. Smithsonian miscellaneous collections. ses and the pleural sclerites of the adult. Though the apparentfacts in the development of the chilopods may be as Becker describesthem, it is difificult to see how they can be interpreted literally as repre- 12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 senting the phylogenetic origin of the definitive pleural plates and theleg bases. It would seem more probable that they are ontogenetic phe-nomena only, and that Beckers observations really show simply thatthe pleurites and the bases of the legs have a common origin. In the decapod crustaceans the i
. Smithsonian miscellaneous collections. ses and the pleural sclerites of the adult. Though the apparentfacts in the development of the chilopods may be as Becker describesthem, it is difificult to see how they can be interpreted literally as repre- 12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 senting the phylogenetic origin of the definitive pleural plates and theleg bases. It would seem more probable that they are ontogenetic phe-nomena only, and that Beckers observations really show simply thatthe pleurites and the bases of the legs have a common origin. In the decapod crustaceans the inner walls of the gill chambers,which are covered externally by lateral folds of the carapace, areformed of large cuticular plates bearing the gills (fig. 7 D). Eachplate, or pleuron, shows subdivisions (ScXiScxa) corresponding withthe body segments of the ambulatory legs, and each subdivision bearsa gill {Brni-Brns). In the second maxilliped (B) the homologue ofthe gill is borne on an epipodite (Eppd) which is distinctly carried by Sex. A Cx Stn Fig. 8.—A body segment of Strigamia bothriopiis (Chllopoda, Geophilidae). A, lateral view, with leg removed beyond the coxa. B, ventral view, includingbases of legs. Cx, coxa; 1st, intersternite; pi, pleurites between the tergum andthe subcoxa; Sex, subcoxa; Sp, spiracle; Stn, primary sternite; T, tergum; Tr,trochanter. the basal segment of the appendage, or coxopodite {Cxpd). In thethird maxilliped (C), however, the gill arises from a subcoxal part ofthe limb basis {Sex). In the ambulatory region (D) the gills on thepleuron are successively more and more removed from the coxae. Itthus becomes evident that the pleural wall of the branchial chamber inthe decapod crustaceans has been formed from dorsal extensions ofthe subcoxal parts of the leg bases, and that the coxae have acquiredspecial articulations with the subcoxae. In the majority of crustaceansthe leg base is an undivided coxopodite. In the Chilopoda there is a definitely circ
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
