270 



SCIENCE. 



[Vol. YI., No. 138. 



my Authropometric laboratory in the International 

 health exhibition last year. They were almost 

 perfect. 



The multiplicity of elements, some derived from 

 one progenitor, some from another, must be the cause 

 of a fact that has proved very convenient in the 

 course of my inquiry. It is, that the stature of the 

 children depends closely on the average stature of 

 the two parents, and may be considered in practice 

 as having nothing to do with their individual heights. 

 The fact was proved as follows : After transmuting 

 the female measurements in the way already ex- 

 plained, I sorted the children of parents who sev- 

 erally differed 1, 2, 3, 4, and 5 or more inches into 

 separate groups. Each group was then divided into 

 similar classes, showing the number of cases in which 

 the children differed 1, 2, 3, etc., inches from the 

 common average of the children in their respective 

 families. I confined my inquiry to large families of 

 six children and upwards, that the common average 

 of each might be a trustworthy point of reference. 

 The entries in each of the different groups were then 

 seen to run in the same way, except that in the last 

 of them the children showed a faint tendency to fall 

 into two sets, one taking afier the tall parent, the 

 other after the short one. Therefore, when dealing 

 with the transmission of stature from parents to 

 children, the average height of the two parents, or, 

 as I prefer to call it, the ' mid-parental ' height, is all 

 we need care to know about them. 



It must be noted that I used the word parent with- 

 out specifying the sex. The methods of statistics 

 permit us to employ this abstract teim, because the 

 cases of a tall father being married to a short mother 

 are balanced by those of a short father being married 

 to a tall mother. I use the word parent to save a 

 complication due to a fact brought out by these in- 

 quiries, that the height of the children of both sexes, 

 but especially that of the daughters, takes after the 

 height of the father more than it does after that of 

 the mother. My parent data are insufficient to deter- 

 mine the ratio satisfactorily. 



Another great merit of stature as a subject for in- 

 quiries into heredity is, that marriage selection takes 

 little or no account of shortness or tallness. There 

 are undoubtedly sexual preferences for moderate con- 

 trast, in height; but the marriage choice appears to be 

 guided by so many and more important considerations, 

 that questions of stature exert no perceptible influence 

 upon it. This is by no means my only inquiry into 

 this subject; but, as regards the present data, my test 

 lay in dividing the 205 male parents, and the 205 female 

 parents, each into three groups, —tall, medium, and 

 short (medium being taken as 67 inches and upwards 

 to 70 inches), — and in counting the number of mar- 

 riages in each possible combination between them. 

 The result was that men and women of contrasted 

 heights, short and tall, or tall and short, married just 

 about as frequently as men and women of similar 

 heights, both tall or both short: there were thirty-two 

 cases of the one to twenty-seven of the other. In 

 applying the law of probabilities to investigations 

 into heredity of stature, we may regard the married 



folk as couples picked out of the general population 

 at haphazard. 



The advantages of stature as a subject in which 

 the simple laws of heredity may be studied will now 

 be understood. It is a nearly constant value that is 

 frequently measured and recorded ; and its discussion 

 is little entangled with considerations of nurture, of 

 the survival of the fittest, or of marriage selection. 

 We have only to consider the mid-parentage, and not 

 to trouble ourselves about the parents separately. 

 The statistical variations of stature are extremely 

 regular; so much so, that their general conformity 

 with the results of calculations, based on the abstract 

 law of frequency of error, is an accepted fact by 

 anthropologists. I have made much use of the prop- 

 erties of that law in cross-testing my various conclu- 

 sions, and always with success. 



The only drawback to the use of stature is its small 

 variability. One-half of the population with whom 

 I dealt varied less than 1.7 inches from the average 

 of all of them ; and one-half of the offspring of sim- 

 ilar mid-parentages varied less than 1.5 inches from 

 the average of their own heights. On the other 

 hand, the precision of my data is so small, partly due 

 to the uncertainty in many cases whether the height 

 was measured with the shoes on or off, that I find by 

 means of an independent inquiry, that each observa- 

 tion, taking one with another, is liable to an error 

 that as often as not exceeds two-thirds of an inch. 



It must be clearly understood, that my inquiry is 

 primarily into the inheritance of different degrees of 

 tallness and shortness; that is to say, of measure- 

 ments made from the crown of the head to the level 

 of mediocrity, upwards or downwards as the case 

 may be, and not from the crown of the head to the 

 ground. In the population with which I deal, the 

 level of mediocrity is 68i inches (without shoes). 

 The same law applying with sufficient closeness 

 both to tallness and shortness, we may include both 

 under the single head of deviations; and I shall call 

 any particular deviation a 'deviate.' By the use of 

 this word, and that of 'mid-parentage,' we can de- 

 fine the law of regression very briefly. It is, that the 

 height-deviate of the offspring is, on the average, 

 two-thirds of the height-deviate of its mid-parentage. 



If this remarkable law had been based only on ex- 

 periments on the diameters of the seeds, it might 

 well be distrusted until confirmed by other inquiries. 

 If it were corroborated merely by the observations 

 on human stature, of which I am about to speak, 

 some hesitation might be expected before its truth 

 could be recognized in opposition to the current be- 

 lief that the child tends to resemble its parents. 

 But more can be urged than this. It is easily to be 

 shown that we ought to expect filial regression, and 

 that it should amount to some constant fractional 

 part of the value of the mid-parental deviation. It 

 is because this explanation confirms the previous ob- 

 servations made both on seeds and on men, that I 

 feel justified on the present occasion in drawing 

 attention to this elementary law. 



The explanation of it is as follows: The child in- 

 herits partly from bis parents, partly from his ances- 



