Discoveries of the last few years do seem to show that such means of a material character, though not the foundation of that order of processes which is inherited, are nevertheless among the most necessary conditions for the accomplishment of inheritance in general. It is scarcely necessary to remind you that for very many years all concrete research on heredity proper--that is, the actual comparison of the various specific characters in the generations of the grandfather, the father, and the child--was due to Galton. You may also be aware that in spite of Galton’s inestimable services it was not till 1900 that one of the active principles concerned in inheritance was found independently by de Vries, Correns, and Tschermak, and that this principle happened to be one that *had* been discovered already, stated with the utmost clearness and precision by the Augustinian monk, Gregor Mendel,[129] as early as 1865, though it had been completely forgotten ever since. [129] New edition in the “Klassiker d. exakt. Wiss.” Leipzig, Engelmann; see also Bateson, *Mendel’s Principles of Heredity*, Cambridge, 1902. The so-called “rule of Mendel” is based upon experiments with hybrids, that is, with the offspring of parents belonging to different species, or, at least, varieties, but it relates not to the characters of the generation resulting immediately from hybridisation, the “first” generation of hybrids, as we shall call it, but to the characters of that generation which is the result of crossing the hybrids with each other, provided that this leads to any offspring at all. There are many cases indeed, both amongst animals and plants, where the offspring of the hybrids, or in other terms the “second” generation, is found to consist of individuals of three different types--the mixed[130] type of the hybrids themselves, and the two pure types of the grandparents. Whenever the individuals of the “second” generation are separated into these three different types, hybrids are said to “split.” It is the fact of this splitting on the one hand, and on the other hand a certain statement about the numbers of individuals in the three different types of the “second” generation, that gives its real importance to Mendel’s rule. [130] For the sake of simplicity I shall not deal here with those cases of hybridisation in which one quality is “recessive,” the other “dominant,” but only allude to the cases, less numerous though they be, where a real mixture of maternal and paternal qualities occurs.