Extraordinary increase in length during the breeding season causes the vasa deferentia in some of the African weaverbirds to protrude, or to bulge out the cloacal walls beyond the vent.
In some bristle-tails and may-flies, the two vasa deferentia open separately, but usually they lead into a sperm-reservoir, whence issues a median C From Miall and Denny, The Cockroach, Lovell Reeve & Co.
The paired oviducts and vasa deferentia are, as we have seen, mesodermal in origin.
Anteriorly their vasa deferentia soon unite into a common duct, which opens into the pouch containing the penes.
B, anterior portion more highly magnified (from Marshall and Hurst, after Sommer); cs, cirrus sac; d, ductus ejaculatorius; f, female aperture; o, ovary; od, oviduct; p, penis; s, shell-gland; t, anterior testis; u, uterus; va, vp, vasa deferentia; us, vesicula seminalis; y, yolk-gland; yd, its duct.
C, genital sinus and neighbouring parts (from Sommer); a, ventral sucker; b, cirrus sac; c, genital pore; d, evaginated cirrus sac: e, end of vagina; f, vasa deferentia; g, vesicula seminalis; h, ductus ejaculatorius; i, accessory gland.
Where the vesiculae join the ampullae of the vasa deferentia the ejaculatory ducts are formed; these are narrow and thin-walled, and run, side by side, through the prostate to open into the floor of the prostatic urethra.
- View of the Base of the Bladder, Prostate, Seminal Vesicles and Vasa Deferentia from behind.
They pass out through short vasa deferentia with internal ciliated funnels, sometimes an enlargement on their course - the seminal vesicles - and a minute external pore situated on the side of the tail.
Thus the condition in the Dermaptera is more primitive than in any other Pterygote order except the Ephemeroptera (Mayflies) which are still more generalized, the primitive mesodermal ducts (oviducts and vasa deferentia) opening by paired apertures as in the Crustacea.
The mouth is terminal or subterminal; there is a weak sucking pharynx situated behind the brain, and a long intestine lying along the medio-ventral body-cavity; it ends in a cloaca which receives the vasa deferentia in the male.
The paired testes extend through the greater part of the body and end in two vasa deferentia which unite with the intestine to form a cloaca.