Judging from the interval between the occurrence of the first smile and of the first laugh in the life of the individual, we may conjecture that laughter did not grow into a full reiterated sound in “primitive man,” or his unknown immediate predecessor, till much later. We should expect that a considerable development of vocal power would be a condition of man’s taking heartily to this mode of emotional utterance. The study of the infant certainly supports this idea. The babble of the second and third months, which is made up of a reiteration of many vocal and consonantal sounds, may prepare for laughter, as it certainly does for speech. The observations of Miss Shinn, quoted above, on the expansion of the range of vocal sound before the occurrence of the first laugh are most significant here. They seem to point to the fact that in the evolution of the species the first laughter was selected from among a great variety of sounds produced in pleasurable states. Let us now suppose that our immediate animal ancestor has reached the level of clear perceptions, and is given to the utterance of certain reiterated sounds during states of pleasure. Let us further conceive of him as having his sympathies developed up to the point of requiring a medium for expressing not only pains but pleasures, and more particularly for calling others’ attention to the presence of cheering and welcome objects, _e.g._, of a member of the family who has been abroad for a time. Such an animal would need to improve on his primal smiles and grins. He would require vocal utterances of some strength in order {174} to reach distant ears, something answering to the cackle of the hen when she has discovered some choice morsel and desires to bring her brood to her side. How is this improvement to be effected?