HEEEDITY, ViVEIATIOE" 117 



the curve marks the average of the whole number measured, 

 there being in this case (though not always) very nearly 

 the same number of individuals above and below the mean 

 height. 



The peculiarity of the curve is that it rises very slowly from 

 the height marking that of the shortest individual measured — 

 here a fraction above 4 feet 8 inches — then more and more 

 rapidly for about one-third of the height, then more rapidly 

 and nearly regularly to near the summit, when it bends in 

 rather abruptly to the mean height, and then descends in a 

 nearly corresponding curve as heights are above the average, 

 till it ends just short of 6 feet 8 inches. 



By adding together the numbers on both sides of the curve 

 we find that in this particular group of 2600 men none were 

 quite so short as 4 feet 8 inches or quite so tall as 6 feet 8 

 inches. But in any other group of the same number the ex- 

 tremes might be a little more or less, perhaps a quarter of 

 an inch or rarely a whole inch. We should have to measure 

 a million, or even several millions, to get the average height 

 and the proportionate greatest and least heights ; and even then 

 we should not get near the absolute limits of our race, as we 

 know that at long intervals giants and dwarfs appear, differing 

 by many inches, or even by a foot, from all others living at 

 the time. But, omitting these rare occurrences, the measure- 

 ments of a few thousand among a fairly mixed population will 

 give us the mean height of the whole, very nearh^; as well 

 as the proportionate numbers of those of particular heights, 

 as, for example, at 5 feet 3 inches or 6 feet 3 inches. But 

 even the mean height does not remain the same if the mode 

 of life changes. It is certain that the larger proportion now 

 living in crowded cities than there were a century ago has 

 considerably dwarfed our population. 



We will now give an example of variation in a wild 

 animal in order to show that man and the animals and plants 

 which he has domesticated or cultivated do not differ in this 

 respect from those existing in a state of nature. 



