I. Haeckel and His Opponents

As Newton by pointing out the general attraction of the heavenly bodies showed why they moved in the set courses determined by Copernicus and Kepler, so did it now become possible to explain with the help of the theory of selection how in Nature the evolution of the living thing takes place, the course of which Goethe, in his Metamorphosis of Plants, has observed: “We can, however, say this, namely, that proceeding from a relationship that is hardly distinguishable between animal and plant, creatures do little by little evolve, carrying on their development in opposite directions—the plant finally reaching its maturity in the form of the tree, and the animal finding its culminating glory in man's freedom and activity.”