456 POPULAR SCIENCE MONTHLY. 



Summary. 



Evolutionary study and thought have been hindered by the confu- 

 sion of two unrelated biological phenomena, (1) evolutionary progress 

 or vital motion, and (3) 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 species are not causes 

 of vital motion; the two processes are quite distinct. The separation 

 of two species is not a focus of the evolutionary problem; it is a mere 

 incident of developmental history. 



Segregation is the principle 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 compo- 

 nent individuals no longer share their variations through interbreeding ; 

 not because new characters are induced by external influences. Evolu- 

 tionary divergence may take place under identical conditions, and in 

 characters which have no relation to the environment 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 evolu- 

 tionary property. Segregation is not necessary for the preservation of 

 variations ; genetic variations are prepotent and are more rapidly propa- 

 gated by crossing with the parent form. 



A second evolutionary property of organisms 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 evolutionary species is not a complex of characters or a mere aggre- 

 gation of similar plants or animals; it is a protoplasmic network 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; evolu- 

 tion 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 i)henomena, but two phases of the 

 same creative process. 



