Transitory Heterosis in Numbers of Basal Bodies in TETRAHYMENA PYRIFORMIS.

The numbers of kinetosomes in ciliary rows on the ventral surface of cells of Tetrahymena pyriformis, syngen 1, are greater by about 10% in young heterozygotes established by crossing two inbred strains than in either homozygote. The difference, apparent at 20 fissions post-fertilization, is essentially gone by 100 fissions. This observation is consistent with a generalized "allelic exclusion" at all loci completed by perhaps 60 fissions after fertilization.