FACTS AND FACTORS OF DEVELOPMENT 7 



same in fundamental principles, and knowl- 

 edge gained in one of these fields must be of 

 value in each of the others. Ontogeny and 

 phylogeny are not wholly distinct phenomena, 

 but are only two aspects of the one general 

 process of organic development. The evolu- 

 tion of races and of species is sufficiently rare 

 and unfamiliar to attract much attention and 

 serious thought; while the development of an 

 individual is a phenomenon of such universal 

 occurrence that it is taken as a matter of course 

 by most people, something so evident that it 

 seems to require no explanation; but famili- 

 arity with the fact of development does not 

 remove the mystery which lies back of it, 

 though it may make plain many of the proc- 

 esses concerned. The development of a human 

 being, of a personality, from a germ cell is the 

 climax of all wonders, greater even than that 

 involved in the evolution of a species or in the 

 making of a world. 



The fact of development is everywhere ap- 

 parent ; its principal steps or stages are known 

 for thousands of animals and plants ; even the 

 precise manner of development and its factors 



