4. I believe it is possible now to arrange the linkage groups in our linkage map still further, so that the linkage groups are oriented in a still more uniform scheme in relation to the chromosomes. In the linkage map sent out with the last corn letter, they are oriented so that the upper end corresponds to, or is in the direction of the short arm end of the chromosome with the exception of #3 and probably #8. My evidence on #3 indicates that this group should be reversed with cr at the zero point or in the direction of the short arm end. For #8, the only data I have are those given below. The numbers are too small, but they suggest that this group should be reversed also, placing j1 at the zero point. This means that the zero point will be moved as new data come along, but that will be true of several other groups as they stand now.