The author criticizes the 'finalistic' explanations of emotional expression as advance in one form or another by Darwin, Spencer, Wundt, Mantegazza and Bechterew, and on the whole agrees with the mechanistic view of Dumas. She goes on to lay stress on the sociological (as distinct from the merely biological) importance of emotional expression. Considered sociologically, the expressions of the emotions constitute a means whereby the members of a group can understand, and therefore react appropriately to, each other's mental state. These expressions are in fact a sort of rudimentary language, from which (as is indicated in conclusion) the more developed and conventionalized forms of gesture language and spoken language may gradually be developed.