158 SEA-SHORE LIFE 



belief it never swims at the surface. The chambers of the shell, 

 the construction of which we hav^e already mentioned, are filled 

 with gas, this being a mixture of oxygen and nitrogen resemb- 

 ling ordinary air, but being richer in nitrogen. This gas prob- 

 ably serves to increase the buoyancy of the shell, so as to 

 enable the animal to move more rapidly. The animal itself is 

 confined to the outermost and largest chamber of the shell. The 

 mouth is provided with a pair of parrot-like beaks composed of a 

 black, horny substance, coated on the outside with shelly matter. 

 There are about 90 tentacles around the mouth. These have poorly 

 developed suckers, and can be retracted each into its own special 

 sheath. The sheaths of two of these tentacles are fused into a 

 broad, flat plate called the hood, that serves to partially close the 

 aperture of the shell when the animal retracts. This hood lies on 

 the back of the head, while on the lower side we find a tube made 

 of two side folds which overlap. This is the "siphon" or fun- 

 nel through which water is expelled, driving the animal back- 

 ward. In this manner it swims through the water near the bottom, 

 gliding along with the aperture of the shell turned upwards and 

 the tentacles held close together and trailing out horizontally. The 

 writer was informed by natives of the Paumotu Islands, however, 

 that the nautilus also crawls over the bottom, and often buries itself 

 beneath the sand. 



In the Philippine Islands the nautilus is captured in traps 

 somewhat similar in construction to our lobster-pots, the bait used 

 being pieces of chicken or even dead dogs and cats. The animal 

 is eaten in these islands but is not highly esteemed, and a better 

 price is now obtained for the shell, which is used in China for the 

 manufacture of pearl buttons. 



The tentacles and funnel-tube are oiDaque-white, while the 

 hood is speckled with brown and yellow spots. There is a simple, 

 pit-like eye mounted on a short stalk on either side of the head, and 

 this is so placed that it can obtain a view of the surroundings even 

 when the creature is almost completely retracted, and the aperture 

 of the shell all but closed by the hood. The shell of the nautilus 

 is smooth and white and marked with bands of reddish-brown, 

 while the inner side of the aperture "is marked with jet-black where 

 the mantle fold is applied to the shell. The partitions of the cham- 



