Similar white factors are known in other animals. It
is worth noting that all the well attested Mendelian characters in man
are abnormalities, no normal character having yet been proved to be
inherited in this manner.]
Apart from multiple factors as properly defined (that is, factors which
produce the same result, either alone or together), extensive analysis
usually reveals that apparently simple characters are in reality
complex. The purple aleurone color of maize seeds is attributed by R. A.
Emerson to five distinct factors, while E. Baur found four factors
responsible for the red color of snapdragon blossoms. There are, as G.
N. Collins says,[49] "still many gross characters that stand as
simple Mendelian units, but few, if any, of these occur in plants or
animals that have been subjected to extensive investigation. There is
now such a large number of characters which at first behaved as units,
but which have since been broken up by crossing with suitable selected
material, that it seems not unreasonable to believe that the remaining
cases await only the discovery of the right strains with which to
hybridize them to bring about corresponding results."
In spite of the fact that there is a real segregation between factors as
has been shown, it must not be supposed that factors and their
determiners are absolutely invariable.
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