We have before us then a number of groups of butterflies each with a series of different colour patterns. In each group a portion of the series overlaps a portion of the series belonging to another more or less distantly related group. In the light of recent discoveries connected with heredity and variation the natural interpretation to such a set of phenomena would be somewhat as follows: Each group of Lepidoptera, such as those just discussed, contains, spread out among its various members, a number of hereditary factors for the determination of colour pattern. Within the group differences of pattern depend upon the presence or absence of this or that factor, the variety of pattern being the result of the many possible permutations and {146} combinations of these colour factors. Within the limits of each group is found a definite number of these factors--more in one group, less in another. But some factors may be common to two or more groups, in which case some of the permutations of the factors would be similar in the groups and would result in identical or nearly identical pattern. To take a simple example in illustration, let us suppose that a given group, ([alpha]), contains the eight factors A-H. Since any species in the group may exhibit any combination of one or more of these factors it follows that a considerable number of different forms are possible. Now suppose that another group, ([beta]), distinguished from ([alpha]) by definite structural features, also contains eight factors within the group, and that these factors are F-M, F, G, and H being common to both ([alpha]) and ([beta]). Any combination therefore in ([alpha]) lacking the factors A-E will be paralleled by any combination in ([beta]) lacking the factors I-M. For in both cases we should be dealing only with the factors F, G, and H, which are common to each group. So again a third group might have some factors in common with ([alpha]) and some with ([beta]), and so on for other groups. In this way certain of the series of colour patterns found in ([beta]) would overlap certain of those in ([alpha]), while others of the groups ([beta]) and ([alpha]) might overlap those found in different groups again. The striking resemblances not infrequently found between species belonging to quite distinct groups would on this view depend upon the hereditary factors for pattern and colour being limited {147} in number, so that the same assortment might not infrequently be brought together even though the group whose members exhibited the resemblance might, owing to structural differences, be placed in different families.