October 16, 1914] 



SCIENCE 



555 



modification of the soma the potentialities of 

 the germ-plasm have been added to and modi- 

 fied, then the dispute as to the inheritance of 

 acquired characters is a futile logomachy. 



The original somatic envelope must have 

 been derived from the original plasma. Why 

 then should their mutual potentialities be 

 denied? Wm. H. Dall 



Septemljer 8, 1914 



HEREDITY AND MENTAL TRAITS 



To THE Editor of Science : In the admirable 

 address of Professor William Bateson'- survey- 

 ing the bearing of modern views of heredity 

 upon psychological and social problems, one 

 admires particularly the staunch presentation 

 of a consistent scheme of inherited traits and 

 the readiness to apply them to a biological 

 view of the social forces in whose intimate 

 workings we have acquired so minute an 

 interest. The same applies to the qualities of 

 mind, of which alone I shall speak. One char- 

 acteristic utterance is the following: 



I have confidence that the artistic gifts of man- 

 kind will prove to be due not to something added 

 to the make-up of an ordinary man, but to the ab- 

 sence of factors which in the normal person inhibit 

 the development of these gifts. They are almost 

 beyond doubt to be looked upon as releases of pow- 

 ers normally suppressed. The instrument is there, 

 but is "stopped down." 



A very differently characteristic expression 

 occurs in comment upon the opinion of Tom 

 Paine inveighing against the notion of hered- 

 itary political institutions, which he r^ards 

 as equally absurd as a " hereditary wise man " 

 or a " hereditary mathematician." 



We on the contrary would feel it something of a 

 puzzle if two parents, both mathematically gifted, 

 had any children not mathematicians. 



The point which I wish to raise interroga- 

 tively rather than critically is this: How far 

 have the holders of such views — ^for there are 

 many similar expressions in the recent litera- 

 ture — considered the problem of the assumptive 

 nature of the unit of mental expression which 

 is involved in such concepts as " artistic gift," 

 " mathematically gifted ? " Take the last of 



1 Science, September 4, 1914. 



the expressions, and put the matter in 

 extreme form: Suppose both parents to have 

 specialized on quaternions, would one ex- 

 pect the children also to be quatem- 

 ionists? Would it answer the biological re- 

 quirement if the children showed ability in 

 physics? in engineering? in science in general 

 of any quantitative form? in a facility for 

 abstract thought, say philosophical or econ- 

 omic? in a taste for study and an intellectual 

 type of mind? Where shall we stop in con- 

 sidering that the trait in the child is of the 

 same nature as the trait in the parents? We 

 seemingly expect that the children of musicians 

 will be musical and not the one a painter and 

 the other a musician ; on what is that expecta- 

 tion based, biologically considered? In brief 

 it seems impossible to discuss mental heredity 

 without coming to some understanding of its 

 evidences and the modes of its expression. 

 The equation is defective without a specific 

 reference to the meaning of both sets of terms. 

 Quite probably the definition is beset with 

 large uncertainties; but it seems to a psychol- 

 ogist that the writers upon heredity, in apply- 

 ing their principles to mental traits, are in 

 duty bound to bring the conception of a mental 

 trait within the scheme of their considerations. 

 Similarly one asks in the same spirit of 

 seeking information, why artistic gifts are in' 

 the nature of a release of powers which every- 

 body has but few show, and why are mathe- 

 matical gifts not of the same description? Is 

 it the sensory dependence of the musical gift 

 that places it in one category, which is a 

 different category from that of the mathe- 

 matical gift? And fundamentally is there 

 such a thing as either? If so is there also a 

 gift for steam-engineering? and why not? 

 And what would have become of one of similar 

 brain inheritance if he happened to be born 

 before the days of steam? The reduction ad 

 absurdum lies near at hand. The moral is 

 simple. It enforces that the application of 

 principles of heredity to mental traits can not 

 go farther and go consistently until a reason- 

 able understanding is reached of the probable 

 nature of a unit of mental trait and of the 

 equivalent forms of its possible expressions. 



