INDEX. 
Optic cap, 452, 472 
development of, 473 
Optic constants of compound eye, 581 
Optic cup, 326 
Optic discs in larva, 80 
in nymph, 327 
Optic ganglion, 451, 469 
in Astacus, 446 
cell-groups in, 471 
development of, 483 
evolution of, in pronymph, 492 
structure of, 469 
Optic nerve, 469, 470 
external chiasma of, 537 
supposed terminations of, in 
great rods, 537 
Optic peduncle, 452, 469 
Optic stalk, 80, 81, 327, 545 
development of, 327 
Optogenic cells, 547 
Oral lobes, 395 
Oral sucker of proboscis, 135 
function of, 397 
inflation of, 397 
internal structure of, 393 
skeleton of, 135 
Orthoptera, auditory organs of, 595 
brain of, 462 
chordotonal organs of, 595 
labium of, 14 
mesosternum of, 168 
metameres of, 15 
protandry in, 723 
sexual act in, 664 
tympana of, 599 
vitellus of, 701 
Orthoraphic Diptera, 29 
Oscornutum, 183 
Osmium peroxide, action of, on nerve 
centres, 66, 468, 473 
Osten-Sacken on chetotaxy, 10 
on metapleuron, 174 
on sensory bristles, 499 
on sutures of thorax, 166 
Ostia of dorsal vessel, 641 
Ouljanin on development of external 
sexual organs, 731 
Ova, origin of, 720. See Ovum, Germ, 
Vitellus, and Egg 
Ovarian follicles, 699 
Ovary, 666 
development of, 691, 698 
epithelial tubes in, 700 
neck of, 689 
767 
Ovary, peritoneal coat of, 669 
structure of, 666 
Oviduct, 666, 671 
development of, 705 
termination of, in Hymenoptera, 
180 
Ovipositor, 733, 745 
Ovum, 12 
changes in, before impregnation, 
714 
development of, 701 
early changes in formation of 
blastoderm, 230 
general observations on, 707 
holoblastic, 236, 707 
meroblastic, 708 
merdistic, 701, 709 
nature of, 707 
pandistic, 701, 708 
Owsjannikow on nerve fibres, 437 
Oxygen, relation of, to work done, 384 
PACHYTYLUS, Miiller’s organ in, 600 
Packard on development of male 
organ, 731 
Pain doubtful in Insects, 497 
Palisade cells of Carriére, 535, 536 
Palmén on morphology of trachez, 
356 
on paired genital ducts, 660, 735 
on tracheal gills, 180 
Palpi. See Labial and Maxillary palpi 
Palpiger, 133 
Palpigerous scales, 135 
Pancreatic glands of Invertebrates, 
416 
Pandistic ova, 701, 708 
Parablast, 234 
origin of, 333 
Parablastic tissues, 270 
Paracephala, 114 
of imago, 121 
of nymph, 116 
Paraderm, 296 
contraction of the, 305 
formation of the, 299 
relation of, to discs, 303 
Parafrontals, 121 
Paragastric trachez, 225 
Paraglosse, 132, 147 
Paragonia, 662 
development of, 691, 692 
functions of, 663 
| Paranucleus, 269 
50 
