Perhaps one reason for the great confusion on this subject arises out of the fact that we have become accustomed to making a sharp distinction between physical characters on the one hand and so-called mental and moral qualities on the other. Every one recognizes family resemblances in physical features. A particular shape of nose or a peculiarity of the hand appears in every member of the family, sometimes for several successive generations. Facts like these we accept as evidence of "heredity" without any question. We also recognize that the Joneses of Centerville always take the measles "hard," whereas with the Andersons vaccination never "takes." But when it comes to mental qualities, which we are not accustomed to measure or to recognize with the same degree of discrimination, most of us fail to see that heredity is just as common for these as for physical traits. Moreover, mental qualities take on such a great variety of forms that their recognition is made doubly difficult. Thus it may be the same mental traits that make of a certain man a successful lawyer, of his brother an able scientist, and of their cousin a clever criminal. No doubt each of these three men has qualities in a degree lacking in the others; but the point is that they have many qualities in common which are obscured by the different lines of development they have followed. The old parable of the wheat cast upon the ground may help us. That which falls upon stony ground fails of germination; that which falls upon poor soil will germinate, but will die of drought or be scorched by the sun; that which falls upon good soil will develop into a good plant. The _kind_ of plant that may develop is determined by the seed, by heredity; _how_ the plant will develop is determined by the surrounding conditions, by the environment. On the physical side these facts are so familiar to us that we never question the connection between development and food, or between development and exercise, or between development and other physical conditions. Of course, we say, an undernourished child will never be strong; of course, an overworked child will never be strong, of course, drinking and smoking and other dissipation will prevent healthy development. And yet, do we not know that of two underfed children, one will show the ill effects more than the other; that of two overworked children, one will survive abuse with less permanent injury than the other.