As foreign symbols, either the two-figure numbers were used or nonsense-words of regularly varying length. As familiar material, nouns, objects, verbs and movements were used. The words were always concrete, not abstract, by which it is meant that their meaning was capable of demonstration to the senses. With the exception of a few later specified series they were monosyllabic words. The nouns might denote objects of any size perceptible to the eye; the objects, however, were all of such a size that they could be shown through a 14×12 cm. aperture and still leave a margin. Their size was therefore limited. Concerning the verbs and movements it is evident that, while still being concrete, they might be simple or complicated activities consuming little or much time, and further, might be movements of parts of the body merely, or movements employing other objects as well. In this experiment complicated activities were avoided even in the verb series. Simple activities which could be easily and quickly imaged or made were better for the purpose in view. THE _A_ SET. The _A_ set contained sixteen series, _A_^{1}, _A_^{2}, _A_^{3}, etc., to _A_^{16}. They were divided as follows: Numbers and nouns: _A_^{1}, _A_^{5}, _A_^{9}, _A_^{13}. Numbers and objects: _A_^{2}, _A_^{6}, _A_^{10}, _A_^{14}. Numbers and verbs: _A_^{3}, _A_^{7}, _A_^{11}, _A_^{15}. Numbers and movements: _A_^{4}, _A_^{8}, _A_^{12}, _A_^{16}. The first week _A_^{1-4} were given, the second week _A_^{5-8}, etc., so that each week one series of each of the four types was given the subject. In place of foreign symbols the numbers from 1 to 99 were used, except in _A_^{13-15}, in which three-figure numbers were used. Each series contained seven couplets, except _A_^{13-16}, which, on account of the greater difficulty of three-figure numbers, contained five. Each couplet was composed of a number and a noun, object, verb, or movement. Certain rules were observed in the composition of the series. Since the test was for permanence, to avoid confusion no number was used in more than one couplet. No two numbers of a given series were chosen from the same decade or contained identical final figures. No word was used in more than one couplet. Their vowels, and initial and final consonants were so varied within a single series as to eliminate phonetic aids, viz., alliteration, rhyme, and assonance. The kind of assonance avoided was identity of final sounded consonants in successive words, _e.g._, lane, vine.