280 



THE INHABITANTS OF THE SEA. 



Argonaut. 



Its two sail-like arms expanding in the air, and the six others 



rowing in the water, 

 the keel of its ele- 

 gant shell is pic- 

 tured as dividing 

 the surface of the 

 tranquil sea. But 

 as soon as the wind 

 rises, or the least 

 danger appears, the 

 cautious argonaut 

 takes in his sails, 

 draws back his oars, 

 creeps into his shell, 

 and sinks instantly into a securer depth. Unfortunately there is 

 not a word of truth in this pleasing tale. Like the common 

 octopus, the argonaut generally creeps about at the bottom of 

 the sea, or when he swims, he places his sails close to his 

 shell, stretches his oars right out before him, and shoots back- 

 wards like most of his class by expelling the water from his 

 respiratory tube. 



As he sits loosely in his shell, he was supposed by some 

 naturalists to be a parasite enjoying the house of the unknown 

 murdered owner ; but this is perfectly erroneous, as the young 

 in the egg already show the . rudiments of the future shell, 

 and the full-grown animal repairs by reproduction any injury 

 that may have happened to it. 



Thetetrabranchiatecepbalopods, or Nautili, are very differently 

 constructed from their dibranchiate relations. Here, instead of 

 mighty muscular arms, furnished with suckers or raptorial claws, 

 vre find a number of small, sheathed, and retractile tentacles (/), 

 surrounding the mouth in successive series, and amounting to 

 little short of a hundred. The head is further provided with a 

 large muscular disk (g), which, besides acting as a defence to the 

 opening of the shell, serves also in all probability as an organ 

 for creeping along the ground, like the foot in the Gastero- 

 pods. The mandibles are strengthened by a dense calcareous 

 substance fit to break up the defensive armour of the crustacean 

 or shell-fish on which the animal feeds. There is no ink-bag, 

 no organ of hearing, and the eyes (h\ are pedunculated, and of a 



