252 THE PRINCIPLES OF HEREDITY 



mental traits were instinctive, and what part acquired as a 

 result of experience. During my passage through life I have 

 acquired certain mental characters a certain amount of 

 miscellaneous information, certain likings and aversions, 

 certain ways of thinking and acting. It is quite conceivable 

 that I might have been born with all these, just as, without 

 experience, a dragon-fly becomes a perfect insect with all his 

 mental traits complete ; in which case they would have been 

 instinctive in me. It was formerly believed by most biolo- 

 gists, and is still believed by the general public, that acquired 

 mental characters are transmissible to offspring. In other 

 words, they believed that characters, which in the parent 

 arise through the stimulus of use and experience, tend to 

 arise in the child through the stimulus of nutrition alone. 

 Nothing in the characters is supposed to be changed except 

 the kind of stimulus that caused them to develop. If then 

 my mental acquirements were transmitted to my child, if 

 they arose in him through the stimulus of nutrition unaided 

 by the experience that developed them in me, they would 

 be instinctive in him. But nobody, again, could distinguish 

 them when inborn from acquirements, except by knowing 

 the mode of origin by knowing the kind of stimulus that 

 developed them. The kind of stimulus alone makes the 

 difference. We see, therefore, more clearly than ever that 

 "acquired" mental traits are mere substitutes for instincts, just 

 as acquired physical characters are mere substitutes for 

 inborn physical characters. Instincts themselves are acquire- 

 ments which are distinguished from the mental acquirements 

 usually so-called by being developed under the influence of 

 different stimuli. All the pother we made in the first and 

 subsequent chapters about the absolute necessity of clearly 

 distinguishing between inborn and acquired characters issues 

 then in this the whole of the traits of an individual are 

 acquirements ; but custom prescribes that the term shall be 

 limited to those characters which result from certain stimuli 

 (injury and use), whereas the term inborn is restricted to 

 characters which result from other forms of stimuli (e.g. 

 nutrition). The reader will have realized, however, that this 

 nomenclature, even if inaccurate, is convenient, and marks a 

 distinction of vital importance. 



413. The particular class of acquired movements which 

 most nearly resemble instinctive and reflex actions are the 

 " automatic " actions. Suppose a woman learns to knit ; then 

 at first all her movements are deliberate involving con- 

 centrated thought. She works slowly and with hesitation, 



