632 



INDEX 



Olfactory capsule, 39, 42, 436, 



493 



Olfactory lobe, 160, 460, 528 

 Olfactory organs : Frog, 180 ; 

 Crayfish, 381 ; Mussel, 409 ; 

 Dogfish, 432, 464 ; Rabbit, 

 534 ; development of, in 

 Vertebrates, 592 



Olfactory pit, 424 



Oligochaeta, 350 



Ommatideum, 380 



Omosternum, 48 



Ontogeny, 224 



Oogenesis, 196, 568 



Oosperm, 198, 572 ; and see 

 under various types 



Oosperm, holoblastic and mero- 

 blastic, 573, 574 



OPALINA : occurrence and general 

 characters, 280 ; nuclei, 280 ; 

 parasitic nutrition, 282 ; re- 

 production, 282 ; means of 

 dispersal, 283 ; development, 

 283 ; practical directions, 293 



Optic chiasma, see Chiasma ; 

 cup, 593 : lobe, 157, 459, 530, 

 590 ; thalamus, 159, 529 ; 

 vesicle, 593 



Optical section, 323, 558 



Oral cavity, see Buccal cavity 



Oral hood, 421 



Orbit, see Skull 



Order, 218 



Organ, 30, 31, 151, 238, 344 



Organism, 231 



Origin : of -muscle, 60 ; of species, 

 225 



Osmosis, 73 



Osphradium, 409 



Ossicles, auditory, see Auditory 

 ossicles 



Ossification, 44 



Osteoblasts, 117 



Ostia : of heart, 376 ; of gills, 

 404 



Otocyst, 315 (see also under 

 Statocyst) 



Otoliths, 1 88, 382 



Ovary : Frog, 23, 193, 195 ; and 

 see Reproductive organs 



Oviduct, 25, 196, 346, 382, 467, 



540, 603 

 Ovisac, 195, 540 

 Ovum, 195, 564, 568 ; and see 



under various types 

 Ovum : microlecithal, megaleci- 



thal, centrolecithal, and telo- 



lecithal, 574 

 Oxidation of protoplasm, 149, 



248 



Palaeontology, 224 



Palate, 494, 507 



Palatoquadrate, 44, 436 



Pallial line, 399 



Pallium, see Mantle 



Palp : Nereis, 351 ; Crayfish, 

 367 ; Mussel, 401 



Pancreas, 22, 70, 133, 204, 447, 

 5 J 6, 597 



Pancreatic juice, 70, 74 



Papillae of tongue, 180, 509 



Parachordal cartilages, 605 



Paragnatha, 370 



Paramylum, 251 



PARAMCECIUM : structure, 262 ; 

 mode of feeding, 266 ; repro- 

 duction, 268 ; conjugation, 

 268 ; practical directions, 277 



Parapod, 350 



Parasite, parasitism, 33, 153. 

 280, 282, 284, 287 



Parietal layer of peritoneum, 26, 

 331 ; see also Mesoderm 



Parthenogenesis, 570 



Patella, 504 



Pectoral arch, 20, 36, 46, 442, 

 500, 606 



Pectoral fin or limb, see Appen- 

 dages 



Pedal ganglion, 408 



Pelecypoda, 411 



Pelvic arch, 20, 36, 50, 442, 503, 

 606 



Pelvic fin or limb, see Appen- 



Pelvis of kidney, 538 

 Penis, 487, 5^0 



