First generation No. 152, Left whirler No. 151, Left whirler Second generation No. 410, Left whirler No. 415, Right whirler Third generation No. 420, Left whirler No. 425, Left whirler One line of descent exhibited no pronounced whirling tendency; the other exhibited a strong tendency to whirl to the left. Are these statements true for the group of one hundred individuals whose distribution among the three classes of whirlers has been given? In order to obtain an answer to this question I have reclassified these individuals according to descent and direction of whirling. INDIVIDUALS OF THE 200 LINE RIGHT WHIRLERS LEFT WHIRLERS MIXED WHIRLERS TOTAL Males 7 6 8 21 Females 5 8 8 21 12 14 16 42 INDIVIDUALS OF THE 400 LINE RIGHT WHIRLERS LEFT WHIRLERS MIXED WHIRLERS TOTAL Males 4 9 1 14 Females 6 9 4 19 10 18 5 33 INDIVIDUALS OF MIXED DESCENT 9 10 6 25 Three interesting facts are indicated by these results: first, the inheritance of a tendency to whirl to the left in the 400 line of descent; second, the lack of any definite whirling tendency in the 200 line; and third, the occurrence of right and left whirlers with equal frequency as a result of the crossing of these two lines of descent. It is quite possible, and I am inclined to consider it probable, that the pure dancer regularly inherits a tendency to whirl to the left, and that this is obscured in the case of the 200 line by the influences of a cross with another variety of mouse. It is to be noted that the individuals of the 200 line were predominantly mixed whirlers, and I may add that many of them whirled so seldom that they might more appropriately be classed as circlers. THE INHERITANCE OF INDIVIDUALLY ACQUIRED FORMS OF BEHAVIOR The white-black discrimination experiments which were made in connection with the study of vision and the modifiability of behavior were so planned that they should furnish evidence of any possible tendency towards the inheritance of modifications in behavior. The problem may be stated thus. If a dancing mouse be thoroughly trained to avoid black, by being subjected to a disagreeable experience every time it enters a black box, will it transmit to its offspring a tendency to avoid black?