If a number of individuals of any species be compared, it will be found that they all show differences from each other either in size, shape, colour, relation of parts, or any other characteristics; in fact, no two of them are exactly alike. Even if off springs be compared with their own parents, similar, though on the whole not much marked, dissimilarities will present themselves. These differences constitute what is know as Variation and it is into the facts of this variation and is importance, as the cornerstone of the whole fabric of Evaluation, that this volume deals with.
