it has slept during transport?1 It is to be hoped that experiments on these lines, the execution of which depends entirely on the means at one's disposal, will help a little towards an understanding of the still unsolved riddle of orientation.
Certain facts in the behaviour of animals suggest to carry out experiments on their orientation in time parallel to those on their orientation in space. It may be that there is a kind of absolute orientation in time similar to their orientation in space, hidden behind the almost time- table-like punctuality with which migratory birds set off from their summer homes or return to them. This is made all the more probable, since experiments with bees, where one would not expect so much, revealed a surprising capacity for orientation in time.
These experiments were begun by Beling2 and developed and confirmed by Wahl.3 Beling succeeded in training bees to come to a place where food was found at a definite time in the day. The bees could be trained to come at any desired hour. It was also found possible to train the bees to come to the feeding-place two or three times in the course of the day. "The memory for time cannot be dissociated from the twenty-four-hour unit. It proved impossible to train to any other unit, even one of forty- eight hours." The bees are clearly not influenced by any external factors in the daily period, since they could be trained in a salt mine, where, so far as our knowledge goes,____________________