The Story of Evolution 109 



ment often reads like an abbreviated recapitulation of the pre- 

 sumed evolution of the race. The mammal's visceral clefts are 

 telltale evidence of remote aquatic ancestors, breathing by gills. 

 Something is known in regard to the historical evolution of 

 antlers in bygone ages; the Red Deer of to-day recapitulates at 

 least the general outlines of the history. The individual develop- 

 ment of an asymmetrical flatfish, like a plaice or sole, which rests 

 and swims on one side, tells us plainly that its ancestors were 

 symmetrical fishes. 



There is what might be called physiological evidence, for 

 many plants and animals are variable before our eyes, and evolu- 

 tion is going on around us to-day. This is familiarly seen among 

 domesticated animals and cultivated plants, but there is abun- 

 dant flux in Wild Nature. It need hardly be said that some 

 organisms are very conservative, and that change need not 

 be expected when a position of stable equilibrium has been 

 secured. 



There is also anatomical evidence of a most convincing 

 quality. In the fore-limbs of backboned animals, say, the paddle 

 of a turtle, the wing of a bird, the flipper of a whale, the foreleg 

 of a horse, and the arm of a man; the same essential bones and 

 muscles are used to such diverse results! What could it mean 

 save blood relationship ? And as to the two sets of teeth in whale- 

 bone whales, which never even cut the gum, is there any alter- 

 native but to regard them as relics of useful teeth which ancestral 

 forms possessed? In short, the evolution theory is justified by 

 the way in which it works. 



Factors in Evolution 



If it be said "So much for the fact of evolution, but 

 what of the factors?" the answer is not easy. For not only is 

 the problem the greatest of all scientific problems, but the in- 

 quiry is still very young. The scientific study of evolution 



