OF CREATION. 



43 



internal skeleton, and a perfect symmetry throughout 

 the animal and vital organs. The muscular system 

 also forms a larger proportion of the body ; the nerv- 

 ous centres, concentrated in the head, have received a 

 marked increase of bulk ; the organs of the external 

 senses are much more perfectly developed, and the re- 

 spiratory tube has received an enormous development, 

 and assists in propelling the cephalopod through the 

 sea. The organs of locomotion and prehension are 

 now arranged round the aperture of the mouth, which 

 besides these possesses jaws working like the beak of 

 a bird, and a strong spiny tongue. The organs of 

 locomotion and prehension are, however, exceedingly 

 simple and very numerous, differing in this respect 

 from the more highly organized cuttle-fish. 



Lastly, in the shell we see a marked approach to 

 a higher form of animal existence than is exhibited 

 in other univalve shells. In the few animals in- 

 closed in shells that are able to swim, we find 

 the shell of very diminutive size, of simple form 

 and structure, and of an extremely light and delicate 

 texture. In the nautilus, on the other hand, we 

 find a large, powerful, and complicated shell, com- 

 posed of a number of separate compartments or 

 air-chambers, all of them together forming a float, 

 and enabling the strong and muscular occupant to 

 rise at will to the surface of the water, or sink down 

 into the depths of the ocean in search of the food of 

 which it no doubt requires an abundant supply. 



It is probable that the nautilus and its shell 

 together are somewhat, though very little, heavier 

 than water, when the animal has retired completely 

 within its habitation. When, however, it expands 



