392 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
the stomatodeum is bent back upon itself as represented in the diagram 
(Fig. 1), and its ectoderm becomes continuous with the epithelium of the 
large ciliated bands. From the reflected stomatodzeum the free edge 
of the mesentery, with the filament, extends outwards, and then arches 
downwards. Consequently, in transverse sections through the column, 
the filament will be cut practically longitudinally above (Fig. 1, DD), 
then somewhat obliquely, and below transversely (Fig. 1, 4A). 
I have represented in Figs. 2, 3 and 4, 
sections through the ciliated bands at ap- 
proximately the levels indicated in Fig. 1 
by AA, BB,CC,and DD. In Fig. 2, two 
mesenteries are shown, and the section 
ca “nutes probably not having been perfectly trans- 
uu verse, and the amount of contraction not 
Ss having béen quite the same in each 
mesentery, the filaments are cut at differ- 
ent levels—2A approximately at the level 
indicated by AA in Fig. 1, and 2B at the 
level indicated by BBS. In 2A the fila- 
ment is cut almost transversely. The 
free edge of the mesentery is occupied by 
a tolerably high epithelium which con- 
tains numerous clear gland cells, probably 
mucous in character ; the free edge of the 
mesogloea is somewhat expanded to sup- 
port this epithelium, and, resting upon it, 
is a layer of very fine longitudinal muscle 
Fic 2.—2A is a section of the ciliated 
band at the level indicated in Fig. 1 by fibres. Probably a layer of nerve fibres 
AA. 2B is at the level indicated in Fig. 
fe, is also present, but I could not be sure of 
it.. From each side of the base of the ex- 
panded edge of the mesogloea a strong wing-like lamella arises, 
lined on the surface next the mesentery by endodermal cells, 
similar to those of the surface of the mesentery ; on the surface, turned 
away from the mesentery, however, the epithelium is of a different 
nature. Nearest the free edge of the mesentery it consists of cells for 
the most part resembling ordinary supporting cells (S¢#¢zzellen) with an 
occasional gland cell, containing numerous deeply staining granules, 
interpose Towards the free edge of the lamella, however, the cells are 
very slender, so that the nuclei seem closely packed, and are provided 
with rather long cilia; no gland cells are to be seen in this region. On 
one lamella of Fig. 2A, these cells form a continuous layer occupying the 
