Sectorial mosaics in the domestic pigeion: 25 more years.

The hypothesis of bipaternity--incorporation of tissue derived from supernumerary sperms into an embryo--to explain the origin of sectorial mosaicism in pigeons was advanced in 1949. Since then, 182 additional examples have come to my attention. Only one was reported to be a gynandromorph; sex ratios generally have been near 1 : 1. No environmental variable has shown significant relation to the origin of the mosaics, and only a slight familial tendency has been indicated. At least 15 color and pattern mutants have been involved, usually contrasting only two alleles. The frequency and its use in crosses. Complex mosaics, involving two or more loci in the contrasts numbered at least 38 cases, of which 11 are examined in more detail, and 6 shown in photographs. Several instances of germinal as well as somatic mosaicism were demonstrated by progeny tests. The bipaternity hypothesis has not been ruled out by evidence in any case.