EVIDENCE OF FOSSIL REMAINS 83 



ited as the result of a freshet. If a skeleton is too 

 greatly broken up or scattered, it may be difficult or 

 even impossible for its discoverer to piece together the 

 various fragments and assemble them in their original 

 relations. Very few individuals have been so buried 

 and preserved as to meet the conditions for the forma- 

 tion of an ideal fossil. To realize how little may be left 

 of even the most abundant of higher organisms, we have 

 only to recall that less than a century ago immense 

 herds of bison and wild horses roamed the Western 

 plains, but very few of their skulls or other bones re- 

 main to be enclosed and fossilized in future strata of 

 rocks. When we appreciate all these difficulties, both 

 geological and biological, we begin to see clearly why 

 the ancient lines of descent cannot be known as we 

 know the path and mode of embryonic transformation. 

 The wonder is not that the palseontological record is 

 incomplete, but that there is any coherent and decipher- 

 able record at all. Yet in view of the many and varied 

 obstacles that must be surmounted by the investigator, 

 and the adverse factors which reduce the available 

 evidence, the rapidly growing body of palaeontological 

 facts is amply sufficient for the naturalist to use in for- 

 mulating definite and conclusive principles of evolution. 



For the purposes of palaeontology, the most essential 

 data of geology are those which indicate the relative 

 ages of the strata that make up the hard outer crust of 

 the earth, for only through them can the order of animal 

 succession be ascertained. It does not matter exactly 

 how old the earth may be. While it is possible to 



