. Zoology : for students and general readers . Zoology. TEE VILIATE INFUSORIA. 37 opens, allows the rejected matter to pass out, and then closes over, leaving no trace of an outlet. This and other Infusoria seem, then, to have a definite digestive tract, hol- lowed out of the parenchyma of the body. " The system," says Clark, " which is analogous to the blood-circulation of the higher animals, is represented in Paramecium by two contractile vesicles {cv, cv^, i, ii, ill), both of which have a degree of complication which, per- haps, exceeds that of any other similar organ"
. Zoology : for students and general readers . Zoology. TEE VILIATE INFUSORIA. 37 opens, allows the rejected matter to pass out, and then closes over, leaving no trace of an outlet. This and other Infusoria seem, then, to have a definite digestive tract, hol- lowed out of the parenchyma of the body. " The system," says Clark, " which is analogous to the blood-circulation of the higher animals, is represented in Paramecium by two contractile vesicles {cv, cv^, i, ii, ill), both of which have a degree of complication which, per- haps, exceeds that of any other similar organ" in these ani- mals. When fully expanded they appear round, as at c f ; but when contracted they appear, observes Clark, as " fine radiating streaks, and as the mam portion lessens they grad- ually broaden and swell until the former is emptied and nearly invisible, and they are extended - " "^ over half the length of the body. In this condition they might be compared to the arterial vessels of the more elevated classes of animals, but they would at the same time represent the veins, since they serve at the next moment to return the fluid to the main reservoir again, which is effected in this very remarkable ; The contents of these vesicles is a clear fluid. The reproductive organ in Paramecium is a small tube («), only seen at the reproductive period when the eggs (n) are fully grown. Clark says that the eggs are arranged in it " in a single line, one after the other, at varying dis- ; It usually lies in the midst of the body, and ex- tends from one half to two thirds of the length of the ani- mal. The eggs pass out from the so-called ovary through an aperture near the mouth. Lasso-cells like those in the jelly-fishes are said by Biitschli to exist in an infusorian named by him Polyhrikos. In the trumpet animalcule (Fig. 25, Stentor polymor-. Flg. 26.—Process of fission in Stentor polyniorplllts. b, a new Stentor bndding out; e, ready
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
