PREFACE VU 



fluenced me. I have come to have the philosophical faith 

 that my views on evolution carry meaning and promise, and 

 that eventually science and philosophy will demonstrate 

 beyond all doubt that the unitary nature of the evolutionary 

 process is a fact. 



I am greatly indebted to my friend, Dr. Florence M. 

 Teagarden, for her great patience in reading the manu- 

 script, for her counsel on my statements about psychology, 

 and for her many helpful suggestions in all parts of the 

 book. 



G. Murray McKinley 



Pittsburgh, Pennsylvania 

 July, 1956 



