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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



to lie in dose proximity, and the eggs may be readily fertilized as they 

 issue from the former. Then the two openings, in the majority of 

 generalized insects, are carried inward by the formation of a copula- 

 tory pouch, the bursa copulatrix, or genital chamber (C, GC), in- 

 vaginated above the eighth sternum. 



Fig. 4. — Diagrams showing the development of the median oviduct, and the 

 evolution of the secondary copulatory structures added to the duct. 



A, origin of primitive median oviduct on seventh abdominal segment. 



B, extension of oviduct to end of eighth segment. 



C, formation of genital chamber (GC) behind eighth sternum to form a copu- 

 latory and fertilization pouch receiving the oviduct and the spermathecal duct. 



D, genital chamber having form of a tubular vagina (i'ag). 



E, vagina extended to ninth segment, where it opens, but retains the original 

 copulatory opening (Vul) on eighth segment. 



F, vagina opening only on ninth segment. 



AcGl, accessory glands; bcpx, copulatory pouch of genital chamber; d, diver- 

 ticulum of vagina ; GC, genital chamber, or bursa copulatrix ; Gpr, gonopore ; 

 Gpr', primary median gonopore ; Ode, oviductus communis ; Ode', primary me- 

 dian oviduct; Odl, oviductus lateralis; Opr, oviporus ; Spt, spermatheca ; I'ul. 

 vulva, ostium vaginae. 



The posterior opening of the genital chamber thus becomes both a 

 copulatory entrance, and the final exit for the fertilized eggs. Tt there- 

 fore may be termed the vidva (Vul). The true gonopore {dpr) is 

 still the ()])ening of the oviduct into the genital chamber. The genital 



