_j._ Tracheal gills of the larvæ of insects 466
The testes 495 The seminal ducts 496 The ejaculatory duct 497 The accessory glands 497 The spermatozoa 497 Formation of the spermatozoön 498
_b._ The female organs of reproduction 500
The ovaries and the ovarian tubes 500 Origin of incipient eggs in the germ of the testes 504 The bursa copulatrix 505 The spermatheca 506 The colleterial glands 506 The vagina or uterus 507 Signs of copulation in insects 507
Mode of deposition 518 Vitality of eggs 520 Appearance and structure of the ripe egg 520 The egg-shell and yolk-membrane 520 The micropyle 522 Internal structure of the egg 524
_b._ Maturation or ripening of the egg 525
_d._ Division and formation of the blastoderm 526
_e._ Formation of the first rudiments of the embryo and of the embryonic membranes 531
Formation of the embryonic membranes 532 The gastrula stage 535 Division of the embryo or primitive band into body-segments 536 Differences between the invaginated and overgrown primitive band 538 Revolution of the embryo where the primitive band is invaginated 540
_f._ Formation of the external form of the body 542
Origin of the body-segments 542 The procephalic lobes 544 Fore-intestine (stomodæum) and hind-intestine (proctodæum), labrum 547 Completion of the head 548
The cephalic appendages 548 The thoracic appendages 550 The abdominal appendages 550 Appendages of the first abdominal segment (pleuropodia) 551 Are the abdominal legs of Lepidoptera and phytophagous Hymenoptera true limbs? 552 The tracheæ 553
Completion of the definite form of the body 555
_i._ Dorsal closure and involution of the embryonic membranes 556
_k._ Farther development of the mesoderm; formation of the body-cavity 563
The nervous system 566 Development of the brain 567 Development of the eyes 567 Intestinal canal and glands 569 The salivary glands 570 The urinary tubes 572 The heart 572 The blood-corpuscles 574 Musculature; connective tissue; fat-body 574 The reproductive organs 575 Development of the male germinal glands 579
_a._ The nymph as distinguished from the larval stage 593
_b._ Stages or stadia of metamorphosis 594
_c._ Ametabolous and metabolous stages 594
_c._ Growth and increase in size of the larva 608