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IS ORG.\NIC EVOLUTION ESTABLISHED ? 59 



apparently unrelated bodies of phenomena. There are evidences of 

 evolution in the grouping of animals into phyla, classes, orders, 

 families, genera, species, varieties, and races; in the homologies that 

 exist in general structure and in particular organs between different 

 groups of animals and plants; in the orderly process of ontogeny or 

 embryonic development of the individual; in actual blood relation- 

 ship, based upon chemical reactions; on the succession of extinct 

 animals and plants found as fossils imbedded in the geologic strata; 

 in the present geographical distribution of the various groups of 

 animals and plants, in the hght of data derived from a study of 

 geological changes; and finally, in experimental evolution, which 

 involves the obser\'ation under experimental control of changes in 

 organisms and the origin of new varieties or elementary species. 



2. The nature of the proof of organic evolution, then, is this: 

 that, using the concept of organic evolution as a working hypothesis 

 it has been possible to rationalize and render intelligible a vast array 

 of observed phenomena, the real facts upon which evolution rests. 

 Thus classification (taxonomy), comparative anatomy, embryology, 

 palaeontology, zoogeography and phytogeography, serology, genetics, 

 become consistent and orderly sciences when based upon evolu- 

 tionary foundations, and when viewed in any other way they are 

 thrown into the utmost confusion. There is no other generalization 

 known to man which is of the least value in giving these bodies of 

 fact any sort of scientific coherence and unity. In other words, the 

 working hj^Dothesis works and is therefore acceptable as truth until 

 overthro\\Ti by a more workable hypothesis. Not only does the 

 hypothesis work, but, with the steady accumulation of further facts, 



/ the weight of evidence is now so great that it overcomes all intelligent 

 opposition by its sheer mas g. There are no rival hypotheses except 

 the outworn and completely refuted idea of special creation, now 

 retained only by the ignorant, the dogmatic, and the prejudiced. 



3. In answer to the question, "What are the evidences of evolution 

 and in what ways do these bear witness that evolution has occurred 

 and is still occurring?" we may present an ordered list of subjects 

 that are to be taken up serially in detail. In connection with each of 

 these bodies of evidence the character of their witness-bcarmg will be 

 discussed. 



Some of the evidences are more direct and freer from purely inter- 

 pretative construction than others. Some evidences are primary and 

 foundational; some are in themselves rather inconclusive, but serve 



