. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. AMPniPODA. 461 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 youno- animal not unfrequently difter from those of the adult animal (Phronima). The segments and the appendages may even be incom- plete in number after birth [Isojwd
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. AMPniPODA. 461 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 youno- animal not unfrequently difter from those of the adult animal (Phronima). The segments and the appendages may even be incom- plete in number after birth [Isojwda). Fossil Arthrostraca are found in the Oolite {Archceoniscus). Pro- soponiscus occurs in the Permian, Am^^Juj^eltis in the 1. Sub order.—Amphipoda.* Arthrostraca with laterally comioressed body, toith gills on the thoracic feet, and an elongated abdomen, of lohich the three anterior segments bear the swimming feet, while the three ^)05ie?'io?' hear j)Osteriorhj di- rected feet adapted for springing (fig. 35G). The Am2)hipoda are small animals, being only in rare cases several inches long [Lysianassa 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 antennae usually consist of a short strong shaft * Besides the older works of Dc Geer, Rosel, M. Edwards, compare C. Spence Bate, " On the Morphology of some Amphipoda of the Division Hyper- iua," Ann. of JVat. Ser. 2, vol. xix., C. Spence Bate, "On the nidification of Crustacea," Ann. of JVat. Hist., Ser. 3, vol. i. C. Spence Bate. '• Catalogue of the specimens of Amphipodous Crustacea in the collection of the British Museum," London, 18G2. E. van Beneden ct Em Be
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
