EVOLUTION DEFINED H 



are due to various influences, one of the leading forces among 

 these being competition in the struggle for existence between 

 individuals and between species, whereby those best adapted 

 to their surroundings live and rejiroduce their kind. 



This theory is now the central axis of all biological investi- 

 gation in all its branches, from ethics to histology, from anthro- 

 pology to bacteriology. In the light of tliis tlieory every 

 peculiarity of structure, every character or (juality of individual 

 or species, has a meaning and a cause. It is the v.ork of the 

 investigator to find tliis meaning as well as to record the fact. 

 ''One of the noblest lessons left to the world by Darwin," says 

 Frank Cramer, "is this, which to him amounted to a profound, 

 almost religious conviction, that every fact in nature, no matter 

 how insignificant, every stripe of color, every tint of flowers, 

 the length of an orchid's nectary, unusual height in a jjlant, all 

 the infinite variety of apparently insignificant things, is full of 

 significance. For him it was an historical record, the revelation 

 of a cause, the lurking place of a principle." It is therefore a 

 fundamental principle of the science of bionomics that every 

 structure and every function of to-day finds its meaning in some 

 condition or in some event of the past. 



