CONCLUSION. 287 



of the ancient seas, than are assigned to their few living 

 representatives in our modern oceans. 



Conclusion. 



It results from the view we have taken of the zoological 

 affinities between living and extinct species of chambered 

 shells, that they are all connected by one plan and organi- 

 zation; each forming a link in the common chain, which 

 unites existing species with those that prevailed among the 

 earliest conditions of life upon our globe ; and all attesting 

 the Identity of the design, that has effected so many similar 

 ends through such a variety of instruments, the principle 

 of whose construction is, in every species, fundamentally 

 the same. 



Throughout the various living and extinct genera of 

 Chambered shells, the use of the air-chambers and siphon, 

 to adjust the specific gravity of the animals in rising and 

 sinking, appears to have been identical. The addition of a 

 new transverse plate within the conical shell added a new 

 air-chamber, larger than the preceding one, to counter- 

 balance the increase of weight that attended the growth of 

 the shell and body of all these animals. 



These beautiful arrangements are, and ever have been, 

 subservient to a common object, viz. the construction of 

 hydraulic instruments of essential importance in the economy 

 of creatures destined to move sometimes at the bottom, and 

 at other times upon or near the surface of the sea. The 

 delicate adjustments whereby the same principle is extended 

 through so many grades and modifications of a single type, 

 show the uniform and constant agency of some controlHng 

 Intelligence ; and in searching for the origin of so much 

 method and regularity amidst variety, the mind can only 

 rest, when it has passed back, through the subordinate 

 series of Second causes, to that great First Cause, which is 

 found in the will and power of a common Creator. 



