Meantime the lip-movements of the _m_ were made without the utterance of sound, as if the child had perceived the difference. Other expressions of sound without assignable cause are _[=a]-au [=a]-[=a]_, _[=a]-[)o]_, _a-u-au_, _na-na_, the latter not with the tone of denial as formerly, and often repeated rapidly in succession. As separate utterances in comfortable mood, besides _oerroe_ came _apa_, _ga au-[)a]_, _acha_. The tenth month is marked by the increasing distinctness of the syllables in the monologues, which are more varied, louder, and more prolonged when the child is left to himself than when any one tries to entertain him. Of new syllables are to be noted _ndae[)e]_, _b[=a]e-b[=a]e_, _ba ell_, _arroe_. From the forty-second week on, especially the syllables _mae_ and _pappa_, _tatta_, _appapa_, _babba_, _taetae_, _pa_, are frequently uttered, and the uvular _rrrr_, _rrra_, are repeated unweariedly. The attempts to make the child repeat syllables pronounced to him, even such syllables as he has before spoken of his own accord, all fail. In place of _tatta_ he says, in the most favorable instance, _tae_ or _ata_; but even here there is progress, for in the previous month even these hints at _imitating_ or even responding to sound were almost entirely lacking. In the eleventh month some syllables emphatically pronounced to the child were for the first time correctly repeated. I said "ada" several times, and the attentive child, after some ineffectual movements of the lips, repeated correctly _ada_, which he had for that matter often said of his own accord long before. But this single repetition was so decided that I was convinced that the _sound-imitation_ was intentional. It was the first _unquestionable_ sound-imitation. It took place on the three hundred and twenty-ninth day. The same day when I said "mamma," the response was _nanna_. In general, it often happens, when something is said for imitation, and the child observes attentively my lips, that evident attempts are made at imitation; but for the most part something different makes its appearance, or else a silent movement of the lips. In the forty-fifth week everything said to the child, in case it received his attention, was responded to with movements of lips and tongue, which gave the impression of being made at random and of serving rather for diversion. Further, at this period the child begins during his long monologues to _whisper_. He produces sounds in abundance, varying in force, pitch, and _timbre_, as if he were speaking an unknown tongue; and some single syllables may gradually be more easily distinguished, although the corresponding positions of the mouth pass into one another, sometimes quite gradually, sometimes rapidly. The following special cases I was able to establish by means of numerous observations: