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AND DISTRIBUTION OF TRILOBITES. 291 
a horizontal direction, render them peculiarly adapted for this 
purpose. They moreover prove that the species of fossil animals 
likewise constitute distinct individual groups, that no species 
can be derived from another, that no metamorphosis and progres- 
sive development of one form into another can have taken place. 
We certainly cannot conceive of a repeated origin of new species, 
a continual act of creation; but let us ask ourselves, is the very 
first appearance of animal life on our earth more comprehensible 
to us? This has always been an enigma to the human under- 
standing and to human science, and will always remain so; the 
constantly recurring production of new forms of animals and 
plants that had never previously existence forms a parallel to it. 
