1 8 PIONEERS OF EVOLUTION. 



errors — to his pioneer work in organic evolution. 

 Here, in the one possible method of reaching the 

 truth, theory follows observation. Stagira lay on the 

 Strymonic gulf, and a boyhood spent by the seashore 

 gave Aristotle ample opportunity for noting the vari- 

 ations, and withal gradations, between marine plants 

 and animals, among which last-named it should be 

 noted as proof of his insight that he was keen enough 

 to include sponges. Here was laid the foundation 

 of a classification of life-forms on which all corre- 

 sponding attempts were based. Then, he saw, as 

 none other before him had seen, and as none after 

 him saw for centuries, the force of heredity, that 

 still unsolved problem of biology. Speaking broadly 

 of his teaching, the details of which would fill pages, 

 its main features are (i) His insistence on observa- 

 tion. In his History of Animals he says " we must 

 not accept a general principle from logic only, but 

 must prove its application to each fact. For it is 

 in facts that we must seek general principles, and 

 these must always accord with facts. Experience 

 furnishes the particular facts from which induction 

 is the pathway to general laws." (2) His rejection 

 of chance and assertion of law, not, following a 

 common error, of law personified as cause, but as 

 the term by which we express the fact that certain 

 phenomena always occur in a certain order. In his 

 Physics Aristotle says that "Jupiter rains not that 

 corn may be increased, but from necessity. Simi- 

 larly, if some one's corn is destroyed by rain, it does 



