20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



In many of the other orders, however, the egg passage is subject to 

 a further extension in a posterior direction, and its opening may then 

 come to be on the venter of the ninth segment behind the ninth 

 sternum. Thus, in Panorpidae, most Trichoptera and Lepidoptera, all 

 Coleoptera, and apparently in some Hemiptera and Diptera, the 

 median egg passage extends into the ninth segment and has an open- 

 ing on the venter of this segment in common with that of the accessory 

 glands, if these glands are present. When the egg passage is thus con- 

 tinued from the eighth segment into the ninth, the added part becomes 

 an extension of the genital chamber, or of its derivative, the vagina, 

 having its opening, the vulva, transferred from the venter of the 

 eighth segment to that of the ninth. The primary oviduct remains 

 unaltered ; but the vaginal region of the exit tract now receives both 

 the spermatheca and the accessory glands, and in most cases serves 

 as a copulatory pouch. 



The morphology of the extension of the efferent passage from the 

 eighth to the ninth segment is not so clear as that of the extension 

 of the oviduct from the seventh to the eighth segment. The onto- 

 genetic processes involved are less simple, and it is difficult to give 

 them a uniform interpretation. 



An intermediate condition in the transference of the functional 

 genital aperture from the eighth segment to the ninth occurs in Lepi- 

 doptera (fig. 4 E), where, in the majority of families, there is retained 

 a copulatory opening on the eighth segment (Vul) leading into a 

 copulatory pouch (bcpx) and the spermatheca (Spt), while, on the 

 ninth segment (or the combined ninth and tenth somites) there is 

 established a posterior vaginal opening (Opr) in common with the 

 aperture of the accessory glands (AcGl). The copulatory opening 

 (Vul) on the eighth segment is the vulva of orthopteroid insects. 

 The tubular passage in the eighth segment leading to the vagina, with 

 its diverticulum known as the bursa copulatrix (bcpx), and the part of 

 the vagina receiving the spermatheca, together represent the genital 

 chamber invagination of the eighth segment. The rest of the vaginal 

 tube (Vag) is a secondary extension through the ninth segment. 

 Since the posterior opening serves only for the discharge of the eggs 

 it may be distinguished as the oviporus {Opr). 



According to the account given by Jackson (1889) of the develop- 

 ment of the female ducts and associated organs in Vanessa io, the 

 definitive egg passage of Lepidoptera is formed, as we should expect, 

 from three sections. The second and third have independent ecto- 

 dermal origins ; the first is formed as an outgrowth from the second. 

 Prior to the appearance of the first rudiment, which is that of the 



