The Preparation for Higher Life 



they cannot lift or cast off. But above these, there is a 

 main Hne that forms the tree of advancing life. 



The jprincipal classes of this main line are the worms, 

 arthropods, ostracoderms, fishes, amphibia, reptiles and 

 mammals. It is through this chain that Organic Evolution 

 has developed the tree of life by progressive changes from 

 the lowest to the highest forms. Unlike the other non- 

 progressive groups, the bodies of the classes above named 

 began to take on a general form and a similar internal struc- 

 ture. They were divided into separate segments for flexibil- 

 ity. They became straighter in order to enable them to 

 travel faster. As a result of this form, their nervous systems, 

 digestive systems and circulation systems all extended in the 

 same direction paralleling each other. Many of the other 

 organs of the bodies of the various classes were compound 

 in their nature but by adaptations to the most economical 

 and practical uses, most of these became paired, two eyes, 

 two ears, two lungs, two nasal passages, two gills, two kid- 

 neys, two fins, two legs, two wings, etc. With this arrange- 

 ment, these classes of animals were better prepared to solve 

 changing conditions of life and to make adjustments to meet 

 changing environments. Many of the segments of which 

 their bodies were composed were combined and enlarged 

 and many were reduced to meet the necessary conditions of 

 adaptive growth and to elirninate a duplication of effort. 

 All the organs of all bodies have been placed in the most 

 advantageous positions, by adaptations, to perform their 

 particular functions with the greatest economy of effort and 

 in coordination with all other organs. 



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