. Elementary text-book of zoology. Zoology. TKEMATODA. cases (Tristomui)i coccineuin) transverse rows of bristles are found. Paired eyes are frequently present. In some species the elongated body presents a kind of external segmentation. They are for the most part ectoparasitic, to a certain extent like the Hirudinea, and they develop directly without alternation of generations from eggs which are usually hatched in the locality inhabited by the mother. Sometimes the development is a metamorphosis (Polystomum), and the young larva? live in another place. The development of Polystomum integerri
. Elementary text-book of zoology. Zoology. TKEMATODA. cases (Tristomui)i coccineuin) transverse rows of bristles are found. Paired eyes are frequently present. In some species the elongated body presents a kind of external segmentation. They are for the most part ectoparasitic, to a certain extent like the Hirudinea, and they develop directly without alternation of generations from eggs which are usually hatched in the locality inhabited by the mother. Sometimes the development is a metamorphosis (Polystomum), and the young larva? live in another place. The development of Polystomum integerri- mum from the bladder of the frog is the best known, owing to the researches of E. Zeller "°- (figs. 258, ). The production of eggs begins W in the spring, when the frog awakes from hibernation and proceeds to pair. It lasts from three " to four weeks. It is easy then to observe the Poli/sto- •mea in the process of reciprocal copulation. When the are being laid, Ov. eggs FIG. 259.—Egg with embryo (a, and hatched larva (6) of PoJystomim/ integerrimum ; ZU-, ,1 operculum (after E. Zeller)! forces the. 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 York : Macmillan
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
