Chapter III

THE BASIS OF THE POPULATION PROBLEM: (2) THE QUALITATIVE ASPECT 64

(1) In the chromatin of the nucleus we have apparently to
recognize the physical basis of the inherited qualities which
(2) take the form of predispositions towards the development of
certain characters. (3) Difference between modifications and
mutations. (4) ‘Pure Line’ and (5) Mendelian investigations
indicate nature and behaviour of latter on crossing. (6)
Germinal change consists in the apparent addition, dropping out,
or modification of ‘factors’, the causes of which (7) are
unknown, and are not due to the inheritance of acquired
characters. (8) Owing to the death-rate being selective,
different germinal constitutions are differently favoured, and
thus (9) permanent change among species in a state of nature
comes about.