Segregation: in dihybrids, 84; Mendelian, 69, 70, 75; of defectives, 318. Seguin, 256. Self-control, importance of, 221, 267, 268, 284, 286, 287. Sex: and chromosomes, 59; and heredity, 53; cells of Volvox, 25; chromosome, 57, 58; determination, 55; differentiation and X-element, 60; evolution of, 25-30; hygiene, question of school instruction in, 285; in certain insects, 56; linked characters, 60, 65; not a necessary factor in heredity, 6; problem, knowledge alone not sufficient, 286. Sexual vice, 284. Sharp, 322. Simplex character, 80, 99. Skill, non-transference in brain, 212, 213. Skin, color of, 92. Smallpox, 152. Social maladies, prevention of, 293. Softening of the brain, 186. Soma, 28. Spermatid, 43. Spermatocyte, primary, secondary, 43. Spermatogenesis, 42. Spermatogonium, 43. Spermatazoon: 26, 40; a cell, 22; formation of, 43; structure of, 43. Spindle, in cell-division, 32. Spottedness of hair-coat, 113. Sprague, 281, 305. Starfish, training a, 204. Statistical methods, 15. Statistics, trustworthy needed, 334. Stature, inheritance of, 17. Stereotropism, 198. Sterility, 182. Sterilization: 322; in epilepsy, 326; laws, 323; laws, on trial, 329; laws, states having, 327. Stevens, 41. Stockard, 174-178. Strength, muscular, 120. Stripes, reversionary, 8. Stutzman, 305. Sullivan, 168. Superior strains, conservation of, 157. Synapse, 210. Synapsis, 41, 42. Syndactyly, 65, 108, 111. Syphilis: 184-190; and prostitutes, 185; cerebro-spinal form, 189-190; prenuptial inspection for, 190-192; prevalence, 186; stages of, 185; tests for, 188. Syphilitics: children of, 187, 188; married, 190. Tabes dorsalis, 186. Taints, 101. Talent, inheritance of, 212. Taylor, 297. Telegony, alleged cases of, 10. Temperament, inheritance of, 19. Thermotropism, 198. Thigmotropism, 198. Third generation, segregation in, 69. Thomsen's disease, 118. Thomson, 55. Thorndike, 296. Tower, 125. Training of children: and heredity, 218; faults in, 221, 222. Transmission, not necessarily inheritance, 163. Tredgold, 170. Treponema pallidum, 185. Tribe of Ishmael, 271. Tropic responses: often purposeful, 201; uncertainties in, 202. Tropisms: 197; complications in, 200; in plants and animals, 198; relations to reflex actions and instincts, 203. Tschermak, 68. Tuberculosis, 118, 148-160, 162. Twins: identical, 55; sex of, 55. Typhoid, 152. Unemployed, frequently morons, 280. Unfit, elimination of, urgent, 313. Unit-character: 12; inheritance of, 13. Unicellular organisms: 21; inheritance in, 22, 23. Use and disuse, 122. Van Ingen, 167. Vasectomy, 322. Venereal disease, 182. Virchow, 147. Voison, 133.