22 ORGANIC EVOLUTION 



So striking is the manner in which the individual 

 history of a man recapitulates the history of the race, 

 that many features of the adult anatomy can be 

 explained only on this " recapitulation theory." 

 Man, for instance, has three useless muscles attached 

 to each of his external ears : muscles which few can 

 throw into action and none can utilise. There is 

 only one explanation of their presence. Similarly 

 he has, upon the front of his neck, a sheet of muscle 

 which he never uses. Lower mammals have a con- 

 tinuous sheet of muscle at the same level all over 

 the body, and can use it to displace annoying insects. 

 How does man come to have this useless appanage ? 

 Again, man possesses a blind pouch, attached to his 

 alimentary canal, which is far worse than useless. 

 Some ninety thousand operations are performed 

 every year in Great Britain for the relief of inflam- 

 mation of this pouch — the appendix vermiformis 

 — and the portion of bowel from which it springs. 

 Their existence is intelligible only when we find 

 them present, in much larger form, in certain of the 

 lower mammals which are of herbivorous habits. 

 Only on the theory of evolution are these facts 

 explicable. 



Lastly, let us consider the evidence of comparative 

 anatomy, the science to which the theory of evolution 

 has given meaning and value. Long before the dawn 

 of the theory, anatomists had observed the similarity 

 of structure between one animal, or one plant, and 

 another. It is to us an enduring instance of the 

 power of preconceived ideas that facts so significant 

 should not have taught them the obvious lesson. 

 Instances of these resemblances are countless. The 



