SS6 



INDEX 



Sensation, 77; (see also sense organs). 



Sense organs — protozoa, 156; porifera, 

 170; coelenterata, 183; echinoder- 

 mata, 218; annulata, 232; moUusca, 

 252; arthropoda, 284; vertebrata, 

 348; reptiles, 389; birds, 406; mam- 

 mals, 447 . 



Sensory epithelium, 52, 53 



Serpentes, 394 



Sexual cells, 30 (see ovum, sperm). 



Shark, 373 



Sheep, 454 



Sheepshead (fish), 374 



Shell, 246 ; structure, 248 



Shipworm, 259 



Shrike, 430 



Shrimp, 296 



Sight, 82 (see sense organs). 



Silk worm,, 305 



Siphon, 241, 256, 257 



Siphonophora, 186, 188 



Sipunculids, 204 



Sipunculoidea, 239 



Siren, 381, 384 



Sirenia, 451, 453 



Skates, 373 



Skin, 327 (see integument), 

 senses, 354 



Skeletal system, 73 — in protozoa, 154; 

 porifera, 169; coelenterates, 183; 

 echinoderms, 213, 217; annulates, 

 229; mollusks, 245; arthropods, 280; 

 vertebrates, 328; fishes, 360; am- 

 phibia, 378; reptiles, 387; birds, 404; 

 mammals, 443 



Skull, 363, 388, 420, 422 



Sloths, 451 



Slugs, 261 



Smell, 81, 354 



Smelt, 371 



Snails, 243, 247, 261 



Snakes, 394 



Snipe, 418 



Snowy grouper, 374 



Social instincts, 121, 288, 450, 472 



Sociology, 472 



Somite (see segment). 



Sow-bug, 270, 294 



Sparrows, 421 



Special senses, 81, 354 



Species, 110-112 



Spermatids, 32, 33, 34 



Spermatocytes, 32, 33, 34 



Spermatozoon, 31 



Sphincter, 336 



Spider, 307, 309 



Spinal cord, 352 

 nerves, 352 



Spinous process, 329 



Spiracle, 273 



Spirostomum, 156 



Spleen, 342 



Sponges, 148, 165 (see porifera). 



Spontaneous generation, 161 



Sporocyst, 195, 196 



Sporozoa, 162 



Sports, 488 



Squamata, 393 



Squamous epithelium, 50 



Squid, 244, 263 



Starfish, 206, 212 



Statocyst, 81, 82, 285 (see otocyst). 



Statoliths, 81, 82 



Steganopodes, 416 



Sientor, 156 



Sternum, 267, 332 



Stigmata, 282 



Stimulus, 13 



Stolon, 185 



Stomach, 336, 445 



Stomodaeum, 68, 281 



Stone flies, 299 



Stork, 416 



Streptoneura, 261 



Striate muscle, 61 



Strobila, 198 



Struggle for existence, 104 



Struthio, 412 



Sturgeon, 373 



Sunfish, 373 



Supplementary studies — protozoa, 164; 

 porifera, 173; coelenterata, 190; un- 

 segmented worms, 206; echinoderms, 

 221; annulata, 239; mollusca, 264; 

 arthropods, 310; fishes, 375; reptiles, 

 397; birds, 437; mammals, 464 



Supportive tissue (see connective). 



Suture, 443 



Swallow-tailed butterfly, 306 



Sweat glands, 327 



