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seen, in the form of broad tapes running freely through the 
body-cavity, inserted at each end into some part of the skin 
by terminations more or less branched and divergent. Some of 
these pull the head down, or to one or the other side, or to the 
back or front; some, attached at the infoldings, produce the 
telescopic inversions ; some draw in the different joints of the 
foot, or move the whole foot, or each joint, in various directions, 
or separate the toes. 
Other muscles are seen in the form of slender elastic threads, 
of which there are very many, crossing the body in various 
directions, attached by expanding ends to the different viscera 
and serving to move them quickly and vigorously. There are 
also bands which go transversely around the body, no one 
band, however, completing more than a part of the circum- 
ference : the action of these appears to be to narrow the 
breadth of the cavity, and so to protrude the extremities, — 
either the head or the foot, or both at once. Minute and com- 
plex muscles are also present in the interior of the head, and 
in the mouth (• mastax ) in great number, effecting the most 
precise and varied movements of these parts. 
In order to render clear the form of the mouth in this order, 
I must again have recourse to a homely comparison. The 
parts, which, in the Builders,* I have endeavoured to illus- 
trate by means of a cut apple and a set of pins, arc all here, 
but they are so modified and changed in form and mutual 
relation that they can no longer be made intelligible by that 
device. Take away then the split apple, and substitute for it 
a pair of gardener’s edging-shears, the blades of which stand 
in a different plane from the handles. Suppose there is but 
one handle (the pair being bound together, if you like), and 
the blades are hinged to its extremity so as to work while it 
remains fixed ; now turn it up, so that the handle stands erect 
upon its top, and the blades work in the air nearly horizon- 
tally. If the blades were considerably widened, and curved 
downward at their tips like some surgical scissors, the resem- 
blance would be perfect. These then are the lower jaws, tech- 
nically termed the incus, the blades being the rami, and the 
handle the fulcr um. 
Now then, for the upper jaws, we will again resort to the 
gardener’s shed and rummage among his tools. We find 
a small digging-fork, such as can be used with one hand. It 
has three teeth, but that is of no consequence, for if it had but 
one, or any other number, up to seven or eight, it would still 
serve to represent the structure in some species or other. We 
take two such forks, and carry them away as lawful prize, in 
* See “ Popular Science Review,” vol. i. p. 478. 
