along lines defined by their characteristic traits, and equally by the capriciousness of the functioning and the remarkably wide range between activity and inactivity which render them aggregations of extremes—the Seri are at once the swiftest and the laziest, the strongest and the most inert, the most warlike and the most docile of tribesmen; and their transitions from rôle to rôle are singularly capricious and sudden. At the same time the observer is impressed by the relatively long intervals between the periods of activity; true, the intense activity may cover hours, as in the chase of a deer, or days, as in a distant predatory raid, or perhaps even weeks, when the tribe is on the warpath; yet all the known facts indicate that far the greater portion of the time of warriors, women, and children is spent in idle lounging about rancherias and camps, in lolling and slumbering in the sun by day and in huddling under the scanty shelter of jacales or shrubbery by night—i. e., when their activity is measured by hours, their intervals of repose must be measured by days. * * * * * Summarizing those somatic traits connected with habitual functioning, the Seri may be considered as characterized by (1) distinctive pedestrian habit, (2) conspicuous hand-and-tooth habit correlated with defective tool-sense, and (3) pronounced segregative habit correlated with a highly specialized race-sense; yet they are characterized no less by extreme alternations from the most intense functioning to complete quiescence—the periods of intensity being relatively short, and the intervals of quiescence notably long. * * * * * On reviewing the more conspicuous somatic structures and functions jointly, they are found to throw some light on their own development, and hence on the natural history of the Seri tribe.