. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. AMPHIPODA. 451 organ. Appendages of the legs may also be present as additional aids to copulation. The mature ova are, as a rule, carried about by the female in brood pouches formed by the lamellar appendages of the thoracic feet (oostegites). Development as a rule takes place without metamorphosis, but the form and appendages of the youn«- animal not unfrequently differ from those of the adult animal (Phroni'fna). The segments and the appendages may even be incom- plete in number after bir
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. AMPHIPODA. 451 organ. Appendages of the legs may also be present as additional aids to copulation. The mature ova are, as a rule, carried about by the female in brood pouches formed by the lamellar appendages of the thoracic feet (oostegites). Development as a rule takes place without metamorphosis, but the form and appendages of the youn«- animal not unfrequently differ from those of the adult animal (Phroni'fna). The segments and the appendages may even be incom- plete in number after birth (Isopoda). Fossil Arthrostraca are found in the Oolite (Archceonlscus). Pro- soponiscus occurs in the Permian, Amphipeltis in the 1. Sub order.—Amphipoda.* ArtJirostraca with laterally compressed body, with gills on the thoracic feet, and an elongated abdomen, of which the three anterior segments bear the swimming feet, ii'ldle th& three posterior bear posteriorly di- rected feet adapted for springing (fig. 35G). The Amphipoda are small animals, being only in rare cases several inches long (Li/sianassa magellanica). They move in the water principally by spring- ing and by swim- ming. The head, which is sometimes small (Crevettina, fig. 356), sometimes large and then much swollen (Ilyperina, fig. 357), is sharply distinct from the thorax and is fused with the first of the seven thoracic segments only in the aberrant group of the Lcemodipoda. The two pairs of antennas usually consist of a short strong shaft >f Besides the oldei' works of Do Geer, Bxisel, M. Edwards, compare C. Spence Bate. " On the Morphology of some Amphipoda of the Division Hyper- ina," Ann. of Nat. Ser. 2. vol. 1857. C. Spence Bate, "On the nidification of Crustacea," Ann. of Nat. Hist., Scr. 3, vol. i. C. Spence Bate. " Catalog-ue of tho specimens of Amphipodous Crustacea in the collection of the British Museum," London, 18G2. E. van Be
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