740 General and Applied Biology 



things constantly changing? What things in your experience do not 

 change? Does it decrease the glory and magnitude of Nature to have 

 living things constantly evolving or changing according to definite, con- 

 trollable laws? Would it increase our respect for the marvels and mag- 

 nificence of Nature by having living things which would be static and 

 unchanging? Could we make progress or educate ourselves if living 

 protoplasm did not have the ability to change and evolve? What would 



Fig. 364. — Chambers of the hearts of vertebrates. 



be the state of affairs if all things remained constant? Is it not logical 

 and desirable to believe that all living things constantly change more or 

 less and that such changes are controlled by certain natural laws? The 

 answers to these questions will prov^e beneficial in laying the foundation 

 for proper study of the descent of organisms with change. 



3. Evidences From Comparative Embryology. — A comparative study 

 of the embryologic stages through which animals pass reveals a wide- 



