r for black the resulting hybrid has a color
produced by only a single determiner, that from the black parent, and
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 ca