. Zoology : for students and general readers . Zoology. session of two or three pairs spW^ Fig. 311.—Anatomy of a epider, diagrammatic longitudinal section through the body, aft, simple eyes and nerves leading to tliem from the brain (supra-cesophageal ganglion, oG); a«2' mandibles ; ta^, palpns of maxilla If; l^, first pair of legs, 6,-^n, succeeding pairs ; K, head ; Br, thorax ; H, hind-body or abdomen; _/?«, heart or dorsal vessel ; L, lung in front of the openinf^ of the oviduct G ; the spinning-glands (,s;;) con- nect with the spinnerets, sp W. The digestive tract is shaded, and in the a
. Zoology : for students and general readers . Zoology. session of two or three pairs spW^ Fig. 311.—Anatomy of a epider, diagrammatic longitudinal section through the body, aft, simple eyes and nerves leading to tliem from the brain (supra-cesophageal ganglion, oG); a«2' mandibles ; ta^, palpns of maxilla If; l^, first pair of legs, 6,-^n, succeeding pairs ; K, head ; Br, thorax ; H, hind-body or abdomen; _/?«, heart or dorsal vessel ; L, lung in front of the openinf^ of the oviduct G ; the spinning-glands (,s;;) con- nect with the spinnerets, sp W. The digestive tract is shaded, and in the abdomen enveloped in the liver.—After Graber. Tlie type of the sub-class is the spider, which is character ized by the pos H p,u / of spinnerets, which are jointed ap- pendages ho- mologous with the legs. Be- sides tracheae, spiders have a so-called lung (Fig. 311, L), composed of several leaves, into which the blood flows, and is thus aerated. In Lycosa the blood flows through the heart from the head backward. There is a great range of structure, from the lowest mites to the spiders, certain mites having no heart, no trachcEe, very rudimentary mouth-parts, and no brain, there being but a single ganglion in the abdomen. Order 1. A carina.—The mites are the simplest Arachnida, the body being oval in form, the head usually small, more or less merged with the thorax, while the latter is not dif- ferentiated from the abdo- men. There is a slight metamorphosis, the mite when first hatched having but three pairs of legs, the fourth (and last) pair being added. Fig. 3i2.—Ixodes ajbipictvs from a partly domesticated moose. The tick natural size, gorged vfith blood, and its six-logged young, much enlarged, a, beak or mandibles armed with teeth ; 6, maxilla, and c, maxillary pal- pus ; d, a foot with sucker and claws, en- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
