[This essay is taken from 'The Descent of Man and Selection in relation to Sex' by Charles Darwin where it appears at the end of Chapter VII which is also the end of Part I. Footnotes are numbered as they appear in 'The Descent of Man.'] The controversy respecting the nature and the extent of the differences in the structure of the brain in man and the apes, which arose some fifteen years ago, has not yet come to an end, though the subject matter of the dispute is, at present, totally different