§26. 



THE NAUTILUS. 



333 



26. The nautilus. — The shell of the Nautilus consists 

 internally of a series of chambers, pierced through the middle 

 by a siphunculus or tube, which extends to the remotest 

 cell. The body of the animal resembles, in some respects, 

 that of the sepia, and is contained in the outer recep- 

 tacle of the shell ; it maintains a connexion with the inner 

 chambers by means of a membranous tube which lines the 

 siphuncle The internal chambers are air-cells, and the 

 creature has the power of filling the siphuncle only, with a 

 fluid secreted for the purpose, and also of exhausting it ; 

 and the difference thus effected in the specific gravity of the 

 animal and its shell, enables the Nautilus to sink or swim 

 at pleasure. If, therefore, you imagine a cuttle-fish placed, 

 with its arms extended, in the outer chamber of a nautilus- 

 shell, and provided with a tube connected with the siphun- 

 culus, but having neither ink-bag nor osselet, these being 

 unnecessary to an animal with the protection and mechanism 



of a chambered shell, 

 you will have a tolera- 

 bly correct idea of the 

 recent Nautilus. The 

 Nautilus is essentially 

 a ground-dwelling ani- 

 mal, living in deep wa- 

 ter, and feeding on the 

 marine plants which 

 grow at the bottom of 

 the sea. Rumphius 

 states that it creeps 

 with the shell above, 

 and that by means of its tentacula it can make quick progress 

 along the ground.* There are several species of Nautilus 

 in the chalk, some of which are of large size : a common 

 marl species is figured in Lign. 64. 



* See Medals of Creation, vol. ii. p. 482. 



Lign. 64. — Nautilus elegans ; from the 

 Chalk- marl, near Lewes. 



