Bateson, however, proceeds to urge that the history of the Sweet Pea
belies those ideas of a continuous evolution with which we had formerly to
contend. The big varieties came first, the little ones arose later by
fractionation, although now the devotees of continuity could arrange them
in a graduated series from white to deep purple. Now this may be
historically true of the Sweet Pea, but I would point out that once the
dogma of the permanent indivisible unit or factor is abandoned, there is
nothing in Mendelism inconsistent with the possibility of the gradual
increase or decrease of a character in evolution. I do not suggest that
the colour and markings of a species or variety were, in all cases, due to
external conditions, but if the effect of external stimuli can be
inherited, can affect the chromosomes, then the evidence concerning unit
factors no longer contradicts the possibility of a character gradually
increasing, under the influence of external stimuli acting on the soma
from zero to any degree whatever.


SEX AND SECONDARY SEXUAL CHARACTERS

The mystery of sex is hidden ultimately in the phenomenon of conjugation,
that union of two cells which in general seems necessary to the
maintenance of life, to be a process of rejuvenation. We know nothing of
the nature of this process, or why in general it should produce a
reinvigoration of the cell resulting from it. We know little if anything
of the relation between the two conjugating cells or gametes, of the real
nature of the attraction that causes them to approach each other and
ultimately unite together. We have, it is true, some evidence that one
cell affects the other by some chemical action, as for instance in the
fact that the mobile male gametes of a fern are attracted to a tube