IS ORGANIC 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 light of data derived from a study of 
geological changes; and finally, in experimental evolution, which 
involves the observation 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, zodgeography 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 hypothesis works and is therefore acceptable as truth until 
overthrown 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 mass. 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-bearing 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 
