CHAPTER XIII. 

 THE DEVELOPMENT THEORY. 



[Lecture delivered in Portland, February, 1883.] 



INTRODUCTORY. 



"Reasoning apriori, we assume that or- 

 ganisms, both plant and animal, have been 

 created by development from pre-existent 

 forms, because it agrees with the general 

 course of nature. All the events in geology, 

 as in physics and astronomy, being due to the 

 operation of natural laws, it is reasonably sup- 

 posed that the production of all the species of 

 plants and animals from original simple forms, 

 like the monera or bacteria, have been the 

 result of natural law. The study of the early 

 forms of life found in the Paleozoic strata; 

 the laws of the succession of types; the cor- 

 relation existing between the development of 

 the individual and of the members of the class 

 to which it belongs; the parallelism between 



