378 MENTAL EVOLUTION IN MAN. 



that Mr. Darwin suggests ; and certainly sooner or later the 

 receptual life of this social animal must have advanced far 

 enough to have become comparable with that of an infant 

 at about two years of age. That is to say, this animal, 

 although not yet having begun to use articulate signs, must 

 have advanced far enough in the conventional use of natural 

 signs (or signs with a natural origin in tone and gesture, 

 whether spontaneous only or intentionally imitative), to have 

 admitted of a tolerably free exchange of receptual ideas, such 

 as would be concerned in animal wants, and even, perhaps, in 

 the simplest forms of co-operative action.* Next, I think it 

 probable that the advance of receptual intelligence which 

 would have been occasioned by this advance in sign-making, 

 would in turn have led to a further development of the 

 latter — the two thus acting and re-acting on one another, 

 until the language of tone and gesture became gradually 

 raised to the level of imperfect pantomime, as in children 

 bsfore they begin to use words. At this stage, however, or 

 even before it, I think very probably vowel-sounds must have 

 been employed in tone-language, if not also a few of the 

 consonants. And I think this not only on account of the 

 analogy furnished by an infant already alluded to, but also 

 because in the case of a " singing " animal, intelligent enough 

 to be constantly using its voice for semiotic purposes, and 

 therefore employing a variety of more or less conventional 

 tones, including clicks, it seems almost necessary that some 

 of the vowel sounds — and possibly also some of the con- 

 sonants — should have been brought into use. But, be this as 

 it may, eventually the action and re-action of receptual intelli- 

 gence and conventional sign-making must have ended in so 

 far developing the former as to have admitted of the breaking 

 up (or articulation) of vocal sounds, as the only direction in 

 which any further improvement of vocal sign-making was 

 possible. I think it not improbable that this important stage 

 in the development of speech was greatly assisted by the 



* Compare quotations from the German philologists in support of the first 

 hypothesis, pp. 361, 362. 



