How do all of these diverse characteristics work out in the child? In the first place, it seems evident that we do not inherit our bodies as wholes, but in parts or units. We may think of the human race as a whole being made up of a great number of unit characters. No one person possesses all of them. Every person is lacking in some of them. His neighbor may be lacking in quite different ones. Now one parent transmits to the child a certain combination of unit characters; the other parent, a different combination. These characteristics may not all appear in the child, but all are transmitted through it to the next generation, and they are transmitted purely. By being transmitted purely, we mean that the characteristic does not seem to lose its identity and disappear in fusions or mixtures. The essential point in this doctrine of heredity is known as Mendelism; it is the principle of inheritance through the pure transmission of unit characters. An illustration will probably make the Mendelian principle clear. Let us select our illustration from the plant world. It is found that if white and yellow corn are crossed, all the corn the first year, resulting from this crossing, will be yellow. Now, if this hybrid yellow corn is planted the second year, and freely cross-fertilized, it turns out that one fourth of it will be white and three fourths yellow. But this yellow consists of three parts: one part being pure yellow which will breed true, producing nothing but yellow; the other two parts transmit white and yellow in equal ratio. That is to say, these two parts are hybrids, the result of crossing white with yellow. It is not meant that one can actually distinguish these two kinds of yellow, the pure yellow and the hybrid yellow, but the results from planting it show that one third of the yellow is pure and that the other two thirds transmit white and yellow in equal ratio. The main point to notice in all this is that when two individuals having diverse characteristics are crossed, the characteristics do not fuse and disappear ultimately, but that the two characteristics are transmitted in equal ratio, and each will appear in succeeding generations, and will appear pure, just as if it had not been crossed with something different. The first offspring resulting from the cross--known as hybrids--may show either one or the other of the diverse characteristics, or, when such a thing is possible, even a blending of the two characteristics. But whatever the actual appearance of the first generation of offspring resulting from crossing parents having diverse characteristics, their germ-cells transmit the diverse characteristics in equal proportion, as explained above.