54 THE MEANING OF EVOLUTION 



Charles Darwin, humanly speaking, may be ac- 

 counted for as the happy combination of a double 

 heredity and a favorable environment. He inherited 

 the scientific inclinations of his grandfather, Erasmus 

 Darwin, and the patient, sturdy honesty of his other 

 grandfather, Josiah Wedgwood. These developed 

 under the stimulus of the long five-year voyage, face 

 to face with the world of nature. This happy com- 

 plex produced the master biologist. To believe that 

 he came about purely by chance requires a great 

 stretch of the imagination. "There's a divinity that 

 shapes our ends." 



We have endeavored to make clear two of the basal 

 ideas underlying evolution. One of these is respon- 

 sible for the continued production of animals or plants 

 of the same kind, preventing the world from becom- 

 ing a wild kaleidoscopic and fantastic dream. Hered- 

 ity is the conservative force of nature. The other idea 

 underlies the development of new departures which 

 keep the world from being a dull, dead, unending 

 repetition of the same monotonous material. Varia- 

 tion is the progressive tendency in nature. 



The third basal idea is that of Multiplication. Ani- 

 mals and plants multiply ; they do not simply increase, 

 they increase in a geometrical ratio. Anyone who 

 has worked out one of these geometrical ratios knows 

 how wondrously they mount up. There is an old fa- 



