Cholera, bacillus of, organisms favouring or checking growth, 242, 243, 246-249 carriers of, 245 causes of, 237 Metchnikoff’s and Pettenkofer’s experiments in connection with, 240-241 definition of word, 237, 238 germs, destruction of, 244, 245 Indian, active development of sanitation in Great Britain, due to panic caused by, 239 date of first appearance in England, 238 diffusion through water-supply, 239 discovery by Koch of bacillus producing, 240 epidemic nature of, 238 Europeans first attacked by, 238 recognition of, by Hindu writers, 238 precautions to be observed for prevention of, 244, 245, 246 Cholera-bacillus. See Cholera Christmas fare, origin of, 356-358 Cilia, animals provided with, and action of, 194, 195, 207 definition of term, 194 uses made of, by unicellular animals, 195-197, 207 “Cirrhipedes,” Darwin’s discovery with regard to, 23, 24 Civilisation, scientific knowledge as affecting, 16 Clothes moths, 341 _Coccidæ_, relationship of aphides to, 323 Colour, in bird’s feathers, 55, 56 nature and properties of light as affecting, 52-55 Comets, ancient records of, exaggeration in, 227, 229 composition of, 234, 235 Donati’s, imposing size of, 227 early superstitions with regard to, 227, 228 elliptical orbits of, 233 Halley’s—Chinese astronomical observations relating to antiquity of, 230 length and breadth of orbit, 233 length of tail, 227 predicted recurrences by discoverer of, 226, 230 recent appearance of, 226, 230, 236 significance of date of return, 228, 229 superstition and consternation caused by, 230, 231 William the Conqueror’s “star,” identical with, 231 important, various, 227 Milton’s reference in _Paradise Lost_ to, 228, 229 periodic and wandering, distinction between, 233, 234 photographs obtained at Royal Observatory, Greenwich, of new, 225, 226 shooting stars and, connection between, 235, 236 signification of name, 227 superstitions with regard to, 229 Corrèze skull, 371 Cromagnards, designation of Reindeer men as, reason for, 390 Cuba, measures adopted for prevention of yellow fever and malaria in, 2, 3 Darwin Centenary Celebration at Cambridge, 18, 33, 38 Darwin, Charles— comparison between theories of Lamarck and, 19, 20 connection with University of Cambridge, 36 establishment of “natural selection” theory, 34 extent of time spent in experiments and observations, 18-19, 22-23 friendly relations between Wallace and, 13, 37 geological discoveries of, 24 Henslow’s influence upon, 36 “Natural selection” theory explained, 27-29 study of disease influenced by discoveries and research of, 39, 40 _Darwinism_ (Wallace), 15, 16 (quotation) Death-rate, diminished, reasons accountable for, 284, 285 health of locality determined by, 283 records of, methods of keeping, 283, 284 Death-watch beetle, 351, 352