78 Experimental Zoology 
At some time in the history of these germ-cells one or the other 
of these two characters comes to dominate in each cell, so that 
half of the cells will be G(W) and half W(G). This will be 
true both for eggs and sperm. Chance meetings of the two 
kinds of sperm and the two kinds of eggs will give — 
G(W) W(G) 
G(W) W(G) 
1 GW) +2 GW) W(G+1WG) 
This is the characteristic Mendelian proportion. The first 
term, G(W), is a gray mouse, the so-called extracted dominant, 
i.e. it is a mouse gray in color, which, if bred to other gray 
extracted dominants, will produce only gray mice. This means 
that the latent white remains in the latent condition in its 
germ-cells, all of which are G(W). 
The second term, G(W) W(G), of the proportion represents also 
a gray mouse, since the gray, G, dominates the white, W, when 
both occur in the ‘‘free” condition in the same body-cell. It 
will be noticed that the presence of the two “free” colors, G 
and W, in the cells of this type indicates that the type is the same 
as the first hybrid formed by crossing G with W; and it is im- 
portant to find that when inbred this type gives exactly the 
same results (z.e. the Mendelian proportion again) as do the 
first hybrids, GW. By the “free” condition I mean to imply 
that the two characters, G and W, have not been brought into 
the intimate relation to each other that is assumed to occur in 
the germ-cells at the time when the alternating dominance and 
latency occurs. 
The third term, W(G), of the proportion is the extracted reces- 
sive. It represents a white mouse containing gray in a latent 
condition. If inbred, these white mice produce only white 
mice, but if crossed in certain ways the latent gray color can 
be brought out again. 
The preceding example will suffice to show how the Men- 
delian proportion can be accounted for on the assumption of 
alternation of the contrasted characters in the germ-cells. 
