a perfect colour-series must result. If, for instance, A = A₁ + A₂, then the hybrids A₁a and A₂a form the developmental series—
A₁ + 2A₁a + a
A₂ + 2A₂a + a.
The members of this series can enter into nine different combinations, and each of these denotes another colour[1]—
| 1 | A₁A₂ | 2 | A₁aA₂ | 1 | A₂a |
| 2 | A₁A₂a | 4 | A₁aA₂a | 2 | A₂aa |
| 1 | A₁a | 2 | A₁aa | 1 | aa. |
The figures prescribed for the separate combinations also indicate how many plants with the corresponding colouring belong to the series. Since the total is sixteen, the whole of the colours are on the average distributed over each sixteen plants, but, as the series itself indicates, in unequal proportions.
Should the colour development really happen in this way, we could offer an explanation of the case above described, viz. that the white flowers and seed-coat colour only appeared once among thirty-one plants of the first generation. This colouring appears only once in the series, and could therefore also only be developed once in the average in each sixteen, and with three colour characters only once even in sixty-four plants.
It must, however, not be forgotten that the explanation here attempted is based on a mere hypothesis, only supported by the very imperfect result of the experiment just described. It would, however, be well worth while to follow up the development of colour in hybrids by similar experi-
- ↑ [It seems very doubtful if the zygotes are correctly represented by the terms A₁aA₂a, A₂aa, A₁aa; for in the hybrids A₁a, &c. the allelomorphs A₁ and a, &c. should by hypothesis be separated in the gametes.]
