MASKED CHARACTERS 205 
the visible characters of the types which appeared 
in F, would be represented by 9AB+3Ab+(3aB + 
tab). On referring to the account given on p. 176 it 
will be seen that one in nine of the purple plants is of 
the constitution ABAB, and may be expected to 
breed true. 
A precisely similar result may be obtained in F, in 
cases where there is no reversion in F,. In the 
following example a white pea, which did not contain 
the masked purple factor, was crossed with a ‘ maple- 
seeded’ pea. The characteristic feature of maple is a 
marbling of brown spots on a grey ground colour. In 
F, the marbling was dominant, and the seeds resembled 
the maple parent. 
In F, there appeared 9 maple : 3 grey : 4 white— 
t.€., the same ratio as in the previous case, this time 
without reversion. This ratio is brought about by the 
simple combinations of two pairs of allelomorphs A-a, 
and C-c, C being unable to manifest itself unless A is 
present in the same zygote. As a matter of fact, in 
this particular case C does sometimes just manage 
to appear in the absence of A, the result being a 
white seed with a sort of faint ‘ghost’ of a maple 
marking. 
When a strain bearing both maple marking and 
purple spots is crossed with a white in which neither 
of these factors is latent, we can easily calculate the 
ratio to be expected in F, by using the formula 
(4+2Ada+a) (B+2Bb+b) (C+2Cc+c). The result 
works out as follows (writing m for maple, # for purple, 
and g for grey): 27mpg, 9mg, opg, 3g, (gmp, 3m, 
