We need not again attempt to indicate how among animals we have the perceptual precursors of the æsthetic and ethical concepts. But we may remind the reader that we endeavoured to show that intercommunication had its foundation in instinctive sounds; and that it passed into the intelligent stage in the perceptual life, when these sounds acquired meaning, and hence became guides to behaviour. This is especially instructive from our present standpoint, since it is probable that the passage of communication from the indicating to the descriptive stage afforded the conditions under which rational thought was evolved. For such thought it is essential that attention should be focussed on the relationships of things. And no description is possible without making distinctly present to consciousness these relationships, in time and space, the data for which are abundantly present in the perceptual life, though lurking in the background, and needing something to fix them and to aid consciousness in distinguishing them clearly. In descriptive communication parts of speech, or their initial equivalents, afford fixation points for these relationships, and serve to render them distinct. If the reader will try to describe even the simplest occurrence without introducing the symbols for the relations which the events bear to each other, his failure will serve to bring home how essential a feature this is. In social communication, then, we probably have the key to the passage from perceptual to ideational process; and in this passage description is the antecedent of, and affords the conditions to, explanation. Words, moreover, as we have already said, form the pegs upon which we can hang up, for ready reference, the products of abstraction and generalization, or, to modify the analogy, they form the bodies of which these products are the rational soul. If we are ever to trace the passage from the instinctive through the indicating stage of communication, and so onwards through the beginnings of description to its higher levels, and thus to the use of language as a medium of explanation, it must be through child-study. In every normal human child the passage does actually take place, though, no doubt, in a condensed and abbreviated form as an epitomized recapitulation in individual development, of the steps of evolutional progress. Thus we may obtain a key to the solution of one of the most difficult problems in evolution by continuous process--that of the transition from animal behaviour to human conduct. INDEX A Abstract and general ideas, 57 Abstraction, 166; germs of, 332 ff. Acceleration, 250 Accommodation defined, 36 Acquired characters, inheritance of, 35, 110 Acquired instincts (Wundt), 66, 106 Acquisition defined, 36; ultimately dependent on natural selection, 289 Adaptation defined, 37 ADDISON on instinct, 63 Æsthetics, animal, 270 Afferent and efferent impulses, 32, 101