where X stands for the mimetic factor and I for the factor which inhibits the action of X. All males are heterozygous for I, but during the segregation of characters at some stage in the formation of the families only the male-producing sperms come to contain the factor I. It is lacking in all the female-producing sperms formed by the male. [M] (1) does not contain the factor for the mimetic condition and gives only daughters of the M form when mated with an M[F]. [M] (2) on the other hand is homozygous for the factor X, and consequently all of his germ cells contain it. This is the male that gives nothing but mimetic daughters with whatever form of female he is bred. [M] (3) is heterozygous for X; that is to say, one half of his germ cells contain it, the other half not. With the M[F] he must give equal numbers {87} of offspring with and without X, _i.e._ half of his daughters will be mimetic and the other half non-mimetic. With a heterozygous mimetic female (iiXx), which is also producing germ cells with and without X in equal numbers, he may be expected to give the usual result, viz. dominants and recessives in the ratio 3:1; or in other words mimetic and non-mimetic females in the ratio 3:1. One of Fryer's experiments may be given here in illustration of the nature of the evidence upon which the above hypothesis depends. H[F](wild) H[F](wild) | | +--------+----------+ +--+------+----------+ | | | | | | 18[M][M] 10M[F][F] 7H[F][F] 26[M][M] 7M[F][F] 26H[F][F] | | +---------+ +------+ | | M[F] × [M] | +---------+ | | 7[M][M] 12H[F][F] | | +-----+ | | \ | | +---------+--------------+ | | \ | [M] × H[F] ------------- [M] × H[F] | | +---------+--+-----+ +---------+----------+ | | | | | | 14[M][M] 6H[F][F] 1M[F] 8[M][M] 10H[F][F] 2M[F][F]