in this case the blackness is not as fully expressed because produced by only this single determiner and the fowl appears gray or "blue"; that is, the black produced by a single determiner is in this case not as black as that produced by the double determiner. Now of course this hybrid fowl forms germ cells containing determiners for color, but these cells, instead of being all alike and with semi-black determiners corresponding with the semi-black characteristics of the individual, are of two different kinds--some are like those of each of the grandparents which fused to give origin to the parent forms, and these are formed in approximately equal numbers--one half with the black determiner, one half without it. When two such fowls are bred together the chances are equal for certain combinations of germ cells; the chances are equal that the "black" or "white" germ cell of the one individual shall meet and conjugate with the "black" or "white" germ cell of the other individual. The result may be expressed algebraically as follows, using the letters _B_ and _W_ to indicate respectively germ cells with and without the black color determiner. Germ cells of first parent _B_ + _W_ Germ cells of second parent _B_ + _W_ ------------- _BB_ + _BW_ _BW_ + _WW_ ----------------- Combinations in the germ of the offspring _1BB_ + _2BW_ + _1WW_ That is, one fourth are pure black (_BB_), one fourth pure white (_WW_), and the remaining half are hybrids, black and white (_BW_). The pure blacks again form germ cells, all possessing the determiner for blackness; the pure whites form germ cells all lacking the determiner for blackness; the hybrid blues produce again equal numbers of germ cells possessing and lacking the determiner for blackness. The relation of the germ cells and the organisms forming them and developing from them is shown in the diagram in Fig. 9. In the more common cases where the phenomenon of dominance appears, as in the guinea pig, this is explained by saying that here a single determiner for blackness is somehow sufficient to produce the color. In such cases the black color observed may result either from a single (_BW_) or from a double (_BB_) black determiner in the germ which forms the organism. Only when the black determiner is entirely absent (_WW_) does the white color appear in the developed organism and the individual is then said to exhibit the recessive characteristic.