VI. 



A EEVIEW OF THE MODEEN DOCTRmE OF EVO- 

 LUTION.* 



The doctrine of evolution of organic types is sometimes appro- 

 priately called the doctrine of derivation, and its supporters, deriv- 

 atists. This is because it teaches the derivation of species, genera, 

 and other divisions, from pre-existent ones, by a process of modi- 

 fication in ordinary descent by reproduction. The opposite or 

 creativist doctrine teaches that these forms were created as we see 

 them to-day, or nearly so ; and that the natural divisions and spe- 

 cies of organic beings have never been capable of change, the one 

 into the other. 



I. THE EVIDENCE FOR EVOLUTIOIS^ 



The reasons w^hich induce me to accept the derivatist doctrine, 

 and to reject the creational, fall under the two heads of probabil- 

 ities and conclusive evidence. The probabilities are cumulative in 

 their pointings, and strengthen that part of the evidence which 

 is, to my mind, conclusive. The reasons why derivation is prob- 

 able are the successional relation of increment or decrement of 

 structure, observed in : 



1. Systematic relation (taxonomy) ; 2. Embryonic growth 

 (embryology) ; 3. In geologic time (paleontology) ; 4. And in the 

 coincidence in the successions seen in Nos. 1, 2, and 3. 



The fact that it is necessary to arrange animals in an order cor- 

 responding with the phases of their embryonic history is remark- 

 able ; but the further fact, shown by paleontology, that the same 

 succession marked the ages of past time, at once brings evolution 

 within the limits of strong probability. Nevertheless, all this 

 might have been a mere system, without transitions between its 



* Abstract of a lecture delivered before the California Academy of Sciences, Oct. 

 27, 1879. 



