. A manual of zoology. 232 MANUAL OF ZOOLOGY 'shgl (Fig. 132) the abdomen with its appendages is imperfectly developed, and not enclosed completely in a hard exoskele- ton, this region being sheltered in the shell of a whelk or other univalve mollusc which the hermit-crab drags about with The crustaceans enumer- ated above, together with the sand-hoppers, woodlice and their allies, and a large number of others, form one or two sub-classes into which the class Crustacea is di- vided—the sub-class Mala- costraca. The Malacostraca are highly organised Crus- tacea, usually of consider- able s
. A manual of zoology. 232 MANUAL OF ZOOLOGY 'shgl (Fig. 132) the abdomen with its appendages is imperfectly developed, and not enclosed completely in a hard exoskele- ton, this region being sheltered in the shell of a whelk or other univalve mollusc which the hermit-crab drags about with The crustaceans enumer- ated above, together with the sand-hoppers, woodlice and their allies, and a large number of others, form one or two sub-classes into which the class Crustacea is di- vided—the sub-class Mala- costraca. The Malacostraca are highly organised Crus- tacea, usually of consider- able size, and nearly all have a thorax of eight and an abdomen of seven seg- ments. The appendages are highly differentiated^ There is a gastric mill, and the renal organs are in the form of antennary glands. The other sub-class is the Entomostraca. The Entomostraca, which are even more numerous than the Malacostraca, are of comparatively simple organisation, and usually of small, often almost microscopic, size. The 1 Our common American hermit-crab is Eupagurus pollicaris; the right chela is still larger than in Pagurus bernhardus of the European 133. — Apus glacialis, ventral aspect. , abdominal feet; ant. r, anten- nule; ant. 2, antenna; Ibr, labrum; md, mandible; mx, first maxilla; ov, aper- ture of oviduct; , sub-frontal plate; , shell-gland; , thoracic feet; , first thoracic foot. (After Bernard.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Haswell, William A. (William Aitcheson), 1854-1925. New York, The Macmillan Company; London, Macmillan & Co. ,Ltd.
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