August 25, 1911] 



SCIENCE 



243 



of some clean-cut faculty such as the mathematical 

 one would yield interesting results. 



The analysis of mental characters will no doubt 

 be very difficult, and possibly the best line of 

 attack is to search for cases where they are asso- 

 ciated with some physical feature such as pig- 

 mentation. If an association of this kind be 

 found, and the pigmentation factors be deter- 

 mined, it is evident that we should thereby obtain 

 an insight into the nature of the units upon which 

 mental conditions depend. Nor must it be forgot- 

 ten that mental qualities, such as quickness, gen- 

 erosity, instability, etc. — qualities which we are 

 accustomed to regard as convenient units in classi- 

 fying the different minds with which we are daily 

 brought in contact — are not necessarily qualities 

 that correspond to heritable units. Effective men- 

 tal ability is largely a matter of temperament, and 

 this in turn is quite possibly dependent upon the 

 various secretions produced by the different tis- 

 sues of the body. Similar nervous systems asso- 

 ciated with different livers might conceivably re- 

 sult in individuals upon whose mental ability the 

 world would pass a very different judgment. 

 Indeed, it is not at all impossible that a particular 

 form of mental ability may depend for its mani- 

 festation, not so much upon an essential difference 

 in the structure of the nervous system, as upon 

 the production by another tissue of some specific 

 poison which causes the nervous system to react 

 in a definite way. We have mentioned these possi- 

 bilities merely to indicate how complex the prob- 

 lem may turn out to be. Though there is no doubt 

 that mental ability is inherited, what it is that is 

 transmitted, whether factors involving the quality 

 and structure of the nervous system itself, or fac- 

 tors involving the production of specific poisons 

 by other tissues, or both together, is at present 

 uncertain. 



Little as is known to-day of heredity in man, 

 that little is of extraordinary significance. The 

 qualities of men and women, physical and mental, 

 depend primarily upon the inherent properties of 

 the gametes which went to their making. Within 

 limits these qualities are elastic, and can be modi- 

 fied to a greater or lesser extent by influences 

 brought to bear upon the growing zygote, pro- 

 vided always that the necessary basis is present 

 upon which these influences can work. If the 

 mathematical faculty has been carried in by the 

 gamete, the education of the zygote will enable 

 him to make the most of it. But if the basis is 

 not there, no amount of education can transform 

 that zygote into a mathematician. This is a mat- 



ter of common experience. Neither is there any 

 reason for supposing that the superior education 

 of a mathematical zygote will thereby increase the 

 mathematical propensities of the gametes which 

 live within him. For the gamete recks little of 

 quaternions. It is true that there is progress of a 

 kind in the world, and that this progress is largely 

 due to improvements in education and hygiene. 

 The people of to-day are better fitted to cope with 

 their material surroundings than were the people 

 of even a few thousand years ago. And as time 

 goes on they are able more and more to control 

 the workings of the world around them. But there 

 is no reason for supposing that this is because the 

 effects of education are inherited. Man stores 

 knowledge as a bee stores honey or a squirrel 

 stores nuts. With man, however, the hoard is of a 

 more lasting nature. Each generation in using it 

 sifts, adds, and rejects, and passes it on to the 

 next a little better and a little fuller. When we 

 speak of progress we generally mean that the 

 hoard has been improved, and is of more service 

 to man in his attempts to control the surroundings. 

 Sometimes this hoarded knowledge is spoken of as 

 the inheritance which a generation receives from 

 those who have gone before. This is misleading. 

 The handing on of such knowledge has nothing 

 more to do with heredity in the biological sense 

 than has the handing on from parent to offspring 

 of a picture, or a title, or a pair of boots. All 

 these things are but the transfer from zygote to 

 zygote of something extrinsic to the species. 

 Heredity, on the other hand, deals with the trans- 

 mission of something intrinsic from gamete to 

 zygote and from zygote to gamete. It is the par- 

 ticipation of the gamete in the process that is our 

 criterion of what is and what is not heredity. 



Better hygiene and better education, then, are 

 good for the zygote, because they help him to 

 make the fullest use of his inherent qualities. But 

 the qualities themselves remain unchanged in so 

 far as the gamete is concerned, since the gamete 

 pays no heed to the intellectual development of 

 the zygote in whom he happens to dwell. Never- 

 theless, upon the gamete depend those inherent 

 faculties which enable the zygote to profit by his 

 opportunities, and, unless the zygote has received 

 them from the gamete, the advantages of educa- 

 tion are of little worth. If we are bent upon pro- 

 ducing a permanent betterment that shall be inde- 

 pendent of external circumstances, if we wish the 

 national stock to become inherently more vigorous 

 in mind and body, more free from congenital 

 physical defect and feeble mentality, better able 



