412 THE EVOLUTIONARY SIGNIFICANCE OF SPECIES. 



systematic study, but this proo^ressive transformation of the " type " 

 carries with it no necessity for subdivision, nor any indication that 

 evolution is concerned with the origination of species. 



SUMMARY. 



Evohitionary study and thought have been hindered by the con- 

 fusion of two unrehited l)iological phenomena, (1) evohitionary 

 progress or vital motion, and (2) the origination or multiplication of 

 species. The " origin " of a species is not more evolutionary than 

 any other stage in its history. The causes of the subdivision of spe- 

 cies are not causes of vital motion : the two processes are quite dis- 

 tinct. The separation of two species is not a focus of the evolutionary 

 problem ; it is a mere incident of developmental history. 



kSegregation is the j^rinciple or active cause of the multiplication 

 of species, but the nature and causes of evolutionary progress are not 

 to be ascertained by discovering that species originate by subdivision. 

 Vital motion is continuous, and is neither actuated nor interrupted 

 by the segregation which multiplies species. 



Natural selection may assist in the segregation of species, but it is 

 not a factor in evolutionary progress except as it influences the direc- 

 tion of vital motion. Specific groups become diverse when the com- 

 ])onent individuals no longer share their variations through symbasic 

 interbreeding; not because new characters are induced by external 

 influences. Evolutionary divergence may take place under identical 

 conditions, and in characters whicli have no relation to the environ- 

 ment and no value to the organism except to permit the necessary 

 vital motion. 



A stationary heredity or the continued repetition of an identical 

 structural type exists nowhere in nature; variation is an inherent 

 evolutionary property. Segregation is not necessary for the preser- 

 vation of variations; genetic variations are prepotent and are more 

 rapidly propagated by crossing with the parent form. 



A second evolutionary propert}^ of organisnts is symbasis, which 

 has built up the complex structure of the higher animals and plants 

 by combining individuals into the interbreeding groups called species. 

 The evolutionar}^ species is not a complex of characters or a mere 

 aggregation of similar ^Dlants or animals; it is a protoplasmic net- 

 work held together by the interbreeding of the component individuals. 

 Symbasis accelerates vital motion, but hinders the multiplication of 

 species. 



Species and evolution are different aspects of the same fact; evo- 

 lution goes forward within specific lines as a manifestation of the 

 same property which necessitates the existence of species; variation 

 and cross-fertilization are not antagonistic phenomena, but are two 

 phases of the same creative process. 



