CTSTICEBCU8 CELLULOSE, AS POimD IN THE MUSCLES OF THE PIG. 113 
deep one. These are connected by a transparent material which composes the chief 
thickness of the membrane, which is deeply wrinkled transversely, and thus formed 
internally into a number of transverse sacculi. The cavity of the neck does not com- 
municate directly by any visible opening with that of the ventral portion. It is almost 
completely filled with oval laminated particles of earthy matter resembling minute 
calculi (see Plate X. fig. 3), which effervesce briskly when put into diluted muriatic acid, 
but which leave a residue of animal matter after all the earthy salt has been dissolved. 
These bodies begin to be formed as soon as the neck appears, and continue to increase in 
number as it increases in size. 
The probable office of bodies so purely mechanical in their form and simple in their 
composition, is most likely one which is purely mechanical also. Perhaps by giving a 
degree of solidity to the neck, they enable the circular and longitudinal fibres entering 
into its composition, to effect its protrusion from the ventral cavity, and thus serve as an 
example of a very low type of an internal skeleton. 
The terminal smfface of the neck is of a quadrangular form, each angle being occupied 
by a circular disc or sucker, and its centre contains an apparatus of booklets (see Plate X. 
fig. 2), and thus the four suckers and booklets are all situated nearly upon the same 
plane, a position which would be advantageous for the employment of these organs 
when the animals are transferred from their deeply-seated and confined position 
between the muscular fibres to the free surface of a mucous membrane. The suckers 
are of a circular figure, with a diameter of about y^th of an inch. See Plate X. fig. 4. 
Each consists of two or three membranous folds, placed at different depths from the 
surface, of about three-fourths of a circle in extent, so that the passage through a sucker 
from the external surface to the interior of the neck is rendered rather tortuous, and 
inclining to a spfral. The external opening of this passage varies very much in different 
Cpticerci, both in size and shape ; but it is always smaller than the internal one. It is 
difficult, if not impossible, to demonstrate by the microscope alone, the existence of a 
passage through a sucker ; however, this fact admits of proof from the circumstance of 
the carbonic acid, which is evolved in the cavity of the neck during the decomposition of 
the calcareous bodies, when these animalcules are in acetic acid, being seen under the 
microscope to pass freely through the openings in the suckers. In the membranous 
folds of the suckers, both circular and radiating fibres are distinctly visible, resembling 
in their general characters those in the neck, already mentioned. See Plate X. fig. 4. 
The booklets, as before observed, are situated in a circle around the centre of the 
square space before described. See Plate X. figs. 2 and 5. They are generally twenty-six 
in number, thirteen long and as many short, arranged alternately, a long and a short 
one. Occasionally, but very rarely, there are more: I have seen as many as twenty-nine. 
The longer booklets are about i^ch in length, the shorter ones are a little 
less. Each consists of a curved part resembling a bird’s claw, and a straight part or 
handle ; and at the junction of these two parts there are rounded processes or tubercles, 
two in the short booklets, and only one in the long ones, an anatomical mark by which 
