206 INVERTEBRATE ANIMALS. 
The body in the Cephalopoda is symmetrical, and is enclosed 
in an integument which may be regarded as a modification of 
the mantle of the other AZo//usca. Ordinarily there is a toler- 
ably distinct division of the body into an anterior portion, car- 
rying the head, and a posterior portion, in which the internal 
organs areenclosed. The head (fig. 109) is very distinct, bearing 
a pair of large globular eyes, and having the mouth in its centre. 
The mouth is surrounded by a circle of eight, ten, or more, long 
muscular processes, or arms, which are generally provided with 
rows of suckers. Each 
sucker consists of a cup- 
shaped cavity, the mus- 
cular fibres of which 
converge to the centre, 
where there is a little 
muscular eminence or 
papilla. When the 
sucker is applied to any 
surface, the contraction 
of the radiating muscu- 
lar fibres depresses the 
papilla so as to produce 
a vacuum below it, and 
in this way each sucker 
acts most efficiently as 
an adhesive organ. The 
whole of this complex 
mechanism of suckers is 
completely. under the 
control of the animal, 
and the irritability of the 
suckers is retained even 
for days after death. In 
Fig. tio.— Diagram of a Cuttle-fish (altered from most of the Cuttle-fishes 
Huxley). 2 Mandibles ; z Cerebral ganglia ; Oeipodavth 1 
7 Liver; Z Intestine ; o Ovary; g Gill ; zInk-bag; ( ctopo a) eee 
_ f Funnel; s Internal skeleton, or ‘‘cuttle- eight arms, and these 
bone.” are nearly similar to one 
another (fig. 111). In others, however (fig. 109), there are ten 
processes round the mouth, of which eight are like each other, 
and constitute the true arms, whilst two—called tentacles— 
are much longer than the others, and bear suckers only towards 
