3. Crosses between interchanges involving the same two chromosomes were studied for pollen and ear sterility and as a possible source of viable deficiencies. If two are crossed which involve exactly the same loci in the two chromosomes, the F1 should show no sterility.

Where the breaks are not at the same loci, the result depends on the position of the breaks relative to the spindle fiber. In certain cases gametic combinations should be possible which carry a deficiency for the piece between the breaks.

In a series of such crosses, one showed about 20% sterility and another 25% where the parents crossed with normals showed semisterility. Variation in size of the filled pollen grains was observed. Crosses with genes which have a chance of being near these loci have been made for deficiency tests; also crosses with sifted pollen.