. Beginners' Zoology . By bending and bringing the end to the mouth, or by shortening and changing its form, or in both ways .-* (Fig. 34, C.) Do the neighbouring tentacles seem to bend over to assist a tentacle in securing (Fig- 34, C.)Digestion. — The food parti- ° ? ^ Pig. 37. — Hydra capturing a cles break up before remaining water POLYPS QCUPLIRE ANIMALS^ 25 long in the stomach, and the nutritive part is absorbedby the lining cells, or endoderm (Fig. 39). The indiges-tible remnants go out through the mouth. The hydra isnot provided with a special vent. Why could the vent not
. Beginners' Zoology . By bending and bringing the end to the mouth, or by shortening and changing its form, or in both ways .-* (Fig. 34, C.) Do the neighbouring tentacles seem to bend over to assist a tentacle in securing (Fig- 34, C.)Digestion. — The food parti- ° ? ^ Pig. 37. — Hydra capturing a cles break up before remaining water POLYPS QCUPLIRE ANIMALS^ 25 long in the stomach, and the nutritive part is absorbedby the lining cells, or endoderm (Fig. 39). The indiges-tible remnants go out through the mouth. The hydra isnot provided with a special vent. Why could the vent notbe situated at the end opposite the mouth . Circulation and Respiration. — Docs water have freeaccess to the body cavity. Does the hydra have few ornearly all of its cells exposed to the water in which itlives} From its structure, decide whether it can breathelike a sponge or whetherspecial respiratory cells arenecessary to supply it withoxygen and give off carbondioxide. Blood vessels areunnecessary for transfer-ring oxygen and food fromcell to cell. Reproduction. - Do you p^^ ^g _ j,^.^^^^ ^^ ^,^^ ^„^,, 3^,.see any swellings upon the face of pondweed. side of the hydra i (Fig. 34, A.) If the swelling is nearthe tentacles, it is a spcrmary; if near the base, it is anovary. A sperm coalesces with or fertilizes the ovum afterthe ovum is e
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