OUR NATURAL INHERITANCE 55 



our mental peculiarities belong to the unit-character 

 type. Thus there is a quite definite ' roving ' impulse, 

 distinguishable from mere restlessness or lack of per- 

 severance, which ' runs in families.' The same may be 

 true of well-defined temperaments — e.g. excitable or 

 nervous, phlegmatic or quiet ; of curious mental twists 

 that make their possessors see everjrthing crooked ; 

 and of those agreeable idiosyncrasies and originalities 

 which add a charm to life. 



It is not, of course, to be assumed that any character 

 is a unit-character ; that has to be proved by its 

 behaviour in inheritance. It looks as if even our more 

 superficial features, whether bodily or mental, included 

 more than non-blending unit characters. For there 

 are some, such as colour of hair and colour of skin, which 

 appear to blend when contrasts are paired. Thus 

 mulattoes apparently illustrate, as to colour of skin, 

 a blend of the skin colour characteristics of the white 

 father and the black mother. We say 'apparently* 

 because the matter is not nearly so simple as it seems. 



(c) Thirdly, besides the old-established racial 

 characters and the well-defined but more superficial 

 traits that run in families, the inheritance includes 

 individual peculiarities or idiosyncrasies. These new 

 departures, novelties, or variations are of great interest — 

 they form the raw material of progress or of retrogression, 

 or of merely indifferent change. They vary from trivial 

 peculiarities such as crinkly hair, to momentous muta- 

 tions, such as we see in genius. Some are rather quanti- 

 tative, a little more of this and a little less of that ; 



