The Chambered Nautilus 



The floor of the cavernous outer chamber is of pearl, secreted 

 by the mantle, which lies next to it. As growth extends the 

 edge of the shell, giving more room, the body is drawn forward, 

 and a pearly wall is formed one-half inch or more outside the 

 last one. It is shaped like a deep saucer, with a little pit in the 

 centre. The siphuncle, a membranous extension of the body, 

 like a piece of delicate rubber hose, passes through all the par- 

 titions, connecting the innermost chamber of the shell with the 

 outermost one. The siphuncle is supported and protected at each 

 passage. 



Some investigators assert with confidence that air is admitted 

 by it to the shell chambers, and that the buoyancy thus acquired 

 enables the Nautilus to float, and to carry the shell with ease 

 when it walks on the deep sea bottom. Analysis shows the gas 

 to be a little richer in nitrogen than the atmosphere, but other- 

 wise to be much the same. "To maintain the relative weight 

 of the growing animal and its shell with the water," is the opinion 

 of many. The last word has not been said upon this interesting 

 question. 



The shell is brightest and most lustrous when inhabited by 

 its living tenant. The body is white as curds, except for brown 

 and yellowish trimmings which harmonise with the markings on 

 the shell. Stout muscle masses attach the body to the walls of 

 the outer chamber. 



"A Nautilus shell with a cauliflower sticking out of its 

 mouth" — thus one surprised scientist characterised the living 

 mollusk. The extended body shows a complicated system of 

 tentacles of varying sizes, with bases of swollen fleshy ridges 

 which conceal the mouth. Three dozen tentacles of greatest 

 length form the outer whorl. These each consist of a stocky, dark 

 brown, basal part surmounted by a slender, white "cirrus" or 

 whip, whose function is prehensile. They are the hands and feet 

 and fins of the Nautilus. There are no suckers. The tentacles 

 cling firmly but delicately to objects, seizing with avidity soft 

 bits of decaying animal matter. The mantle rim twitches while 

 the tentacles are active. When a live animal like a crab 

 is seized, the head protrudes, the two horny parts of the 

 beak are seen to tear the creature's tough body cover, or 

 cut it like a pair of shears, and the rasping mollusk tongue 

 comminutes the flesh. 



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