J. F. Tocher 
189 
what colour class is more virile than another or whether there is any difference 
among the classes. Is such an hypothesis necessary ? This question is put, because 
it can be quite easily seen that if there is a large proportion of the medium class 
living in very densely populated areas, deaths among medium haired persons will 
be more frequent there than in the rest of the country. But this does not explain 
why medium haired persons are in excess in densely populated parts. No reason 
is known why darkening with age should be more intense in densely populated 
centres, but it is a possible explanation of the excess of medium in these centres 
and the hypothesis should be proved or disproved by observation. If there was 
any special force tending to send medium haired and dark-eyed persons in from 
the country to towns, that would explain the excess. But no such force is known 
to exist. If foreign immigrants had a high percentage of medium hair this 
might be a factor, but foreigners coming into this country are, on an average. 
Diagram XIX 
.Relationship between Density and tlie other characteristics of the Scottish Population 
