instead
of appearing in different zygotes (A zygote is a fertilised ovum, i.e. a
new organism resulting from the fusion of an ovum and a spermatozoon.),
they are present in the same zygote though at different times in its
life-history. They are of the same order as the mutational variations
of the modern biologist upon which the appearance of a new character
depends. What is a genetic or mutational variation? It is a genetic
character which was not present in either of the parents. But these
"growth variations" were present in the parents, and in this they differ
from mutational variations. But what are genetic characters? They are
characters which must appear if any development occurs. They are usually
contrasted with "acquired characters," using the expression "acquired
character" in the Lamarckian sense. But strictly speaking they ARE
acquired characters, for the zygote at first has none of the characters
which it subsequently acquires, but only the power of acquiring them
in response to the action of the environment. But the characters so
acquired are not what we technically understand and what Lamarck meant
by "acquired characters." They are genetic characters, as defined above.
What then are Lamarck's "acquired characters"? They are variations in
genetic characters caused in a particular way. There are, in fact,
two kinds of variation in genetic characters depending on the mode
of causation. Firstly, there are those variations consequent upon a
variation in the constitution of the protoplasm of a particular zygote,
and independent of the environment in which the organism develops,
save in so far as this simply calls them forth: these are the so-called
genetic or mutational variations. Secondly, there are those variations
which occur in zygotes of similar germinal constitution and which are
caused solely by differences in the environment to which the individuals
are respectively exposed: these are the "acquired characters" of Lamarck
and of authors generally. In consequence of this double sense in which
the term "acquired characters" may be used, great confusion may and
does occur. If the protoplasm be compared to a machine, and the external
conditions to the hand that works the machine, then it may be said that,
as the machine can only work in one way, it can only produce one kind
of result (genetic character), but the particular form or quality
(Lamarckian "acquired character") of the result will depend upon the