The Journal of experimental zoology . leg movement ISOPOD NUMBER No. trials No. legmove-ments No. centimeters covered Ave. nocenti-meters covered per leg movement 6 357 269 VII 10 367 455 8 607 8 560 593 3 146 69 6 547 429 7 462 269 10 749 657 /Ave. cm. per\\ leg movement/ 9 642 175 I 10 907 254 VI 10 868 219 II 1 35 11 6 348 116 0,33 XI 10 775 397 VIII 7 507 232 XV 10 7 879548 577338 76 5676 / Totals and \\ averages / 52 3685 3060 RHEOTAXIS IN ISOPODA 263 greater care was exercised
The Journal of experimental zoology . leg movement ISOPOD NUMBER No. trials No. legmove-ments No. centimeters covered Ave. nocenti-meters covered per leg movement 6 357 269 VII 10 367 455 8 607 8 560 593 3 146 69 6 547 429 7 462 269 10 749 657 /Ave. cm. per\\ leg movement/ 9 642 175 I 10 907 254 VI 10 868 219 II 1 35 11 6 348 116 0,33 XI 10 775 397 VIII 7 507 232 XV 10 7 879548 577338 76 5676 / Totals and \\ averages / 52 3685 3060 RHEOTAXIS IN ISOPODA 263 greater care was exercised to produce a uniform rate of currentin the successive trials than during the preceding experiments. Reaction to concussion In testing rheotaxis in a circular current there is no meansof measuring the stimulus acting at any given time; consequentlyone is not sure that the isopod is reacting to equivalent stimuliin successive tests. This is more especially the case since thecircular current has a spiral rather than a direct course. It. Fig. 1 Concussion apparatus. seemed possible that an adaptation of the concussion methodemployed by Banta (10, p. 453) might therefore furnish a moreexact method for determining the differing physiological states. Banta dropped a steel or lead ball to a pine board upon whichthe isopod to be tested was placed in a wax bottomed Stenderdish. He does not speak of precautions to prevent the ballfrom rebounding, and presumably none were taken. Of coursethe vigor and number of the rebounds would vary partially asthe distance through which the ball was dropped; but whenthis rebound is present the animals may and probably do reactto the succession of smaller shocks after being aroused by the 264 W. C. ALLEE initial shock. This might happen although no reaction was givento the initial stimulus. In order to eliminate these rebounds, the apparatus was de-vised as shown in figure 1. A short cylinder A was fasteneddirectly above the slanted portion of the steel
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1913
