. Elementary text-book of zoology. Zoology. HIRUDINEA. 395 surrounding the mouth. There are no parapodia few exceptions, are absent. A sharply distinct head is never developed, since the first rings are not essentially different from those following and are never furnished with tentacles or cirri. Alimentary canal.—The mouth is situated near the anterior end of the body, sometimes at the bottom of a small anterior sucker (RhynchobdelUdce), sometimes at the base of a projecting spoon-shaped hood, which resembles a sucker (G nathobdellidcr} (fig. 319). The mouth leads into a muscular pharynx pro
. Elementary text-book of zoology. Zoology. HIRUDINEA. 395 surrounding the mouth. There are no parapodia few exceptions, are absent. A sharply distinct head is never developed, since the first rings are not essentially different from those following and are never furnished with tentacles or cirri. Alimentary canal.—The mouth is situated near the anterior end of the body, sometimes at the bottom of a small anterior sucker (RhynchobdelUdce), sometimes at the base of a projecting spoon-shaped hood, which resembles a sucker (G nathobdellidcr} (fig. 319). The mouth leads into a muscular pharynx provided with glands. The anterior part of the pharynx, which may be distinguished as the buccal cavity, is armed (Gnathobdetti- dce) with three serrated chiti- nous plates (fig. 319, a, b), or more rarely with a dorsal and ventral plate (Branchi- obdellidce), or it is provided with a protru- sible proboscis, which lies free in its anterior part (Shynchobdellidce). The pharynx leads into a stomach, which forms a straight tube in the axis of the body and sometimes shows con- strictions, which correspond with the segments; sometimes it is produced into a larger or smaller number of lateral caeca. From the stomach a short rectum, which is sometimes also provided with cfeca, leads to the anus. The anus is placed at the posterior pole of the body, dorsal to the sucker. Excretory organs.—Segmental organs are pre- sent, one pair to each segment in the middle region of the body. Their number, however, and setje, with a. FIG. 319.—c Cephalic region of the Medicinal Leech. The three jaws are visible, b, One of the jaws isolated with the finely serrated free 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 Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1913; Sinclair, F. G. (Frederick Granville), b. 1858. New Yo
Size: 1623px × 1539px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
