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body, and also along the circular line on top of the jaws, and this 
last adhesion is not broad but almost linear (fig. 5, s). 
Leathery in spirit and water, its structures are not then 
readily distinguished ; but a fresh Ophiuran’s stomach mem- 
brane is semi or quite transparent, and yields some interesting 
points to the microscope. There is a muscular coat, consisting 
of sets of separate fibres, unstriped and sometimes branching, 
which radiate from many centres. Those of one locality join 
on to those of another, and form a series of close meshes* 
The fibres are distinct, delicate, and are outside a mass of cells, 
which are spread out as an indefinite membrane, and are ciliated. 
The cilia are numerous, small, and are readily cast off with their 
cell. It would appear that, although the lower limit of the 
stomach around the mouth within, is an irregular circle made 
by the jaw plates and the sloping sides of the jaws (producing 
five re-entering festoons and loops external to the jaw plate), 
there is a film of probably ciliated membrane passing down 
between the angles to the surface. But really the entrance to the 
stomach is central only, and not also between the side of each 
jaw angle. The teeth form five buttresses around the open- 
ing. The large tentacles in each angle are muscular, tubular, 
and ciliated, and they come out of the jaws by holes, one of 
which is nearer the stomach than the other. They fill up 
the angle greatly, and as they move radially, they assist the 
food in entering, and expel undigested matters, and, as Forbes 
wrote years since, they are in constant movement. Water 
passes readily into the mouth and stomach, when the teeth, set 
in longitudinal series on to the jaw plates, are slightly removed 
from each other (fig. 7, e .); but when they touch by their points 
the passage cannot be free. The question arises — Do the ver- 
tical true teeth act as chewers ? By what structures do they 
approach and regress in order to chew? Mr. Lyman calls the 
five angles of the mouth and the supported teeth the chewing' 
apparatus. We distinguish between biting, masticating, and 
chewing : the last term relating especially to the particular 
lateral movement used by mammals, and to a constant move- 
ment, in which the teeth are not much separated, and which is 
used by man to enjoy tobacco. 
There is evidently no lateral movement in the angles of the 
jaws, and that which is directly to or from the central or axial 
line of the vertical mouth, must be very slight. It would appear 
that the jaw plate is made up of more than one piece, although 
this is by no means always to be seen, and the teeth which it 
supports on its inner face (figs. 9 and 7, e) are said to be con- 
nected to it with muscular fibres. Microscopic, indeed, are 
they, and they can only relax and contract and fix the teeth 
laxly or rigidly to the jaw plate. Their power of assisting biting 
