Smithsonian miscellaneous collections . he inner ends of the ejaculatory ducts (C), but toavoid a multiplicity of names the term gonopore is applied to theopening of any genital duct, whether primary or secondary. A com-bination of ejaculatory ducts with external penes is of commonoccurrence (D). The primitive paired condition of the genital openings and associ-ated structures is retained in some members of most of the arthropodgroups, and is characteristic of Xiphosurida. Crustacea, and Diplop-oda. In other groups, and in some of the crustaceans and diplopods,an unpaired condition of the term
Smithsonian miscellaneous collections . he inner ends of the ejaculatory ducts (C), but toavoid a multiplicity of names the term gonopore is applied to theopening of any genital duct, whether primary or secondary. A com-bination of ejaculatory ducts with external penes is of commonoccurrence (D). The primitive paired condition of the genital openings and associ-ated structures is retained in some members of most of the arthropodgroups, and is characteristic of Xiphosurida. Crustacea, and Diplop-oda. In other groups, and in some of the crustaceans and diplopods,an unpaired condition of the terminal parts arises in various ways,and is subject to great modifications, which reach an extreme degreeof development in the insects. In the first place, the penis may be asingle median organ (fig. 4 E, Pen) with two separate openings forthe ducts; but in general there is associated with a median penis asingle ejaculatory duct (F, Dej), which receives the two vasa defer- i6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 §^10 0 0 0 e A B. Fig. 4.—Diagrams showing some of tiie principal variations of the genitalducts and accessory structures. A, simple condition with gonoducts opening separately through pores ofbody wall. B, vasa deferentia opening on a pair of penes. C, each vas deferensdischarging through an ectodermal ductus ejaculatorius. D, the ejaculatory ductsopening on a pair of penes. E, the ejaculatory ducts opening separately on asingle penis. F, a single ejaculatory duct and a single penis. G, the vasadeferentia discharging into a bursa genitalis, or genital chamber (GC). H, thevasa deferentia united distally in a ductus conjunctus (Den). I, the ductusconjunctus enlarged to form a saccus internus (Si), as in many , a penis evaginated from the genital chamber, traversed by an ectodermal ductfrom an ejaculatory bulb (Bej), as in Phalangida. K, simple condition ininsects, with ejaculatory duct, penis, and genital chamber. L, more complexcondition in insects:
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Keywords: ., bookcentury1800, bookdecade1860, bookidsmiths, booksubjectscience
