Skeletal calcite in living scleractinian corals: microboring fillings, not primary skeletal deposits.

1. For reviews, see S. Appelle, Psychol. Bull. 78, 266 (1971); M. M. Taylor, J. Opt. Soc. Am. 53,763 (1963). 2. Although the fact of orientation anisotropy is well established, its incidence has not been documented, as far as we are aware. Two earlier studies of anisotropy [H. Leibowitz, N. A. Myers, D. A. Grant, J. Opt. Soc. Am. 45, 76 (1955); J. C. Ogilvie and M. M. Taylor, ibid. 49, 898 (1955)] used a total of 11 subjects. Of these subjects, one showed no difference in performance for different orientations and two performed better for obliques. 3. M. H. Segall, D. T. Campbell, M. J. Herskovits, The Influence of Culture on Visual Perception (Bobbs-Merrill, Indianapolis, Indiana, 1966). 4. R. C. Annis and B. Frost, Science 182, 729 (1973). 5. Titmus Optical Company, Petersburg, Virginia. 6. Subjects with prescribed corrective lenses were required to wear them during testing. If any subjects scored below normal values on the T-O vision tester or exhibited large differences in acuity for orthogonal gratings in the experimental situation, we attempted to improve their performance to normal with lenses. Those with obvious amblyopias were dropped from the sample. Since we did not refract our subjects to ensure a perfect optical correction, we were concerned that some cases of uncorrected astigmatism might have influenced our results. However, when we computed an astigmatism ratio by dividing the acuity for one axis by that for the orthogonal axis, the distribution for both Chinese and Caucasian samples approximated that reported for normal subjects by D. E. Mitchell et al. (11). Thus, we conclude that the differences between Chinese and Caucasian scores reported here were not produced by systematic differences in astigmatism. 7. Contrast is defined as Lmax -Lmn