Evidences of Evolution 53 



§4. Evidences of Evolution. 



The root-idea of organic evolution is that the present 

 is the child of the past and the parent of the future. 

 Our present-day fauna and flora must be regarded 

 as arising by natural processes out of an antecedent 

 fauna and flora, on the whole somewhat simpler and 

 more generalized, and so on backwards through the 

 ages until we lose clue after clue and find ourselves 

 in the thick mist of life's beginnings. Apart from 

 occasional simplifications and relapses and what 

 might be called "eddies," there has been an age-long 

 progression from the simple to the complex, a general 

 advance in differentiation and integration, and a 

 frequent emergence of the distinctively new. It is 

 not merely that one type of crocodile evolved from 

 another, as the rock records show very clearly ; there 

 has also been an occasional appearance of great novel- 

 ties, such as birds are when compared with their dimly 

 descried ancestors among the extinct dinosaurian 

 reptiles. The Proteus leaps as well as creeps ! 



It is not difficult to verify the law or descriptive 

 formula of gravitation; it is not difficult to give an 

 approximate experimental proof of the laws of the 

 conservation of matter and the conservation of 

 energy; but it is not possible to give this kind of 

 demonstration of the validity of the evolution theory. 

 Yet we do not know of any competent naturalist who 

 has any hesitation in accepting the general doctrine. 

 All naturalists are dissatisfied with their knowledge 

 of the factors that have operated and still operate in 



