Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 438 ABACHNIDA. be regarded as the FIG. 377.— Pentattomum ttcnticuliitum. Young form of P. teeuioidn. O, Mouth; Hf, the four hooks; 7), intes- tine ; A, anus. anterior appendages, are lost in the course of development. The nervous system is confined to a simple suboesophageal nervous mass, with cesophageal ring and giving off numerous ner- vous trunks. Eyes and organs of respiration and circulation are wanting. The a
Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 438 ABACHNIDA. be regarded as the FIG. 377.— Pentattomum ttcnticuliitum. Young form of P. teeuioidn. O, Mouth; Hf, the four hooks; 7), intes- tine ; A, anus. anterior appendages, are lost in the course of development. The nervous system is confined to a simple suboesophageal nervous mass, with cesophageal ring and giving off numerous ner- vous trunks. Eyes and organs of respiration and circulation are wanting. The alimentary tract is a simple canal in the middle of the body, which opens by an anus at the posterior end. Special cutaneous glands are present in great numbers and strongly developed. Male and female are distinguished by considerable differences in size and by the different position of the genital openings. While the genita opening of the surprisingly small male lies not far behind the mouth, that of the female is situ- ated near the anus, at the hinder end of the body. The Linguatulida, when sexually adult, in- habit the air chambers of warm-blooded animals and Amphibia. The developmental history of Pentastomum tcenioides, which lives in the nasal cavities and in the frontal sinuses of dogs and wolves, is known from the researches of Leuck- art. The embryos of this species, while still enveloped in the egg-membranes, pass out the nasal mucus on to plants, and thence into the stomach of Rabbits and Hares, more rarely into that of Man. When freed from the egg- niembranes, they pierce the walls of the in-
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