A Story Outline of Evolution 



ancestral cousins. But suitable materials for shell making 

 could not always be found, so some species of the snail fam- 

 ily ceased to struggle for these materials and began to cast 

 off their shells as useless armor. In some species of the snail, 

 the shell has nearly disappeared while others still cling to 

 ancestral habits of manufacturing sea shells for their bodies 

 though a thousand miles removed from any part of the sea. 

 They gather In great numbers in some shady places where 

 the limey skeletons of the dwellers of the ancient sea are 

 exposed and there they may be found working over the life's 

 work of their ancestral relatives. 



In the Echo River, in the dark recesses of the Mam- 

 moth Cave of Kentucky, there Is found a species of fish. 

 It is not known from whence they came but they have been 

 hidden from the light of day for such a long period of time 

 that Nature has robbed them of their eyes. Evolution has 

 cast off and sealed up their eyes as a useless organ In the 

 environment in which they have been placed, doubtless, for 

 millions of years. When their heads are dissected, a nerve 

 is found leading to the atrophied eye which Is proof that. In 

 the dim ages past, their ancestors enjoyed the light of day. 



We have seen In an earlier chapter that the human 

 embryo in its development repeats the forms of all life that 

 preceded the human form. We shall now examine the 

 human body for relics of an animal ancestral past that have 

 played their part In the scheme of human life but have become 

 outgrown. In the development of the human embryo, at an 

 early stage, a tail is developed that Is nearly as long as the 

 body. As the embryo Is developed into human form, this 

 tail is drawn up and disappears from external view but at the 

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