. Behavior of the lower organisms. Animal behavior; Invertebrates. Fro. 45- — Parame- cium at rest against a cotton fibre, showing the motionless cilia in con- tact with the fibre. come in contact with a solid. Observing ming specimen, it is often seen to react as follows. When it first strikes against an object it responds with a weak avoiding reaction, — swimming backward a short distance, turning a little toward the aboral side, then swimming for- ward again. Its path carries it against the object again, whereupon it stops and comes to rest against the surface. The objects against which Par
. Behavior of the lower organisms. Animal behavior; Invertebrates. Fro. 45- — Parame- cium at rest against a cotton fibre, showing the motionless cilia in con- tact with the fibre. come in contact with a solid. Observing ming specimen, it is often seen to react as follows. When it first strikes against an object it responds with a weak avoiding reaction, — swimming backward a short distance, turning a little toward the aboral side, then swimming for- ward again. Its path carries it against the object again, whereupon it stops and comes to rest against the surface. The objects against which Paramecium strikes under normal con- ditions are usually pieces of decaying vegetable matter or bits of bacte- rial zooglcea. Remaining in contact with these helps it to obtain food. The cilia that come in contact with the solid cease moving, and become stiff and set, seeming to hold the Parame- cium against the object (Fig. 45). Often it is only the cilia of the anterior end that are thus in contact and im- movable; in other cases cilia of the general surface of the body show the same condition. Meanwhile, the cilia of the oral groove continue in active motion, so that a rapid current passes from the anterior end down the groove to the mouth (Fig. 46). This cur-. FiG. 46. — Paramecium at rest with anterior end against a mass of bacte- rial zooglcea (a), showing the currents produced by 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 Jennings, H. S. (Herbert Spencer), 1868-1947. New York, The Columbia university press, The Macmillan company, agents; [etc. , etc. ]
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