Text-book of comparative anatomy . , as the equivalent of thesecond pair of book-leaf trachea?of the Tetrapnevmones — tubulartrachea?, which generally openthrough an unpaired stigma in theshape of a transverse fissure placedfar back on the abdomen. Thisunpaired stigma no doubt arisesfrom a posteriorly placed pair ofstigmata, which have united. Thissupposition is supported by the factthat in some Araneidce (Dysdera,Segestria, Argyroneta) two separatemore anteriorly placed stigmata forthe tubular trachea? occur (behindthe pair for the book-leaf tracheae),and also by the circumstance thatin a few
Text-book of comparative anatomy . , as the equivalent of thesecond pair of book-leaf trachea?of the Tetrapnevmones — tubulartrachea?, which generally openthrough an unpaired stigma in theshape of a transverse fissure placedfar back on the abdomen. Thisunpaired stigma no doubt arisesfrom a posteriorly placed pair ofstigmata, which have united. Thissupposition is supported by the factthat in some Araneidce (Dysdera,Segestria, Argyroneta) two separatemore anteriorly placed stigmata forthe tubular trachea? occur (behindthe pair for the book-leaf tracheae),and also by the circumstance thatin a few cases (Dictyna) the trachealtrunks which open through the un-paired stigma are distinctly recog-nisable as double. The Solpuyidcc have tubulartrachea? with tree - like ramifica-tions, opening through 3 pairs ofstigmata, the first pair lying in the first thoracic segment, the second and third pairsin the second and third abdominal segments. The position of the first pair of stig-mata in the thorax deserves to be specially FIG. 374.—Mygale, from the ventral side. Theventral wall of the cephalo-thorax removed to show thelarge cephalo-thoracic ganglion (bg) and the 2d smallganglion at the base of the abdomen. The ventral wallof the abdomen on the left side opened out. m, Ventralmuscles of the abdomen ; I, lamellae of the book-leaftrachea;; ft, book-leaf trachea;; s, stigmata of thesame ; or, ovary ; sp, spinning mammilla;; 1-6, 1st to6th pairs of extremities. 2-6, not completely drawn(Regne animal). 532 COMPARATIVE ANATOMY CHAP. The Pseudoseorpionidae have tubular tracheae with 2 pairs of stigmata, which lie inthe 2d and 3d abdominal segments. In Chciridium there is only one pair of stigmata,which has perhaps arisen by the fusing of the two pairs found in other Pseudo-scorpionidce. The ramified tracheae of the Phalangidce, are said to open through a single pair ofstigmata, lying ventrally at the anterior end of the abdomen, which is closely appliedalong its whole bread
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
