Under the first type all those matings where both parents were epileptic, one was epileptic and the other feeble-minded, or both were feeble-minded, are classified. According to Mendel's Law, all of the children should be nulliplex. The data showed all of the children defective. Under the type nulliplex × simplex, all matings where one parent was epileptic or feeble-minded and the other "tainted," that is, alcoholic, neurotic, migrainous, or showed some mental weakness, are classified. From this type of mating, 50% of the offspring are expected to be nulliplex and 50% simplex. From the matings where one parent was epileptic or feeble-minded and the other alcoholic, there were 61% mentally deficient or nulliplex, the remainder simplex. The figures for the offspring from the other matings showed 47% nulliplex, and 53% simplex. For the third type, nulliplex by normal, all those matings where one parent was epileptic or feeble-minded and the other reported as mentally normal are classified. From this type of mating, the expectations are that all of the children would be simplex. A study of the ancestors of the normal parents showed these parents simplex rather than normal. The analysis of the offspring showed at least 43% nulliplex, which is a close fitting to the type of mating nulliplex × simplex. The fourth type of mating is simplex × simplex. Here, all matings where both of the parents were "tainted" are classified. The expectation is that 25% of the offspring would be nulliplex, in reality 35% were found to be mentally deficient. Simplex × normal is the fifth type of mating considered. The matings where one parent was tainted and the other supposedly normal, are classified here. From a study of their ancestors these normal parents appeared to be simplex, and the classification of the offspring showed more than 25% nulliplex, which is the expectation from simplex × simplex mating. The sixth type is normal × normal, and the matings where both parents were reported normal is studied under this heading. Here, as before, a study of the ancestors of these normal parents indicates that they are simplex, and not normal. The classification of the children showed a close fitting to the expectation from a simplex × simplex mating. A special study of the matings where one or both of the parents was migrainous or alcoholic, shows a close relationship between these conditions and epilepsy. The following conclusions are drawn from the study. The common types of epileptics lack some element necessary for complete mental development. This is also true of the feeble-minded. Two epileptic parents produce only defectives. When both parents are either epileptic or feeble-minded their offspring are also mentally defective. Epilepsy tends in successive generations to form a larger part of the population. The normal parents of epileptics are not normal but simplex, and have descended from tainted ancestors.