CONTRIBUTIOXS TO THE THEORY OF EVOLUTION. 
453 
were married between 14 and 15 years of age, and all tlie curves begin with a 
sensibly finite ordinate at 14'5 ; it is accordingly possible that a somewhat lower age 
than 13'5 actually occurs in Italy. 
Equation (xvi.) gives us for the distance from mode to mean : 
d = 17694, 
or the modal age at marriage is 20’4183 years. This is only about •053 of a year or 
about 19 days difierent from the modal age as given l)y Type VI., a most satisfactory 
agreement. 
For the skewness we have from Equation (xvii.) : 
Sk. = -4845, 
or, it differs by less than 3 per cent, from the skewness as given by Type (VI.). 
The diagram (fig. i.) shows the two curves, and the table compares the results 
obtained from either with the observations."^" 
It is clear that for all practical purposes the curve of Type V. is as good as that 
of Type VI. Indeed, there is jn’actically no difference between them except for the 
* The observation data are really areas, while to save lengthy calculations we have compared both in 
diagram and table the ordinates of the theoretical curves. This is in general legitimate, if, as in this 
case, the number of groups is very large. 
