Reactions of daphnia pulex to light and heat / Robert Mearns Yerkes.

  • Yerkes, Robert M. (Robert Mearns), 1876-1956.
Date:
[1903]
Catalogue details

Licence: In copyright

Credit: Reactions of daphnia pulex to light and heat / Robert Mearns Yerkes. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    was 3.5. After experiment 1 of Table III the mean position was 4, which indicates that there had been an average movement of half a space toward the end of the trough Table III. CHECK EXPERIMENTS IN DARKNESS. NO HEAT. Period 3 min. Dec. 12, 1901, 7 p.m. Spaces Location of Animals at Beginning j of Each Experiment. I I +■ Find* 2 2 3 2 4 2 5 2 6 — End. j Average ( Movement. Experiment 1 0 3 0 0 4 1 -0.500 “ 2 0 2 1 2 0 3 -0.375 “ 3 4 2 1 1 0 0 + 1.375 “ 4 1 1 0 3 1 2 -0.500 “ 5 2 2 0 3 0 1 +0.500 “ 6 1 2 1 2 0 2 0.000 “ 7 1 3 0 2 0 2 + 0.125 “ 8 0 3 1 2 2 0 + 0.125 “ 9 3 2 1 1 1 0 + 1.125 “ 10 2 2 1 0 1 2 + 0.250 Movement for series + .3125 (i.e., .3125 of a space toward the + end). marked space 6. Since in the experiments heat was applied at the end next space 1, it will be convenient to designate that as the + end, and the opposite as the — end, in order that without confusion movement of the animals toward the heat may be designated as +, and away from it as — (see Table III). For this reason the move- ment in experiment 1, Table III, is expressed as —0.50 (i.e., the average movement of the eight Daphnia was a half-space toward the — end of the trough). The check series of ten experiments in Table III resulted in six + movements, with an average for the series of +0.3125. There is therefore indication of a slight tendency toward the + end. This may have been due to undetected rays of light or to slight jarring of the trough. The movement is so slight, however, that it is not of great importance; a large number of observations would in all probability have resulted in an average of 0. As soon as this check series was ended the heat was turned on and a similar series of experiments made to test the influence of heat upon the movements of the animals. At the beginning of the heat series the temperature of the water throughout the trough was about 21° C. At the end of the series it was 28° at the + end of the trough, and 25° at the — end. Table IV gives the result of this test of the effect of radiant heat. The first ex- periment resulted in a marked movement toward the heated ( + ) end, but thereafter every experiment resulted in a movement in the opposite (—) direction. In experi- ment 1 it is almost certain that the heat had not yet had time to affect the water to