INDEX 



325 



Mouse-fish in gulf-weed (illus), 208. 

 Mt. Orizaba (illus.), 300. 

 Multiplication, 50 ; of animals, 



114; simplest method of, 53; 



slightly complex methods of, 54. 

 Murres, Pallas's (illus.). 165. 

 Mussel, alimentary canal of (illus.), 



72. 

 Mutual aid, 163. 



Narcine brasiliensis (illus.), 135. 



Natural selection, 117. 



Neotropical realm, 301. 



Nerve cells, 240. 



Nerve fibers, 240. 



Nest-making habits of birds, 264 ; 

 of fishes, 264; of insects, 262; 

 of invertebrates, 258 ; of spiders, 

 259 ; of vertebrates, 264. 



Nest of Baltimore oriole (illus.), 

 267; of beavers (illus.), 269; of 

 California!! bush-tit (illus.), 270; 

 of Cteniza californica (illus.), 

 261; of pocket -gopher (illus.), 

 271; of rufus humming-bird 

 (illus.), 265, 266; of tailor-bird 

 (illus.), 268 ; of trap-door spider 

 (illus.), 261 ; of turret - spider 

 (illus.), 262. 



Nokee (illus.), 132. 



Nomeus gronovii (illus.), 175. 



North Temperate realm, 299. 



Nuclear membrane, 3. 



Nucleus, 3. 



Obelia, alimentary sac of (illus.), 



69. 



(Esophagus, 67. 

 Omasum, 67. 

 One-celled animals, 2. 

 Organ, 63 ; auditory, of cray-fish 



(illus.), 233; of cricket (illus.), 



234 ; of grasshopper (illus.), 234 ; 

 of mosquito (illus.), 235 ; of mol- 

 lusk (illus.), 233. 



Organic matter, 112. 



Organs, auditory, 232 ; of smell, 

 229; of sound-making, 235; of 

 taste, 228; of touch, 226; spe- 

 cialization of, 66 ; vestigial, 147. 



Oriole, Baltimore, nest of (illus.), 

 267. 



Ornithotomous sutorius, nest of, 

 268. 



Osprey Falls (illus.), 285. 



Otolith, 232. 



Ox, alimentary canal of (illus.) 67. 



Oxygen, necessary to animal life, 

 107. 



Pagurus (illus.), 176. 

 Pandorina, 26. 

 Pandorina sp. (illus.), 26. 

 Pandorina morum (illus.), 27. 

 Papilio, chrysalid of (illus.). 205. 

 Papilla, tactile, of skin of man 



(illus.), 227. 

 Papillae, 67. 

 Paramcecium, 9. 

 Paramcecium aurelia (illus.), 10. 

 Paramcecium caudatum (illus.), 11. 

 Paramcecium plutorinum (illus.), 



11. 

 Parasite of caterpillar (illus.), 190 ; 



relation to host, 179. 

 Parasites, simple structure of, 181. 

 Parasitism, 179; kinds of, 180. 

 Parthenogenesis, 60. 

 Patagonian realm, 302. 

 Pediculus (illus.), 188. 

 Pelagic fauna, 304. 

 Pelican, brown (illus.), 125. 

 Peneus, adult and larva (illus.), 



195. 



