CHAPTER I 



Introduction 



The earliest indications of a recognition of the essential 

 principle embodied in the theory of organic evolution — that 

 the more complex organisms have evolved from simpler — is, 

 perhaps, to be found in the writings of ancient scholars. 

 These early writings do not state a definitely formulated 

 theory of evolution, but they contain hazy references that 

 similar forms of life may have had a relationship in origin. 

 Such deductions were reasonable conclusions drawn from 

 observations of the more superficial resemblances of many 

 animal groups. Since these earlier times, the study of 

 plants and animals has developed into two major fields of 

 scientific research, botany and zoology, each with a munber 

 of distinct subdivisions. During the development of these 

 sciences, particularly zoology, there gradually crystalHzed a 

 conception of organic evolution. The similarity of animals 

 was found to be not only superficial, but the minute struc- 

 tural details exhibited a close resemblance in large groups of 

 animals. Through a large series of observations and re- 

 searches by a host of pioneer investigators, data accumu- 

 lated which prepared a firm foundation for the theory of 

 organic evolution. Although Linnaeus upheld the separate 

 creation theory in the origin of species, the introduction of 

 his binomial system of nomenclature served in great measure 

 to emphasize the relationships of plants and animals. It 

 was perhaps Lamarck who first clearly stated the theory of 

 organic evolution as we understand it today. 



In the earUer stages of the postulated theory, philosophic 

 speculation occupied the center of the stage. Nevertheless, 

 we gained the principles of "The Struggle for Existence" and 



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