Guide to the Crustacea, Arachnida, Onychophora and Myriopoda exhibited in the Department of Zoology, British Museum (Natural History) .. . this conclusion iscorrect is proved by comparison with some of the lower Crustacea,for instance, Anaspides (see Table-case No. 5), in which there is no 14 Guide to Crustacea. Wall-casesNos. 1-3. carapace, and the fore part of the body has eight distinct somiteseach bearing a pair of walking legs. In front of these eightsomites, which form what is called the thorax, is the head,a part of the body which is never, in any Crustacean, distinctlysegmented, but wh
Guide to the Crustacea, Arachnida, Onychophora and Myriopoda exhibited in the Department of Zoology, British Museum (Natural History) .. . this conclusion iscorrect is proved by comparison with some of the lower Crustacea,for instance, Anaspides (see Table-case No. 5), in which there is no 14 Guide to Crustacea. Wall-casesNos. 1-3. carapace, and the fore part of the body has eight distinct somiteseach bearing a pair of walking legs. In front of these eightsomites, which form what is called the thorax, is the head,a part of the body which is never, in any Crustacean, distinctlysegmented, but which, since it bears five pairs of appendages,must contain at least five somites. The part of the body coveredby the carapace of the Lobster includes the head and the thoraxand is known as the cephalothorax. It is necessary to remark,however, that the regions of the body named head, thorax, andabdomen in the Crustacea are by no means exactly equivalent tothose so named in the other Arthropoda, for instance in Insects, and still less to the parts bearing the same names among Vertebrate body, or not only covering, Pleu Tvn. Ajifiendage One of the abdominal somites ofthe lobster, with its appendages,separated and viewed from infront. [Wall-case No. 1.] segmentation of thedivision into somites, isshown by the externalbut affects some of theinternal organs as well. Leavingthese aside for the present, how-ever, and considering only theexoskeleton, the structure of atypical somite will be best un-derstood by examining one of theseparated abdominal somites of theLobster (Fig. 2). This consists ofa ring of shelly substance, connectedwith the rings in front and behind by areas of thin membranewhich permit movement in a vertical plane. For convenienceof description the upper or dorsal part of this ring is calledthe tergum (or tergite ) and the under or ventral part the sternum (or sternite ). To the sternum are attached theappendages (or swimmerets), while the tergum
Size: 1257px × 1988px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectcrustacea, bookyear19
