PAPERS PRESENTED AT GENERAL SESSIONS 37 



THE ZOOLOGIST'S VIEW OF EVOLUTION 

 (Abstract.) 



Charles Zeleny, University of Illinois 



As time goes on it becomes more and move certain that 

 plants and animals have come to their present condition 

 by a long series of changes. Eecent advances along many 

 biological lines have furnished what are perhaps the 

 most striking of all the confirmations. There is now no 

 biologist who is not firmly convinced that the only ex- 

 planation of the present day similarity with diversity 

 among organisms is to be found in the view of blood rela- 

 tionship. And the evidence that man must be included in 

 this statement is equally strong. Any one who is willing 

 to subject this evidence to careful examination will be 

 convinced of its soundness. 



"When biologists became certain of the fact of evolu- 

 tion they centered their attack on the determination of 

 the way in which evolution acts, upon the conditions or 

 factors of the process. These investigations have gone 

 on step by step, demonstration of each step being gained 

 by accurate observation and experiment with critical dis- 

 cussions. These discussions of the problems at the 

 frontier of investigation have been taken by superficial 

 observers to indicate difference of opinion among biolo- 

 gists as to the fact of evolution itself. The real situa- 

 tion is that as our knowledge of the method of evolution 

 increases there is always a border zone of new problems 

 under active investigation and discussion. In such a 

 zone there will always be differences of opinion. It 

 should not be necessary to state that such differences do 

 not affect belief in evolution itself. 



In the time at my disposal I shall pick out a few of 

 the zoological facts upon which our belief in evolution 

 is based, laying special emphasis upon the more recent 

 work : 



1. Evidence from comparative anatomy. 



2. Evidence from embryology. 



3. Evidence from classification. 



4. Evidence from geographical distribution. 



