Smithsonian miscellaneous collections . emale. The termi-nal parts of the oviducts in some species of isopods are enlarged toserve as sperm receptacula, and the eggs are fertilized in the mating, the female moults and in most species acquires a broodpouch (marsupium) on the under surface of the body, into which thefertilized eggs are discharged, and within which they are carrieduntil the young hatch. The brood pouch is formed typically by broad NO. 14 INSECT ABDOMEN SNODGRASS 43 overlapping plates (oostegites) that grow over the thoracic venterfrom the bases of the legs, but in som
Smithsonian miscellaneous collections . emale. The termi-nal parts of the oviducts in some species of isopods are enlarged toserve as sperm receptacula, and the eggs are fertilized in the mating, the female moults and in most species acquires a broodpouch (marsupium) on the under surface of the body, into which thefertilized eggs are discharged, and within which they are carrieduntil the young hatch. The brood pouch is formed typically by broad NO. 14 INSECT ABDOMEN SNODGRASS 43 overlapping plates (oostegites) that grow over the thoracic venterfrom the bases of the legs, but in some species it is formed by anteriorand posterior folds of the ventral integument, and in others by aninvagination or a series of sacklike ingrowths of the membranousventral wall of the thorax. In one genus, Paragnathia, the young aresaid to develop in the ovaries, which serve as uteri. The Amphipoda are provided with a pair of small penes, but theyhave no organs of sperm intromission; the eggs are fertilized outside Gprs XnStn XmStn Pen. Stn Trtpd ?~-Expd ?~-Endpd E t6.—Crustacea-Malacostraca-Peracarida : male genitalia of Isopoda andAmphipoda, A, Scrolls (isopod), ventral view of last thoracic and first abdominal seg-ments, showing gonopores on sternum of somite XII. B, Gammarus locusta(amphipod), ventral view of last thoracic segment, showing penes arising atbases of coxopodites. C, Porccllio laevls (isopod), testis and exit duct of oneside, and median penis. D, same, penis and first pleopods, ventral view. E,same, second pleopods. Brn, branchia; Cxpd, coxopodite; Dct, genital exit duct; Endpd, endopodite;Expd, exopodite ; Gprs, gonopores; Pen, penis ; Prtpd, protopodite ; Stn, sternum ;T, tergum ; Tcs, testis ; Vsm, vesicula seminalis ; XllStn, sternum of male genitalsegment; XlllStn, sternum of first abdominal segment. the body of the female. The penes, as illustrated in Gammarus locusta(fig. 16 B, Pen), are a pair of short cylindrical processes arising frommembranous area
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