. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 180 V. G. DETHIER tion derived from random series, to be above threshold. After two seconds each fly is then presented directly with the next lower concentration and so on down the series until the proboscis is withdrawn. When this occurs, the animal is retested against the starting concentration as a check against absolute refractoriness. If he continues down to the lowest concentration in the series with no sign of cessation of response, he is retested in water. Such a fly invariably drinks greedily, and the test is discar
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 180 V. G. DETHIER tion derived from random series, to be above threshold. After two seconds each fly is then presented directly with the next lower concentration and so on down the series until the proboscis is withdrawn. When this occurs, the animal is retested against the starting concentration as a check against absolute refractoriness. If he continues down to the lowest concentration in the series with no sign of cessation of response, he is retested in water. Such a fly invariably drinks greedily, and the test is discarded. Not infrequently flies which are negative to water at the begin- ning of a run develop a desire for water in the course of the run. Data are accumu- lated and manipulated as already described. No significant difference in threshold is obtained if the feet are washed in water between successive concentrations pro- vided the time consumed does not exceed a few seconds. It is important to keep in mind the fact that descending series may be started at any supraliminal concentration. 100 60 CO 60 LJ tr o CE 40 LJ a. •'- RANDOM • ASCENDING 0 ADAPTED AT, o DESCENDING FROM 0 0156 DESCENDING FROM I .0. 00001 001 CONCENTRATION OF SUCROSE 10 FIGURE 1. Change in the acceptance threshold of the blowfly to sucrose brought about by altering the order of presentation of different concentrations. Adapted at One Concentration. It was feasible to start these series at any con- centration, either subliminal or supraliminal. If, for example, a supraliminal con- centration such as M was chosen as the starting point, each fly in turn was held with its feet in the solution until extension of the proboscis finally ceased. The animal was then run up the series in the usual manner until a fresh proboscis re- sponse was elicited. Again the data were random-sampled and treated as in the case of a normal ascending series. An alternative method was to random sample after adapt
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
