483 



therefore, in their origin, probably independent of correct scien- 

 tific knowledge. * 



You have learned from the geologists, and mostly from those of 

 the present century, that the strata of the earth have been suc- 

 cessively formed from fragments more or less comminuted by me- 

 chanical action, more or less altered by chemical combination and 

 molecular rearrangement. These fragments were derived from 

 strata previously deposited, or from material brought up from 

 below, or even thrown down from above, or from the debris of 

 organic beings which extracted their mineral constituents from 

 surrounding media. Nothing new has been added, everything is 

 old : only the arrangement of the parts is new, but in this arrange- 

 ment definite and recognizable unchanged fragments of the old 

 frequently remain. Geological observation is now so extended 

 and accurate that an experienced student can tell from what for- 

 mation, and even from what particular locality these fragments 

 have been derived. 



I wish to show that this same process has taken place in the 

 organic world, and that by proper methods we can discover in our 

 fauna and flora the remnants of the inhabitants of former geologic 



of variation which are supposed to account for the differences in 

 the organic beings of different periods. 



groups of animals which are rarely preserved in fossil condition, 

 to reconstruct, in some measure, the otherwise extinct faunas, and 

 thus to have a better idea of the sequence of generic forms in time. 



have taken place in the outline of the land and the sea. More im- 

 portant still, we will have some indications of the time when 



buried at thcf bottom of the ocean, or perhaps entirely destroyed 



through evidence to be gained in the manner of which I am about 

 to speak. 



My illustrations will naturally be drawn from that branch of 

 zoology, with which I am most familiar ; and it is indeed to your 



