. A manual of zoology. Zoology. II. ACERATA: SCORPIONIDA 391 In development the arachnidan trachese arise in connection with the ab- dominal appendages, as do the lungs. (In the Solpugidce and some mites cephalothoracic trachea; occur.) This shows that the arachnidan tracheas are entirely different in origin from the tracheae of insects. The gonads (only the Tardigrades are hermaphroditic) are aljdominal in position and open by paired ducts (sometimes with a single mouth) on the first abdominal somite. In most cases the animals are oviparous, but the scorpions and many mites bear hving young.
. A manual of zoology. Zoology. II. ACERATA: SCORPIONIDA 391 In development the arachnidan trachese arise in connection with the ab- dominal appendages, as do the lungs. (In the Solpugidce and some mites cephalothoracic trachea; occur.) This shows that the arachnidan tracheas are entirely different in origin from the tracheae of insects. The gonads (only the Tardigrades are hermaphroditic) are aljdominal in position and open by paired ducts (sometimes with a single mouth) on the first abdominal somite. In most cases the animals are oviparous, but the scorpions and many mites bear hving young. In many instances the mothers care for their eggs and young, the scorpions carrying their families on their bodies. Only rarely is there a metamorphosis, and then in the aberrant forms like the Linguatulida and Acarina, where the young have but two or three pairs of appendages, acquiring the others later. Legion I. Arthrogastrida. Arachnida in which the abdominal somites are distinct. Order I. Scorpionida. The scorpions bear a superficial resemblance to crayfish and for a long time were associated with them, since (figs. 366, 421) they have four pairs of walking feet (3-6), while the pedipalpi (2) are large and bear Fig. 421.—Under surface of scorpion, showing the combs and the outlines of the lung sacs with their spiracles (orig.). The cheliceras are also chelate. The pedipalpi and the two anterior pairs of legs have the basal joint expanded for chewing. The peculiarities of the abdomen mark the group off from all other arachnids. It consists of seven broader somites attached by their whole width to the cephalo- thorax and six narrower somites behind, forming a postabdomen. The last somite is produced into a sharp spine and contains two large poison. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
