SPERM WHALE’S FOOD. 
57 
mechanism is more artificial than the simple construc- 
tion already described, for when the surface of the disk 
is fully expanded, we find that it is formed of a great 
number of small slender pieces, resembling teeth, closely 
set together, and extending from the inner margin of the 
cartilaginous rings in the form of converging radii, to 
within a short distance of the centre, where they leave 
a circular aperture. 
“ In the flattened state of the sucker, this aperture is 
filled by the projecting part of a softer substance, which 
forms an interior portion capable of being detached from 
the flat circle of the teeth when the sucker is in action, 
and of leaving an intervening cavity. It is evident 
that by this mechanism, which combines the properties 
of an accurate valve with an extensive cavity for pro- 
ducing rarefaction or the tendency to vacuum, the power 
of adhesion is considerably augmented. So great is the 
force with which the tentacula of the cuttle-fish adhere 
to bodies by means of this apparatus, that while their 
muscular fibres continue contracted, it is easier to tear 
away the substance of the limb than to release it from 
its attachment. Even in the dead animal, I have found 
that the suckers retain considerable power of adhesion 
to any smooth surface to which they may be applied. 
“ The octopus , which was the animal denominated 
polypus by Aristotle, has eight arms of equal length, 
and contains in its interior two very small rudimentary 
shells, formed by the inner surface of the mantle. This 
shell becomes much more distinct in the loligo, where it 
is cartilaginous, and shaped like the blade of a sword. 
d 2 
