Complex Life — The Invertebrates 



the entire body. The sense organs that have developed a 

 high degree of acuteness now render Hfe much more com- 

 plex than it has been before. 



All vertebrates are bilaterally symmetrical with their 

 body parts basically the same but modified to function best 

 in the environment with which they are surrounded. The 

 fins of the fishes, the legs of the animals and the wings of 

 the birds are simply locomotor appendages developed to 

 perform their functions in the most advantageous manner. 

 The most important cranial nerves and eye muscles of a 

 fish, frog, reptile or bird have their corresponding parts in 

 man and the other mammals. 



The forces of Nature are immutable — they always were 

 and always will be the same. The vibrations of light, sound, 

 heat, the forces of gravitation, adhesion, cohesion, mole- 

 cular and atomic were the same at the time of the first life 

 spark as they are today. It was the function of Evolution 

 to develop the special sense organs of animal life so that 

 the agencies of Nature could be made use of In the advance- 

 ment of the animal kingdom. 



Evolution's foot prints may be traced with convincing 

 certainty, with the chief steps In the modification of all of 

 their body changes from the fishes up to man. The devel- 

 opment of the highly organized special senses and the loco- 

 motor appendages made it possible for nearly all vertebrate 

 animals to transport their bodies to new environments in a 

 shorter time, to reach new food supplies and to protect 

 themselves against their enemies. Different environments 

 called for different adaptations and as a consequence, differ- 

 ent forms. From the first true fishes, to the present time 



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