The Journal of microscopy and natural science . f Vol. I., we come to ClassAfitennata, sub-class Hexapoda or Insecta, which is thus described : The body of the Hexapoda falls typically into three parts, quitedistinct from each other : head, thorax, and hind body (abdomen).The unsegmented head probably originally consisted of four seg- 280 COMPARATIVE ANATOMY. ments. The thorax is composed of three segments : prothorax,mesothorax, and metathorax, answering to the three anterior trunksegments of the Myriapoda. The typical number of segments inthe hind-body is ten or eleven. The thorax and the ab
The Journal of microscopy and natural science . f Vol. I., we come to ClassAfitennata, sub-class Hexapoda or Insecta, which is thus described : The body of the Hexapoda falls typically into three parts, quitedistinct from each other : head, thorax, and hind body (abdomen).The unsegmented head probably originally consisted of four seg- 280 COMPARATIVE ANATOMY. ments. The thorax is composed of three segments : prothorax,mesothorax, and metathorax, answering to the three anterior trunksegments of the Myriapoda. The typical number of segments inthe hind-body is ten or eleven. The thorax and the abdomentogether form the trunk, which may be compared with the trunkof the Symphyla. Among the Apterygota the Thysaiiura possessten abdominal segments, and the CoUembola a varying number, butalways less than ten. In the Pterygota the number of abdominalsegments in the adult animals varies, and is generally less than diminution is caused by the fusing of those segments whichare connected with the genital apparatus and lie in front of the. Fig. 21, A— Nervous Systems of Four Species of Diptera,to demonstrate their various degrees of , Non-concentrated nervous system of CJiirononms plumosus, with threethoracic and six abdominal ganglionic masses.^i5, Nervous system of Einpissterco7-ea, with two thoracic and five abdominal ganglionic masses.—C, Nervoussystem of Tabanus bovinus, with one thoracic ganglionic mass, and the abdo-minal ganglia moved towards each other.—D, Nervous system ot Sarcophagacarnaria. All the ganglia of the ventral chord except the infra-oesophagealganglion, which always remains separate, are here united into one singlethoracic ganglion mass.—(After E. Brand.) COMPARATIVE ANATOMY. 281 last; and, secondly, by the fusing of the anterior abdominal seg-ments (usually only the first) with the thorax. On the other hand,in a few insects {Macrolcpidoptera, Diptera, and Rhyfuhota), thelast (third) thoracic segment is joined with the abd
Size: 1951px × 1281px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectmicroscopes, booksubjectmicroscopy
