MATERIALIST MONISM 



instead of the hatching of eggs. Now some rep- 

 tiles develop these wings still more, retaining at 

 the same time propagation by means of eggs. 

 Other reptiles spend their surplus-energy in the 

 development of a new method of propagation 

 and evolve a placenta in the womb of the female. 

 Again the brain, nerves, ringer system, and bones 

 are affected accordingly. 



Wings prove after all of less value in the fur- 

 ther evolution than a placenta. With the de- 

 velopment of the sex-system of the mammalia, 

 the nerve and brain systems are far more directly 

 and profoundly affected than they are by the 

 comparatively slight modification of lizard wings 

 and scales into bird wings and feathers. The 

 internal adaptation is the more valuable. Thanks 

 to it the mammals rise superior to the birds and 

 the other animals. The mammalian brain, nerve, 

 and finger systems outstrip those of the birds, 

 and at the end of the Secondary period, the 

 brain and its accompanying marks of evolution 

 have arrived at the highest type of man-ape. 



With the terrestrial changes of the Tertiary 

 period, the man-ape becomes an ape-man with 

 erect body, greater brain volume, and better 

 hands and feet. The further accentuation of 

 these factors results in the birth of man. The 



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