[132] Quatrefages (_op. cit._, pp. 219-222) gives a great number of definitions of species. A few may be quoted: “Species should be defined as a succession of wholly similar individuals, perpetuated by means of generation” (De Jussieu).—“Species is a constant succession of like individuals, which reproduce themselves” (Buffon).—“By species we mean any collection of similar individuals, that have been produced by individuals like unto themselves” (Lamarck).—“Species is the individual repeated and continued in time and space” (Blainville).—“Species is the totality of all individuals that have the same origin, and of those that are as like them, as they are among themselves” (Brown), etc., etc. [133] For the transformists, as is well known, variety, race, and species are not fixed concepts. “From variety to race, from race to species, there is a continuous insensible passage. Individual modifications, at first slight, give rise to a variety or to a race. Continuing to augment, and extending to a constantly increasing number of individuals, they may come to constitute specific characters. Pursuing its evolution, the species then finally reaches the rank of the genus, family, etc.” [134] _De l’Espèce_, Ch. II., §§ 6 and 7. [135] _Nouveaux Essais_, III, § 6, 23. [136] _Psychology of Attention_, Ch. I. (Chicago: Open Court Publishing Co.) [137] For a study of the function and practical value of symbolism consult Ferrero, _Les lois psychologiques du symbolisme_; Paris, F. Alcan. [138] _The Concepts and Theories of Modern Physics_, Ch. IX., p. 137, 3rd ed. INDEX. Abstraction, a positive operation, 2; a process of secondary formation, 216 et seq.; has followed three principal directions: practical, speculative, scientific, 220 et seq.; higher forms of, 111 et seq.; implies a dissociative process, 8; intermediate forms of, 86 et seq.; prior to speech, 1 et seq.; stages of, 10 et seq. Abstract thought, a skeleton, 135. Acoustic space, 148. Adjective, the, 76. Agassiz, 7, 105, 107, 211. Ampère, 219. Analogy, 27, 84. Animals, causality in, 184; counting of, 19; language of, 58; psychology of, 11 et seq.; reasoning of, 30; time-sense of, 169. Antecedent and consequent, 180, 183 et seq. Ants, intelligence of, 12 et seq., 27, 55. Arabic, 76. Archimedes, 190. Architecture, 28. Aristotle, 45, 105 et seq. Arithmogenesis, 139. Articulation, 63. Artists, 134. Association of images, 18; by similarity, 24. Astronomers, the first, 173. Attention, 134, 217. Auditory types, 112, 121 et seq. Aztec language, 73. Baer, Von, 108. Bain, 7. Barter, 109. Bees, intelligence of, 14, 56. Belief in a universal law of causality, 185 et seq. Belt, Mr., 13. Bergson, 178. Binet, 37. Blainville, 206. Boole, 38. Boutroux, 203. Bradley, 25. Bréal, 70, 71. Brehm, 170. Brown, 205, 206. Buffon, 206, 207.