This note presents data relating to the relative vitality of articulate and inarticulate brachiopods and submits that representatives of each are probably fitted to and limited by particular, though in some instances very different, ranges of ecologic conditions. Information available suggests the life-span of the inarticulate Lingula unguis to be 5 years or more and that of the articulate Terebratella inconspicua about 4 years, although it appears that less than 10% of the latter live to the 3d year. The proportion of [male] [male] to [female] [female] among adult Terebratulina septentrionalis and Terebratella inconspicua appears to be about equal in both instances. Brief descr. of the sex products of Terebratulina is given, and the reader is referred to published sources of embryological data. Attention is called to certain implications of E. Percival''s recent significant paper on the embryology of Terebratella inconspicua.