No. 2:] A NEW MARINE TRICLAD. ba 8 | 
over a flame—either in the fresh state or after long preser- 
vation in alcohol —a beautiful net-work appeared on its sur- 
face (Fig. 6). The net itself is dark-colored, but the polygonal 
spaces enclosed by its meshes are much paler. In sections, 
when the knife skims off.the surface of the body, the same 
structure is apparent, but with the tones of color reversed: the 
net being colorless while the spaces take the stain. The same 
structure is also visible in sections of large specimens of &. 
candida. The ciliated membrane so closely resembles the 
pharyngeal epithelium of fresh-water Triclads after treatment 
with silver nitrate (see the Figs. of Woodworth, '91, and Chich- 
koff, '92), that I take the net-work to be an indication of 
cellular structure. Each polygonal area probably represents a 
cell. The lack of any traces of nuclei in these areas puzzled 
me at first, but I believe that they are to be found just 
beneath the longitudinal muscles (Fig. 10 Zy). Occasional 
processes from these hypodermal cells may be seen extending 
out between the muscle-strands and joining the plaque-like 
polygonal pieces of the ciliated membrane. Sometimes the 
nuclei lie between the muscle-strands or even nearer the 
surface. From these conditions I conclude that the hypoder- 
mal cells of Syxcelidium are mushroom-shaped, the cell-body 
being represented by a polygonal ciliated umbrellar portion 
with a stem in which the nucleus is lodged and which extends 
in some distance below the surface and between the muscle- 
- strands. The portion of the hypodermal cells which I have 
called the ciliated membrane — and which, if my interpretation 
be correct, is really no membrane at all —is liable to separate 
from the underlying muscle layer in specimens killed in hot 
sea water (Fig. 10). 
2. Musculature. 
Immediately beneath the ciliated portion of the hypodermis 
— providing I have not overlooked some structure corre- 
sponding to the basilar membrane of the fresh-water Triclads 
—lies a very delicate layer of transverse muscles, which 
may be detected in thin tangential sections. The smooth 
fibres, of which this layer is composed, vary somewhat in 
