The" MiilIer-Lyer illusion" was described and interpreted by many authors since 1889 (I).E.B. Titchener (3) mentioned twelve theories, which had been issued before 1901.E.G. Boring (5) also arranged twelve theories and yet he said that among all these theories there could be no decision.In addition to these theories many notions about this illusion have been presented up to now.Nevertheless, it remains unsolved.K. Motokawa (8) revealed by a physiological method that an optical image formed on the retina produces a "field of induction" in the surrounding retinal area, and suggested that the experience of illusion may perhaps be accounted for by the deformations in the field of retinal induction.According to his finding, the Miiller-Lyer illusion depends upon a conspicuous discotinuity arising in the gradients of the field at some distance away from the end of the principal line in the Miiller-Lyer figure.