PHOOFS OF EVOLUTION. 
15 
plained to you Solar and Planetary Evolution, as 
also the Evolution of the Earth as a whole, of 
Vegetal and Animal Life, of Mind, of Man, of 
Society, Theology and Morals.* It is in the field 
of Biology, however, that the proofs of Evolution 
are most abundant and conclusive. To this line 
of proof I shall mainly confine my attention. 
But before proceeding to details, it may be well to 
point out the four great factors of Evolution, on 
which the entire theory rests. 
* See “Evolution: Popular Lectures and Discussions before 
the Brooklyn Ethical Association.” One vol., 408 pages, illus¬ 
trated, complete index, cloth, $2.00. Boston : James H. West, 
Publisher. 
