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lost its scales because it buries itself in tbe sand and does not need them, 

 or whether it buries itself in the sand because it has no scales and needs 

 protection, or whether burying itself in the sand there has come to be a 

 gradual selection of those whose scales are fewest and thinnest. Anyhow, 

 we were sure of its origin, and that it was descended from some of the 

 other forms of dwarf perch to that called the Johnny Darter. 



Many men before Darwin had taught the theory of descent, but Dar- 

 win gave the first rational exposition of how it came about by natural 

 processes. He showed that adaptation is the natural result of the sur- 

 vival of the adapted in the struggle for existence. Variation is every- 

 where among animals and plants. No two animals or plants are ever 

 alike. There is everywhere a great wealth of life — more are born than 

 can mature, and those survive and live who are able to fit themselves into 

 the scheme of life. Darwin did not believe in evolution in vacuo, that is, 

 evolution wholly independent of external circumstances and conditions, 

 but this heresy that the laws of evolution, which are simply the way 

 things come about, can produce evolution and divergence without any ex- 

 cept metaphysical causes, still has a large body of followers. It is, in my 

 judgment, one of the heresies of the present time. 



In the evolution of any species in the rough-and-tumble of life, we 

 have these four elements : Variation, heredity, selection and segregation. 

 Variation is the starter. It is interwoven with the operation of heredity. 

 The favorable variation survives, and the animal or plant possessing it 

 gives rise to the next generation. This is selection. 



The operation of isolation is this : A group becomes separated by some 

 barrier which the individual can not cross. Little by little the species be- 

 come separated into two or more species, one just as well adapted as the 

 other. It is not often that differences between species are differences in 

 adaptation. It is therefore not often that they are due to natural selec- 

 tion. The final difference, the final polishing or rounding off of the species 

 giving it its distinctive minor character, is due to isolation. Variation 

 and heredity are inside the individual. The incidents of selection and 

 isolation are of the outside world. They are part of the modifying con- 

 ditions of life. Without ((intact with the outside influences, in my be- 

 lief, there is no evolution. 



Darwin may lie compared to an explorer in a new country. From 

 some high point he makes a map of the country, locating its salient fefl* 



