444 TEXT-BOOK OF ZOOLOGY 



rapidly over the body, something like the fugitive red blush on the 

 human face.) The cuttle-fish resorts to further means of rendering itself 

 unrecognisable by covering its body with sand and pebbles. (Compare 

 with plaice.) 



(b) Being, however, unprovided with articulated limbs, the mollusc 

 requires organs for capturing and holding fast its fugitive prey. This is 

 accomplished by the ten arms attached to the head. Two of these, which 

 are considerably longer than the rest, are thrown out like lassos, and by 

 means of their numerous suckers apply themselves so tightly to the body 

 of the prey that escape is no longer possible. These tentacles next, by 

 shortening, bring the victim within the grasp of the eight shorter arms 

 which encompass it, and hold it fast by hundreds of suckers. Each of 

 the latter is carried like a berry upon a small stalk, or peduncle, and 

 consists of an external ring, strengthened by an internal cartilaginous 

 support and a central muscular piston. When the ring is tightly 

 applied to an object and the piston retracted, a vacuum is produced 

 underneath the latter, so that the disc adheres to the object like a 

 cupping-glass. (Mention some physical experiment based on the same 

 principle.) By the aid of these sucking-discs the cuttle-fish is also able 

 to progress, walking upon its arms, with its head directed downwards 

 (cephalopod, i.e., head-footed). 



(c) The cuttle-fish cannot swallow its prey, and is accordingly 

 provided with powerful jaws and a radula in the buccal cavity, like 

 gastropods, for the purpose of dividing it into smaller pieces (see p. 432). 



(d) Closely connected with its predatory mode of life are* 1 also the 

 extraordinarily large, keen- sighted eyes of the animal, which are con- 

 structed very similarly to those of vertebrate animals (see Part I., p. 12 ; 

 and contrast with gastropods and lamellibranchs). 



5. Enemies. The predaceous cuttle-fish is itself actively pursued by 

 large fish and toothed whales. With two important means of protection 

 against these viz., its capacity of rapidly adapting its colour to the 

 bottom and of swiftly hurrying backwards through the water we have 

 already become acquainted. When both these means fail it, the animal 

 can still fall back upon a third and extremely remarkable method of 

 escape : it discharges into the mantle cavity a blackish-brown colouring 

 matter, expels the water thus discoloured through the funnel, and thus 

 envelops itself in a dark cloud, in which it vanishes from the sight of its 

 pursuer. This colouring matter (sepia ; see Section 1) is produced in a 

 gland, and stored up to be used when required in the so-called ink-bag. 

 (Why is the name " cuttle-fish " only half correct ?) 



