Evolution 407 



However, as we know living things did not exist always, there must 

 have been a time when they did come into existence. The physico- 

 mechanists say, that while no living matter comes from non-living 

 to-day, yet, as there must have been a time when it did, we must 

 assume that different conditions once held sway from those we now 

 know. 



But, such being the case, we break the most important law known 

 to science — that of continuity. It is for this reason that it has been said, 

 that the breaking of this law of continuity is the only heresy known to 

 evolutionary science. 



The theory that life always comes from life is known as biogenesis, 

 while the theory which holds that life can come from non-living matter 

 is called abiogenesis. 



It will be noted that the evolutionary theories so far discussed have 

 only taken the physical side of the individual into consideration to the 

 entire neglect of the mental and intellectual. 



It was Alfred Russel Wallace, co-founder with Darwin of the nat- 

 ural selection theory, who saw this quite early, and insisted that the 

 psychical or mental side must also be considered if we are to form truly 

 valid conclusions. He contended that once mentality enters, as it does 

 in man, such an organism could use this mentality to set aside or change 

 the physical selection which nature carried on. In other words, the 

 earlier evolutionists were interested in the structure of nerves and nerve 

 elements, while Wallace saw the necessity of taking the thought which 

 is carried by the higher nerve centers into consideration. 



It is well for the student to know both the evidence adduced in 

 support of evolution and evolutionary theories, and the objections which 

 have been hurled against it. We have, therefore, summed up the argu- 

 ments of both sides, whether such support and objections are always 

 conclusive or not. 



EVIDENCES FOR EVOLUTION 



1. Paleontological. 



(a) Many new kinds of plants and animals are found in each suc- 

 cessive strata as shown by their fossil remains. 



(b) The later organisms are more complex than earlier ones. 



(c) The more recent fossils prove that they are quite closely' 

 related to the modern forms now living. 



2. Genetics. 



Breeding experiments, as well as observation, prove that all organ- 

 isms are constantly varying, and that constant variations in the same 

 group of organisms are transmitted to succeeding generations. 



