10 



Fig. 4. 



Pillar descend- 

 ing from the 

 floors of the 

 chambers in the 

 Pearly Nautilus, 

 and serving as a 

 partial protec- 

 tion to the Si- 

 phuncle. 



most exterior, mathematically diminishing in size, yet each room 

 having a connection with the next, by a tube inserted in a short 

 hollow pillar (fig. 4). This short hollow pillar occupies the centre 

 of each floor, and follows the same curvature (only of 

 less radius) as that which the outer edge of the Nautilus 

 presents when placed on the flattened side. Eich then is 

 the creature in rooms, truly the possessor of a many- 

 roomed house, but miser-like, it occupies only one, the 

 exterior and largest. When it outgrows this one, it sets 

 to work to build another chamber, puts in a floor, adds 

 a descending pillar, shuts up the old apartment, and 

 having removed to the more modern chamber, lives 

 as before, but with increased accommodation. 



The use of the hollow tube or siphuncle (see figs. 3 

 and 4), partially enclosed in a series of short and un- 

 connected calcareous pillars, and the reason for the empty rooms or 

 chambers, have given rise to speculations not a few. Of these the 

 most reasonable refer the hollow pillar as a protective covering to a 

 membrane arising from the heart, which membrane also touching 

 the walls of the empty chambers can secrete shelly matter, and ac- 

 cordingly repair injuries to its external covering. The empty chambers 

 also are supposed to act as a counterbalance against the animal's 

 weight, making the whole mass almost of the same specific gravity 

 as that of sea- water, and therefore causing that mass to be capable 

 of being raised or depressed in the ocean by a slight muscular ex- 

 pansion or contraction of the body of the creature. 



Eespecting the habits of the Nautilus in a living state, recent in- 

 vestigations prove that it seizes small shells, crabs, and such like 

 things ; that with its hardened beaks, it breaks through their outer 

 coverings and drags forth their inmates ; that when pursuing its usual 

 course, or when in search of prey, it creeps along the bottom of the 

 sea, head downwards ; and that only after storms, as though driven 

 upwards by under currents, does it rise towards the surface, remaining 

 there a little while, with tentacles outspread upon the water, but never 

 raising them by way of sail. 1 



1 The tradition of the Nautilus sailing on the surface of the waves has reference in 

 reality to the Paper Nautilus (fig. 5), and that only in a mistake. 



