338 SEA MONSTERS UNMASKED. 



ink of the cephalopods serves by its colour as a means of 

 defence, as corresponding secretions in some of the mam- 

 malia by their odour. 



It is worthy of notice that the pearly nautilus and the 

 allied fossil forms are without this means of concealment, 

 which their strong external shells render unnecessary for 

 their protection. 



From the sac-like body containing the various organs 

 protrudes a head, globose in shape, and containing a brain, 

 and furnished with a pair of strong, horny mandibles, which 

 bite vertically, like the beak of a parrot. By these the 

 flesh of prey is torn and partly masticated, and within 

 them lies the tongue, covered with recurved and retrac- 

 tile teeth, like that of its distant relatives, the whelk, 

 limpet, &c., by which the food is conducted to the gullet. 

 Around this head is, as I have said, the organ which is 

 -equivalent to the foot in other mollusks that by which 

 the slug and the snail crawl only that the head is 

 placed in the centre, instead of in the front of it, and it 

 is divided into segments, which radiate from this central 

 head. These segments are very flexible, and capable of 

 movement in every direction, and are thus developed 

 into arms, prehensile limbs, by which their owner can 

 seize and hold its living prey. That this may be more 

 perfectly accomplished, these arms are studded along 

 their inner surface with rows of sucking disks, in each of 

 which, by means of a retractile piston, a vacuum can 

 be produced. The consequent pressure of the outer at- 

 mosphere or water, causes them to adhere firmly to any 

 substance to which they are applied, whether stone, fish, 

 crustacean, or flesh of man. 



But, although in all these highly-organised head-footed 

 mollusks the same general build prevails, it is admirably 



