84 HEREDITY AND ENVIRONMENT 



B. FACTORS OF DEVELOPMENT 



These are some of the facts of development, 

 — a very incomplete resume of some of the 

 stages through which a human being passes 

 in the course of his development from the 

 germ. What are the factors of development? 

 By what processes is it possible to derive from 

 a relatively simple germ cell the complexities 

 of an adult animal? How can mind and con- 

 sciousness develop out of the relatively simple 

 psychical elements of the germ? These are 

 some of the great problems of development — 

 the greatest and most far-reaching theme 

 which has ever occupied the minds of men. 



1. Preformation. — When the mind is once 

 lost in the mystery of this ever-recurring mira- 

 cle it is not surprising to find that there have 

 been those who have refused to believe it 

 possible and who have practically denied de- 

 velopment altogether. The old doctrine of 

 "evolution," as it was called by the scientists of 

 the eighteenth century, or of preformation as 

 we know it to-day, held that all the organs or 

 parts of the adult were present in the germ in 



