312 EXTINCTION OP SPECIES. 



offer us subjects of contemplation of the most interesting 

 character, in which the mind is at one time carried back 

 to what has been "before the world was," and at others, 

 stretches equally forward to what shall be hereafter. In 

 tracing fossil remains in strata, deposited at successive 

 periods, we come to beds in which remarkable forms, 

 such as the Ammonite, meet us for the first time ; and, 

 having ascertained that none exist in any lower bed, we 

 are forced to admit that, at the time when that bed was 

 in course of formation, these creatures were first intro- 

 duced on the stage of life. All lower beds tell of a cre- 

 ation existing before them, and the animals contained in 

 such are therefore older denizens of the world. Again, 

 having fixed the stratum in which the Ammonite first 

 appears, we examine the strata above it, and find the 

 number of those fossils gradually increasing, until we 

 reach a bed in which the genus attains its maximum ; 

 and thence we find a gradual diminution of species in 

 all superior beds. No new forms are introduced, but 

 the old ones drop off one by one, until at last the whole 

 race disappears every species of the extensive group 

 being numbered with the dead. Nor is this a solitary 

 instance of what researches into the fossil world reveal 

 to us. It is the general lot of every organic being in- 

 troduced into the world. Not only are the individual 

 animals mortal, but the very species are destined to 

 destruction. Some types have a longer life than others. 

 The Nautilus still maintains its ground, though its 

 genus dates back untold ages before the creation of the 

 Ammonite, whose last representative must have perished 

 ages before the creation of man. We see the whole life 



