INDEX 



689 



Thallophytes, 194-195, 596-607; 404- 

 408 

 life history of, 255-257 

 origin and evolution of, 401-408 

 Thallus, 195, 598, 601 

 Therapod dinosaurs, 448; 449, 451 

 Therapsid reptiles, 458-459, 631 

 Thiamine, 60 



Thrombin, thrombokinase, 97, 98 

 Thymus, 132; 1 27 

 Thyroid gland and thyroxin, 129-130, 



240; 127 

 Time scales, 392 

 geological, 392-395 

 of Pleistocene, 491 ; 502 

 Tissue fluid, 88rc. 

 Tissues, of animals, 12, 22, 29, 82 



of plants, 136, 143-146, 153-158, 166- 

 169 

 Toleration, limits of, 553-554 

 Tone in nerves, 95 

 Tools, Neolithic, 534 



Paleolithic, 503n.; 502, 532 

 Touch, 109 

 Toxins, 99 



Trace elements, '147-148 

 Trachea in man, 74; 75 

 Tracheae, of insects, 187; 188 



of plants, 160 

 Tracheophyta, 597, 610-611 

 Traits, inheritance of, 318-325 

 older and newer, 513 

 phenotypic, as racial criteria, 511-513 

 Transpiration, 162-163, 167-169 

 Transpiration pull, 150, 162-163 

 Transport, in human body, 81-97, 164 

 in plants, of solutes, 150, 163-165 

 of water, 146-150, 161-165 

 Tree ferns, 198n., 616; 199, 581 

 Tree rings, 156-157 



use of, in dating, 493 

 Tree shrews, 470; 471 

 Triassic period, 394, 414, 441, 446-450 

 Trihybrid cross, 283, 287-288 

 Trilobites, 420, 435, 630, 648; 393, 649 

 Triploblastic characters, 362, 627, 629 

 Tropisms, 554 

 Trypsin, 68, 70 

 Trypsinogen, 70n. 

 Tryptophan, 61 

 Tuatara, 444, 631 

 Tube nucleus, 269; 270 

 Tube-within-tube plan, 183, 236, 628; 185 

 Tunicates, 656; 424 

 Turgor, 147 



Turgor pressure, 149-150 

 Turtles, 441, 631, 661; 662 

 Twig, 152-155 



Twins, 322-323 



uniovular and biovular, 322, 508 

 Tympanic membrane, 112; 113 



U 



Unconformity, geological, 391 

 Ungulates, 464-465, 666; 467 



even-toed, 464-465, 667 



odd-toed, 465, 666 

 Unicellular organisms, 178-179, 193-195 



potential immortality of, 213 



reproduction in, 211-213 

 Uniformitarianism, 334-337, 387-388 

 Unisexual reproduction, 224 

 Unit characters, 304 

 Uranium-lead ratios, dating by, 392n. 

 Ureter, 79; 75, 185 

 Urethra, 79, 291; 75, 243, 292 

 Urinary bladder, 79; 25, 75, 242, 243 

 Urine, 79 



Urinogenital system, 25, 26 

 Use and disuse, 311, 319, 343, 344 

 Uterus, 244; 248 

 Utriculus, 114; 113 



Vacuoles, 17, 136, 184; 186 

 Vagus nerves, 70, 95, 104, 121 

 Valves, of heart, 84; 85, 86 



of veins and lymphatics, 92, 94 

 Variations, 277, 311-317 



autogenous, 312-316, 345 



and chromosomal changes, 312-313 



environmentally induced, 311 



and evolution, 345-346 



and gene mutations, 313-316 



and heredity, 277 

 Vascular bundles, 158-159 

 Vascular cylinder, 155 

 Vascular plants, 597, 610-611; 594 



earliest known, 409-410 

 Vascular rays, 156, 161 

 Vascular system, 145, 159-165; 594 

 Vascular tissue, 145-146, 155-165 

 Vegetal (vegetative) pole of egg, 231; 235 

 Vegetative reproduction, 254-255 

 Veins, of human body, 86-88, 94; 89 

 portal, 88; 89 



of leaf, 166 

 Vena cava, 87; 85, 89 

 Venter, ventral, definition of, 32n. 

 Ventricles, 84; 85, 86 

 Vertebrates, 237-240, 655, 657-667; 185 



origin and early history of, 421-425 

 Vessels of xylem, 160; 154, 156 

 Vestigial structures, 359-361 



