388 ELEMENTS OF BIOLOGY 



bodies that preoccupy the attention o£ the astronomer; Terrestrial 

 Evolution, or the origin of the Earth, which receives the attention 

 of the geologist; Inorganic Evolution, or the evolution of the ele- 

 ments, which concerns the chemist and the physicist;. Organic Evo- 

 lution, or the origin and history of living forms, both plant and 

 animal, a major doctrine for the guidance of the biologist. 



Organic Evolution. No single field of thought has been so 

 controversial and none has provoked more acrimonious debate than 

 the subject of organic evolution. The reasons for the controversv are 

 several. The facts of organic evolution are in apparent conflxt 

 with some religious beliefs and hence the concept meets with the 

 opposition of powerful social and educational groups. Secondly, there 

 is something acutely personal about the concept that Man has been 

 derived from lower animals, something that is resented on the 

 grounds of personal and racial pride. Thirdly, the opposition to the 

 concept of evolution is strengthened by controversies between sci- 

 entists. All competent biologists are agreed that the fact of organic 

 evolution has been established by sound and far-reaching evidence, 

 but there is no general agreement as to the method of evolution. 

 This controversy as to the manner in which it has occurred has 

 weakened the case for organic evolution in the minds of the unin- 

 formed and results in the withholding of confidence in the con- 

 clusions of the specialists. Then, too, perhaps because he in a way 

 recognizes his relation to lower animals, the average human usually 

 reserves to himself the right to an opinion on vital phenomena, 

 notwithstanding the fact that in other technical fields he is willing 

 to accept the decisions of specialists. Frequently, in the case of evo- 

 lution as well as other sound biological principles, not only is the 

 decision of the biologist rejected, but the evidence itself is denied. 



The Mechanism of Evolution. While all who are competent 

 agree that in the light of our present knowledge organic evolution 

 is the historical background of living things, there are wide differ- 

 ences of opinion among biologists as to the method and manner by 



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