Molluscs. 23 



fishes ; tlieir predaceous habits and the rapidit}/ of their 

 rao\'ements have, m most cases, ahowed them to dispense with 

 the shell which affords such effective protection to other Molluscs. 

 As the name Cephalopods suggests, the front part of the foot 

 has come to surround the head, and it is divided into a number 

 of long mobile arms, or tentacles, which, at least m all the 

 Britislr representatives, are provided with large suckers. The 

 lunder part of the foot is modified to form a muscular pro- 

 trusible funnel directed forwards on the middle line, just m 

 front of the mantle-ca^dty, which opens to the exterior by a 

 sht-like orifice at its base. Water is continuaUy taken in 

 through this slit, and, after passing over the giUs, is expelled 

 through the funnel with sufficient force to propel the whole 

 ammal backwards when swimming. The mantle-ca\'ity also 

 receives the openings of the kidneys and the gut, and in con- 

 nexion with the latter there is, in all the British forms at 

 least, a peculiar gland which secretes an ink-like fluid, stored 

 in a tough bag and expelled through the funnels by the animal 

 when alarmed, with the e\adent object of obscuring the water 

 in view of facilitating its escape. The mouth, arrned with 

 two black, horny jaws, hke the beak of a parrot, is in the middle, 

 between the bases of the arms. The Cephalopods found on our 

 coasts have no external shell ; but all except the Octopus 

 have a sort of internal shell or " bone " embedded m the 

 muscles of the body. That of the Cuttlefish is often found 

 on the beach, and is utilised m canaries' cages for those birds 

 to sharpen their bills ; it is of large size and formed of chalky 

 substance, whicli is ground to make tooth-powder, and was 

 formerly much used in pharmacy' as an anti-acid. In the 

 Squids the " bone " is very different, thin and horny, in some 

 species resembhng a quill pen. It is represented by two minute 

 vestiges in the Octopus. The Cuttlefish furnishes the best 

 sepia ink of commerce. The sexes are distinct in all Cepha- 

 lopods, the males being distinguished by some modification 

 of one of the arms in connexion with the reproductive function. 

 Some of these animals attain a gigantic size. On April 28th, 

 1911, a huge Sqmd, probably Architeuthis hirveyi, was caught 

 in the Atlantic off the coast of Ireland and landed at Milford 

 Haven. The body is stated to have measured seven feet m 

 length and two feet in width, the longest tentacles measuring 

 about twenty-four feet. We have seen a photograph of this 

 monster, of wfuch, unfortunately, notlring was preserved. 



The largest species to be found close to the shore is the well- 

 known Octopus, Odopiis vulgaris (Fig. lo^.TOth the head confluent 



