English: Title: The Cambridge natural history

Identifier: cu31924024535464 Year: 1895 (1890s) Authors: Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed Subjects: Zoology Publisher: [London, Macmillan and Co. , Limited; New York, The Macmillan Company Contributing Library: Cornell University Library Digitizing Sponsor: MSN

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Text Appearing Before Image: 490 PENTASTOMIDA CHAP. line, lies the mouth, elevated on an oral papilla, and on each side of the mouth are a pair of hooks whose bases are sunk in pits. The hooks can be protruded from the pits, and serve as organs of attachment. Their shape has some systematic value. There are a pair of peculiar papillae which bear the openings of the " hook-glands," lying just in front of the pairs of hooks, and other smaller papillae are arranged in pairs on the cephalo- thorax and anterior annuli. The entire body is covered by a cuticle which is tucked in at the several orifices. This is secreted by a continuous layer of ectoderm cells. Some of these subcuticular cells are aggregated together to form very definite glands opening through the cuticle by pores which have somewhat unfortunately received the name of stigmata. Spencer attributes to these glands a general excretory function. There is, how- ever, a very special pair of glands, the hook-glands, which extend almost from one end to the other of the body; anteriorly these two lateral glands unite and form the head-gland (Fig. 257). From this on each side three ducts pass, one of which opens to the surface on the primary papilla; the other two ducts open at the base of the two hooks which lie on each side of the mouth. Leuckart has suggested that these important glands secrete some fluid like the irritating saliva of a Mosquito which induces an increased flow of blood to the place where it is of use to the parasite. Spencer, however, regards the secretion as having, like the secretion of the so-called salivary cells of the Leech, a retard- ing action on the coagulation of the blood of the host. The muscles of Pentastomids are striated. There is a circular layer within the sub-cuticular cells, and within this a longitudinal

Text Appearing After Image: Fig. 256. — Porocephalus aiinulattcs, Baird. A, Ventral view of head, x 6 ; B, ventral view of animal, x 2.

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