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Lower jointed (Annulosa), worms, millipedes, etc. are characterized bya large number of their component segments, reaching in some cases up toseveral hundreds; but as going to move to a higherjointed - stonozka, crayfish, insects, spiders, we'll find the number isnow reduced - to twenty-two, thirteen, and even less, andthe reduction is accompanied by a shortening or integration of the whole body,which reach from crabs and spiders to the extreme limit. The same noteif you follow the development of the species of crustacean or insect. The chest cavitysea of cancer, which in the period of maturity is head onethe receptacle containing the viscera, formed by connecting segments,which in the Bud was separate. Thirteen separate parts, we noticethe body of the caterpillar, are integrated subsequently into a butterfly: some segmentscombine to form the thoracic cavity, the abdominal segmentscloser closer still. The same note, going to the internal organs. Inlower jointed forms and larvae of higher food channel is ormonotonous from one end to the other tube, or of the convex parts likeconsistent stomachs, one to each segment; well developed formsfound one well-defined stomach. In the nervous, vascular andthe respiratory system can be traced to a similar concentration. In the development ofvertebrates we find different examples of longitudinal integration. Connectionseveral vertebrae for the formation of the skull is one such example. The samefound in the coccygeal bones, which come from the merger of severalthe caudal vertebrae; a good example is the fusion of sacralthe vertebrae of birds.
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