THE FACTORIAL HYPOTHESIS 269 
be nothing but a condition produced by the factor 
which ordinarily makes the fully purple flower, quanti- 
tatively diminished. The pied animal, such as the 
Dutch rabbit, must similarly be regarded as the re- 
sult of partial defect of the chromogen from which the 
pigment is formed, or conceivably of the factor which 
effects its oxidation. On such lines I think we may 
with great confidence interpret all those intergrading 
forms which breed true and are not produced by 
factorial interference. 
“Tt is to be inferred that these fractional degrada~- 
tions are the consequences of irregularities in segrega- 
tion. We constantly see irregularities in the ordinary 
meristic processes, and in the distribution of somatic 
differentiation. We are familiar with half seg- 
ments, with imperfect twinning, with leaves partially 
petaloid, with petals partially sepaloid. All these 
are evidences of departures from the normal regu- 
larity in the rhythms of repetition, or in those waves 
of differentiation by which the qualities are sorted 
out among the parts of the body. Similarly, when 
in segregation the qualities are sorted out among the 
germ cells in certain critical cell divisions we can not 
expect these differentiating divisions to be exempt 
from the imperfections and irregularities which are 
found in all the grosser divisions that we can observe.” 
Bateson has assumed because the character ap- 
pears to fractionate that we are to infer that some 
particular factor, that stands for it, fractionates too, 
but such a conclusion overlooks the fact that a char- 
acter is produced by many factors in co-operation, 
