514 THE POPULAR SCIENCE MONTHLY. 



individuality further by clothing it in a particular color, or even 

 personifying it outright as in the two cases given. Color audition 

 and association of color with written characters are explained by 

 many as due to physiological conditions, especially to the contigu- 

 ity of the cortical center involved. Dr. Krohn, in a recent review 

 of the subject in the American Journal of Psychology, adopts 

 this explanation in part. It is doubtful whether this hypothesis 

 is necessary to explain the comparatively rare cases of color 

 associations ; it certainly is not necessary for explaining number 

 forms. In any case, physiological association would be due, 

 either in its origin or as a justification of its survival, to useful 

 psychic associations. Now, in the matter of number forms, sup- 



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Fig. 18. 



pose that the child is required, as is very early the case in count- 

 ing, to think of the numbers not separately, but in relation to 

 each other. He has then the problem of arranging abstractions 

 in a series, and, if he is naturally an ear-minded child, will ar- 

 range them as a mere series of associated sounds. If, however, 

 he is eye-minded, he may consciously or unconsciously hit upon 

 the device of a visual spatial image, and thus enable himself to 

 comprehend and remember the numbers as he does other things 

 by a mental picture. A number form thus becomes a little sys- 

 tem of topical mnemonics. Its continuance, either in the indi- 

 vidual or, in cases of inherited forms, in the family, is of course 

 due to physiological conditions. In every case, however, its ori- 

 gin is probably to be traced to useful psychic associations. 



M. Stanislas Heunier has been able to produce artificially, by a process of 

 reflection, an appearance like that of the gemination or doubling of the canals 

 of Mars, and suggests hypothetically that the phenomenon in question may be one 

 of that character. 



