xiv TEXT-BOOK OF ENTOMOLOGY 



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c. The oenocytes ........... 423 



d. The phosphorescent organs .... ... 424 



Physiology of the phosphorescence ...... 426 



THE RESPIRATORY SYSTEM . . .... . . 430 



a. The tracheae . . 431 



Distribution of the tracheae ....... 432 



b. The spiracles or stigmata 437 



The position and number of pairs of stigmata .... 439 



The closing apparatus of the stigma 441 



c. Morphology and homologies of the tracheal system . . . 442 



d. The spiral threads or tsenidia ........ 444 



e. Origin of the tracheae and of the " spiral thread ". . . 447 



Internal, hair-like bodies ........ 451 



/. The mechanism of respiration and the respiratory movements of 



insects .......... 451 



g. The air-sacs 456 



The use of the air-sacs 457 



h. The closed or partly closed tracheal system ..... 459 



i. The rectal, tracheal gills, and rectal respiration of larval Odonata 



and other insects ........ 463 



j. Tracheal gills of the larvfe of insects ...... 466 



Blood-gills 475 



k. Tracheal gills of adult insects . . 476 



THE ORGANS OF REPRODUCTION . 485 



a. The male organs of reproduction ....... 494 



The testes . 495 



The seminal ducts ......... 496 



The ejaculatory duct ........ 497 



The accessory glands 497 



The spermatozoa ......... 497 



Formation of the spermatozoon .... . 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 



PART II. EMBRYOLOGY OF INSECTS 



a. The egg .... 515 



Mode of deposition .518 



Vitality of eggs 520 



