File:Animal and vegetable physiology, considered with reference to natural theology (1836) (14784608603).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

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
mination, been able to disting-uish no less than twenty-two diflercntspecies amoni^ those found in the neighbourhood of Paris alone. f Home; Lectures, &c. Vol i. p. 115. 198 THE MECHANICAL FUNCTIONS. ceeding segments are necessarily elongated: these are nextcontracted; and so on, in succession, till the whole is broughtforwards to the head: after which the same series of actionsis repeated, beginning with the advance of the head. Wormsoften reverse this motion, and are thus enabled to move back-wards, or with the tail foremost.* Great variety exists in the forms of the animals referribleto the type of Annelida. The Gordius, or hair-worm, (Fig.) 32,) is that which exhibits the greatest development inlength compared with the breadth of the body. It has theform of a very long and slender thread: the annular structurebeing indicated only by very slight transverse folds of theinteguments. No external members, nor even tentacula,have^been given to this simplest of vermiform animals. 135
Text Appearing After Image:
Many of the animals of this class being soft and defence-less, are obliged to consult their safety by retreating intoholes and recesses, or by burrowing in the sand or mud.One genus only, the Serpula (Fig. 133,) forms for itself anexternal shell, which is shaped into a spiral tube. Others,as the Sabella and the Terebella, accomplish the same ob-ject by collecting grains of sand, or fragments of decayedshells, or other substances, which they agglutinate togetherby means of a viscid exudation, so as to form a firm defen-sive covering, like a coat of mail. Fig. 134 shows thisrude architecture in the Terehella conchilega. These co-verings, however, composed as they are of extraneous ma- * See Home? Lectures on Coipparalive Anatomy, Vol. i. p. 114, ANNELIDA. l.QO terlals, and not being orjranin produnllons of Ihr animalsthemselves, are structures wholly foreign to their systems.These inhabitants of tubes, the Tubicolae of Cuvier, are gene-rally furnished with tentacula, issuing from the he

Note About Images