IOWA ACADEMY OF SCIENCES. 37 



characters developing to meet changed conditions. For when 

 the environment remains constant for a large number of 

 generations, those qualities of the germinal substance 

 which lead to the development of unfavorable characters 

 under the influence of the environment in question will be 

 eliminated by the extinction through selection of the indi- 

 viduals arising from that germinal substance. There will 

 thus arise a gradually increasing fixity of type. But this 

 fixity, while implying an absence of qualities in the germ- 

 inal substance that would cause variations under the 

 environment in question, does not imply the absence of 

 variable qualities in the germ which take no part in devel- 

 opment under the given environment, but might do so 

 under some other environment; for such variability has 

 never been eliminated by selection. Hence when conditions 

 change, such variations are likely to become at once con- 

 spicuous. 



Perhaps this may be brought out more clearly after 

 contrasting briefly the opposing views as to the method by 

 which a species is modified. 



Neo-Lamarckians, noting the undoubted modification 

 of individuals through change of function caused by 

 changed environment, assume that characters so produced 

 are inheritable, and thus account for the gradual modifi- 

 cation of a race to fit such changed environment. 



Neo-Darwinians, regarding characters as developing 

 almost wholly under the control of the internal factor 

 (heredity) cannot conceive of acquired characters being 

 inherited, because there is no way in which characters of 

 the soma produced by the direct influence of the environ- 

 ment can produce such representative changes in the 

 germ plasm. Changes w4iich appear to arise because of 

 increased function of certain organs to meet changed 

 environment are really established as racial characters 

 through natural selection acting on chance variations. 



These two views are regarded as wholly mutually 

 exclusive. Are they really so ? Let us remember that what 

 we call a new character is always the result of a change in 

 the degree or direction of development of some previously 



