. A manual of elementary zoology . Zoology. 216 MANUAL OF ELEMENTARY ZOOLOGY the There are about 150 segments. At about one-third of the length of the body from its front ,,, end, in segments 32-37 inclusive, a glandular thickening of the epider- mis lies athwart the back like a saddle and is often mistaken for the scar of a wound. This is known as the clitellum. The skin of the worm is brownish above and paler below; it is covered with a fine, tough, iridescent cuticle secreted by the underlying cells. In every segment except the first and the last there are eight bristles or se
. A manual of elementary zoology . Zoology. 216 MANUAL OF ELEMENTARY ZOOLOGY the There are about 150 segments. At about one-third of the length of the body from its front ,,, end, in segments 32-37 inclusive, a glandular thickening of the epider- mis lies athwart the back like a saddle and is often mistaken for the scar of a wound. This is known as the clitellum. The skin of the worm is brownish above and paler below; it is covered with a fine, tough, iridescent cuticle secreted by the underlying cells. In every segment except the first and the last there are eight bristles or seta, placed in two pairs on each side, a lateral pair, slightly above the middle of the side, and a ventral pair between the lateral and the mid-ventral line. The setas can be felt with the fingers; they are embedded in sacs of the epidermis, by which they are secreted, and to these sacs are attached muscles, by which they can be moved. The setae are organs of locomotion. The worm extends its body with the bristles withdrawn. Then it thrusts out those of the forepart, so that they catch in the soil and hold firm while 1 In the related Alloloboplwra the prostomium reaches only half-way across the Fig. 134.—A, The forepart of the body of an earthworm (Lum- bricus herculeus), from the right side; B, the first five segments from below; C, the same from above ; D, worms in coition. id., Band of mucus; elm., clitellum; , lateral setas; m., mouth ; per., peristomium; pro., prostomium; , , , , , numbers of seg- ments ; , ventral setse ; o*, open- ing of vas deferens; ? , opening of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Borradaile, L. A. (Lancelot Alexander), 1872-1945. London : H. Frowde, Hodder & Stoughton
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
