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?
Systematic training experiments were carried on with individuals of both the 200 and 400 lines of descent. For each of these lines a male and a female were trained at the age of four weeks to discriminate between the white and the black electric-boxes and to choose the former. After they had been thoroughly trained these individuals were mated, and in course of time a male and female, chosen at random from their first litter, were similarly trained. All the individuals were trained in the same way and under as nearly the same conditions as could be maintained, and accurate records were kept of the behavior of each animal and of the number of errors of choice which it made in series after series of tests. What do these records indicate concerning the influence of individually acquired forms of behavior upon the behavior of the race?
TABLE 53
THE INHERITANCE OF THE HABIT OF WHITE-BLACK DISCRIMINATION
Number of Errors in Daily Series of Ten Tests
MALES FEMALES
SERIES FIRST SECOND THIRD FOURTH FIRST SECOND THIRD FOURTH GENERA- GENERA- GENERA- GENERA- GENERA- GENERA- GENERA- GENERA- TION TION TION TION TION TION TION TION
No. 210 No. 220 No. 230 No. 240 No. 215 No. 225 No. 235 No. 245
A 6 5 6 7 8 4 4 7 B 6 8 8 8 8 7 6 5
1 6 7 6 5 7 6 5 4
2 4 3 1 5 5 6 4 5
3 3 1 4 5 3 4 4 3
4 5 0 3 4 2 1 3 1
5 3 0 4 2 1 3 3 0
6 2 1 4 2 2 1 1 1
7 1 0 3 1 1 1 2 0
8 0 0 1 0 0 0 2 3
9 0 0 0 1 1 0 0 0
10 0 0 1 0 2 1 1
11 0 0 0 3 0 0
12 0 0 0 0 0
13 0 0 0 0
14 0
I have records for four generations in the 200 line and for three generations in the 400 line.[1] As the results are practically the same for each, I shall present the detailed records for the former group alone. In Table 53 are to be found the number of errors made in successive series of ten tests each by the various individuals of the 200 line which were trained in this experiment. The most careful examination fails to reveal any indication of the inheritance of a tendency to avoid the black box. No. 240, in fact, chose the black box more frequently in the preference series than did No. 210, and he required thirty more tests for the establishment of a perfect habit than did No. 210. Apparently descent from individuals which had thoroughly learned to avoid the black box gives the dancer no advantage in the formation of a white-black discrimination habit. There is absolutely no evidence of the inheritance of this particular individually acquired form of behavior in the dancer.
[Footnote 1: This experiment was interrupted by the death of the animals of both lines of descent.]