A Story Outline of Evolution 



The earlier groups were eyeless as were all other groups of 

 animals that had preceded them. There finally appeared a 

 tiny "eye speck" which in the course of many millions of 

 years developed into a compound eye containing as many as 

 15,000 lenses. The efforts of Nature to develop an eye to 

 fit the surrounding conditions of early life may be clearly 

 traced. Changing environments changed the plans of Nature 

 and many of the eyes became useless, atrophied and were 

 cast into the discard. 



The next great era of geologic time is known as the 

 Paleozoic Era and this is subdivided into periods known as 

 the Cambrian, Ordovician, Silurian, Devonian, Mississip- 

 pian, Pennsylvanian and Permian. In the Cambrian Period, 

 the first fossil sea weeds are found but there is, as yet, no 

 evidence of any land plants that can be distinguished, while 

 on the animal side of the tree of life, animal forms are rap- 

 Idly increasing. In the shallow beds of the ancient oceans, 

 sea scorpions, trilobites, corals, clams, snails, starfish, cri- 

 noids, sponges, great worms and other forms play their 

 parts in evolutionary development. 



In the Ordovician and Silurian Periods great changes 

 were taking place on both land and in the sea. It was dur- 

 ing these periods that the first land plants and land animals 

 by adaptation came into being. As the seas receded, the 

 marine plants began to adapt themselves to the changing 

 conditions, to develop and to send down roots into the soil 

 for food and water and to drink in oxygen from the air , and 

 the sun's energy as well. It was during these periods also 

 that some of the sea animals cast upon or left on the land, 

 as a matter of necessity, changed their habits to enable them 



[184] 



