VI. 



The Role of Sex. 



Fig. I. 



APPENDIX. 



OUETELET, in his " Anthropometrie de Thomme " (1870) has 

 shown that if the height-measurements of a large number of 

 men are compared with one another, the following very interesting 

 facts may be observed. The greater number of men are of average 

 height, many are just above or just below it, and fewer and fewer are 

 found at heights further and further removed from the average. Not 

 only is this true as regards height, but it is also true of every measur- 

 able quality, whether of body or mind, that man possesses. This 

 fact can be represented in the form of a diagram (Fig. i). Along the 



horizontal line from a to b mark 

 ofT equal divisions corresponding 

 to the inches between the shortest 

 man, a, and the tallest man, b. 

 Let the vertical heights correspond 

 with the number of individuals whose 

 heights are found to be the same. 

 At A, which we may suppose is 

 five feet, there will, perhaps, be but a single man, and the curve will 

 be very low in height at that spot. At the next division, corresponding 

 to 5 ft. I in., there will, perhaps, be two men, and the curve will rise. 

 When we have finished constructing the curve, it will be observed 

 that its highest point is in the middle, and that its slopes are quite 

 symmetrical. According to Quetelet, the above statement applies to 

 the measurable qualities of every living species, whether of plants 

 or animals. But, as we shall see, it does not apply to groups of 

 inorganic objects. 



So far as I can make out, lakes, mountains, rivers, stones on a 

 beach, crystals growing in a mother liquid, and a hundred other 

 groups of objects, present quite a different curve from Fig. i. To 

 illustrate this by an example, I give the weights of 327 stones taken 

 haphazard by a spade from the beach. The smaller stones are by 

 far the most numerous, and the highest part of the curve is, there- 

 fore, situated at its commencement (Fig. 2). Thus it appears that 

 the symmetrical curve showing a convergence towards a mean is 

 characteristic rather of groups of living than of non-living bodies. 



Francis Galton,' who has investigated man's mental qualities by 

 the same method that Quetelet used for his physical qualities, would 



1 " Hereditary Genius," pp. 26, 27, and 29. 



