108 EVOLUTION AND GENETICS 



chapter, but even this has not resulted in the undisputed origin 

 of species under human observation. 



Since relationship as indicated by structural and functional 

 similarity is evidence of development through similar processes 

 from similar things in all cases which we can examine, however, 

 it is indicative of a similar origin of related species. Through the 

 concentration of all factors in the production of living things in 

 organic matter alone, we may logically conclude that robins and 

 bluebirds, or butterflies and moths, are related because they came 

 from common beginnings, and that birds and Lepidoptera are 

 likewise related in more fundamental particulars because of a 

 more remote derivation from a common source. This view is 

 logically tenable, but in the evaluation of details it is likely to be 

 confusing if not substantiated by extensive knowledge. 



Examination of the several evidences of relationship supplies 

 the needed support for details of evolution. The field is so vast 

 that complete analysis is not to be expected, but as many examples 

 are available as the individual may care to seek. 



In such species as are found in the genus Euxoa, of the moths, 

 the most intimate degree of relationship is apparent. Some have 

 been named from one region, others from another, and material 

 from intermediate regions has later resulted in their union. Those 

 individuals which occur in the Rocky Mountain region have no 

 direct association with those which fly in the Mississippi valley. 

 They are related in structure, pattern, color and habits. Why? 

 Careful evaluation of the facts leaves only one possible conclusion. 

 They must have been derived from the same source, and since 

 they are individuals of the same species, such derivation is easily 

 understood. 



In connection with this case, one step leads us to that of ob- 

 viously different species belonging to the same genus. Suppose 

 that the two widely separated lots just mentioned should have 

 proved to be actually different, no matter how much material 

 from intervening regions might have been secured. They are no 

 more independent in fact than the extremes of the one species, yet 

 we are unable to demonstrate any connection between them other 

 than a certain similarity. Why should they display this simi- 

 larity? Again the only possible answer is because of a similar 

 origin. Through the characters of the genus, the two are the same. 

 They must then, have had a common origin a little more remote 



