Note 364 — Chapter XXIV · [360]

In the instincts of mammals, and even of lower creatures, the uniformity and infallibility which, a generation ago, were considered as essential characters do not exist. The minuter study of recent years has found continuity, transition, variation, and mistake, wherever it has looked for them, and decided that what is called an instinct is usually only a tendency to act in a way of which the average is pretty constant, but which need not be mathematically 'true.' Cf. on this point Darwin's Origin of Species: Romanes's Mental Evol., chaps. xi to xvi incl., and Appendix; W. L. Lindsay's Mind in Lower Animals, vol. i. 133-141: ii. chaps. v, xx; and K. Semper's Conditions of Existence in Animals, where a great many instances will be found.