548 



INDEX 



Sperm centrosome, 17 

 Sperm nucleus, 17, 28 

 Spermatocytes, 135 

 Spermatogenesis of Ancyracan- 



thus, 138 

 Spermatogonia, 134 

 Spermatozoon, 14, 16, 20 



formation of, 144 

 Spina bifida, 332 

 Spinal cord, development, 31 

 Spindle, mitotic, 22, 28, 117 

 Spireme, 117 

 Spirilla, reactions to chemicals, 



55 

 "Sports," 216, 217 

 Standfuss, mutations of insects, 



357 

 Star-fish, isolated cleavage cells, 



322 

 Statistical methods, strength 

 and weakness of, 225, 227 

 Statistical Study of Inheri- 

 tance, 220-229 

 Stature, inheritance of, 202, 221, 

 226 

 tendency to mediocrity 224 

 influence of food on, 311 

 Stentor, modifiable behavior, 73 

 Sterile insects, 456 

 Sterility, 422, 451-454 

 Sterilization, 435-438 

 Stevens, on sex determination, 



148, 149, 171 

 Stimuli, chemical and physical, 

 483 

 conflicting, 73, 480 

 definition, 316 

 Developmental, 315-318 

 chemical, 316 

 non-specific, 317 

 physical, 316 

 external and internal, 72, 



471, 481, 482 

 range of, 484 



rational, social ethical 483 

 summation of, 63 



Stockard, alcohol on spermato- 

 zoa, 319, 320, 358 

 experimental cyclopia, 159, 

 833 

 Structures and functions, recip- 

 rocal relations, 41, 48, 208 

 Styela, anterior half-embryos, 

 327 

 dislocated organs, 830 

 egg substances, 123-127 

 gastrulation and larva, 130 

 half and three-quarter em- 

 bryos, 825 

 maturation, fertilization and 

 cleavage, 123, 126, 127, 130 

 posterior half-embryos, 828 

 Summation of Stimuli, 63 

 Sumner, effect of cold on mice, 



358 

 Superman, 426, 455 

 Sweden, extinct noble families, 



451 

 Swine, wild and domestic, 881 

 Symmetry, 176-180 

 Synapsis, 137 

 Syndactylism, 205, 302 



Tadpoles, fed on thyroid, thy- 

 mus, adrenal, 334 



Talents, unused, 487 

 parable of, 489 



Temperament, inheritance of, 

 210, 301 



Temperature, influence on mu- 

 tation, 318 

 influence on cell division, 

 319 



Tenebrio, sex differentiation in, 

 149 



Tennent, modified dominance 

 in echinoderm hybrids, 274 



Teratological characters inheri- 

 ted, 205 



Tertullian, 44 



Tetrads, 141 



