Aud. Interval (sec.) 1 1-1/2 2 3 4 Vis. Interval (sec.) .083 .083 .083 .083 .083 Obs. B Av. num. Trials 8.5 6.8 6.2 4.8 4.8 Num. Series av. 10 10 10 10 10 Aver. Error (sec.) .097 .108 .106 .097 .101 Mean Displacement (sec.) +.097 +.108 +.106 +.097 +.101 Bo Av. num. Trials 6.0 5.0 4.2 3.2 3.1 Num. Series av. 10 10 10 10 10 Aver. Error (sec.) .103 .080 .081 .092 .082 Mean Displacement (sec.) +.102 +.073 +.078 +.089 +.075 M Av. num. Trials 4.4 3.8 3.4 3.0 2.8 Num. Series av. 10 10 10 10 10 Aver. Error (sec.) .088 .084 .081 .068 .052 Mean Displacement (sec.) +.086 +.079 +.072 +.051 +.048 H Av. num. Trials Num. Series av. 10 10 10 10 10 Aver. Error (sec.) .043 .036 .047 .040 .037 Mean Displacement (sec.) -.022 -.012 -.027 -.017 -.013 One series of ten of each of these combinations was given during each hour of experimentation with each observer. These were also given in a different order each day, so that no combination should have the advantage, by practice or lack of fatigue, in the average of the ten series. Here again it was evident, in the records of each of the observers for whom the count was made, that the largest number of trials was necessary in the 1-.083 sec. combination. It thus appears that it was not the short visual interval, .040, in Table I, that was responsible for the large number of trials necessary in the first combination. Here, where there is the same visual interval of .083 sec. throughout, it must be the short auditory interval which makes particularly difficult conditions for attention. This agreement between the results in both groups of experiments seems to indicate unfavorable conditions for accurate coördination at auditory intervals as short as one second. The large changes in the mean displacement for B and M between the first two combinations in the first group (Table I) was kept especially in mind in planning this second series of combined intervals. It was presumed from the results given by these observers in Table I that they would each, with the range of auditory interval presented them in these experiments, show a point of no displacement, or a very slight one, and an increasing displacement on each side of this point. They both seemed to indicate a time-interval favorable for the "ripening of apperception" as Wundt and Von Tschisch call it, and I planned these experiments especially to bring it out more clearly.