File:Animal and vegetable physiology, considered with reference to natural theology (1836) (14578282327).jpg

Identifier: animalvegetable01roge (find matches)
Title: Animal and vegetable physiology, considered with reference to natural theology
Year: 1836 (1830s)
Authors: Roget, Peter Mark, 1779-1869
Subjects: Biology Physiology Plant physiology Natural theology
Publisher: Philadelphia, Carey, Lea & Blanchard
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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ies which characterize the several species belongingto each tribe and family. In the progress of development, we may recognise twoprinciples, which, though apparently opposite to each other,concur and harmonize in their operation: these are expaii-sion and concentration. Thus, while those segments of bodywhich follow the head are greatly enlarged, in order to sup-port the more recently developed organs of progressive mo-tion, they are also more consolidated, and rendered strongerby the union of several pieces which were before separate.The hinder segments, having no such appendages to support,are less dilated, and the whole body is much shortened bythe approximation of the segments, which, in this way, com-pose the abdomen, or hinder division of the insect. The progress of the metamorphoses of insects is moststrikingly displayed in the history of the Lepidopterous, orbutterfly and moth tribe.* The egg, which is deposited bythe butterfly, gives birth to a caterpillar; an animal, which,
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in outward shape, bears not the slightest resemblance to itsparent, or to the form it is itself afterwards to assume. Ithas, in fact, both the external appearance, and the mechani-cal structure, of a worm. The same elongated cylindric * The four periods of the existence of the Bomhyx mori, or the moth ofthe silk-worm, are shown in the annexed cng-raviiigs: Fig-. 145 are tlie ci,-gs;Fig. 146, the Larva, or caterpillar; Fig-. 147, the Pupa, or chr^sidis; andFig. 148, the I?nagOy or perfect insect. Vol. I. 28 218 THE MECHANICAL FUNCTIONS. shape, the same annular structure of the denser parts of Itsintegument, the same arrangements of longitudinal and ob-lique muscles connecting these rings, the same apparatus ofshort feet, with claws, or bristles, or tufts of hairs, for faci-litating progression; in short, all the circumstances mostcharacteristic of the vermiformx type are equally exemplifiedin the different tribes of caterpillars, as in the proper An-nelida. But these vermiform insects

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