addrEkSs bv the president. 



0. p. Hay, Eutler T'niversity, Irvington, Ind. 



A COXSIDERATION 01" SOME THEORIES OF EVOLUTION. 



We find in the physical history of the earth an illustration of evolution 

 in the modern sense of the word, a progress in accordance with fixed laws 

 from the simple to the complex, from the undifferentiated to the difi"er- 

 entiated. 



That philosophical minds should suspect that the world of organic be- 

 ings, animals and plants, had been the subject of a similar course of evo- 

 lution is not strange ; and we find that such a suggestion has been often 

 and long ago made. In modern times Lamarck has led the way; but 

 neither were his theories adequate, nor were the men of his time ready 

 to abandon their ancient conceptions. But when, in 1859, Darwin and 

 Wallace pviblished the results of their independently pursued studies and 

 proposed a theory, definite and supported by a multitude of facts, their 

 works attracted immediate and sustained attention. It is doubtful if any 

 doctrine so subversive of universally accepted ideas has ever, in so short 

 a time, received the recognition of so many of the educated and thought- 

 ful minds of the world. 



The doctrine of organic evolution, which attempts to explain the vari- 

 ous differences and resemblances which exist among organic beings, de- 

 pends on two laws, lieredity and variability. The one law ordains that the 

 living thing shall possess the essential characters of its parent or parents; 

 the other law that it shall depart from those characters to a greater or 

 less extent. Neither law can be questioned by anybody ; only the extent 

 to which the one law prevails over the other is in dispute. The evolu- 

 tionists maintain that the law of variability may prevail over heredity 

 to such an extent that after a greater or less number of generations, the 

 deviations from the original form and structure may be so great that a 

 new species may be produced. 



In the attempt to explain how it is that new species originate, Darwin 

 and Wallace hit upon the idea of " natural selection." In nature ho two 



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