64 FOOT-NOTES TO EVOLUTION. 



result of common descent. The differences are due to 

 various influences, chief among these being competition 

 in the struggle for existence between individuals and 

 between species, whereby those best adapted to their 

 surroundings live and reproduce their kind. 



This theory is now the central axis of all biological 

 investigation in all its branches, from ethics to histology, 

 from anthropology to bacteriology. In the light of this 

 theory every peculiarity of structure, every character or 

 quality of individual or species, has a meaning and a 

 cause. It is the work of the investigator to find this 

 meaning as well as to record the fact. " One of the 

 noblest lessons left to the world " by Darwin, Frank 

 Cramer says, " is this, which to him amounted to a pro- 

 found, almost religious, conviction, that 

 Each fact has a every f act j n >J ature no matter how in- 

 meaning. : ... 



significant, every stripe of colour, every 



tint of flowers, the length of an orchid's nectary, un- 

 usual height in a plant, all the infinite variety of appar- 

 ently insignificant things, is full of significance. For 

 him it was an historical record, the revelation of a cause, 

 the lurking place of a principle." 



According to the theory of evolution every structure 

 of to-day finds its meaning in some condition of the 

 past. The inside of an animal tells what it really is, for 

 it bears the record of heredity. The outside of an ani- 

 mal tells where its. ancestors have been, for it bears 

 record of concessions to environment. Similarity in 

 essential structure is known as homology. By the theory 

 of evolution homology, wherever it is found, is proof of 

 blood relationship. 



The theory of organic evolution through natural 

 law was first placed on a stable footing by the observa- 

 tions and inductions of Darwin. It has therefore been 

 long known as Darwinism, although that term has been 



