470 ELEMENTARY BIOLOGY 



evidence of fossil remains; (2) systematic and morphological, 

 the evidence from the structure of plants and animals ; (3) em- 

 bryological, the evidence from development ; (4) anatomical, 

 the evidence from rudimentary, or vestigial, organs; (5) regional, 

 the evidence from geographic distribution. 



The important thing to note is that all the facts in these 

 several groups of facts can be harmonized by the idea of evo- 

 lution and by no other explanation. 



There are many attempts to explain how evolution is brought 

 about, and these may be called theories of evolution ; but as to 

 the fact of evolution biologists are in substantial agreement. 



