The whole of the forms may be classed into three essentially different groups. The first embraces those with the signs _AB_, _Ab_, _aB_, and _ab_ : they possess only constant characters and do not vary again in the next generation. Each of these forms is represented on the average thirty-three times. The second group embraces the signs _ABb_, _aBb_, _AaB_, _Aab_ : these are constant in one character and hybrid in another, and vary in the next generation only as regards the hybrid character. Each of these appears on an average sixty-five times. The form _AaBb_ occurs 138 times: it is hybrid in both characters, and behaves exactly as do the hybrids from which it is derived. If the numbers in which the forms belonging to these classes appear be compared, the ratios of 1, 2, 4 are unmistakably evident. The numbers 32, 65, 138 present very fair approximations to the ratio numbers of 33, 66, 132. The developmental series consists, therefore, of nine classes, of which four appear therein always once and are constant in both characters; the forms _AB_, _ab_, resemble the parental forms, the two others present combinations between the conjoined characters _A_, _a_, _B_, _b_, which combinations are likewise possibly constant. Four classes appear always twice, and are constant in one character and hybrid in the other. One class appears four times, and is hybrid in both characters. Consequently the offspring of the hybrids, if two kinds of differentiating characters are combined therein, are represented by the expression _AB_ + _Ab_ + _aB_ + _ab_ + 2_ABb_ + 2_aBb_ + 2_AaB_ + 2_Aab_ + 4_AaBb_. This expression is indisputably a combination series in which the two expressions for the characters _A_ and _a_, _B_ and _b_, are combined. We arrive at the full number of the classes of the series by the combination of the expressions: _A_ + 2_Aa_ + _a_ _B_ + 2_Bb_ + _b_. Second Expt. _ABC_, seed parents; _abc_, pollen parents; _A_, form round; _a_, form angular; _B_, albumen yellow; _b_, albumen green; _C_, seed-coat grey-brown. _c_, seed-coat white. This experiment was made in precisely the same way as the previous one. Among all the experiments it demanded the most time and trouble. From 24 hybrids 687 seeds were obtained in all: these were all either spotted, grey-brown or grey-green, round or angular[37]. From these in the following year 639 plants fruited, and, as further investigation showed, there were among them: