Congenital and Acquired Characters 35 



the congenital hereditary impulses which characterize the 

 species. This is true both of mind and body ; and the 

 relation of the respective functions of mind and body 

 varies with the place of the creature in question in the 

 scale of life — with what we may call, technically, its 'grade.' 

 The correlation already pointed out between increasing 

 plasticity of the nervous system and increasing mental 

 endowment holds as we ascend from a lower to a higher 

 stage. We accordingly have an increasing dependence 

 upon accommodation of the mental type as we ascend 

 higher in the scale. The range of possible accommodation 

 of the 07'ganisin of a whole becojnes, therefore^ wider and 

 its congenital impulses less fixed as evolution advances ; 

 there is constantly less dependence upon definite heredity, 

 and more upon the inheritance of a general mechanism 

 of accommodation of a psychophysical sort, as we ascend 

 the animal series.^ Recognizing progress in progressive 

 accommodation, with plasticity of mind and body, as the 

 direction in v/hich evolution is determined, we may set that 

 down as the first point in our argument. The method of 

 accommodation, its progress by the selection of adaptive 

 movements and thoughts from overproduced cases by trial 

 and error, may be left over for the present. 



Second, it follows that the distinction so long dominant 

 in biology between * congenital ' and * acquired ' characters, 

 cannot be sharply drawn. All characters are partly con- 

 genital and partly acquired. The hereditary impulse is at 

 the start in each case a rudiment {A7ilage), which is to de- 

 velop into what the environment, within which its native 

 tendencies must show themselves, may permit it to become. 



1 Professor Ray Lankester has paralleled this with the advance in size and 

 complexity of the mammalian fossil brain {Nature, LXT, p. 624). 



