fact that according to my observation it required something like thirty to forty-five seconds for the mice to become adapted to the light. This came upon them suddenly when I raised from over them a second box in which they habitually stayed. As a rule they began to move about only after the lapse of this length of time.
Three tests were made on the first day and four each day following. After the seventh trial the mice could not have been very hungry, as bread crusts were inside their hiding place or on the floor of the cage. Meat or most often cheese was placed inside the sawdust box as a food more to their liking and as an incentive for their digging through.
So far as this single series is concerned, the mice learned more rapidly than the white rats tested by Dr. Small with the same apparatus. The initial times are shorter and the reduction of this to a minimum is more rapid with the mice. The fact that the mice had no hiding place except as they dug their way through the sawdust, may, in connection with their greater wildness, explain why they learned more rapidly than the white rats. The minimal time is about the same for both animals. The time required for adaptation of the eyes to the light is a rather constant factor for all the trials for the mice.
Another box with a zinc door held closed by narrow paper strips secured by wax, an apparatus very similar to another of Dr. Small's boxes, was used with the mice with practically the same, though less uniform, results.
We may ask (and this is the chief reason for introducing these results just here) how are we to determine to what extent and in what sense one mouse was imitated by the other? In several of the tests the one following seemed to dig in through the banked-up sawdust in its own way. Could the action of the other be then of any more than of the merest suggestive value? Was it merely the following instinct which is so prevalent in many species of animals and to some extent in man? Did one use the odor left by the other and thus have a stimulus at every step? If an odor stimulus does guide the animal at each turn, then it is not following a copy furnished by another, though the human observer would be unable to distinguish what was imitation and what was not.
These mice, as well as Berry's White Rats and Cats, and also the Raccoons studied by Cole and Davis, may all use the odor left by the animal which is acting as the model. This would seem, therefore, to suggest that all odors should be thoroughly removed from the apparatus before the animal to do the imitating is allowed to try. Spaulding, in testing the learning process in Crayfish, had to do this and all would agree
