coeloplana. 55 
“Ciliated Rosettes” as described by Chun 1880. These are identical 
in every way with those of pelagic Ctenophora. They lie in the 
walls of the gastric canals and consist of two layers of 8 cells each, 
surrounding a central cavity into which project strong cilia from 
the “rosette” cells (fig. 3 and 8). The beating of these cilia may 
cause a strong current to flow between the parenchyma and the 
lumen of the gastric canal. 
c) Tentacles and related structures. 
General description. 
The sheathes of the pinnate tentacles are capacious pouches and 
when the tentacles are fully retracted, are swelled out into pro- 
minent bulging masses on either side of the otolith. Notwithstanding 
the size and capacity of these sacs, it is a constant marvel how 
the whole of the tentacle with its secondary branches, — often 
stretching down to a distance of six or eight times the diameter of 
the whole animal — can be accommodated within. In very trans- 
parent specimens it is seen that the pouch is not a simple sac or 
tube but that there are secondary diverticula leading off from the 
main cavity, — all crowded with writhing filaments, closely packed. 
In such clear specimens an appearance may be noted that is con- 
fusing and difficult to interpret without the aid of sections. The 
central end of the sheath appears rounded and bent back upon it- 
self like a fishhook, the termination being directed toward the 
periphery. In sectioned material it may be seen that the central 
end of the sheath, 1. e. the point nearest the otolith is expanded 
into a bell from the wall of which the heavy root of the tentacular 
muscle takes its origin in part. Lying normally below the main 
cavity of the sheath, but sometimes pushed to one side is what may 
be called the accessory sheath, a large diverticulum of the main 
sheath, that in surface view appears to be a continuation of the 
main sheath and gives the appearance of the latter being turned 
back, away from the center. The tentacle itself may be said to be 
anchored to the whole floor of this accessory sheath which spreads 
out into a broad flat cavity and is lined with formative tissue. The 
development and growth of these lining cells and of the muscle fibres 
connected with them is centripetal. The muscle of the tentacle, 
formed in this accessory branch bends sharply in the neighborhood 
of the otolith and enters the true sheath, forming the flaming “bell” 
structure alluded to. The tentacle consists of a main filament of 
