OF CREATION. 145 



that it could have assisted to raise or sink the animal 

 in the water in the case of the ammonite. 



The cephalopods we have hitherto considered 

 form a group differing from the common cuttle- 

 fish in some important anatomical characters, and 

 having an external shell into which they could retire. 

 They also differed in the absence of any defensive 

 contrivance like that possessed by the cuttle-fish, 

 which is known to emit an inky fluid in order to es- 

 cape from its enemies. It is probable that all those 

 species provided with chambered shells belonged, like 

 the nautilus, to the less highly organized division of 

 the Cephalopoda, the animals of this group, as is the 

 case with the other shell-clad mollusca, being gene- 

 rally too well protected to need any means of tem- 

 porary concealment. They were doubtless able to 

 shelter themselves completely within their houses of 

 stone ; and it is not unlikely that the very act of 

 retirement into its shell would tend to sink the ani- 

 mal, by diminishing the quantity of surface exposed 

 to the water. 



But there exists another group of cephalopods 

 besides those provided with shells, and comprising 

 animals of higher organization ; obeying in this re- 

 spect the law which I have already had occasion 

 to notice, that animals having defensive armour are, 

 on the whole, not so high in the scale of beings as 

 those which resemble them in other points of struc- 

 ture, but whose bodies are naked and apparently 

 more exposed to danger. 



That division of the Cephalopoda which approxi- 

 mates most nearly to the Vertebrata comprises se- 

 veral families, of one of which the common cuttle- 



H 



