The Making of Species 
continuous and discontinuous variations. The 
former are slight departures from the normal ; 
the latter are considerable deviations from the 
mean or mode; great jumps, as it were, taken by 
nature, as, for example, the pea and the rose 
combs of fowls, which were derived from the 
normal single comb. 
“At long intervals of time,” wrote Darwin, 
“out of millions of individuals reared in the 
same country and fed on nearly the same food, 
deviations of structure so strongly pronounced as 
to deserve to be called monstrosities arise, but 
monstrosities cannot be separated by any distinct 
line from slighter variations.” Therefore it is 
evident that he regarded the difference between 
continuous and discontinuous variations as not 
one of kind, but merely of degree. To the 
discontinuous variations Darwin attached very 
little importance from an evolutionary point of 
view. He looked upon them as something 
abnormal. 
“It may be doubted,” he wrote, ‘whether 
such sudden and _ considerable deviations of 
structure such as we occasionally see in our 
domestic productions, more especially with plants, 
are ever permanently propagated in a state of 
nature. Almost every part of every organic 
being is so beautifully related to its complex 
conditions of life that it seems as improbable 
that any part should have been suddenly pro- 
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