180 THE PEARLY NAUTILUS. 



of the hood. All these tentacula, whether oral, or be- 

 longing to the hood, receive large nerves, and are evi- 

 dently endowed with an acute sense of touch ; and when 

 we consider the number of these moveable worm-like 

 feelers, we cannot but be convinced that their presence 

 raises the animal to the highest point in the scale of the 

 mollusca, and renders it the recipient of impressions 

 more varied and accurate than in the lower vertebrata, 

 as, for instance, amphibia and fishes. 



With regard to the habits of the pearly nautilus, little 

 is ascertained. The extent to which the animal is 

 covered by its shell, caused Aristotle to compare it to a 

 snail ; and, as Professor Owen remarks, " the general 

 resemblance must be sufficiently striking when with his 

 house above him, and in the supine position, he makes his 

 way along the sand, with a moderate degree of rapidity." 

 This, indeed, is probably the animal's ordinary mode of 

 progression ; but it is certain that it frequently rises to 

 the surface of the water and floats, drifted along by the 

 current or the breeze. This navigation is indeed only 

 passive, or at most influenced by the jets of water ex- 

 pelled from the branchial cavities, through the funnel, 

 at regular intervals. 



Rumphius, alluding to the fact of the floating of the 

 pearly nautilus, says, " When he thus floats he puts out 



