_Albida_, _nanella_ and _rubrinervis_ appeared in large numbers, and even _scintillans_, of which I had but a single plant in the previous generation, was repeated sixfold. New forms did not arise, and the capacity of my strain seemed exhausted. This conclusion was strengthened by the results of the next three generations, which were made on a much smaller scale and yielded the same, or at least the mutants most commonly seen in previous years. Instead of giving the figures for these last two years separately, I will now summarize my whole experiment in the form of a pedigree. In this the normal _lamarckiana_ was the main line, and seeds were only sown from plants after sufficient isolation either of the plants themselves, or in the latter years by means of paper bags enclosing the inflorescences. I have given the number of seedlings of _lamarckiana_ which were examined each year in the table below. Of course by far the largest number of them were [556] thrown away as soon as they showed their differentiating characters in order to make room for the remaining ones. At last only a few plants were left to blossom in order to perpetuate the race. I have indicated for each generation the number of mutants of each of the observed forms, placing them in vertical columns underneath their respective heads. The three first generations were biennial, but the five last annual. PEDIGREE OF A MUTATING FAMILY OF _OENOTHERA LAMARCKIANA_ IN THE EXPERIMENTAL GARDEN AT AMSTERDAM Gener: O.gig. albida obl. rubrin. Lam. nanella lata. scint. VIII. 5 1 0 1700 21 1 VII. 9 0 3000 11 VI. 11 29 3 1800 9 5 1 V. 25 135 20 8000 49 142 6 IV. 1 15 176 8 14000 60 73 1 III. 1 10000 3 3 II. 15000 5 5 I. 9 It is most striking that the various mutations of the evening-primrose display a great degree of regularity. There is no chaos of forms, no indefinite varying in all degrees and in all directions. Quite on the contrary, it is at once evident that very simple rules govern the whole phenomenon.