. Fresh-water biology. Freshwater biology. 5S8' FRESH-WATER BIOLOGY' may be floating in the water, or that are easily washed from sur- rounding objects. The mouth, situated in the posterior part of the corona, opens, and so admits or seizes such food as is adapted to the rotifer. In many rotifers the cilia are the chief direct agents in obtaining food, and in practically all species they are either directly or indirectly of the greatest importance for this function. A. Fig. 859. Corona of Froales tigridia Gosse. A, surface view, from ventral side. By side view, m, moutli. (After Wesenberg-Lund
. Fresh-water biology. Freshwater biology. 5S8' FRESH-WATER BIOLOGY' may be floating in the water, or that are easily washed from sur- rounding objects. The mouth, situated in the posterior part of the corona, opens, and so admits or seizes such food as is adapted to the rotifer. In many rotifers the cilia are the chief direct agents in obtaining food, and in practically all species they are either directly or indirectly of the greatest importance for this function. A. Fig. 859. Corona of Froales tigridia Gosse. A, surface view, from ventral side. By side view, m, moutli. (After Wesenberg-Lund.) 3. In place of bringing food and oxygen backward to the rotifer, the cilia may carry the animal forward to new suppHes of these necessities. This is the case in all free-swimming rotifers; the cilia are the main organs of locomotion. In thus moving the animals about, the cilia of course play as important a part in food-getting as when they bring the food to the rotifer. In most species the cilia act in both ways at once, bearing the animal forward and the food backward, so that the two meet. 4. The water currents remove the products of respiration and excretion, which the rotifer, like other animals, is continually giving off. Carbon dioxide is doubtless given off over the whole surface of the body, while other waste products are discharged by the contractile vesicle (see p. 561). If these waste products were allowed to accumulate, they would be most injurious. While these are the main uses of the ciHa, they assist, in a num- ber of rotifers, in other important operations, such as the con- struction of a tube or nest. The further course of the food may now be followed. The mouth, situated in the posterior part of the corona (Fig. 859, m), leads into a cavity with thick, muscular walls, known as the mastax (Figs. 856 and 857, mx). The mastax is armed with a complicated set of jaws, which have little resemblance to jaws found anywhere else in the animal kingdom. They are known
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
