| CHARACTER | GENERATION | -13 | -12 | -11 | -10 | -9 | -8 | -7 | -6 | -5 | -4 | -3 | -2 | -1 | 0 | 1 | 2 | 3 | 4 | 5 | |
| Length of |
| F1 | |||||||||||||||||||
| skull | B.C. | 3 | 6 | 4 | 13 | 18 | 42 | 32 | |||||||||||||
| Length of |
| F1 | 1 | 2 | |||||||||||||||||
| ulna | B.C. | 1 | 1 | 2 | 3 | 1 | 2 | 4 | 4 | 12 | 11 | 20 | 26 | 17 | 19 | ||||||
same table continued
| CHARACTER | GENERATION | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | |
| Length of |
| F1 | 2 | 2 | 8 | 5 | 10 | 7 | 3 | 2 | 2 | |||||||||||
| skull | B.C. | 38 | 34 | 16 | 16 | 8 | 4 | 3 | 1 | |||||||||||||
| Length of |
| F1 | 1 | 1 | 1 | 2 | 2 | 5 | 3 | 1 | 7 | 3 | 2 | 1 | 2 | 1 | 1 | |||||
| ulna | B.C. | 18 | 15 | 12 | 13 | 15 | 11 | 5 | 2 | 4 | 2 | 2 | 1 | 1 | ||||||||
He found that the variability was smaller in the first generation than in the second
generation (back cross). This is what is expected if several factor-differences were involved, because the hybrids of the first generation are expected to be more uniform in factorial composition than are those in the second generation which are produced by recombination of the factors introduced through their grandparents. Excellent illustrations of the same kinds of results have been found in Indian corn. As shown in figure 85 the length of the cob in F1 is intermediate between the parent types while in F2 the range is wider and both of the original types are recovered. East states that similar relations have been found for 18 characters in corn. Emerson has recently furnished further illustrations of the same relations in the length of stalks in beans.
Fig. 85. Cross between two races of Indian corn, one with short cobs and one with long cobs. The range of variability in F1 is less than that in F2. (After East.)
A similar case is shown by a cross between fantail and common pigeons (fig. 86). The latter have twelve feathers in the tail, while the selected race from which the fantails came had between 28 and 38 feathers in the tail. The F1 offspring (forty-one individuals) showed (fig. 87) between 12 and 20 tail feathers, while in F2 the numbers varied between 12 and 25. Here one of the grand-parental types reappears in large numbers, while the extreme of the other grand-parental type did not reappear (in the counts obtained), although the F2 number would probably overlap the lower limits of the race of fantail grandparents had not a selected (surviving) lot been taken for the figures given in the table.