Genes and Mutations 57 



survival. But very occasionally valuable mutations may occur some- 

 where in the population of a species and the sexual process ensures 

 that the new gene will be combined with the others present. In fact, 

 sexual combination of genes, together with natural selection even- 

 tually leads to the combination of all the best genes in the species. 



According to this view, evolution is the result of two qualities of 

 the genie substance; it has to be permanent and pass on the same 

 characteristic through many generations. Some species, e.g. the 

 primitive coelacanth fish Latimeria chaliimnae, have remained essen- 

 tially unchanged since the tertiary times. If it were not so, a species 

 would not continue to exist and exhibit recognizable characters. But 

 the ability to change must also be present or evolution would not 

 occur at all. 



