16 Journal of the Mitchell Society [July 



I may the background of Darwinism upon which mutation 

 may be most effectively projected. Darwin, as you well know, 

 based his theory of the origin of species upon the minute 

 variations presented by all living things. There are no two 

 human beings, no two trees, no two flowers, in fact no two 

 living things of any kind exactly alike. Nevertheless, organ- 

 isms continue to produce offspring which in the main re- 

 semble their parents. The developing plant or animal be- 

 haves as if it were acted upon by two opposing forces, one 

 heredity, a centripetal force tending to hold it down to type, 

 the other variation, a centrifugal force tending to throw it off 

 at a tangent. These variations occur in all directions, some 

 of advantage to their possessors, some possibly without effect, 

 othejF positively detrimental. 



Couple with this the further fact that vastly more plants 

 and animals are produced than can possibly find room and 

 food for development. Tt is difficult to conceive the prodig- 

 ious members of every species that would exist were it not 

 for cheeks put upon them by the environment. The conger- 

 eel it is said lays 15,000,000 eggs. If these all reached ma- 

 turity it has been computed that in less than ten years, the 

 waters of the globe would be solidly full of conger-eels, all 

 the progeny of a single pair. "Even slow-breeding man," 

 says Darwin, ''has doubled in 25 years.'' ''At this rate in 

 less than a thousand years there would literally not be stand- 

 ing room for his progeny." In the keen competition that 

 must thus necessarily ensue in a state of nature the great ma- 

 jority of these are doomed to early destruction. Manifestly 

 it is the best endowed, the fittest in Darwin's phrase who 

 survive. For this process Darwin coined the term natural 

 seJection and looked upon it as the controlling principle in 

 shaping the course of evolution. It operated on those minute 

 variations already referred to, weeding out those individuals 

 which did not vary in directions tending to adapt the organ- 

 ism more perfectly to its environment. The summation of 

 these favorable variations in the course of time would be suffi- 



