and selection--Direct action of the environment--The American
school of evolutionists--Origin of the feet of the
ungulates--Supposed action of animal intelligence--Semper on the
direct influence of the environment--Professor Geddes's theory
of variation in plants--Objections to the theory--On the origin
of spines--Variation and selection overpower the effects of use
and disuse--Supposed action of the environment in imitating
variations--Weismann's theory of heredity--The cause of
variation--The non-heredity of acquired characters--The theory
of instinct--Concluding remarks



CHAPTER XV

DARWINISM APPLIED TO MAN


General identity of human and animal structure--Rudiments and
variations showing relation of man to other mammals--The
embryonic development of man and other mammalia--Diseases common
to man and the lower animals--The animals most nearly allied to
man--The brains of man and apes--External differences of man and
apes--Summary of the animal characteristics of man--The
geological antiquity of man--The probable birthplace of man--The
origin of the moral and intellectual nature of man--The argument
from continuity--The origin of the mathematical faculty--The
origin of the musical and artistic faculties--Independent proof
that these faculties have not been developed by natural
selection--The interpretation of the facts--Concluding remarks