of low type, has no appliances for combining the actions of its remoter parts. When coöperation of them against an enemy is called for, there is nothing but the spread of an alarm from man to man throughout the scattered population; just as, in an undeveloped kind of animal, there is merely a slow, undirected diffusion of stimulus from one point to all others. In either case, the evolution of a larger, more complex, more active organism, implies an increasingly-efficient set of agencies for conveying from part to part the material products of the respective parts, and an increasingly-efficient set of agencies for making the parts coöperate, so that the times and amounts of their activities may be kept in fit relations. And this is what we find. In the individual organism, as it advances to a high structure, no matter of what class, there arises an elaborate system of channels through which the common stock of nutritive matters (here added to by absorption, there changed by secretion, in this place purified by excretion, and in another modified by exchange of gases) is distributed throughout the body for the feeding of the various parts, severally occupied in their special actions; while in the social organism, as it advances to a high structure, no matter of what political type, there develops an extensive and complicated trading organization for the distribution of commodities, which, sending its heterogeneous currents through the kingdom by channels that end in retailers' shops, brings within reach of each citizen the necessaries and luxuries that have been produced by others, while he has been producing his commodity or small part of a commodity, or performing some other function or small part of a function, beneficial to the rest. Similarly, development of the individual organism, be its class what it may, is always accompanied by development of a nervous system which renders the combined actions of the parts prompt and duly proportioned, so making possible the adjustments required for meeting the varying contingencies; while along with development of the social organism there always goes development of directive centres, general and local, with established arrangements for interchanging information and instigation, serving to adjust the rates and kinds of activities going on in different parts.
Now, if there exists this fundamental kinship, there can be no rational apprehension of the truths of Sociology until there has been reached a rational apprehension of the truths of Biology. The services of the two sciences are, indeed, reciprocal. We have but to glance back at its progress, to see that Biology owes the cardinal idea, on which we have been dwelling, to Sociology; and that, having derived from Sociology this explanation of development, it gives it back to Sociology greatly increased in definiteness, enriched by multitudinous illustrations, and fit for extension in new directions. The luminous conception first enunciated by one whom we may claim as our countryman by blood, though French by birth, M. Milne-Edwards—the conception of "the physiological division of labor"—obviously origi-