544 



INDEX 



Sea lilies, 219 



Sea squirts, 312 



Sea urchins, 220 



Seals, 454 



Secretion, 17, 69 



Sections, defined, 91 



Segment, 278 (see metamere, somite). 



Segmentation (see cleavage, metamer- 

 ism). 



Segmentation cavity, 38, 39 



Segmented worms (see annulata). 



Segregation of characters, 494 



Segregation of germ cells, 42 



Semi-circular canals, 354 



Seminal vesicles, 232 



Sensation, 76, 148; see also sense organs. 



Sense organs protozoa, 155; porifera, 

 169; ccelenterata, 182; echinoder- 

 mata, 217; annulata, 231; mollusca, 

 251; arthropoda, 283; vertebrata, 

 347; reptiles, 388; birds, 405; mam- 

 mals, 446 



Sensory epithelium, 51, 52 



Sexual cells, 30 (see ovum, sperm). 



Shark, 372 



Sheep, 453 



Sheepshead (fish), 373 



Shell, 245; structure, 247 



Ship worm, 258 



Shrike, 429 



Shrimp, 295 



Sight, 8 1 (see sense organs). 



Silk worm, 304 



Siphon, 240, 255, 256 



Siphonophora, 185, 187 



Sipunculids, 203 



Sipunculoidea, 238 



Siren, 380, 383 



Sirenia, 450, 452 



Skates, 372 



Skin, 326 (see integument). 



Skin senses, 353 



Skeletal system, 72 in protozoa, 153; 

 porifera, 168; ccelenterates, 182; 

 echinoderms, 212, 216; annulates, 

 228; mollusks, 244; arthropods, 279; 

 vertebrates, 327; fishes, 359; am- 

 phibia, 377; reptiles, 386; birds, 403; 

 mammals, 442 



Skull, 362, 387, 4i9i 422 



Sloths, 451 



Slugs, 260 



Smell, 80, 353 



Smelt, 370 



Snails, 242, 246, 260 



Snakes, 393 



Snipe, 417 



Snowy grouper, 373 



Social instincts, 120, 287, 449, 470 



Sociology, 470 



Somite (see segment). 



Sow-bug, 269, 293 



Sparrows, 420 



Special senses, 80, 353 



Species, 109-111 



Spermatids, 32, 33, 34 



Spermatocytes, 32, 33, 34 



Spermatozoon, 31 



Sphincter, 335 



Spider, 306, 308 



Spinal cord, 351 



Spinal nerves, 351 



Spinous process, 328 



Spinus, 426 



Spiracle, 272 



Spirostomum, 155 



Spleen, 341 



Sponges, 147, 164 (see porifera) . 



Spontaneous generation, 160 



Sporocyst, 195, 196 



Sporozoa, 161 



Sports, 488 



Squamous epithelium, 49 



Squid, 243, 262 



Starfish, 205, 211 



Statocyst, 80, 8 1, 284 (see otocyst) 



Statoliths, 80, 8 1 



Steganopodes, 415 



Stentor, 155 



Sternum, 266, 331 



Stigmata, 281 



Stimulus, 13 



Stolon, 184 



Stomach, 335, 444 



Stomodaeum, 67, 280 



Stone flies, 298 



Stork, 415 



Streptoneura, 260 



