. An introduction to zoology : for the use of high schools . ls of Limulus, and opening by slits on the ventral surface. Development shows that these lungs arise as infoldings at the bases of appendages, and that they are homologous with the gills of the horse-shoe ci-ab. The abdomen differs from that of the crayfish, in being differentiated, intotwo regions, a preabdomen of seven, anda postabdomen of six segments, the last ofwhich terminates in a curved claw, per-forated by the duct of a poison-gland. The little book-scorpions {CheUfer) have nopoison-gland in the tail, nor is the abdomen sub-
. An introduction to zoology : for the use of high schools . ls of Limulus, and opening by slits on the ventral surface. Development shows that these lungs arise as infoldings at the bases of appendages, and that they are homologous with the gills of the horse-shoe ci-ab. The abdomen differs from that of the crayfish, in being differentiated, intotwo regions, a preabdomen of seven, anda postabdomen of six segments, the last ofwhich terminates in a curved claw, per-forated by the duct of a poison-gland. The little book-scorpions {CheUfer) have nopoison-gland in the tail, nor is the abdomen sub-divided into two regions ; they belong to an in-dependent sub-order, the Pseudoscorjnonlna, asdo the daddy-long-legs (Phalangina), with theirshort abdomen and long walking legs. Both ofthese groups feed on minute insects and mites ;with the Scorpions they form the order 17. Of the various orders of Arachnida, 7ij. \Z~—Aqdle)ia luivia, , ., ,. .. ^ ?, , k • \ V ith the ocelli the (Araneina) and mites (Acarina) (After Einerton). HIGH SCHOOL ZOOLOGY. 203 are the most important. Both have the two pairs of mouth-appendages and the four pairs of walking legs, but the form ofthe body is very different in the two groups, on account ofthe separation of the abdomen in the spiders pi-oper, by aslender stalk, and the presence at its extremity of the spin-nerets (Fig. 137). Some of the chief structural peculiarities of the spidersmay be gathered from Fig. 138. The two-jointed cheliceriBterminate in a powerful claw, perforated by the duct of a
Size: 1069px × 2339px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1889
