14 POPULAR SCIENCE MONTHLY. 



STAGES OF VITAL MOTION. 



By O. F. cook, 

 v. s. depaetment of agriculture. 



^T^HAT the organic universe moves, all evolutionists believe; but the 

 -L opinion is still prevalent that species change only as the result 

 of external influences, and that evolution is thus a merely passive 

 process, a biological malleability or plasticity. What have been termed 

 static theories of evolution are based on this bald assumption that 

 species are normally in a state of rest or constancy, a notion contra- 

 dicted by every pertinent fact. Motion in the biological field is, in- 

 deed, more obvious than in astronomy, since every separate group of 

 organisms becomes different from its relatives, quite independent of 

 external conditions, except as these may influence the direction of 

 progressive change. 



Adaptation and Environment. 

 No direct and causal connection between environment and genetic 

 variation has been demonstrated, in spite of many assertions and 

 theories. It is axiomatic that evolving organisms must vary from 

 where they are, or in characters they already possess; and as continued 

 existence presupposes adaptation to environment, variations often 

 strengthen adaptations, especially since characters favoring the geo- 

 graphical and numerical increase of the species are likewise best fitted 

 for distribution inside the species. In this way it is possible to under- 

 stand adaptations without the inheritance of 'acquired' characters 

 impressed upon the organism by the environment. Under the static 

 assumption that species normally maintain a stable average each specific 

 difference needs a separate explanation as the result of an external in- 

 fluence, and the preservation of each new variation must be supposed 

 to require the segregation of a new species. To make place for the 

 modified progeny and protect it against admixture it was thought 

 necessary that the parental type be eliminated, a method gratuitously 

 sanguinary and wasteful, since the new character can be much more 

 rapidly propagated by grafting it into the old species than by found- 

 ing a new species with a single ancestor — a suggestion often quite 

 impracticable. In contrast with the infinite complexity of this theory 

 is the general explanation afforded by the recognition of biological 

 motion, through which species achieve adaptation because they are 

 able to put forth variations in the necessary directions; not because 

 environment causes the variations, nor because the variants are isolated 



