THE PROGRESSION OF LIFE ON EARTH 

 By Sir Arthur Smith Woodward 



Past-President of the Linnaean and Geological Societies 



If we compare the various groups of animals of the present 

 day we shall find that they can be arranged in a series that 

 gradually leads from the simplest to the most complicated — 

 from the lowest to the highest. The lowest forms are minute 

 specks of jelly-like substance, in which feeding does little 

 beyond helping multiplication. Next higher we find animals 

 of more elaborate structure, in which feeding is improved by 

 the presence of small muscles that make grasping easier. 

 Muscles next form a greater proportion of the body and are 

 used for moving about; and in forms still higher we find 

 nerves to control them. Muscles for locomotion work better 

 by being attached to a skeleton, and in the early forms of life 

 this is altogether an outside shell like that of a cockle, a 

 lobster, or a fly. The nerves next gradually become more 

 elaborate and usually tend to be thickest in the head. 



New possibilities arise in still higher forms, in which the 

 muscles are fixed to an internal skeleton, around a backbone, 

 and the front end of the nervous system becomes a brain. 

 Next, the blood no longer remains of the same temperature 

 as the surrounding water or air, but is warmed by an improve- 

 ment in the heart. The brain grows in size and complexity, 

 fostering activity and leading to the development of higher 

 intelligence. Finally, there comes Man, mastering the world 

 by his greatly developed brain. 



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