. Outlines of zoology. Zoology. 292 PERIPATUS, MYRIOPODS, AND INSECTS. to adjacent parts. There are three pairs of ganglia in the thorax, and six in the abdomen, of which the last is the largest. From the oesophageal commissures two visceral nerves are given off, which form in a somewhat complex manner the innervation of gullet, crop, and gizzard. Besides the large compound eyes, there are other sensory structures —some of the hairs on the skin, the maxillae (to some extent organs of taste), the antennae (tactile and olfactory), the anal cerci (tactile), and possibly the oval white patches on
. Outlines of zoology. Zoology. 292 PERIPATUS, MYRIOPODS, AND INSECTS. to adjacent parts. There are three pairs of ganglia in the thorax, and six in the abdomen, of which the last is the largest. From the oesophageal commissures two visceral nerves are given off, which form in a somewhat complex manner the innervation of gullet, crop, and gizzard. Besides the large compound eyes, there are other sensory structures —some of the hairs on the skin, the maxillae (to some extent organs of taste), the antennae (tactile and olfactory), the anal cerci (tactile), and possibly the oval white patches on the head. Alimentary system.—(i) The fore-gut (stomodaeum) is lined by a chitinous cuticle continuous with that of the outer surface of the body. It includes —(a) the buccal or mouth cavity, in which there is a tongue - like ridge, and into which there opens the duct of the salivary glands; (6) the narrow gullet or oesophagus; (c) the swollen crop; (d) the gizzard, with muscular walls; six hard cuticular teeth, and some bristly pads. There is a pair of diffuse salivary glands on each side of the crop, and between each pair of glands a salivary receptacle. The ducts of the two salivary glands on each side unite ; the two ducts thus formed combine in a median duct, and this unites with another median duct formed from the union of the ducts of the receptacles. The common duct opens into the mouth. (2) The mid-gut (mesenteron) is lined by endoderm. It is short and narrow, and with its anterior end seven or eight club-shaped digestive (pancreatic) outgrowths are connected. (3) The hind-gut (proctodaeum) is lined by a chitinous cuticle. It is convoluted and divided into narrow ileum, wider colon, and dilated rectum with six internal ridges. Respiratory system.—The tracheal tubes, which have. Fig. 129.—Transverse section of insect.— After Packard. \/t., Heart; g., gut; «., nerve-cord ; st., stigma ; tr., trachea; w., wing;./, femur of Please note that these images a
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
