The requisite knowledge and proficiency of ways and means is a product, perhaps a by-product, of the life of the community at large; and it can also be maintained and retained only by the community at large. Whatever may be true for the unsearchable prehistoric phases of the life-history of the race, it appears to be true for the most primitive human groups and phases of which there is available information that the mass of technological knowledge possessed by any community, and necessary to its maintenance and to the maintenance of each of its members or subgroups, is too large a burden for any one individual or any single line of descent to carry. This holds true, of course, all the more rigorously and consistently, the more advanced the "state of the industrial arts" may be. But it seems to hold true with a generality that is fairly startling, that whenever a given cultural community is broken up or suffers a serious diminution of numbers, its technological heritage deteriorates and dwindles, even though it may have been apparently meager enough before. On the other hand, it seems to hold true with a similar uniformity that, when an individual member or a fraction of a community on what we call a lower stage of economic development is drawn away and trained and instructed in the ways of a larger and more efficient technology, and is then thrown back into his home community, such an individual or fraction proves unable to make head against the technological bent of the community at large or even to create a serious diversion. Slight, perhaps transient, and gradually effective technological consequences may result from such an experiment; but they become effective by diffusion and assimilation through the body of the community, not in any marked degree in the way of an exceptional efficiency on the part of the individual or fraction which has been subjected to exceptional training. And inheritance in technological matters runs not in the channels of consanguinity, but in those of tradition and habituation, which are necessarily as wide as the scheme of life of the community. Even in a relatively small and primitive community the mass of detail comprised in its knowledge and practice of ways and means is large,--too large for any one individual or household to become competently expert in it all; and its ramifications are extensive and diverse, at the same time that all these ramifications bear, directly or indirectly, on the life and work of each member of the community. Neither the standard and routine of living nor the daily work of any individual in the community would remain the same after the introduction of an appreciable change, for good or ill, in any branch of the community's equipment of technological expedients. If the community grows larger, to the dimensions of a modern civilised people, and this immaterial equipment grows proportionately great and various, then it